Application of Boron in Olefin Metathesis

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Application of Boron in Olefin Metathesis
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Simocko, Chester Kent
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Doctorate ( Ph.D.)
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Chemistry
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Wagener, Kenneth B
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Enholm, Jonathan E
Sumerlin, Brent S
Murray, Leslie Justin
Batich, Christopher D

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acids -- admet -- boron -- catalyst -- metathesis -- olefin -- polymer
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Abstract:
Controlling polymer morphology is key to controlling andpredicting physical and electronic properties. However, in many cases polymer morphology is unknown because the primarystructure of the polymer is unknown. This can be for a variety of reasons, butthe most common is the use of imprecise polymerization techniques. Acyclicdiene metathesis (ADMET) polymerization is unique in its ability to createpolymers with precisely spaced pendant functionality. Many functional groupshave been polymerized using ADMET, from alkyl pendant groups to ion liquids.Precision ADMET polymers synthesized with pendant phosphonic and carboxylicacid moieties have shown never before seen morphologies. This dissertation willdiscuss the compatibility of boron-containing Lewis acids with olefinmetathesis, the use of ionic liquids in ADMET polymerization, the synthesis ofboronic acid containing ADMET monomers, and the morphology of precisionpolymers bearing pendant boronic acids and esters.   Boron-containingLewis acids have shown a profound effect on the cross metathesis reaction of1-hexene. Grubbs 1st generation catalyst shows over 100% improvementin conversion in some cases, while the yields of Grubbs 2ndgeneration increase by up to 50%. With the inclusion of boron-containing Lewisacids, compounds prepared using Grubbs 2nd generation-type catalystsdisplay significantly reduced levels of isomerization. To manage the high viscosity of these polymers, ionicliquids were studied and can be an ideal medium for ADMET polymerization. Shortreaction times of only 48 hours were observed even with low catalyst loading.Some common ionic liquid impurities were studied and only imidazole was shownto have a negative effect on molecular weight. Additives were also studied toneutralize the impurities and phosphoric acid has been shown to preventcatalyst poisoning with imidazole.  Whenthis system was applied to a triptycene monomer, high molecular weights werereached only at high temperatures. Boronic acid ADMET monomers have been synthesized. Alkylboronic acids and esters were first attempted but these proved difficultsynthesize due to the deboronation of the monomer. To prevent this, arylboronic acid and ester monomers were synthesized successfully. Deprotection ofboronic acid was studied. Pinacol was found to be difficult to removequantitatively, however protecting groups with benzylic alcohols proved to bereadily cleavable under hydrogenation conditions. Finally, precision boronic acid polymers were made. Theseprecision polymers show unique thermal behaviors due to the interaction betweenpendant Lewis acids, further X-ray scattering studies to probe morphology arebeing pursued by collaborators.
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by Chester Kent Simocko.
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Thesis (Ph.D.)--University of Florida, 2013.
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1 Applications of Boron i n Olefin Metathesis By Chester Kent Simocko A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILO SOPHY UNIVERSITY OF FLORIDA 2013

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2 2013 Chester Kent Simocko

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3 To my parents, family, and friends

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4 ACKNOWLEDGMENTS I would like to thank my advisor, Dr. Kenneth Wagener. He was always supportive, and al lowed me to pursue projects I was interested in. He is always willing to help both within the labs and without. He has guided me through my graduate career and will continue to be a role model and friend throughout my professional career. I would also like to thank my committee members (Professor Brent Sumerlin, Eric Enholm, Leslie Murray, and Christopher Batich) for taking time out of their busy schedule to advise me i n graduate school. I would also like thank Dr. Kathryn Williams for deciphering my rambli ng manuscripts and turning them into cohesive publications. students have made my stay at UF memorable and bearable. I would like to thank Dr. James Leonard for helping me get star ted in the lab. I would like to thank Dr. Bora Inci, Dr. Brian Aitken, Dr. Paula Delgado, and Dr. Sam Popwell for our many discussions, advice and friendship throughout the years. Michael Schulz gets special thanks for our many discussions and plans for re search idea and schemes that will probably never get off the ground. Thomas Young and Elliot Mackrell former undergraduate students, deserve special thanks for following me down many research paths and for running many of my columns for me. I would also l ike to thank Alexander Pemba, Pascale Attallah, Chip Few, Ashlyn Dennis, Donovan Thompson, Nicolas Sauty, Taylor Gaines, Lucas Caire de Silva, Hong Li, Patricia Bachler, Rachel Ford, Chelsea Sparks, and Cristian Perez for their friendship. Mrs. Sarah Kloss ner deserves special thanks for keeping all of the Butler Labs up and running, without her it would be bedlam. I would like to thank the rest of the Butler Labs, there are far too many to name and I would invariably forget someone. Working in the Butler P olymer Labs has been an

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5 excellent experience and I am lucky to have been part of the Butler Polymer Program. Finally, I would like to thank my collaborators at University of Pennsylvania, Dr. Karen Winey and Franc i s co Buitrago, and Massachusetts Institute of Technology, Dr. Timothy Swager. Collaboration enriches the scientific community and leads to new and grand scientific discoveries.

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6 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 TABLE OF CONTENTS ................................ ................................ ................................ .. 6 LIST OF TABLES ................................ ................................ ................................ ............ 8 LIST OF FIGURES ................................ ................................ ................................ .......... 9 LIST OF ABBREVIATIONS ................................ ................................ ........................... 14 ABSTRACT ................................ ................................ ................................ ................... 15 Chapter 1 Introduction ................................ ................................ ................................ ............. 17 1.1 Origins of Olefin Metathesis ................................ ................................ .............. 17 1.2 Effects of Precision on Polymer Properties ................................ ....................... 23 1.3 Precision Acid and Ionic Polymers ................................ ................................ .... 27 2 Effects of Boron Containing Lewis Acids on Olefin Metathesis ............................... 35 2.1 Background ................................ ................................ ................................ ....... 35 2.2 Results and Discussion ................................ ................................ ..................... 37 2.3 Conclusions ................................ ................................ ................................ ...... 44 2.4 Experimental ................................ ................................ ................................ ..... 44 2.4.1 Materials and I nstrumentation ................................ ................................ 44 2.4.2 Procedures ................................ ................................ .............................. 45 2.5 Representative Spectra ................................ ................................ .................... 46 3 Use of Ionic Liquids as a Medium for Acyclic Diene Metathesis Polymerization ..... 52 3.1 Background ................................ ................................ ................................ ....... 52 3.2 Results and Discussi on ................................ ................................ ..................... 55 3.3 Conclusion ................................ ................................ ................................ ........ 62 3.4 Experimental ................................ ................................ ................................ ..... 63 3.4.1 Materials and Instrumentation ................................ ................................ 63 3.4.2 Procedures ................................ ................................ .............................. 63 4 Boronic Acid Chemistry: Synthesis of Boronic Acid Monomer ................................ 69 4.1 Background ................................ ................................ ................................ ....... 69 4.2 Synthesis of Alkyl Boronic Acid Monomers ................................ ....................... 73

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7 4.2.1 Synthesis of 4,4,5 ,5 tetra methyl 2 (tricosa 1,22 dien 12 yl) 1,3,2 dioxaborolane (5) monomer. ................................ ................................ ......... 73 4.2.2 Synthesis of 4,4,5,5 tetra methyl 2 (2 (undec 10 enyl)tridec 12 enyl) 1,3,2 dioxaborolane (13). ................................ ................................ .............. 74 4.3 Aryl Boronic Acid Monomer Synthesis ................................ .............................. 76 4.3.1 Synthesis of 2 (4 (heptacosa 1,26 dien 14 yl)phenyl) 4,4,5 trimethyl 1,3,2 dioxaborola ne (16) ................................ ................................ ............... 76 4.3.2 Synthesis of 4,4,5,5 tetramethyl 2 (4 (tricosa 1,22 dien 12 yloxy)phenyl) 1,3,2 dioxaborolane. ................................ ............................... 81 4.3.3 Synthes is of 4,4,5,5 tetramethyl 2 (4 ((tricosa 1,22 dien 12 yloxy)methyl)phenyl) 1,3,2 dioxaborolane. ................................ .................... 82 4.3.4 Synthesis of I n C hain B oronic A cid M onomer. ................................ ........ 84 4.4 Deprotection of Boronic Acids ................................ ................................ ........... 85 4.5 Conclusions ................................ ................................ ................................ ...... 88 4.6 Experimental ................................ ................................ ................................ ..... 88 4.6.1 Materials and Instrumentation ................................ ................................ 88 4.6.2 Procedures ................................ ................................ .............................. 89 5 Boronic Acid and Ester Polymers ................................ ................................ ......... 106 5.1 Background ................................ ................................ ................................ ..... 106 5.2 Results and Discussion ................................ ................................ ................... 112 5.2.1 Pol ymerization and Characterization of Poly(4,4,5,5 tetramethyl 2 (4 ((tricosa 1,22 dien 12 yloxy)methyl)phenyl) 1,3,2 dioxaborolane) (29). ...... 112 5.2.2 Polymerization and Characterization of In Cha in Boronic Acid Polymers (SPP39 41). ................................ ................................ ................ 117 5.3 Conclusions ................................ ................................ ................................ .... 120 5.4 Experimental ................................ ................................ ................................ ... 121 5.4.1 Materials and Instrumentation ................................ ............................... 121 5.4.2 Procedures ................................ ................................ ............................ 122 6 Summary and Future Work ................................ ................................ ................... 124 6.1 Summary ................................ ................................ ................................ ........ 124 6.2 Future Work ................................ ................................ ................................ .... 125 6.2.1 Analysis of B oronic A cid P olymers via X r ay S cattering ........................ 125 6.2.2 Synthesis of O ther B oron C ontaining Lewis A cid M onomers ................ 126 LIST OF REFERENCES ................................ ................................ ............................. 128 BIOGRAPHICAL SKETCH ................................ ................................ .......................... 136

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8 LIST OF TABLES Table page 1 1 Pendant Group Effect on Melting Point and Lamell ar Thickness ......................... 25 1 2 Effect of Butyl Branch Concentration on Melting Point ................................ ......... 26 2 1 CM C onversion of 1 hexene ................................ ................................ ................. 38 3 1 Polymerization of 1,9 decadiene at various catalyst concentrations ..................... 56 3 2 Polymerization of T9 and T3 ................................ ................................ ................ 61

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9 LIST OF FIGURES Figure page 1 1 ................................ ............................ 17 1 2 Proposed mechanism of olef in metathesi s 17 1 3 Variety of olefin metathesis catalysts. ................................ ................................ .. 18 1 4 Types of olefin metathesis. ................................ ................................ ................... 19 1 5 Precision polymer via ADMET polymerization. ................................ ..................... 20 1 6 Statistical co polymer via tradional radical polymerization. ................................ .. 21 1 7 Isomerization of the ter minal olefin in ADMET polymer ization ............................. 22 1 8 Synthesis of precision alkyl polymers ................................ ................................ ... 23 1 9 Effect of pendant group on polymer melting temperature. ................................ .... 24 1 10 Melting temperature of precision butyl branch polymer as a function of bra nch concentration.. ................................ ................................ ........................ 27 1 11 Synthesis of precision carboxylic acid polymers ................................ ................. 28 1 12 M orphology of precision carboxylic acid polymer 29 1 13 Synthesis of precision mono phosphonic acid polymers ................................ .... 31 1 14 Synthesis of precision gemin al phosphonic acid polymers ................................ 32 1 15 Unique morphologies observed with geminal phosphonic acid polymers 33 1 16 Acid monomers ranked by pK a ................................ ................................ ........... 33 2 1 Two paths of hydride isomerization mechanism 36 2 2 Bo ron containing Lewis acids ................................ ................................ ............... 37 2 3 Model reaction used to study the effects of Lewis acids on olefin metathesis ...... 38 2 4 Phosph ine dissociation mechanism for activation of Grubbs type olefin metathesis catalysts ................................ ................................ ........................... 39 2 5 Proposed mechanism for the increase in conversion observed in the presence of boron containing Lew is acids. ................................ ................................ ........ 40

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10 2 6 GC traces show a reduction in isomerization with the addition of Lewis acids ..... 42 2 7 Concentration effects o f PinB Lewis acid on CM reaction using G2 ..................... 43 2 8 1 H NMR of cross metathesis reaction. 5 decene is produced from control experiment using Hoveyda Grubbs 1 st generation catalyst. ............................... 46 2 9 13 C NMR of cross metathesis reaction. 5 decene is produced from control experiment using Hoveyda Grubbs 1 st generation catalyst. ............................... 47 2 10 1 H NMR of cross metathesis reaction. 5 decene is produced from control experiment using Hoveyda Grubbs 2 nd generation catalyst. ............................... 47 2 11 13 C NMR of cross metathesis reaction. 5 decene is produced from control experiment using Hoveyda Grubbs 2 nd generation catalyst. ............................... 48 2 12 1 H NMR of cross metathesis reaction. 5 decene is produced using Hoveyda Grubbs 2 nd generation cataly st ................................ ................................ ........... 48 2 13 13 C NMR of cross metathesis reaction. 5 decene is produced using Hoveyda Grubbs 2 nd generation catalyst. ................................ ........................... 49 2 14 1 H NMR of cross metathesis reaction. 5 decene is produced from control experiment using Grubbs 2 nd generation ................................ ............................ 49 2 15 13C NMR of cross metathesis reaction. 5 decene is produced from control experiment using Grubbs 2nd generation catalyst. ................................ ............. 50 2 16 1 H NMR of cross metathesis reaction. 5 decene is produced using Grubbs 2 nd generation catalyst, ................................ ................................ ....................... 50 2 17 13 C NMR of cross metathesis reaction. 5 decene is produced using Grubbs 2 nd generation catalyst. ................................ ................................ ....................... 51 2 18 31 P NMR of Grubbs 1 st generation catalyst in the presence of Bpin Lewis acid. ................................ ................................ ................................ .................... 51 3 1 ADMET equilibrium reaction ................................ ................................ ................. 52 3 2 Polymerization of tri ptycene monomers with Grubbs 2 n d gen eration catalyst in ionic liquid ................................ ................................ ................................ ........... 54 3 3 Model polymerization of 1,9 decadiene to optimize ionic liquid polymerization techniques ................................ ................................ ................................ .......... 55 3 4 Common impurities found in1 butyl 3 methylimidazolium hexafluorophosphate (BMIMPF6) ................................ ................................ ................................ ......... 56 3 5 Kinetics of ADMET polymerization o f 1,9 decadiene in ionic liquid ...................... 57

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11 3 6 The effects of common ionic liquid impurities on ADMET polymerization 59 3 7 Synthesis of triptycene monomer ( T9 ) and polymerizat ion with Grubbs 1st generation catalyst ................................ ................................ ............................. 60 3 8 Synthesis of triptycene monomer ( T3 ) and polymerization with Grubbs 1st and 2nd generation catalyst ................................ ................................ ...................... 62 4 1 Planar boron compound with empty p orbitals ................................ ...................... 69 4 2 Nucleophilic attack on a planar boron compound to yield the tetrahedral boron species ................................ ................................ ................................ ............... 69 4 3 Lewis acidity as a function of boron substitution. ................................ .................. 70 4 4 Deboron ation of alkyl boron compounds ................................ ............................. 70 4 5 Alkyl carbon boron bond. ................................ ................................ ..................... 70 4 6 The boron oxygen bond ................................ ................................ ...................... 71 4 7 An aryl C B bond ................................ ................................ ................................ .. 71 4 8 Effects of pH on conformation of boronic acid ................................ ...................... 72 4 9 Formation of boron anhydride and boroxinet. ................................ ....................... 72 4 11 Synthesis of 4,4,5,5 tetra methyl 2 (2 (undec 10 enyl)tridec 12 enyl) 1,3,2 dioxaborolane ( 13 ) via Grignard addition of boronic ester 74 4 1 2 Synthesis of 2 (4 (heptacosa 1,26 dien 14 yl)phenyl) 4,4,5 trimethyl 1,3,2 dioxaborolane ( 16 ) via dialkylation of 15 ............. 76 4 13 Synthesis of 12 (4 (4,4,5,5 tetramet hyl 1,3,2 dioxaborolan 2 yl)phenyl)tricosa 1,22 dien 12 ol ( 17 ) using a boron containing electrophile ..... 77 4 14 Synthesis of 12 (4 (4,4,5,5 tetramethyl 1,3,2 dioxaborolan 2 yl)phenyl)tricos a 1,22 dien 12 ol ( 17 ) using a boron containing nucleophile ...... 78 4 15 Synthesis of 12 (4 bromophenyl)tricosa 1,22 dien 12 ol ( 21 ) via Grignard reaction 79 4 16 Reduction of tertiary alcohols 80 4 17 Synthesis of 4,4,5,5 tetramethyl 2 (4 (tricosa 1,22 dien 12 ylo xy)phenyl) 1,3,2 dioxaborolane ( 27 ) via ether synthesis of 4 with 4 bromo phenol 82

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12 4 18 Synthesis of 4,4,5,5 tetramethyl 2 (4 ((tricosa 1,22 dien 12 yloxy)m ethyl)phenyl) 1,3,2 dioxaborolane ( 29 ) via ether synthesis of 3 with 4 bromobenzyl bromide ................................ ................................ ......................... 83 4 19 Synthesis of in chain boronic acid monomer ( 39 41 ) ................................ ........ 85 4 21 Deprotection of alkyl boronic esters ................................ ................................ ... 86 4 22 Deprotection of aryl boronic esters via hydrogenation ................................ ........ 87 5 1 Synthesis of a variety of boron containing Lewis acids via post polymerization modification ................................ ................................ ................................ ...... 107 5 2 Tetraaryl boronate polymers used as solid support for catalysts. ....................... 108 5 3 Boron containing Lewis acid polymer used for ion conduction ........................... 109 5 4 Stimuli responsive boronic acid polymers for the encapsu lation and release of small molecules ................................ ................................ ................................ 110 5 5 Use of boronic acid polymers as a glucose sensor 111 5 6 Polymeri zation of 4,4,5,5 tetramethyl 2 (4 ((tricosa 1,22 dien 12 yloxy)methyl)phenyl) 1,3,2 dioxaborolane ( 29 ) ................................ ................. 112 5 7 Poly(4,4,5,5 tetramethyl 2 (4 ((tricosa 1,22 dien 12 yloxy)methyl)phenyl) 1,3, 2 dioxaborolane) ( UPP29 ) ................................ ................................ .......... 113 5 8 DSC of poly(4,4,5,5 tetramethyl 2 (4 ((tricosa 1,22 dien 12 yloxy)methyl)phenyl) 1,3,2 dioxaborolane) ( UPP29 ) ................................ ........ 114 5 9 Hydrogenation of poly(4,4,5,5 tetramethyl 2 (4 ((tricosa 1,22 dien 12 yloxy)methyl)phenyl) 1,3,2 dioxaborolane) ( UPP29 ). ................................ ....... 115 5 10 DSC of hydrogenated poly(4,4,5,5 tetramethyl 2 (4 ((tricosa 1,22 dien 12 yloxy)methyl)phenyl) 1,3,2 dioxaborolane) ( SPP29 ) ................................ ........ 116 5 11 Precise polymerization of in chain boronic acid monomers ( 39 41 ) ................. 117 5 12 IR of 41 and UPP41 ................................ ................................ ........................ 117 5 13 Thermal stability of UPP39 and UPP41 ................................ ............................ 118 6 1 S ynthesis of boron containing Lewis acid monomers ( 42, 44 ) ........................... 126 6 2 Precise polymerization and hydrogenation of 2 (3,5 bis(undec 10 en 1 yloxy)phenyl) 4,4,5,5 tetramethyl 1,3,2 dioxaborolane ( 42 ) ............................. 127

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13 6 3 Precise polymerization and hydrogenation of (3,5 bis(undec 10 en 1 yloxy)phenyl)diphenylborane ( 44 ) ................................ ................................ ..... 127

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14 LIST OF ABBREVIATIONS ADMET Acyclic di ene metathesis DSC Differential scanning calorimetry GC Gas chromatography GPC Gel permeation chromatography HRMS High resolution mass spectrometry IR Infrared spectroscopy MS Mass spectrometry NMR Nuclear magnetic resonance SAXS Small Angle X ray scatt ering TFAA Triflouroacetic anhydride

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15 Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy APPLICATION OF B ORON ON O LE FIN M ETATHESIS By Chester Kent Simocko August 2013 Chair: Kenneth B. Wagener Major: Chemistry Controlling polymer morphology is key to controlling and predicting physical and electronic properties. However, in many cases polymer morphology is unknown b ecause the primary structure of the polymer is unknown. This can be for a variety of reasons, but the most common is the use of imprecise polymerization techniques. Acyclic diene metathesis (ADMET) polymerization is unique in its ability to create polymers with precisely spaced pendant functionality. Many functional groups have been polymerized using ADMET, from alkyl pendant groups to ion ic liquids. Precision ADMET polymers synthesized with pendant phosphonic and carboxylic acid moieties have shown never b efore seen morphologies. T his dissertation will discuss the compatibility of boron containing Lewis acids with olefin metathesis, the use of ionic liquids in ADMET polymerization, the synthesis of boronic acid containing ADMET monomers, and the morphology of precision polymers bearing pendant boronic acids and esters Boron containing Lewis acids have shown a profound effect on the cross metathesis reaction of 1 hexene. Grubbs 1 st generation catalyst shows over 100% improvement in conversion in some cases, while the yields of Grubbs 2 nd generation

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16 increase by up to 50%. With the inclusion of boron containing Lewis acids, compounds prepared using Grubbs 2 nd generation type catalysts display significantly reduced levels of isomerization. To manage the high vi scosity of these polymers, ionic liquids were studied and can be an ideal medium for ADMET polymerization. Short reaction times of only 48 hours were observed even with low catalyst loading. Some common ionic liquid impurities were studied and only imidazo le was shown to have a nega tive effect on molecular weight. Additives were also studied to neutralize the impurities and phosphoric acid has been shown to prevent catalyst poisoning with imidazole. When this system was applied to a triptycene monomer, hig h molecular weights were reached only at high temperatures. Boronic acid ADMET monomers have been synthesized. Alkyl boronic acids and esters were first attempted but these proved difficult synthesize due to the deboronation of the monomer. To prevent this aryl boronic acid and ester monomers were synthesized successfully. Deprotection of boronic acid was studied. Pinacol was found to be difficult to remove quantitatively, however protecting groups with benzylic alcohols proved to be readily cleavable unde r hydrogenation conditions. Finally, precision boronic acid polymers were made. These precision polymers show unique thermal behaviors due to the interaction between pendant Lewis acids, further X ray scattering studies to probe morphology are being pursue d by collaborators.

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17 CHAPTER 1 Introduction 1.1 Origins of Olefin Metathesis Olefin metathesis was first reported in the early 1960s at Phillips Petroleum, Standard Oil, and Du Pont. 1 3 It was described as a of the su bstituents of the double bonds (Figure 1 1 ). Figure 1 1 The mechanism of this reaction was larg ely unknown until 1971, when Chauvin and Hrisson proposed the formation of a metal alkylidene and metallacyclobutane as intermediates of olefin metathesis (Figure 1 2 ). 4 The reaction proceeds in three steps that are all in equilibrium. The first step is the association of the metal alkylidene with the reactive olefin. These react to form the metal l ocyclic butane intermediate, which then falls apart into the product olefin and the new metal alkylidine Figure 1 2 Proposed mechanism of olefin metathesis. 1) Metal alkylidene and starting olefin; 2) Metallacyclobutane; 3) Metal alkylidene a nd product. The traditional catalysts used at the time were poorly defined, typically transition metal halides activated with an alkylation agent. 5, 6 These catalysts suffered from poor activity and a myriad of side reactions. 7 Later well defined molybdenum and tungs ten catalysts were designed by Richard Schrock and ruthenium centered catalysts were

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18 synthesized by the Grubbs group 8 11 Hoveyda further improved upon the Grubbs type catalysts, creating Hoveyda Grubbs catalysts (Figure 1 3 ). 12,13 Figure 1 3 Variety of olefin metathesis catalysts: Grubbs 1 st generation (G1), Grubbs 2 nd Generation (G2), Schrock Molybdenu m Catalyst (S1), Hoyveda Grubbs 1 st Generation (HG1), Hoyveda Grubbs 2 nd Generation (HG2), and Grubbs 3 rd Generation (G3). tungsten and molybdenum (S1) catalysts display excellent r eactivity and has no unwanted side reactions but the metal centers are extremely oxyphillic 14 reducing the functional group tolerance of the catalyst. Grubbs 1 st generation catal yst (G1) is descr ibed as the first non nucleophillic catalyst, which increases the functional group tol erance significantly. T he price of this tolerance is reduced reactivity, making it the least active of the well defined olefin metathesis catalysts. 15 Hoveyda Grubbs 1 st generation catalyst (HG1) displays many similar traits as G1, with slightly higher reactivity and functional group tolerance 12 Both HG1 and G1 have minimal tenden cy to

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19 cause doub le bond isomerization 16 Grubbs 2 nd generation catalyst (G2) displays r eactivity nearly as high as Schrock type catalysts and high levels of functional groups tolerance 15 This activity comes at a price, as the G2 catalyst has been known to cause significant isomerization 16 18 Hoveyda Grubbs 2 nd generation catalyst (HG2) rivals Schrock type catalysts in terms of reactivity and also is the most f unctional group tolerant of all the catalysts 13,19 HG2, however, also displays the highest level of isomerization 20 Grubbs 3 rd generation catalyst (G3) displays high reactivity partially due the initiation step being much faster than any of the previous catalysts 21 The development of these well defined catalysts has opened the door to a number of syntheti cally useful reactions (Figure 1 4 ) that have been used for synthesis of pharmaceuticals 22,23 total synthesis products 24 uniqu e polymers 25 and materials 26 These reactions include: ring opening metathesis (ROM) 27 ring closing metathesis (RCM) 14,28,29 ring opening metathesis polymerization (ROMP) 6,30 cross metathesis (CM) 31 and acyclic diene metathesis polymerization (ADMET) 32 Figure 1 4 Types of olefin metathesis: ring closin g metathesis (RCM), ring opening metathesis (ROM), acyclic diene metathesis polymerization (ADMET), ring opening metathesis polymerization (ROMP), and cross metathesis (CM). ROMP and ADMET are the two predominant forms of polymerization that utilize olefi n metathesis. ROMP is a chain growth contr olled polymerization method that utilizes cyclic ol e fins and can result in very high molecular weight polymers with very

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20 narrow polydispersities. 33 The driving force of ring opening metathesis polymerization is the release of ring strain, so that only monome rs with strained rings will undergo polymerization. 34 Since ROMP is a controlled polymerization technique, it has been used to create a variety of polymers with unique architectures, including di block, tri block, and alternating polymers. ADMET, on the other hand, is the step growth condensation polymerization of a symmetric and has the ability to create precise polymers by building the precision into the monomer 35 After polymerization, the backbone is saturated to give to yield a material that is analogous to a polyethylene copolymer (Figure 1 5 ) Figure 1 5. Precision polymer via ADMET polym diene is polymerized with an olefin metathesis catalyst, then the resi dual double bonds are saturated yielding a polymer with pendant groups at known and repeatable distances. Traditional copolymerization techniques distribute th e pendant groups in a statistical manner which leads to a non uniform distribution (Figure 1 6 ). 8C 8C 8C 8C

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21 Figure 1 6. Statistical co polymer via tradional radical polymerization : the pendant groups are at random and unknown distance s. To create precise polymers via ADMET, several requirements must be met during the polymerization process. The removal of ethylene is required to reach high degrees of polymerization. The equilibrium constant for ADMET is relatively low, ranging from 10 1 down to 10 6 32 To drive the equilibrium forward, the ethylene must be r emoved either with the use of very low vacuum conditions or by purging the reaction with a neutral atmosphere such as argon The second criteria for precise polymer synthesis is the need for a clean reaction pathway. Isomerization of the terminal olefin can ruin the precision of the polymer (Figure 1 7 ). 16 13C 1C 6C 10C

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22 Figure 1 7. Isomerization of the terminal olefin ruins the precision in an ADMET polymer The best catalyst t o avoid isomerization is Schroc k type catalysts. G1 and HG1 also display little tendency for isomerization, however, at elevated temperatur es any ruthenium catalyst will cause isomerization 36 G2 and HG2 display high levels of isomeriz ation at all temperatures, so are not suitable for synthesis of precise polymers 15,16 In the past acyclic diene metathesis has been used to make polymers with a number of different functional groups including; h alogens 37 39 ethers 40 44 acids 45 47 esters 48 52 alkyl branches 53 55 and metals 56 59

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23 1.2 Effects of P recision on P olymer P roperties Precision ADMET polymers display drastic differences in properties as compared to their random analogues. Early work done by Rojas et al. studied the effect of pendant alkyl group size on polymer mo rphology (Figure 1 8 ) 54,60,61 Figure 1 8 Synthesis of precision alkyl polymers The size of the pendant group had an immediate effect on the melting temperature. ADMET polyethylen e has a melting temperature of 134 C. A pendant methyl group on every 21 st carbon reduces the melting point to 63 C and an ethyl group even more to 24 C. With propyl and larger pe n dant groups the melting point stabilizes at about 12 C. This is seen not onl y for linear alkyl chains such as butyl, pentyl, hexyl, and so on but also large bulky pendant groups like adamantly, tert butyl, and cyclohexyl ( Figure 1 9 ) 54

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24 Figure 1 9 Effect of pendant group on polymer melting temperature Larger pendant groups expelled from the polyethylene crys tal structure, leading to a plateau in melting temperature. Data adapted from Rojas, G.; Inci, B.; Wei, Y.; Wagener, K. B. Journal of the American Chemical Society 2009 131 17376 86. 54 What causes this leveling effect? In random polymers large pe ndant groups result in complete loss of T m However, with precision polymers the small pendant groups (methyl and ethyl) are incorporated into the polyethylene crystal structure. Large pendant grou ps are excluded, this allows the polyethylene spacer length s between pendant groups to organize into crystalline lamellae 54,62 With carbon spacers of shorter than 20 carbons, crystallinity is not observed 53 Bora et al. continued this research by synthesizing prec ision ADMET polymers with alkyl pendant groups on every 39 th carbon. 61 Again, small pen dant groups (methyl ) are shown to be incorporated into the polyethylene crystal. Larger pendant groups are excluded, leading to the leveling e ffect as seen in other studies. T he T m leveled off at

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25 about 72 C due to the longer run length of polyethylene between each pendant group ( Table 1 1 ) 61 Table 1 1 Pendant Group Effect on Melting Point and Lamellar Thickness Branch identity on every every 39 th carbon T m ( o C) m (J/g) M w (kg/mol) (PDI) Thiness (nm) No branch 134 211 70.2 (2.7) 9.75 M ethyl 92 137 92.7 (2.0) 7.09 E thyl 76 93 53.1 (2.4) 4.79 P ropyl 78 71 225 (3.0) N/A I sopropyl 77 74 114 (3.5) N/A B utyl 75 66 66.5 (2.5) 4.25 I sobutyl 73 51 54.8 (2.4) N/A P entyl 74 88 30.2 (2.0) 5.03 H exyl 73 85 30.5 (1.9) 4.17 H eptyl 74 85 74.2 (2.9) 4.39 O ctyl 74 73 181 (3.3) 4.06 N onyl 73 84 34.3 (2.2) 4.67 D ecyl 71 76 27.2 (1.8) 4.16 P entydecyl 70 83 55.9 (2.4) 5.33 Data adapted from Inci, B.; Lieberwirth, I.; Ste ffen, W.; Mezger, M.; Graf, R.; Landfester, K.; Wagener, K. B. Macromolecules 2012 45 3367 3376. 61 Exclusion of the pendant group is further supported by studying the lamellar thickness. The ADMET polyethylene displayed a thickness of 9.75nm and the methy l polymer was 7.09nm thick. Precision polymers with pendant groups larger then methyl, which were excluded from the crystal structure, all had thicknesses ranging from 4 5nm

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26 regardless of the size of the pendant group. 61 This correspond s to a thickness of 30 40 carbons in a chain, approximately the number of carbons between each pendant group. Finally, to fully understand short chain bran ching in a polyethylene, a precision ADMET polymer with a butyl branch on every 75 th carbon was studied 60 This works out to only 13 butyl branches per 1000 carbon atoms, whi ch allows, for the first time, for direct comparison with commercial polyethylene systems. Table 1 2 shows the melting temperature of precision polymers as a function of butyl branch concentration. Table 1 2 Effect of Buty l Branch Concentration on Melting Point Butyl branch on every nth carbon, n Butyl branches per 1000 carbon atoms T m ( o C) m (J/g) 5 200 amorphous -15 67 33 13 21 48 14 47 39 26 75 66 75 13 104 152 ADMET PE 0 134 204 Data adapted from Inci, B.; Wagener, K. B. Journal of the American Chemical Society 2011 133 11872 5. 60 This final polymer allows for an experimental model to be determined that can project the branch concentration as a function of melting temperature (Figure 1 10 ). 60

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27 Figure 1 10 Melting temperature of precision butyl branch polymer as a function of branch concentration Reprinted with permission from Journal of the American Chemical Society 2011 133 11872 5. Copyright 20 11 American Chemical Society. Alkyl branch polymers are not unique among precision ADMET polymers Precise polymers with pendant halides 37 39 phenyl rings 63 esters 64 imidazolium hexaflourophosphate 65,66 chromophores 67 69 and many others have displayed unique properties 1.3 Precision Acid and Ionic P olymers Precision a cid and ionic polymers also demonstrate unique morphologies and properties. In the past, the morphology of these materials has been poorly defined due to the random nature of the polymerization. 70 These polymers tend to be difficult to polymerize via ADMET due nucleophilicity of the acid groups 25 However, even with this difficulty, a number of precision analogues have been synthesized using ADMET, including carboxylic acids 45 phosphonic acids 46 an d carboxyla te ionomers 71

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28 Baughman et al. prepared precision carboxylic acid polymers with varying acid concentrations via ADMET polymerization (Figure 1 11 ) 45 Figure 1 11. Synthesis of precision carboxylic acid polymers 45 The polymers with the lo west concentration of acid groups x=9, form dimers around the PE lamellar and create a layered stacking morphology (Figure 1 1 2 ) This morphology is not seen in the analogous random polymers.

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29 Figure 1 12 Layered morpholo gy of carboxylic acid polymer (left) converts to an organized cluster morphology (right) on neutralization. Both the precision and random polymers were then neutralized with either Li + or Zn 2+ counter ions and the morphologies of unneutralized and neut ralized polymers were compared via DSC, SAXS, 1 H, 13 C, and 7 Li NMR. 71 73 Work done by Seitz et al. demonstrates that upon neutralization the polymer converts from the layered acid morphology to a cluster morphology 71 The extent of neutralization ranged from 0% (parent polymer) up to 116% (only for the polymer with acid groups on every 21 st carbon atom). As the percent neutralization increased, the crystall inity decreased as demonstrated by DSC and SAXS In the case of the zinc ionomer, spherical aggregates formed and disrupted the layered morphology described above for the pure acid polymer. At the highest ne utralized acid content, the packing of the aggreg ates (Figure 1 1 2 ) transforms from random packing shown by polymers with ionic groups on every 21 st and 15 th carbon atom, to a body centered cubic lattice shown in the polymer with a carboxylate substituent on every 9 th carbon. H igh concentration of carb oxylate ions promotes self assembly of the polymer into a cubic lattice. 71 This is the first time this type of behavior has been observed and is presumably a result of the precise nature of the polymers.

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30 NMR studies have been conducted on both the zinc and lithium neutral ized acid polymers. Solid state 13 C NMR experiments have been utilized by Jenkins et al. at Sandia National Laboratory to study the crystallization of the zinc neutralized ionomer 72 They demonstrated that h ighe r concentrations of protonated acid groups increase the neutralization was also found to decrease the crystallinity due to aggregation of the pendant groups around the zinc ions. These studies also found an increase in motion along the chain axis in the crystalline phase of the precision polymers, but a restriction of movement in the amorphous phase. Proton and 7 Li NMR were carried out to examine the proton environment in lithium neutralized polymers. 73 The results indicated the presence of several different carboxylate structures, but only one environment for the lithium neutralized portion of the polymer. These results are consistent across acid concentrations and neutralization percentages, with the major structural differences among the acid groups depending on their coordination to a lithium ion. These NMR studies demonstrate how structure and morphology can be contr olled with precise carboxylate spacing, percent neutralization, and counter ion identity.

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31 Figure 1 13. Synthesis of precision mono phosphonic acid polymers 46 Opper et al. have prepared a variety of precision phosphonic acid polymers. 46,47 The first polymers synthesized were the phosphonic acid analogues to the carboxylic acid pol ymers described above. The distance between the phosphonic acid groups of these polymers were the same as those for the carboxylic acid polymers, and each repeat unit contained only a single phosphonic acid group (Figure 1 13 ). The behavior of these poly mers is similar to that of the corresponding carboxylic acids; as the acid concentration increases the crystallinity decreases. 46 Geminal phosphonic acid polymers have also been synthesized, as shown in Figure 1 1 4 effectively doubling the acid content of the polymer with the same branch frequency. 47

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32 Figure 1 14. Synthesis of precision geminal phosphonic acid polymers 47 The crystalline behavior of the geminal di phosphonic acid polymer is similar to that of the monoacid polymer, with the exception that increased concentration of acid groups causes an increase in melting temperature with a broader DSC en dotherm. This could indicate a less perfect crystal formation due to the higher order of hydrogen bonding available with phosphonic acids. The SAXS data collected by Buitrago et al. indicates that microphase separation of the polyethylene backbone and the phosphonic acid is occurring. 74 The geminal phosphonic acids phase aggregate in a face centered cubic lattice, which is persistent well above the melting point of the polyethylene backbone (Figure 1 15 ) Work is currently ongoing to study the morphology of the mono phosphon ic acid polymer.

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33 Figure 1 15. Unique morphologies observed with geminal phosphonic acid polymers a) SAXS of the drawn polymer. b) SAXS as a function of angle at different q values. c) Simulated diffraction pattern in the [1 1 0] direction. d) Si mulated diffraction pattern along the [1 2 1] direction. Reprinted with permission from Buitrago, C. F.; Opper, K L.; Wagener, K. B.; Winey, K. I. ACS Macro Letters 2012 1, 71 74. Copyri ght 2012 American Chemical Society. Both the precise carb oxylic acid and phosphonic acid polymers have demonstrated unique and different morphologies, presumably controlled by their pK a The purpose of this study is to determine the effect on acid pK a on morphology (Figure 1 16 ). Research on precision sulfonic acid polymers (pK a 1) is currently underway. Figure 1 16. Acid monomers ranked by pK a

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34 This disser tation will describe the use of boron containing compounds in ADMET polymerization. Chapter 2 will explore the effects of boron containing Lewis acid s on olefin metathesis. Isomerization and conversions are discussed. Chapter 3 examines the use of ionic liquids as an ADMET polymerization reaction medium. Catalyst concentration, reaction time, and temperatures are explored. Common impurities are evalua ted for their effect on ADMET polymerization as well additive s that can be used to neutralize the impurities. Finally, a variety of triptycene monomers were polymerized to fully evaluate the new reaction medium. Chapter 4 discusses the synthesis of boroni c acid and ester monomers. First, the synthesis of alky boronic esters is investigated. Next, t he synthesis of aryl boronic acids and esters are explore d and finally deprotection of boronic acids is discussed Chapter 5 examines the polymerization of bor onic acid and ester monomers. Polymerization conditions are discussed and thermal stability is investigated. Both precision and random boronic acid polymers are investigated.

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35 CHAPTER 2 Effects of Boron Containing Lewis Acids on Olefin Metathesis 2 .1 Background Increasing the yields and decreasing the isomerization of olefin metathesis reactions is important in the fields of organic synthesis, polymer chemistry, and pharmaceuticals. Herein, we use a model system to prove that boron containing Lewi s acids increase the yields of olefin metathesis reactions containing Grubbs 1 st and 2 nd generation catalysts. By use of GC MS we demonstrate that olefin isomerization is nearly eliminated in the presence of boron containing Lewis acids. Olefin metathesi s has opened many new avenues for the synthesis of carbon carbon double bonds and has proven invaluable for many fields of chemistry. 27 Ring closing metathesis (RCM) and cross metathesis (CM) have revolutionized the synthesis of pharmaceuticals and large total synthesis targets. 28,29,31 Ring opening metathesis polymerization (ROMP) and acyclic diene metathesis (ADMET) polymerization have provided ways to synthesize new materials, often with unique morphologies. 25,26,32,33 As knowledge of these techniques increases, researchers are continuing to expand the range of olefin metathesis applications. Numerous Grubbs type olefin metathesis catalysts have been developed over the past 15 years. 75 Each catalyst has specific strengths and weaknesses, generally in reference to stability, activity, and tendency for isomerization of the olefin. 16 Grubbs 1 st generation catalyst (G1) is less active and less stable than 2 nd generation Grubbs catalysts, but G1 does not display a propensity towards isomerization. 15 Hoveyda Grubbs 1 st generation catalyst (HG1) has a higher stability and is slightly more active than G1, although sti ll less active than the 2 nd generation catalysts. 12 Grubbs 2 nd

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36 generation catalyst (G2) is quite active and stable but it can lead to significant isomerization of the double bond. 15,17,18 Hoveyda Grubbs 2 nd generation catalyst (HG2) scores highest in all of the m etrics above, being the most stable and active, but also having the greatest tendency for isomerization. 13,19,20 Isomerization of the double bond in olefin metathesis has been attributed to the formation of ruthenium hydride (Figure 2 1) 36,76 Figure 2 1 Two paths of hydride isomerization mechanism. Top: Isomerization via 1,2 hydride shift. Bottom: Isomerization via 1,3 hydride shift. 16 Metal centered Lewi s acids and protic acids reduce isomerization in reaction s involving Grubbs 2 nd generation type catalysts. 66,77 79 Lewis acids have been shown to activate molybdenum nitride catalysts leading to increased yields and rates of alkyne metathesis. 80,81 Vedrenne et al. studied how Lewis acids, including some containing boron, facilitate the CM of certain olefins having func tional groups that interfere with the catalyst or undergo some other side reaction. In these cases, the Lewis acids are thought to coordinate with the functional group, leaving the metathesis catalyst unencumbered. 82

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37 2.2 Results and Discussion Lewis acids that contain boron were chosen for this study due to the wide range of acid strengths that are available. Recently boron containing moieties have been used ex tensively in organic synthesis 83 85 pharmaceuticals 86 88 and polymers 89 91 open many doors in these fields. The calculated values for fluorine affinities were used as a measure of Lewis acidity as shown in Figure 2 2 triphenyl borane (PhenB) displays the highest Lewis acidity to boric acid (OHB), which is the weakest and pinacol phenyl borate (PinB) in the middle. 92 94 These Lewis acids were studied for their impact on yield and olefin isomerization tendency of a variety of Hoveyda and Grubbs type metathesis catalys ts. As the model system, we used the cross metathesis (CM) of 1 hexene ( Figure 2 3 ) monitored by GC and NMR. Deuterated chloroform was chosen as solvent to aid in NMR analysis and to solvate the Lewis acid. Chlorinated solvents have also been shown to fa cilitate olefin metathesis. 95 97 Figure 2 2 Boron containing Lewis acids which exhibit a range of Lewis acidities. Fluorine affinity is used as a metric of Lewis acidity, PhenB being the strongest Lewis acid and OH B being the weakest. 92 94

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38 Figure 2 3 Model reaction used to study the effects of Lew is acids on olefin metathesis. Reaction conditions: 100mg (1.2 mmol) of 1 hexene, 20 mol% Lewis acid, 1 mol% catalyst reacted at 45 o C in CDCl 3 for 15 hours. The yields were studied for all four catalysts with each of the boron containing Lewis acids. As shown in Table 2 1, HG1 provided similar yields when used with PhenB, PinB, and OHB. Table 2 1 CM conversion of 1 hexene Catalysts HG1 G1 H G2 G2 Lewis Acids yield a (%) yield a (%) yield a (%) yield a (%) Control b 84 29 99+ 63 OHB 78 71 24 60 PinB 74 62 33 69 PhenB 81 5 50 5 a. Yields determined by NMR. b. Control reactions were performed without Lewis acids. Reaction conditions: 100mg 1 hexene, 20 mol% Lewis acid, 1 mol% catalyst reacted at 45 o C in CDCl 3 for 15 hours. The standard deviation was found to be 7.9%. For Grubbs 1 st generation (G1) catalyst the control reaction yielded 29% CM, but addition of OHB and PinB significantly inc reased the yields to 71% and 62%

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39 respectively (Table 1). G1 and G2 are phosp hine containing catalysts; the first step in their initiation is the dissociation of the tricyclohexylphosphine ligand which is the rate limiting step (Figure 2 4). Figure 2 4 Phosphine dissociation mechanism for acti vation of Grubbs type olefin metathesis catalysts In these cases, the Lewis acid behaves as a phosphine sponge. It removes the tricyclohexyl phosphin e ligand from the catalyst and presumably increases the rate of the initiation step (Figure 2 5)

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40 Figure 2 5 Proposed mechanism for the increase in conversion observed in the presen ce of boron containing Lewis acids The boron containing Lewis acid behaves as a phosphine sponge, removing the tricyclohexyl phosphine (PCy 3 ) ligand from the equilibrium. This capture of phosphine ligands has been shown with a variety of boron containin g and metal containing Lewis acids, these include; triphenyl borane 98 tris(pentafluoro phenyl) borane 99 9 borabicylco[3.3.1]nonane 100 and copp er iodide 101 Furthermore, metal containing Lewis acids such as tin(III) chloride 77 and copper iodide 102 have displayed yield and ra te increases in metathesis reactions, presumably from the phosphine sponge effect. This effect is supported by a shift in the 31 P NMR of G1 in the presence of PinB presumably caused by the complexation of the phosphine ligand with the Lewis acid (Figure 2 18) This effect was not observed for the HG1 c atalyst because the isopropyl phenyl ether ligand does not undergo a dissociative mechanism, limiting the effect of the Lewis acid The PhenB Lewis acid surprisingly led to only about 5% conversion. Similar results with PhenB were found with Grubbs 2 nd generation catalyst (G2) and will be discussed in more detail below.

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41 The trend in yields for Hoveda Grubbs 2 nd generation catalyst (HG2) was expected to be similar to that of HG1, but this was not the case. A s seen in Table 1, the control reaction achieved nearly quantitative conversion, but the addition of a Lewis acid dramatically decreased the yields in the order; PhenB at 50%, PinB at 33%, and OHB at 24%,. This is contrary to current thought, since the HG2 catalyst is expected to show increased stability compared to G1 and G2. The yields follow the trend in acid strength; the stronger Lewis acids causing the catalyst to decay more slowly. When studying the effects of Lewis acids on hard to metathesize olef in s, Vedrenne et al. showed that chloro catachol borane at 10 mol% enhanced the cross metathesis reaction using HG2 of methyl vinyl ketone and BOC protected 2 propene 1 amine, but at 40mol% borane the reaction was retarded. 82 These results indicate that there is an optimal concentration of Lewis acid before it causes decomposition of HG2 catalyst.

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42 Figure 2 6 GC traces show a red uction in isomerization with the addition of Lewis acids 103 The results for HG2 were not entirely negative. When the isomerization was studied by GC MS, it was found that the addition of any of the Lewis acids led to an significant reduction in isomerization. When compared to the GC traces from the HG1 reactions, which show only very minimal isomerization, the traces with Lewis acids and HG2 are almost identical (Figure 2 6 ). The boron containing Lewis acid presumably reacts with any hydride formed to shut down that isomerization path. Grubbs 2 nd generation catalyst (G2) behaves as a hybrid of HG2 and G1. The control reaction yielded 63% conversion. With OHB and PinB added to the reaction, the yields were 61% and 69%, respectively, indicating that there was a competition between the decomposition tendency of HG2 and the phosphine sponge effect observed with G1 This competition was also observed when the concentration of the Lewis acid was

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43 varied. Figure 2 7 displays the CM yields as a function of Lewis acid concentration. PinB was used for this study because it displayed the greatest effect in terms of yield enhancement and isomerization reduction. When PinB was added at 5 mol%, the yield increased to 97%, a dramatic change from the 63% control experiment. When the concentration of PinB was increased to 10 20%, the yields dropped to about 68%. At 30 50% Lewis acid the yields further decreased to about 50 55%. These results demonstrate a competition between the increase in the rate of initiation and the decomposition of the catalyst. At low concentrations the PinB only removes the phosphine from the catalyst, c ausing an increase in yield. However, once the concentration of PinB is increased, the catalyst begins to decompose. Figure 2 7 Concentration effects of PinB Lewis acid on CM reaction using G2. The standard deviation was f ound to be 7.9%. 103 With PhenB and either G1 or G2, small amounts of the CM product were observed. But wit h HG1 or HG2, PhenB was one of the better Lewis acids. To further investigate this behavior the reaction was run neat. The control experiments for G1 and

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44 G2 resulted in yields of 76% and 55% respectively. However, in the experiments containing BPhen, the G 1 and G2 yields were 93% and 68%, respectively, an increase in converstion of 122% and 124% for G1 and G2, respectively, from the control reactions. These results lead to the conclusion that BPhen is good Lewis acid choice, but it is sensitive to the solve nt impurities when using Grubbs 1 st and 2 nd generation catalysts. When compared to the increases in conversion from control experiments observed with OHB and PinB for G1, 245% and 214%, respectively, PhenB is not as effective at increasing the yield of the CM reaction. 2.3 Conclusions This work has demonstrated the effect of boron containing Lewis acids on olefin metathesis yield and isomerization tendency. Grubbs series of catalysts show improvements in both yield and isomerization tendency in the presenc e of boron containing Lewis acids, while the Hoveyda type catalysts show no change in yield for HG1 and a decrease in both yield and isomerization with HG2. These results have implications for olefin metathesis reactions in chemistry, polymer synthesis and polymerization, and pharmaceutical science. 2. 4 Experimental 2.4 .1 Materials and Instrumentation All materials were purchased from Aldrich and used without further purification unless noted. Grubbs 1 st and 2 nd generation catalyst (G1 and G2) as well as H oveyda Grubbs 1 st and 2 nd generation catalyst (HG1 and HG2) were kindly provided by Materia, Inc. The deuterated chloroform solvent was used from a freshly opened bottle and stored under nitrogen in a desiccator. All 1 H NMR, 13 C, and 31 P were obtained on a Varian Mercury 300MHz spectrometer and recorded in CDCl 3 All Gas Chromatography

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45 Mass Spectrometry (GC MS) were obtained using a Thermo Scientific Trace GC DSQ equipped with a 60m AT 5ms column, heating from 40 o C to 280 o C at 20 o C/min. 2.4 .2 Procedures General procedure for olefin cross metathesis of 1 hexene with no Lewis acid in CDCl 3 (Table 1, Control). A test tube equipped with a magnetic stirrer was charged with 100mg of 1 hexene (.149mL, 1.19mmol), and 1mL of CDCl 3 1 mol% of catalyst (G1, G2, HG1, or HG2) was then added. The reaction was then capped with a septum and stirred under a constant argon atmosphere at 45 o C for 15 hours. General procedure for olefin cross metathesis of 1 hexene with Lewis acids in CDCl 3 (Table 1). A test tube equipped w ith a magnetic stirrer was charged with 100mg of 1 hexene (.149mL, 1.19mmol), 20 mol% of boron containing Lewis acid (FPB, PhenB, PinB, or OHB) (237mol), and 1mL of CDCl 3 1 mol% of catalyst (G1,G2, HG1, or HG2) was then added. The reaction was then cappe d with a septum and stirred under constant argon atmosphere at 45 o C for 15 hours. Bulk olefin cross metathesis 1 hexene. A test tube equipped with a magnetic stirrer was charged with 250mg of 1 hexene. 1 mol% of catalyst (G1 or G2) was then added. The r eaction was then capped with a septum and stirred under constant argon atmosphere at 45 o C for 15 hours. Bulk olefin cross metathesis 1 hexene with PhenB. A test tube equipped with a magnetic stirrer was charged with 250mg of 1 hexene (.149mL, 1.19mmol), 2 0 mol% of triphenyl borane (PhenB) (30mol). 1 mol% of catalyst (G1 or G2) was then added. The reaction was then capped with a septum and stirred under constant argon atmosphere at 45 o C for 15 hours.

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46 General procedure for Lewis acid optimization (Figure 4 ). A test tube equipped with a magnetic stirrer was charged with 100mg of 1 hexene (.149mL, 1.19mmol) and 1mL CDCl 3 The amount of pinacol phenylboronate (PinB) was varied (5, 10, 15, 20, 30, 40, or 50 mol%) and added to the test tube. 1 mol% of Grubbs 2 nd generation catalyst was then added. The reaction was then capped with a septum and stirred under constant argon atomosphere at 45 o C for 15 hours. 2.5 Representative Spectra Figure 2 8 1 H NMR of cross metathesis reaction. 5 decene is produced from control experiment using Hoveyda Grubbs 1 st generation catalyst.

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47 Figure 2 9 13 C NMR of cross metathesis reaction. 5 decene is produced from control experiment using Hoveyda Grubbs 1 st generation catalyst. Figure 2 10 1 H NMR of cross metathesis reaction. 5 decene is produced from control experiment using Hoveyda Grubbs 2 nd generation catalyst.

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48 Figure 2 11 13 C NMR of cross metathe sis reaction. 5 decene is produced from control experiment using Hoveyda Grubbs 2 nd generation catalyst. Figure 2 12 1 H NMR of cross metathesis reaction. 5 decene is produced using Hoveyda Grubbs 2 nd generation catalyst, residual pinacol phenylboronate is still observed in the NMR.

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49 Figure 2 13 13 C NMR of cross metathesis reaction. 5 decene is produced using Hoveyda Grubbs 2 nd generation catalyst, residual pinacol phenylboronate is still ob served in the NMR. Figure 2 14 1 H NMR of cross metathesis reaction. 5 decene is produced from control experiment using Grubbs 2 nd generation catalyst, residual 1 hexene is observed.

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50 Figure 2 15 13C NMR of cross metathesis reaction. 5 decene is produced from control experiment using Grubbs 2nd generation catalyst, residual 1 hexene is observed. Figure 2 16 1 H NMR of cross metathesis reaction. 5 decene is produced using Grubbs 2 nd generation catalyst, residual 1 hexene and pinacol phenylboronnate are observed.

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51 Figure 2 17 13 C NMR of cross metathesis reaction. 5 decene is produced using Grubbs 2 nd generation catalyst, resid ual 1 hexene and pinacol phenylboronate are observed. Figure 2 18 31 P NMR of Grubbs 1 st generation catalyst in the presence of Bpin Lewis acid.

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52 CHAPTER 3 Use of Ionic Liquids as a Medium for ADMET Polymerization 3.1 Back ground ADMET has the ability to create high molecular weight polymer. However, this is not a favorable reaction since the equilibrium constant is very low. Fortunately, the polymerization can be driven forward by removal of ethylene which is formed as a b yproduct of olefin metathesis (Figure 3 1). Several methods have been developed accomplish this task and, as a result, high molecular weight polymers have been made via ADMET. Figure 3 1 ADMET equilibrium reaction The earliest and most widely employed method of ethylene removal is the u se of high vacuum conditions 63 This technique proves to be extremely versatile, easy to set up, and mini mizes impurities in the system. Though wid ely used successfully, bulk ADMET polymerization has several drawbacks In a bulk system, only liquid monomers can be used effectively. Investigations into solid state ADMET polymerization have shown to be successful, however reaction times are ge nerally o n the order of weeks 104,105 Another drawback is viscosity; as the polymerization proceeds, the viscosity of the reaction medium increases making r emoval of the ethylene inefficient Finally, ADMET monomers are largely non p olar Non polar solvents have been shown to reduce the effectiveness of olefin metathesis catalyst 95 97 This is because non polar solvents Non coordi nating polar solvents on the other hand, tend to increas e the rate of olefin metathesis So while

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53 bulk polymerization is the simplest to set up and most widely used, there are some areas of improvement The next ADMET polymerization method that is wide vacuum system to remove the ethylene. This technique utilizes a fairly high boiling solvent, such as toluene, to dissolve the monomer and catalyst followed by purging the reacti on with a neutral atmosphere during the polymerizatio n 106 This method allows for solid monomers to polymerized, keep s the viscosity low, and provides a solvent that both dissolves and stabilize s the olefin metathesis catalyst. However this technique has some drawbacks as well. The use of solvent introduces another possible source of impurities to contaminate the reaction, so only solvents that have been extensively purified and degassed can be u sed. Another problem is that the solvent evaporates due to being constantly purged, so more h as to be added, risking exposing the reaction to air and other impurities. Most importantly the removal of ethylene by this method is not always the most efficient Fortunately this problem can be solv ed using a slight modification The final method for ADMET polymerization is known as the h igh boiling solvent method 107 As the name suggests a high boiling solvent is u sed, generally 1,2 dibromobenzene with a boiling point of 224 C. The polymerization is then held under a gentle vacuum, around 40 torr, while simultaneously purging with a neutral atmosphere. This method benefits from many of the same advantages as seen in the previous neutral atmosphere method. However, it also comes with many of the same drawbacks. Fortunately, ethylene removal is more efficient that by purging with neutral atmosphere alone.

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54 By using ionic liquids (ILs) as an ADMET solvent, it is poss ibly to combine many of the a dvantages of previous methods This method was first attempted in the dissertation of Yong Yang in Dr. Tim othy of Techno logy but was never optimized 108 Ionic liquids are ideal so lvents for ADMET polymerization. ILs have very low vapor pressure making them perfect for high vacuum applications They are known to dissolve metal catalysts and many organic molecules, but are generally immiscib le with many organic solvents ILs provide polar, non coordinating environments that can enhance catalyst activity, and they are stable over a wide range of temperatures. 109 However, despite all of these advantages, using ILs as a reacti on medium for ADMET remained elusive. Yong Yang observed that only oligomers were formed when attempting to polymerize triptycene c ontaining dienes (Figure 3 2). H owever at high catalyst loading, 11 mol%, and long polymerization times, moderate molecula r weight polymer was obtained The goal of this project, in collaboration with the Swager g roup, is to optimize the use of ILs for use in ADMET polymerization and study the cause of the low conversions observed. Figure 3 2 Polymerization of triptycene monomer s with Grubbs 2nd generation catalyst in ionic liquid 108

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55 3.2 Results and Discussion A simple model polymerization was used to optimize the use ionic liquids in ADMET polymerization. 1 ,9 decadiene was polymerized at 50 C using G1 catalyst (Figure 3 3). Figure 3 3 Model polymerization of 1,9 dec adiene to optimize ionic liquid polymerization techniques 1 b utyl 3 methyli midazolium hexafluorophosphate was chosen as the ionic liquid to study as it has shown to be highly compatible with small molecule olefin metathesis. G1 was chosen as the catalyst since olefin, but the result s can translate to other ruthenium centered olefin metathesis catalysts. The first concern with using ILs is their purity. Purity of ILs varies greatly d epending on the batch and supplier ILs can come in a range of colors from colorless to orange, indicat ing more or less impurities. Common impurities found in 1 butyl 3 methylimidazolium hexafluorophosphate include water, 1 b utyl 3 methylimidazolium chloride, and 1 b utyl 3 methy limidazole (Figure 3 4). 95

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56 Figure 3 4 Common impurities found in1 butyl 3 methylimidazolium hexafluorophosphate (BMIMPF6) 95 The IL was purified via a neutra l alumina plug; this caused the IL to go from yellow to nearly colorless. ILs are also extr eme proficient at dissolving ga ses, some of which such as oxygeen, can inhibit the ADMET polymerization To remove these gas es the solvent is freeze pump thawed in triplicate. The IL is then handled using dry techniques to avoid absorption of water or non neutral gasses. Table 3 1 Polymerization of 1,9 decadiene at various catalyst concentration s [G1] (mol%) M n (g/mol) M w (g/mol) PDI .25 5554 8649 1.56 .5 18454 41790 2.27 1 12746 26656 2.09 2 10717 24676 2.3 3 12457 26664 2.14 4 9541 22851 2.4 7 8847 20379 2.28 11 8737 19177 2.2

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57 The first studies that were conducted with the purified IL were catalyst concentration experiment s (Table 3 1) Polymerizations were run with the concentration of catalysts at .25, .5, 1, 2, 3, 4, 7, and 11 mol%. Low catalyst concentrations, .25 mol%, resulted in fairly low molecular weight polymer. At .5 mol% catalyst, however, the molecular weight sharply increased to over 18000 g/mol. As the catalyst concentration was increase past this point the molecular weights decreased. F or the purpose of these studies .5 mol% was selected. This catalyst concentration is comparable to the amount of catalyst used in both bulk and high boiling solvent polymerization techniques. A kinetic study was then run to determine the optimal duration of the polymerization. Polymerizations were conducted and stopped at intervals of 6, 18, 24, 48, 72, and 96 hours (Figure 3 5). Figure 3 5 Kinetics of ADMET polymerization of 1,9 decadiene in ionic liquid maximum molecular weights were achieved after 48 hours.

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58 Maximum molecular weights were reached after only 48 hours, significantly sho rter than many of the reported polymerizations using the bulk and high boiling solvent methods. With the purified IL, the high catalyst loading and long reaction times were no longer needed. To study the effects of known IL impurities on ADMET polymerizat ion, a number of test reactions were run and small amounts of impurities were added (Figure 3 6, blue bar). The control reaction obtained a M n of about 11900 g/mol. Upon addition of water and the imidazolium chloride, no reduction in molecular we ight was of ob served. Addition of the imidazole compound resulted in no polymer formation Imidazole is a known Grubbs catalyst poison. In fact, it poisons the catalysts in a catalytic manner. This means that an almost undetectable amount of imidazole can complete ly disrupt the ADMET polymerization. 66,79

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59 Figure 3 6 The e ffects o f common ionic liquid im purities on ADMET polymerization. Blue bar: Polymerization was run with only the impurity stated. Maroon bar: Polymerization was run with impurity as well as pinacol phenyl borate (PinB). Yellow bar: Polymerization was run with imp urity and phosphoric acid (H3PO4). In an attempt to neutralize the effects of the impurities, several additives were tested The first additive was phenyl pinacol borate (PinB), this Lewis acid has been shown to increase the activity of phosphine containi ng Grubbs catalysts. 103 In the control reaction molecular weights involving PinB were slightly higher as exp ected (Figure 3 6, maroon bar). Similar results were seen for both the water and the imidazolium chloride experiments. Unfortunately, imidazole still prevented any polymer from being formed The other additive investigated was phosphoric acid, which ha s also been shown to be compatible with olefin metathesis. 66,79 In the control experiment no differen ce in molecular weight was seen (Figure 3 6, off white bar). T he molecular weights

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60 decrease d slightly in the presence of both water and imidazolium chloride. However, in the imidazol e containing experiment, polymer was formed. This is believed to be due to the protination of the imidazole, shutting dow n the pathway of catalyst poisoning So while the phosphoric acid resulted in slightly lower molecular weights in the water and imidiazolium chloride polymerization, it allowed the formation of polymer in th e presence of the imidazole compound. These optminizations were applied to a well studied system and compared to the high boiling solvent method. First 1,4 bis(undec 10 en 1 yloxy) triptycene ( T9 ) was synthesized following the procedure discribed by Delga do et al 110 T9 was then polymerized using G1(Figure 3 7). Figure 3 7 Synthesis of triptycene monomer ( T9 ) and polymerization with Grubbs 1st generation catalyst Three pol ymerizations were conducted at different temperatures : 50, 80, and 100 C for 48 hours in BMIMPF6 ( Table 3 2 ).

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61 Table 3 2 Polymerization of T9 and T3 Monomer Temperature ( C) Catalyst M n (g/mol) M w (g/mol) PDI DP n DP w T9 50 G1 2511 5966 2.38 4.5 10.6 T9 80 G1 1814 5087 2.8 3.2 9.1 T9 100 G1 2209 6362 2.9 3.9 11.3 T3 100 G 1 1482 2271 1.53 3.8 5.8 T3 100 G2 2079 3621 1.74 5.28 9.2 At low temperatures, 50 o C, the monomer T9 was minimally soluble in the ionic liquid so only oligomers were formed, M n of 2511 g/mol As the temperature increases the monomer begins to melt and disolve in the ionic liquid however no increase in moleculare weights are observed At 100 o C the monomer is a liquid, and was miscible with the ionic liquid sovent but still no increase in moleular weights These results lead to the conclusion that the mole cular weight of T9 is determined by the solubility of the polymer, which is this case only leads to oligomers. The next study compared the optimized polymerization methods to the rechnique used by Yang et al 108 The 1,4 bis(pent 5 en 1 yloxy) triptycene ( T3 ) was synthesized following the reported procedure and polymer ized via G1 and G2 (Figure 3 8 )

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62 Figure 3 8 Synthesis of triptycene monomer ( T3 ) and polymerization with Grubbs 1st and 2nd generation catalyst Using the optimization reactions above, T3 was polymerized for 48 hours at 100 o C using both G1 and G2 at .5 mol% catalyst (Table 3 2) The shorter alkyl chain length leads to an increase in crystallinity of the monomer and lower solubility. As a result low mo lecular weights were observed; similar to the polymer created from T9 3.3 Conclusion This study has optimized the use of ionic liquids in ADMET polymerization. It has demonstrated that ILs are compatible with catalyst loading level comparable to that of both bulk and high boiling solvent polymerization methods. Polymerization times were significantly shorter than many reported ADMET polymerization techniques. Impurities can be detrimental to the polymerization; however some impurities such as water and im idazolium chloride have shown to have no effect on molecular weight. Imidazole impurities completely shut down the polymerization, but can be neutralized using a protic acid. Solubility played an important role in the polymerization of triptycene

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63 containin g monomers. Higher temperatures resulted in no increase in molecular weights due to insolubility of the polymer All of these studies demonstrate that ionic liquids are a viable medium for ADMET polymerization. 3.4 Experimental 3.4.1 Materials and Instrume ntation 1,9 decadiene was purchased from Sigma Aldrich and purified via silica plug. It was then degassed in triplicate. 1 Butyl 3 methylimidazolium hexafluorophosphate was purchased from AK Scientific and purified via a neutral alumina plug followed by d egassing via freeze pump thaw in triplicate. All other materials were purchased from Aldrich and used without further purification unless noted. Grubbs 1 st and 2 nd generation catalyst (G1 and G2) as well as Hoveyda Grubbs 1 st and 2 nd generation catalyst ( HG1 and HG2) were kindly provided by Materia, Inc. The deuterated chloroform solvent was used from a freshly opened bottle and stored under nitrogen in a desiccator. All 1 H NMR, and 13 C NMR were obtained on a Varian Mercury 300MHz spectrometer and recorded in CDCl 3 3.4.2 Procedures General procedure for catalyst concentration study. Under constant argon flow, .25g of 1,9 decadiene was added to flame dried Schlenk flask equipped with a magnetic stir bar. Also under constant argon flow 1.5mL of 1 b utyl 3 m ethylimidazolium hexafluorophosphate was added. Grubbs 1 st generation catalyst was then added to the reaction mixture. The amount was varied between .25, .5, 1, 2, 3, 4, 7, and 11mol%. The reaction was then placed under high vacuum at 50 C while stirring. After 48 hours the reaction quenched with a solution of 2mL of ethyl vinyl ether in 10mL of toluene. The toluene layer was separated from the ionic liquid via pipette and the solvent removed

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64 under vacuum. The polymer was then dissolved in a minimal amount of toluene and precipitated into 250mL of cold ethanol. The polymer was filtered out and NMR was used to determine molecular weights. General procedure for kinetic study. Under constant argon flow, .25g of 1,9 decadiene was added to flame dried Schlenk fl ask equipped with a magnetic stir bar. Also under constant argon flow 1.5mL of 1 b utyl 3 methylimidazolium hexafluorophosphate was added. .5 mol% of Grubbs 1 st generation catalyst was then added to the reaction mixture. The reaction was then placed under h igh vacuum at 50 C while stirring. The polymerization was run for 6, 18, 24, 48, 72, and 96 hours. After the requisite time hours the reaction quenched with a solution of 2mL of ethyl vinyl ether in 10mL of toluene. The toluene layer was separated from the ionic liquid via pipette and the solvent removed under vacuum. The polymer was then dissolved in a minimal amount of toluene and precipitated into 250mL of cold ethanol. The polymer was filtered out and NMR was used to determine molecular weights. Genera l procedure for the control impurity study. Under constant argon flow, .25g of 1,9 decadiene was added to flame dried Schlenk flask equipped with a magnetic stir bar. Also under constant argon flow 1.5mL of 1 b utyl 3 methylimidazolium hexafluorophosphate w as added. .5 mol% of Grubbs 1 st generation catalyst was then added to the reaction mixture. Finally, .5 mol% of the impurity; water, 1 b utyl 3 methy limidazolium bromide, or 1 butyl imidazole was added to the reaction mixture. The reaction was then placed under high vacuum at 50 C while stirring. After 48 hours the reaction quenched with a solution of 2mL of ethyl vinyl ether in 10mL of toluene. The toluene layer was separated from the ionic liquid via pipette and the solvent removed

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65 under vacuum. The polym er was then dissolved in a minimal amount of toluene and precipitated into 250mL of cold ethanol. The polymer was filtered and NMR was used to determine molecular weights. General procedure for impurity study with phenyl pinacol borate. Under constant arg on flow, .25g of 1, 9 decadiene and 20 mol% of phenyl pinacol borate were added to flame dried Schlenk flask equipped with a magnetic stir bar. Also under constant argon flow 1.5mL of 1 b utyl 3 methylimidazolium hexafluorophosphate was added. .5 mol% of Gr ubbs 1 st generation catalyst was then added to the reaction mixture. Finally, .5 mol% of the impurity; water, 1 b utyl 3 methy limidazolium bromide, or 1 butyl imidazole was added to the reaction mixture. The reaction was then placed under high vacuum at 50 C while stirring. After 48 hours the reaction quenched with a solution of 2mL of ethyl vinyl ether in 10mL of toluene. The toluene layer was separated from the ionic liquid via pipette and the solvent removed under vacuum. The polymer was then dissolved i n a minimal amount of toluene and precipitated into 250mL of cold ethanol. The polymer was filtered and NMR was used to determine molecular weights. General procedure for impurity study with phosphoric acid. Under constant argon flow, .25g of 1, 9 decadie ne and 20 mol% of solid phosphoric acid were added to flame dried Schlenk flask equipped with a magnetic stir bar. Also under constant argon flow 1.5mL of 1 b utyl 3 methylimidazolium hexafluorophosphate was added. .5 mol% of Grubbs 1 st generation catalyst was then added to the reaction mixture. Finally, .5 mol% of the impurity; water, 1 b utyl 3 methy limidazolium bromide, or 1 butyl imidazole was added to the reaction mixture. The reaction was then placed under high vacuum at 50 C while stirring. After 48 h ours the reaction quenched with a solution of 2mL of ethyl

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66 vinyl ether in 10mL of toluene. The toluene layer was separated from the ionic liquid via pipette and the solvent removed under vacuum. The polymer was then dissolved in a minimal amount of toluene and precipitated into 250mL of cold ethanol. The polymer was filtered and NMR was used to determine molecular weights. Synthesis of 1,4 bis(undec 10 en 1 yloxy) triptycene (T9). A round bottom flask equipped with a magnetic stirbar was charged with 50mL of water and 50mL of THF. To this solution 4g (14 mmol) of triptycene 1,4 diol, 13.25g (57 mmol) of 11 bromo 1 undecene, 1.35g (4.2 mmol) of tetrabutyl ammonium bromide, 7.26g (182 mmol) of sodium hydroxide, and 2.18g (14 mmol) of sodium dithionite and ref luxed overnight. The reaction was then cooled to room temperature and diethyl ether was added. The solution was separated and the aqueous phase was then extracted once more with diethyl ether. The organic phases were combined and washed with a 3M solution of sodium hydroxide and dried over magnesium sulfate. The solvent was evaporated in vacuo The resulting residue was then disolved in the minimum amount of dichloromethane and precipitated twice into cold ethanol to give 2.5g of T9 Yield: 30% 1 H NMR (300 MHz, CDCl 3 ppm): = 7.40 (t, 4H), 6.99 (t, 4H), 6.45 (s, 2H), 5.92 5.79 (m, 4H), 5.10 4.9 (m, 4H), 3.95 (t, 4H), 2.15 2.00 (q, 4H), 1.90 1.79 (m, 4H), 1.70 1.20 (m, 24H). 13 C NMR (75 MHz, CDCl 3 ppm): = 148.44, 145.82, 139.23, 135.65, 124.88, 123.73, 11 4.18, 110.64, 69.65, 47.49, 29.66, 29.51, 29.45, 29.21, 28.98, 26.23. Polymerization of 1,4 bis(undec 10 en 1 yloxy) triptycene Under constant argon flow, .5g of T9 was added to flame dried Schlenk flask equipped with a magnetic stir bar. Also under con stant argon flow 1.5mL of 1 b utyl 3 methylimidazolium

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67 hexafluorophosphate was added. .5 mol% of Grubbs 1 st generation catalyst was then added to the reaction mixture. The reaction was then placed under high vacuum and polymerized for 48 hours. The temperat ure was kept at 50, 80, or 100 C. After the requisite time hours the reaction quenched with a solution of 2mL of ethyl vinyl ether in 10mL of toluene. The toluene layer was separated from the ionic liquid via pipette and the solvent removed under vacuum. T he polymer was then dissolved in a minimal amount of toluene and precipitated into 250mL of cold ethanol. The polymer was filtered out and NMR was used to determine molecular weights. Synthesis of 1,4 bis(pent 5 en 1 yloxy) triptycene (T3). A flame dried 3 neck flask charged with a magnetic stir bar was charged with 4.3g (15 mmol) of triptycene 1,4 diol, 4.35g ( 31.5 mmol) of potassium carbonate, .and .33g (2 mmol) of potassium iodide was suspended in anhydrous DMF. The suspension was heated to 65 C for 30 minutes, then 4.65 mL (37.5 mmol) 5 bromo 1 pentene was added dropwise. The reaction was heated overnight at 65 C. It was then cooled to room temperature and the solvent was removed via vacuum distillation. The remaining residue was dissolved in dichlorom ethane washed three times with 1M HCl, and twice with deionized water. The solvent was removed in vacuo and the residue was then dissolved in the minimum amount of dichloromethane and precipitated into cold methanol. The product was filtered and then purif ied via column chromatography (hexane:ethyl acetate 8:1) yielding 4.07g of T3 Yield: 65% 1 H NMR (300 MHz, CDCl 3 ppm): = 7.40 (m, 4H), 6.99 (m, 4H), 6.50 (s, 2H), 6.02 5.85 (m, 4H), 5.20 5.03 (m, 4H), 3.95 (t, 4H), 2.35 (q, 4H), 1.95 (m, 4H).

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68 13 C NMR (75 MHz, CDCl 3 ppm): = 148.55, 145.92, 138.23, 135.87, 125.12, 123.92, 115.37, 110.80, 68.98, 47.67, 30.56, 28.92 Polyme rization of 1,4 bis(pent 5 en 1 yloxy) triptycene Under constant argon flow, .5g of T3 was added to flame dried Schlenk flask equipped with a magnetic stir bar. Also under constant argon flow 1.5mL of 1 b utyl 3 methylimidazolium hexafluorophosphate was a dded. .5 mol% of Grubbs 1 st generation catalyst was then added to the reaction mixture. The reaction was then placed under high vacuum and polymerized for 48 hours at 100 o C. After the requisite time hours the reaction quenched with a solution of 2mL of et hyl vinyl ether in 10mL of toluene. The toluene layer was separated from the ionic liquid via pipette and the solvent removed under vacuum. The polymer was then dissolved in a minimal amount of toluene and precipitated into 250mL of cold ethanol. The polym er was filtered out and NMR was used to determine molecular weights.

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69 CHAPTER 4 Boronic Acid Chemistry: Synthesis of Boronic Acid Monomer 4.1 Background The chemistry of boron is unique and different from that of carbon chemistry. The most st riking difference between carbon and boron is that many boron compounds naturally form planar triva lent species (Figure 4 1). 111 Figure 4 1 Planar boron com pound with empty p orbitals Due to this, boron contains an empty P orbital so is naturally sp 2 hybridized. Ano ther consequence of having an empty P propensity towards Lewis acidity. In the presence of a nucleophile, boron will accept the electrons and adopt a charged sp 3 hybridized conformation ( Figure 4 2). 111 Figure 4 2 Nucleophilic attack on a planar bo ron compound to yield the tetrahedral boron species The Lewis acidity of boron can easily be tuned from some of the weakest Lewis acids, such as boric acid, to one of the strongest, bor on tribromide (Figure 4 3). 112 This is done by altering the substituents attach ed to the boron. Substituents that have the ability to donate electrons into the empty orbital yield weaker Lewis acids, while substituents that are unable to donate electron lead to very strong Lewis acids.

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70 Figure 4 3. Lewis acidity as a function of boron substitution by changing substutuent on the boron a wide range of Lewis acidities can be achieved. Alkyl boron compou nds are known to undergo deboronation (Figure 4 4). 111 This is where the boron is cleaved from the alkyl branch with the addition of water or other ox i dative process, across the bond. Figure 4 4 Deboron ation of alkyl boron comp ounds in the presence o f water or other nucleophilic oxygen compounds. This can be explained if we look at the bond strengths of an alkyl C B bond and a C O bond. A carbon boron bond has a bond dissociation energy of about 107 kcal/mol. When compared to the boron oxygen bond, which has bond dissoci ation energy of 192 kcal/mol, d eboron ation is thermodynamically very favorable, bu t generally kinetically slow. 111 The reason for the difference in bond energies is explained in Figure 4 5 and Figure 4 6. Figure 4 5 Alkyl carbon boron bond The car bon is unable to don ate electrons into the B bond. Lewis acidity

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71 Figure 4 6 The oxygen in a B O bond is capable of donat ing electrons to the empty p orbital of boron, this leads to partial double bond character. In an alkyl carbon boron system, the sp 3 hybridized carbon has no free electrons orbital. In the boron oxygen bond, the lone pair from the oxygen is able to donate i nto the empty orbital of the boron, lending some double bond character to the system (Figure 4 6). This is also seen in the boron oxygen bond lengths which are around 135 pm. 111 These bonds length are indicative of some double bond character. A stable boron carbon bond can be made by taking advantage of the same effect that stren gthens the boron oxy gen bond; specifically electrons empty orbital cause formation of the stable bonds This is found to be true with vinyl and aryl carbon boron bonds (Figure 4 7). 111 Figure 4 7 An aryl C B bond is much more stable th an the alkyl B C bond due to donation of electron density from the pi system of the aryl system into the boron p orbital, increasing the strength of the B C bond. In an aryl boron carbon bond, the conjugated system donates electrons into the orbital and strengthens the bond. This fo rms boron carbon bond s that are compara ble in strength to the boron oxygen bond. Keeping these facts in mind will be necessary to successfully synthesize boronic acid ADMET monomers.

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72 B oronic acid s are unique because the acidity does not come from its prot ons, but instead from t 111 At low pH, boronic acids are sp 2 hybridized and adopt a trigonal planar conformation; however as the pH increases they become sp 3 hybridized and conform to a tetrahedral geometry (Figure 4 8). The pK a of boronic acid s is defined by when there is an equal concentra tion of both t he planar and tetrahedral species present. 111 Figure 4 8 Boronic acids are trigonal planar at low pH, but as the pH increase they assume a charged tetrahedral configuration Boronic acids do share some similarities with other organic acids. They have the ability to form boronic acid anhydrides. Th ese are created when two or more boronic acids condense together and expel water. Unlike carboxylic acids, boronic acids are not limited to dimer formation they can form cyclical boroxines and other boronic anhydride systems (Figure 4 9). 111 Figure 4 9 Formation of boron anhydride and boroxine T hese compounds can be formed simply by applying vacuum to a boronic acid solution or recrystallization from a dry solvent. By keeping the unique chemistry of boron in mind, the following chapter will describe a number of methods used to attempt a nd fina lly succeed in creating boronic acid monomer s This chapter will discuss monomer synthesis, and boronic acid deprotection both which provide a unique challenge when applied to boron chemistry.

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73 4.2 Synthesis of Alkyl Boronic Acid Monomers Figure 4 10 Synthesis of 4,4,5,5 tetra methyl 2 (tricosa 1,22 dien 12 yl) 1,3,2 dioxaborolane ( 5 ) via borylation by grignard reaction 4.2.1 Synthesis of 4,4,5,5 tetra methyl 2 (tricosa 1,22 dien 12 yl) 1,3,2 dioxaborolane (5) monom er. A s shown in Figure 4 10, the 9 spacer alcohol 1 was reacted with triphenyl phosphine and carbon tetrabromide to form the 9 spacer bromide 2 This reaction was near ly quantitative; the loss in yield is a result of the distillation to remove the br om oform side product which can not be removed via chromatography. The 9 spacer bromide was then reacted with Mg t o form a Grignard reagent followed by the addition of ethyl fo rmate to form the 9, 9 alcohol 3 The 9,9 alcohol 3 was then reacted with triphenyl phosphine and carbon tetrab romide to make the 9,9 bromide 4 This proceeded in excellent yield. The bromoform could be removed via flash chromatography instead of having to be distilled off a s in the synthesis of compound 2 A Grignard reagent was used t o perform the boronation since lithiation reactions do not proceed to high converstion on sp 3 hybridized carbons. Lithium reagents are also more basic then Grignard reagents, which could lead to more elimination o f the

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74 secondary bromide 4 After formation of the Grignard reagent 2 isopropoxy 4,4,5,5 tetra methyl 1,3,2 dioxaborolane was added to the reaction. Unfortunately, even using the less basic Grignard reagent the elimination product predominated. The 9,9, boronic ester 5 was made but only in about 5 % yield. The major products of the reaction were 6 and 7 After trying a number of conditions there was no improvement of yield, so this line of synthesis was reconsidered. Figure 4 11 Synthesis of 4,4,5,5 tetra methyl 2 (2 (undec 10 enyl)tridec 12 enyl) 1,3,2 dioxaborolane ( 13 ) via Grignard addi tion of boronic ester to a primary bromide 4.2.2 Synthesis of 4,4,5,5 tetra methyl 2 (2 (undec 10 enyl)tridec 12 enyl) 1,3,2 dioxaborolane (13). The next line of synthes is was designed to form a primary bromide compound in an effort to curb the elimination reaction seen in Figure 4 10 To a slurry of NaH in THF, diethyl malonate was slowly added Compound 2 was then added and the reaction was allowed to reflux for sever al days, until no monoalkylation product was seen via TLC. This forms the 9,9 diester 8 Upon saponification of the crude product the diester is converted into the 9,9 diacid 9 The crude product of that reaction is then dissolved in a minimal amount of de calin with a catalytic amount of N,N Dimethyl aminopyridine and

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75 heated to 160 O C to undergo the decarboxylation. Once the decalin is removed via flash chromatography and solvent evaporated the crude mixture of compound 10 was reacted with lithium aluminum h ydride t o form the 9, 9 methyl alcohol 11 Compound 11 was purified via column chromatography and reacted with triphenyl phosphine a nd carbon tetrabromide to form 12 12 was reacted with Mg to form a Grignard reagent. 2 isopropoxy 4,4,5,5 tetra methyl 1,3, 2 dioxaborolane is added and the substitution reactio n takes place to form compound 13 13 was purified via flash chromatography, and then reacted with Grubbs 1 st generatio n catalyst to form the polymer 14 Unfortunately the polymer only reached a molecula r weight of 2500 g/mol, about 5 6 repeat units. The overall yield of this synthetic approach we rather low due to the number of steps and the low yielding boronation reaction. Also, as mentioned earlier the alkyl boronic ester was unstable, and it is belie ved that decomposition products lead to the low molecular weights obtained after polymerization. To prevent this decomposition, the next synthetic scheme was designed for aryl boronic acids and esters.

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76 4.3 Aryl Boronic Acid Monomer Synthesis Figure 4 12 Synthesis of 2 (4 (heptacosa 1,26 dien 14 yl)phenyl) 4,4,5 trimethyl 1,3,2 dioxaborolane ( 16 ) via dialkylation of 15 4.3.1 Synthesis of 2 (4 (heptacosa 1,26 dien 14 yl)phenyl) 4,4,5 trimethyl 1,3,2 dioxaborolane (16) The synth esis of the aryl boronic ester 16 is shown in Figure 4 12. The 9 spacer alcoho l 1 is conve rted into the 9 spacer bromide 2 Then para chlorotoluene ( 17 ) is converted to the Grignard reagent with Mg and reacted with 2 isopropoxy 4,4,5,5 t etra methyl 1,3,2 dioxaborolane to form para toluene boronic ester ( 18 ). The di alkylation reaction is attempte d by reacting LDA and compound 2 with the boronic ester 18 Unfortunately, under the reaction conditions attempted, 0 O C reacted for 6 hours, the alkylation was unsuccessful. By modifying the method used to make the 9,9 alcoh ols it w as hypothesized that a boronic acid/ester monomer could be made the same way. In this case the ethyl ester

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77 of a protected boronic acid was used instead of the ethyl f ormate. The Grignard was formed from the 9 spacer bromide 2 which then would react twice with the ester to form a carbon center with both an alcohol and the protected boronic acid. The next step would then be to remove the tertiary alcohol resulting in t he desired protected boronic acid monomer. Unfortunately this was not the case. As shown in Figure 4 13, the Grignard reaction failed to produce the desired product, in fact no reaction was observed even though the Grignard reagent did form This is thou ght to be caused by the electrophilicity of the boronic ester. Instead of the Grignard reagent attacking at the carbonyl, it instead binds to the boron. Upon aqueous work up the alkyl group is cleaved, recreating the starting ester Figure 4 13 Synthesis of 12 (4 (4,4,5,5 tetramethyl 1,3,2 dioxaborolan 2 yl)phenyl)tricosa 1,22 dien 12 ol ( 17 ) using a boron containing electrophile In an attempt to circumvent the electrophilicity problem the reaction was reversed. The boron containing compound would become the nucleophile and the alkyl substrate would be the electrophile (Figure 4 14). The hypothesis behind this approach was that by creating a Grignard reagent that was conjugated with boron, the increased electro n density of the system would be enough to reduce th e electrophilicity of boron. The 9,9 ketone 18 was made from reacting the 9,9 alcohol 3 with pyridinium

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78 chlorochromate (PCC). This reaction progressed well, creating the ketone 18 in 90+% yields. The 9, 9 ketone 18 was then reacted with 19 in a Grignard reaction with the goal of forming 20 Unfortunately, no reaction appeared to take place yet the Grignard reagent was formed. Most likely the boron was still too electrophilic to allow any useful nucleophilic reaction to take place. Figure 4 14 Synthesis of 12 (4 (4,4,5,5 tetramethyl 1,3,2 dioxaborolan 2 yl)phenyl)tricosa 1,22 dien 12 ol ( 17 ) using a boron containing nucleophile To avoid complications with the boron compo und, a synthetic scheme was designed to synthesize a substrate that could then have the boronic acid or ester attached in the final step (Figure 4 15). This was carried out much the same way as the reaction above, except 19 was replaced with 1,4 dibromob enzene as the Grignard reagent By controlling the stoichiometry of the magne sium, it can be assured that 1,4 dib romobenzene will only from one Grignard reagent This was found to be the case in fairly good yields, about 80%. The next step was to removal o f the tertiary alcohol.

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79 Figure 4 15 Synthesis of 12 (4 bromophenyl)tricosa 1,22 dien 12 ol ( 21 ) via Grignard reaction. Reduction of tertiary alcohols has traditionally been a difficult proposition. Methods that work for primary and secondary alcohols, such as substitution with lithium aluminum hydride, seldom work on their tertiary counterparts. This is because many of these techniques rely on a SN 2 sterically hindered te rtiary carbons. Figure 4 16 demonstrates a number of techniques attempted to reduce the alcohol.

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80 Figure 4 16 Reduction of tertiary alcohols a) Reduction with InCl 3 and chloro diphenylsilane resulting alcohol reductio n but also olefin isomerization. b) Reduction with InCl3 and chloro di meth ylsilane no improvement was seen. c) Barton McCombie radical deoxygenation results in elimination of the alcohol instead of reduction. d) Using triflouroacytyl as a method for re duction of the tertiary alcohol; results in elimination and acylation. The first method attempted was reported by Yasuda et al. 113 This technique uses a indium trichloride as a catalyst and diphenyl chlorosilane as a mild hydride source. The reported reaction demonstrates good conve rsion even at low temperatures for both tertiary and secondary alcohols. Tertiary alcohols seem to react more quickly, indicative of a SN 1 type reaction mechanism. Unfortunately, these reaction conditions cause the isomerization of the terminal double bond s. When studied, neither reagent alone produced isomerization but it was hypothesized that the electronics of the phenyl rings

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81 lead to the silane behaving more as a proton source than a hydride source, allowing for isomerization. To prevent this dimethyl c hlorosilane, which is a stronger hydride source, was used. Unfortunately, the isomerization was still present. The next method attempted was Barton McCombie radical deoxygenation. 114 First the xanthate was formed from the alcohol by deprotonation with s odium hydride, which then reacted with carbon di sulfide and methyl iodide to form 23 Azobisisobutyronitrile (AIBN) was used as a radical source which causes the xanthate to decompose to carbon oxide sulfide, leaving a tertiary radical which reacts with a hydride source to form the final product. Unfortunately, tertiary Barton McCombie reactions can form the elimination product 24 instead of the reducti on product. One method to prevent elimination, reported by Holbert et al. is to form the triflouroacetyl species instead of the xanthate. 115 This was done by reacting the alcohol with triflouroacetic anhydride in the presence of tripropyl amine as a proton sponge to form 25 Unfortunately, the triflouroacetyl functional group is also an excellent leaving and even a gentle workup caused elimination and formation of 24 With these oxygen reduction techniques exhausted, a new method was neede d to attach the phenyl boronic acid or ester functionality 4.3.2 Synthesis of 4,4,5,5 tetramethyl 2 (4 (tricosa 1,22 dien 12 yloxy)phenyl) 1,3,2 dioxaborolane To avoid the problem s associated with removal of the tertiary alcohol, the use of an ether lin kage to attach the phenyl boronic acid or ester was evaluated. Ethers are versatile, stabile, and there exists a large number of ways to synthesizes them. To this end synthesis of 27 was attempted (Figure 4 17).

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82 Figure 4 17 Synthesis of 4,4,5,5 tetramethyl 2 (4 (tricosa 1,22 dien 12 yloxy)phenyl) 1,3,2 dioxaborolane ( 27 ) via ether synthesis of 4 with 4 bromo phenol This reaction scheme began with the synthesis of the 9, 9 bromide 4 as mentioned earlier this ser ies of reactions is facile and high yielding. The next step was the synthesis of the ether. This was done using 4 bromo phenol as the nucleophile and sodium hydride as the base in DMF. This reaction proceeded but in fairly low yields of only about 45%. Th is is due to the nature of the using a secondary bromide as t he leaving group, it can easily underg o elimination, which was seen here. Changing reaction condition to using sodium hydroxide, and tetrabutyl ammonium bromide in a biphasic water/THF reaction d id not improve the yields While this reaction scheme did work, the yields were rather low so another monomer synthesis was attempted below. 4.3.3 Synthesis of 4,4,5,5 tetramethyl 2 (4 ((tricosa 1,22 dien 12 yloxy)methyl)phenyl) 1,3,2 dioxaborolane In an attempt to increase the overall yield of the ether synthesis and cut down on the number of steps, the compounds used for the nucleophile and the electrophile were reversed (Figure 4 18).

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83 Figure 4 18 Synthesis of 4,4 ,5,5 tetramethyl 2 (4 ((tricosa 1,22 dien 12 yloxy)methyl)phenyl) 1,3,2 dioxaborolane ( 29 ) via ether synthesis of 3 with 4 bromobenzyl bromide followed by a G rignard reaction to attach the boronic ester Instead of synthesizing the 9, 9 bromide 4 and using it as the electrophile, the 9,9 alcohol 3 was used. This increased yields in several ways; fi rst it cut down on the number of steps and second it allowed the electrophile to be a primary bromide. In this case the electrophile was chosen to be 4 bromobenz ylbromide. When reacted under the same conditions as above a 90% yield was achieved. Finally, a Grignard reaction was used to attach the boronic ester. This reaction progressed at about 60% yield with fresh reagent, but the yield was drastically reduced in the presence of any hydrolyzed 2 isopropoxy 4,4,5,5 tetra methyl 1,3,2 dioxaborolane This is a common problem when using Grignard reaction s to produce boron compounds. While the presence of isopropanol (or water) would be expected to lower the yields of a Grignard reaction in a stoichometric fashion, when in the presence of boronic ester, the yields are reduced in a more catalytic fashion. This indicates a differen ce mechanism is at work that de activated the Grignard reagent. This method proved effective in the synthesis of

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84 boronic ester monomers. However, upon polymerization this monomer proved challenging. These difficulties will be discussed in the next chapter. 4.3.4 Synthesis of in chain boronic acid monomer The final syntheetic route was another va riation using an ether synthesis, combining the stability of phenolic ether with reactivity of a primary electrophile (Figure 4 19). This reaction began with the the alkenyl bromide with carbon spacers of 3, 6, or 9 34 35 or 2 respectively This was t hen reacted with 1 bromo 3,5 hyd roxybenzene to form 36 37 or 38 in good yield s Due to the excessive cost of 1 bromo 3,5 hyrdroxybenzene, it was synthesize by reacting the much cheaper 1 bromo 3,5 methoxybenzene ( 30 ) with boron tribromide. Boron tribrom ide is an extremely strong Lewis acid that is commonly used to cleave phenolic ethers. In this case the reaction proceeded splendidly, in about 80% yield. The final step is to introduce the boronic acid to the monomer. This is done using a lithiation proce dure as to avoid the problems mentioned with use of Grignard reagents. Trisopropyl borate was used since under standard aqueous work up conditions yield the free boronic acid. Purification of the lithiation reaction also made it an attractive option. A sim ple silica plug followed by recrystallization in hexanes resulted in unoptimized yields of 60% for 39 and 53% for 41

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85 Figure 4 19 Synthesis of in chain boronic acid monomer ( 39 41 ) The alkenyl groups are attached via ether synthesis then the bor onic acid is added using a standard lithiation reaction. 4.4 Deprotection of Boronic Acids Deprotecting the boronic esters to the acids has presented difficulties. Figure 4 21 shows several different techniques that have bee n attempted.

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86 Figure 4 21 Deprotection of alkyl boronic esters a) Acid/ base hydrolysis yielded no reaction b+c) Use of hydrogenation technique s only reduced the terminal alkenes d) Use of boron trichloride also resulte d in no reaction All of the deprotections were done on the monomer for test purposes, once promising deprotection conditions are found it would be attempted on the polymer. The first attempt at deprotections was a simple hydrolysis. Both acid and base hyd rolysis were attempted in a refluxing water/ethanol solution. Unfortunately, no reaction occurred presumably due to the sterics of the pinacol methyl groups Next hydrogenation conditions were attempted to remove the pinacole protective group. This would be ideal, as the finished ADMET polymer gets hydrogenated to remove the residual double bonds. Unfortunately, neither the Wilkinson's catalyst or the Pd/C accomplished nothing more than hydrogenation of the double bond. The final attempt

PAGE 87

87 was to use boron t richloride to cleave the boron oxygen bond. This is then converted back to the acid upon aqueous work up This attempt also yielded no useful reaction. Benzylic boronic esters have been shown to be cleaved in a similar fashion to benzylic ethers. 116 To this end a series of protecting groups were synthesized and studied (Figure 4 22). Figure 4 22 Deprotection of aryl boronic esters via hydrogenation Changing the protection grou p to one containing benzylic oxygens allow for their removal The model compound 46 was used for these experiments. Since many ADMET yst, this was the first system tested Unfortunately, the catalyst did not remove the protecting group. In an attempt to replicate the publish ed procedure, Pd/C was used as the hydrogenation catalyst. This system worked flawless, demonstrating that the pro tecting groups can be removed under hydrogenation procedures. This study demons trated that the correct protecting group could be removed using mild hydrogenation conditions.

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88 Shortly after these studies were concluded, other work (Chapter 2 ) de monstrated t hat free boric acid d id not hinder olefin metathesis, in fact, can even enhance it. This result leads to the conclusion tha t protection of the boronic acid is unnecessary. 4.5 Conclusions This chapter discusses many important aspects of boron chemistry. The instability of alky boronic esters was demonstrated; both by the decomposition of monomer, and the difficulty of the synthesis. Aryl boronic acids were proven to be the synthetic target of choice. Numerous methods were demonstrated to synthesize these compounds. Use of boron containing compounds in nucleophilic reactions was proven to be fruitless. This is caused by the Lewis acidity of the boron species interfering with free electrons of the nucleophile. Finally, boronic acid and ester monomers were s ynthesized using ether li nkages Protection and deprotection of boronic acid compounds were also studied. The pinacol protection groups were found to be extremely stable but difficult to remove, however the diphenyl protection group was easily cleaved vi a hydrogenation yielding the free boronic acid. With these discoveries in hand, precision boronic acids polymers can be synthesized and their morphologies studied. 4.6 Experimental 4.6.1 Materials and Instrumentation 1 Butyl 3 methylimidazolium hexafluoro phosphate was purchased from AK Scientific and purified via a neutral alumina plug followed by degassing via freeze pump thaw in triplicate. All other materials were purchased from Aldrich and used without further purification unless noted. Grubbs 1 st and 2 nd generation catalyst (G1 and G2) as well as Hoveyda Grubbs 1 st and 2 nd generation catalyst (HG1 and HG2) were kindly

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89 provided by Materia, Inc. Anhydrous solvents were obtained from an anhydrous solvent system. All 1 H NMR, and 13 C NMR were obtained on a Varian Mercury 300MHz spectrometer and recorded in CDCl 3 1 H and 13 C chemical shifts were referenced to signals from CDCl 3 Mass spectrograms were carried out on a Thermo Scientific DSQ MS. Elemental analyses were carried out by Atlantic Microlab, Inc. Th ermogravimetric analysis (TGA) was performed on TA Instruments TGA Q1000 Series using dynamic scans under nitrogen. Differential scanning calorimetry (DSC) analysis was performed using a TA Instruments Q1000 series equipped with a controlled cooling access ory (refrigerated cooling system) at 10 C/min. Differential scanning calorimetry (DSC) analysis was performed using a TA Instruments Q1000 series equipped with a controlled cooling accessory (liquid nitrogen cooling system) at 10 C/min. Gel permeation ch romatography (GPC) was performed at 40 C using a Waters Associates GPCV2000 liquid chromatography system with an internal differential refractive index detector and two Waters Styragel HR 5E columns (10 m PD, 7.8 mm i.d., 300 mm length) using HPLC grade THF as the mobile phase at a flow rate of 1.0 mL/min. 4.6.2 Procedures Synthesis of 11 bromo 1 undecene (2) 40.00g of undecene 11 ol and 93.52g of carbon tetrabromide were dissolved in 350mL of dichloromethane in a round bottom flask with a stir bar. The mixture was chilled to 0C. Triphenyl Phosphine was added slowly, keeping the temperature cold. The reaction was allowed to stir overnight at room temperature under argon. The solid triphenyl phosphine oxide was then filtered out of solution and washed with hexane. The solvent was then removed under vacuum, and the solid was recrystallized in ether. The solid was filtered off, and filtrate was run through a silica plug to remove the remaining triphenyl phosphine oxide. The collected

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90 product is a mixture of b romoform and desired 11 bromo 1 undecene. The bromoform was distilled off under vacuum. Yield: 90% 1 H NMR (300MHz, CDCl 3 5.7 (m, 1H); 5.05 4.85 (m, 2H); 3.45 3.35 (t, 2H); 2.10 2.00 (m, 2H); 1.92 1.80 (m, 2H); 1.50 1.20 (m, 12H) Synthesis of tricosa 1,22 dien 12 ol (3) A flame dried three neck flask with a stir bar was charged with 40mL of THF and 1.90g Mg under argon. The flask was chilled in an ice bath, and 1.7mL of 1,2 Dibromoethane was added to the solution and stirred at RT for 30 min utes. 10 g of 11 bromo 1 undecene was added to drop wise to the reaction mixture and refluxed for 2 hours. The reaction was then cooled to RT and 1.44g of ethyl formate was added to the reaction. The mixture was then refluxed overnight, still under argon. The reaction is then cooled in an ice bath and neutralized with 1M HCl. The mixture was then extracted with ether. The solvent was removed under vacuum and the resulting solid was recrystallized in acetone. Yield: 90% 1 H NMR (300MHz, CDCl 3 5 .73ppm (m, 2H); 5.05 4.85ppm (m, 4H); 3.6 3.5ppm (s, 1H); 2.1 2.0ppm (q, 4H) 1.6 1.1ppm (m, 41H) (grease impurity overlaps alkyl peaks) Synthesis of 12 bromotricosa 1,22 diene (4) The same bromination procedure was followed as outlined in the synthesis of 11 bromo 1 undecene. 5.92g of (3) 6.96g carbon tetrabromide, and 6.82g triphenyl phosphine. The work up was the same as outlined above except the bromoform was removed via flash chromatography in hexane.

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91 Yield: 95% 1 H NMR (300MHz, CDCl 3 5.73 (m, 2H); 5.05 4.85 (m, 4H); 4.1 3.95 (m, 1H); 2.10 2.00 (m, 4H); 1.85 1.75 (m, 4H); 1.6 1.1 (m, 30H) (grease impurity overlaps alkyl peaks) Synthesis of 2 (undec 10 enyl)tridec 12 enoic acid (10) 3.1g of NaH was added to a three necked flask with a stir bar along with 30mL of dry THF. 6.88g of diethyl malonate was added slowly drop wise, and stirred for 30 minutes. 25 g of compound (2) was added dropwise and refluxed under argon for 48 hours. The reaction was then cooled and 1g of NaH a nd compound (2) were added and refluxed for another 24 hours. The reaction was then cooled in an ice bath and nuetralized with 1M HCl. The reaction mixture was then extracted with ether. The ether was removed under reduced pressure. The recovered oil was t hen disolved in 250mL of 6M NaOH solution and ethanol. This was then refluxed under argon for 24 hours. The reaction mixture was chilled in the ice bath, neutralized with concentrated HCl, and extracted with ether. The ether was removed under vacuum and th e crude mixture was dissolved in 30mL of hot decalin. A catalytic amount, about 20mg, of DMAP was added to the reaction and heated to 160C for 4 hours. The reaction was then cooled and the decalin removed via flash chromatography in hexane, the solvent wa s then changed to a 3:1 hexane/ ethyl acetate mixture to remove the desired 2 (undec 10 enyl)tridec 12 enoic acid in a 63% yield. Synthesis of 2 (undec 10 enyl)tridec 12 en 1 ol (11) 1.9g of lithium aluminum hydride was added to dry THF to make a slurry a nd then chilled in an ice bath. Then 5.5g of compound (10) dissolved in THF was added slowly to the slurry. This was allowed to react over night at room temperature. The reaction was chilled in an ice bath

PAGE 92

92 and slowly neutralized with water followed by 1M H Cl. The mixture was then extracted with ether, and condensed under vacuum. The desired product was recovered in near quantitative yields. Synthesis of 12 (bromomethyl)tricosa 1,22 diene (12) The same bromination procedure was followed as outlined in the s ynthesis of 11 bromo 1 undecene. 4.94g of (11) 5.6g carbon tetrabromide, and 5.25g triphenyl phosphine. The work up was the same as outlined above except the bromoform was removed via flash chromatography in hexane. The desired product was isolated in 95% yield. Synthesis of 4,4,5,5 tetramethyl 2 (2 (undec 10 enyl)tridec 12 enyl) 1,3,2 dioxaborolane (13). A flame dried three neck flask with a stir bar was charged with 20mL of THF and .95g Mg under argon. The flask was chilled in an ice bath, and .89mL of 1,2 Dibromoethane was added to the solution and stirred at RT for 30 minutes. 4.05g of compound (12) was then added drop wise and refluxed for 3 hours under argon. The reaction was cooled and 2.75g of 2 isopropoxy 4,4,5,5 tetramethyl 1,3,2 dioxaborolane wa s added drop wise and refluxed overnight still under argon. The reaction was the cooled and quenched with water in an ice bath. The mixture was extracted with ether and condensed under vacuum. The recovered oil was then purified by flash chromatography, st arting with hexane then moving to a 20% ethyle acetate and 80% hexane eluent to recover desired product in about 80% yield. Synthesis of 4,4,5,5 tetramethyl 2 p tolyl 1,3,2 dioxaborolane (18) A flame dried three neck flask with a stir bar was charged with 50mL of THF and 2.13g Mg under argon. The flask was chilled in an ice bath, and 2.53mL of 1,2 Dibromoethane was added to the solution and stirred at RT for 30 minutes. 5.00g of 1 chloro 4 methyl

PAGE 93

93 benzene was then added drop wise and refluxed for 3 hours un der argon. The reaction was cooled and 6.53g of 2 isopropoxy 4,4,5,5 tetramethyl 1,3,2 dioxaborolane was added drop wise and refluxed overnight still under argon. The reaction was the cooled and quenched with water and 1M HCl in an ice bath. The mixture wa s extracted with ether and condensed under vacuum. The crude oil was then separated using flash chromatography using a 5:1 hexane/ethyl acetate as the eluent. Solvent was removed under vacuum and the desired product was isolated in 60% yield. Synthesis o f 8 bromo 1 octene (26) 462.25g of 1,8 dibromo octane, 1.25L of THF, and 1.25L of toluene were added to a 5L round bottom flask. The mixture was chilled in an ice bath and 407.1g of potassium tert butoxide was added over the course of an hour. The reaction was removed from the ice bath and allowed to react for another 2 hours at RT. The reaction was then chilled again in an ice bath and quenched with water and HCl. Once the solution was neutralized and the water removed. The organic solution was washed wit h water in a 2:1 water/toluene ratio. This was repeated until the THF was removed. The toluene solution was the washed with brine. The toluene was then removed by vacuum distillation. The unreacted 1,8 dibromo octane was distilled under vacuum using azeotr opic distillation. A mixture of water and ethanol was used to form an azeotrope with the 1,8 dibromo octane, allowing for its removal. Synthesis of 2,2 di(oct 7 enyl)malonic acid (28) 10.00g of NaH was added to a three necked flask with a stir bar along w ith 100mL of dry THF. 12.01g of diethyl malonate was added slowly drop wise, and stirred for 30 minutes. 31.9 g of compound (26) was added dropwise and refluxed under argon for 48 hours. The reaction was then cooled and 2g of NaH and 3g compound (26) were added and refluxed for another 48

PAGE 94

94 hours. The reaction was then cooled in an ice bath and nuetralized with 1M HCl. The reaction mixture was then extracted with ether. The ether was removed under reduced pressure. The recovered oil was then disolved in 100mL of 6M NaOH solution and 50mL ethanol. This was then refluxed under argon for 24 hours. The reaction mixture was chilled in the ice bath, neutralized with concentrated HCl, and extracted with ether. The ether was removed and the crude oil was separated via flash chromatography using 5% methanol/ 95% hexane eluent. The solvent was removed and the desired product was recovered. Yield: 45% 1 H NMR (300MHz, CDCl 3 5.9 5.73 (m, 2H); 5.05 4.90 (m, 4H); 2.10 2.00 (q, 4H); 2.00 1.88 (m, 4H); 1.6 1.1 (m, 16 H) General synthesis of 12 (4 (4,4,5,5 tetramethyl 1,3,2 dioxaborolan 2 yl)phenyl)tricosa 1,22 dien 12 ol via boronic ester electrophile (17). A flame dried three neck flask with a stir bar was charged with dry THF and 4 equiv. of Mg under argon. The fla sk was chilled in an ice bath, and 1 equiv. of 1,2 dibromoethane was added to the solution and stirred at RT for 30 minutes. 2.2 equiv. of 11 bromo 1 undecene was added to drop wise to the reaction mixture and refluxed for 2 hours. The reaction was then co oled to RT and 1 equiv. of ethyl 4 (4,4,5,5 tetramethyl 1,3,2 dioxaborolan 2 yl)benzoate was added to the reaction. The mixture was then refluxed overnight under argon. The reaction is then cooled in an ice bath and neutralized with 1M HCl. The aqueous sol ution was extracted three times with ether. The organic phases were combined and the solvent was removed under vacuum. An NMR of the resulting residue indicated no product had been formed.

PAGE 95

95 General synthesis of 12 (4 (4,4,5,5 tetramethyl 1,3,2 dioxaborolan 2 yl)phenyl)tricosa 1,22 dien 12 ol via boronic ester nucleophile (17). A flame dried three neck flask with a stir bar was charged with dry THF and 2.5 equiv. Mg under argon. The flask was chilled in an ice bath, and 1 equiv. of 1,2 dibromoethane was adde d to the solution and stirred at RT for 30 minutes. 1.2 equiv. of 2 (4 bromophenyl) 4,4,5,5 tetramethyl 1,3,2 dioxaborolane (19) was added to the reaction mixture and refluxed for 2 hours. The reaction was then cooled to RT and 1 equiv. of tricosa 1,22 die n 12 one was added to the reaction. The mixture was then refluxed overnight under argon. The reaction is then cooled in an ice bath and neutralized with 1M HCl. The aqueous solution was extracted three times with ether. The organic phases were combined and the solvent was removed under vacuum. An NMR of the resulting residue indicated no product had been formed. Synthesis of tricosa 1,22 dien 12 one (18). In a flame dried 1L flask equipped with a stir bar 15.5g pyridinium chlorochromate and 15.5g of celite were suspended in 100mL of dry dichloromethane. 16g of tricosa 1, 22 dien 12 ol was dissolved in in 30mL of dichloromethane and added drop wise to the slurry. The reaction was stirred overnight and quenched with addition of 200mL of diethyl ether. The slu rry was then filtered through a silica plug and the solvent was evaporated under vacuum. The crude ketone was then recrystallized in acetone to yield 13.5g of (18) Yield: 85% 1 H NMR (300MHz, CDCl 3 ppm) 5.7 (m, 2H); 5.05 4.85 (m, 4H); 2.41 2.32 (t, 4H); 2.10 1.95 (q, 4H); 1.61 1.49 (m, 4H); 1.91 1.70 (m, 24H) General synthesis of 12 (4 bromophenyl)tricosa 1,22 dien 12 ol (20). A flame dried three neck flask with a stir bar was charged with dry T HF and 1.5 equiv. Mg

PAGE 96

96 under argon. The flask was chilled in an ice bath, and .1 equiv. of 1,2 dibromoethane was added to the solution and stirred at RT for 30 minutes. 1.5 equiv. of 1,4 dibromobenzene was added to the reaction mixture and refluxed for 2 hou rs. The reaction was then cooled to RT and 1 equiv. of tricosa 1,22 dien 12 one was added to the reaction. The mixture was then refluxed overnight under argon. The reaction is then cooled in an ice bath and neutralized with 1M HCl. The aqueous solution was extracted three times with ether. The organic phases were combined and the solvent was removed under vacuum. Yield: 80% 1 H NMR (300MHz, CDCl 3 5.7 (m, 2H); 5.05 4.85 (m, 4H);2.35 2.10 (q, 4H); 1.91 1.70 (m, 4H); 1.60 1.20 (m, 28H) Tertiary alcohol reduction via indium trichloride and diphenyl chlorosilane. In a flame dried flask equipped with a stir bar, .05 equiv. of InCl 3 was added to 1.0 equiv. of tertiary alcohol in dichloromethane. 2.0 equiv. of diphenyl chl orosilane was added under argon. The reaction was refluxed for 4 hours then poured into a mixture of diethyl ether:water (5:3). The mixture was extracted with diethyl ether three times and the organic phases were combined. The solvent was evaporated under vacuum. The crude residue was analyzed via NMR and found the while the alcohol was reduced, the terminal olefins were also isomerized. Tertiary alcohol reduction via indium trichloride and dimethyl chlorosilane. In a flame dried flask equipped with a s tir bar, .05 equiv. of InCl 3 was added to 1.0 equiv. of tertiary alcohol in dichloromethane. 2.0 equiv. of diethyl chlorosilane was added under argon. The reaction was refluxed for 4 hours then poured into a mixture of diethyl ether:water (5:3). The mixtur e was extracted with diethyl ether three times and

PAGE 97

97 the organic phases were combined. The solvent was evaporated under vacuum. The crude residue was analyzed via NMR and found the while the alcohol was reduced, the terminal olefins were also isomerized. Tertiary alcohol reduction via Barton McCombie radical deoxygenation. In a flame dried three neck round bottom flask equipped with a flask, 1 equiv. of tertiary alcohol was added to a slurry of THF (3.5mL of solvent per mmol of tertiary alcohol), 1.6 equi v. of sodium hydride, and .05 equiv. of imidazole. The slurry was stirred for 2 hours at RT, then cooled to 0C and 3 equiv. of carbon disulfide was added. The reaction was stirred overnight at RT, then cooled to 0C and 1.5 equiv. of methyl iodide was add ed. The reaction was stirred for 2 hours then quenched with water and extracted three times with diethyl ether. The solvent was removed under vacuum, and the residue was purified via column chromatography using 95:5 hexane:ethyl acetate. The purified produ ct was then added to a flame dried flask, with 5 equiv. of N ethylpiperidine hypophosphite in dioxane. The reaction was refluxed for 2 3 hours. Aliquots of 2,2 azobisisobutyronitrile (.1 equiv.) dissolved in dioxane was added over the course of the reacti on. The solvent was removed under vacuum, and the crude product was purified via column chromatography in pure hexane. The pure product was analyzed via NMR and found that while the tertiary alcohol was removed, it formed the elimination product not the p ure reduction product. Tertiary alcohol reduction via triflouroacetic anhydride. A flame dried flask was charged with 1 equiv. of tertiary alcohol and 1 equiv. of tripropyl amine in dichloromethane. 1.2 equiv. of trifouroacetic anhydride was added to the solution drop wise and the reaction was stirred overnight under argon. The reaction was quenched

PAGE 98

98 with water and extracted three times with diethyl ether. The solvent was removed under vacuum and the crude product was analyzed via NMR. The isolated product was found to contain some of triflouro acylated product, but also large amount of the elimination product as well. Synthesis of 1 bromo 4 (tricosa 1,22 dien 12 yloxy)benzene (26). .46g of 4 bromophenol dissolved in dry DMF was added drop wise to a slurry of .12g sodium hydride in DMF at 0C. The reaction was stirred at RT for 30 minutes, then 1g of 12 bromotricosa 1,22 diene (4) was added. The reaction was heated to 65C overnight then cooled to 0C and quenched with water. The reaction was extracted thre e times with diethyl ether. The organic phases were combined and washed three times with 1M HCl followed by three washes with 3M NaOH solution. The organic phase was dried of magnesium sulfate and the solvent was removed in vacuo The product was purified v ia silica column chromatography. Yield: 45% 1 H NMR (300MHz, CDCl 3 ppm) 5.7 (m, 2H); 5.05 4.85 (m, 4H); 3.45 (d, 1H); 2.15 2.00 (q, 4H); 1.85 1.10 (m, 32H) 13 C NMR (75 MHz, CDCl 3 ppm): = 154.96, 139.46, 132.67, 117.41, 114.32, 112.99, 39.95, 39.72, 34.03, 32.78, 29.98, 29.92, 29.77, 29.70 29.35, 29.15, 26.76 Synthesis of 1 bromo 4 ((tricosa 1,22 dien 12 yloxy)methyl)benzene (28). In a flame dried three neck flask, a slurry was made of 1.43g (60 mmol) of sodium hydride in DMF and cooled to 0C. 5.0g (14.85 mmol) of (3) was added drop wise and stirred at room temperature for 30 minutes. 4.08g (16.3 mmol) of 1 bromo 4 (bromomethyl)benzene was then added. The reaction was heated to 60C and stirred overnight. The reaction was quenched with water and extracted three times with ether.

PAGE 99

99 The organ ic phase was washed with 1M HCl and dried over magnesium sulfate. The solvent was evaporated under vacuum. The crude product was then purified via column chromatography with hexanes as the eluent. Yield: 90% HRMS: Actual [M+NH 4 ] + =522.3314 Theory [M+NH 4 ] + =522.3305 1 H NMR (300MHz, CDCl 3 ppm) 5.75 (m, 2H); 5.05 4.85 (m, 4H); 4.5 (s, 2H); 3.4 (m, 1H); 2.15 2.00 (q, 4H); 1.75 1.10 (m, 32H) 13 C NMR (75 MHz, CDCl 3 ppm): = 139.46, 138.42, 131.50, 129.45, 121.32, 114.32, 79.44, 70.08, 34.00, 33.98, 30.01, 29.91, 29.82, 29.76, 29.69, 29.34, 29.13, 25.12. Synthesis of 4,4,5,5 tetramethyl 2 (4 ((tricosa 1,22 dien 12 yloxy)methyl)phenyl) 1,3,2 dioxaborolane (29). A flame dried three neck flask with a stir bar was charged with THF and 4 equiv. of magnesium under argo n. The flask was chilled in an ice bath, and 1 equiv. of 1,2 dibromoethane was added to the solution and stirred at RT for 30 minutes. 1 equiv. of 1 bromo 4 ((tricosa 1,22 dien 12 yloxy)methyl)benzene (28) was added to drop wise to the reaction mixture and refluxed for 2 hours. The reaction was then cooled to RT and 1.3 equiv. of Isopropoxyboronic acid pinacol ester was added to the reaction. The mixture was then refluxed overnight, still under argon. The reaction was then cooled in an ice bath and neutrali zed with 1M HCl. The mixture was then extracted three times with ether. The solvent was removed under vacuum and crude product was purified via column chromatography in 19:1 hexane:ethyl acetate eluent. Yield: 60% HRMS: Actual [M+NH 4 ] + =570.5087 Theory [M+ NH 4 ] + =570.5059 Elemental Analysis: Theory C:78.23 H:11.12 Actual C:78.45 H:11.16 1 H NMR (300MHz, CDCl 3 5.75 (m, 2H); 5.05 4.90 (m, 4H); 4.55 (s,

PAGE 100

100 2H); 3.4 (m, 1H); 2.10 2.00 (q, 4H); 1.75 1.10 (m, 44H) 13 C NMR (75 M Hz, CDCl 3 ppm): = 142.67, 139.37, 134.97, 127.01, 114.30, 83.84, 79.22, 70.70, 34.02, 33.99, 30.04, 29.81, 29.76, 29.69, 29.34, 29.14, 25.17, 25.04. Synthesis of 5 bromobenzene 1,3 diol (31). In a flame dried three neck flask, 25.0g (115.3 mmol) of 5 br omo 1,3 dimethoxybenzene (30) was added to dry dichloromethane. The reaction was cooled to 78C and 86.6g (345 mmol) tribromobenzene was added slowly with stirring. The reaction as allowed to stir overnight at room temperature. The mixture was then chille d to 0C and quenched with water. The reaction was extracted three times with ethyl acetate, and the solvent was then removed under vacuum. The crude product was purified via silica plug in 1:1 hexane:ethyl acetate. Once the solvent was removed, the residu e was dissolved in toluene which was then removed under vacuum. This yielded a pure off white solid. Yield: 80% 1 H NMR (300MHz, CDCl 3 13 C NMR (75 MHz, CDCl 3 ppm): = 160.67, 122.95, 110.35, 100.72 General procedure for alkylation of 5 bromobenzene 1,3 diol via biphasic reaction. In a single neck round bottom flask, 1 equiv. of 5 bromobenzene 1,3 diol (30) 1 equiv. of Na 2 S 2 O 4 13 equiv. of sodium hydroxide, and .3 equiv. of tetrabutyl ammonium bromide was dissolved i n a 1:1 mixture THF:H 2 O. 4 equiv. of alkenyl bromide was then added drop wise to the reaction mixture. The reaction was refluxed overnight then cooled to RT and quenched with diethyl ether. The aqueous phase was extracted three times with diethyl ether. Th e solvent was removed under vacuum and the crude product was then purified via a column chromatography.

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101 General procedure for alkylation of 5 bromobenzene 1,3 diol via potassium carbonate in DMF. A flame dried 3 neck flask charged with a magnetic stir ba r was charged with 1 equiv. of 5 bromobenzene 1,3 diol, 3 equiv. of potassium carbonate, .and .25 equiv. of potassium iodide was suspended in anhydrous DMF. The suspension was heated to 65 C for 30 minutes, then 2.5 equiv. of 5 bromo 1 pentene was added dropwise. The reaction was heated overnight at 65 C. It was then cooled to room temperature and the solvent was removed via vacuum distillation. The remaining residue was dissolved in dichloromethane washed three times with 2M NaOH, and dried over magnesiu m sulfate. The solvent was removed in vacuo and the residue was then purified via column chromatography in hexanes. Synthesis of 1 bromo 3,5 bis(undec 10 en 1 yloxy)benzene (38). 3g (15.9 mmol) of 5 bromobenzene 1,3 diol (30) 2.48g (15.9 mmol) Na 2 S 2 O 4 8 .25g (206.3 mmol) of sodium hydroxide, 1.54g (4.76mmol) of tetrabutyl ammonium bromide, and 14.8g (63.5 mmol) of 11 bromo 1 undecene purified via column chromatography in hexanes. Yield: 3.91g, 52.5% 1 H NMR (300MHz, CDCl 3 1H); 5.9 5.75 (m, 2H); 5.05 4.90 (m, 4H); 3 .95 3 .85 (t, 4H); 2.10 2.00 (q, 4H); 1.82 1.70 (m,4H); 1.50 1.10 (m, 24H) 13 C NMR (75 MHz, CDCl 3 ppm): = 160.90, 139.34, 122.99, 114.33, 110.37, 100.74, 68.44, 34.02, 29.71, 29.63, 29.53, 29.33, 29.13, 26.19. Synthesis of 1 bromo 3,5 bis(oct 7 en 1 yloxy)benzene (37). 3g (15.9 mmol) of 5 bromobenzene 1,3 diol ( 30 ) 6.58g (47.6 mmol) of potassium carbonate, .66g (4 mmol) of potassium iodide, 6.66 mL ( 7.58 g, 39.7 mmol) of 5 bromo 1 pentene.

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102 Yield: 5. 15 79.3 % 1 H NMR (300MHz, CDCl 3 65 (s, 2H); 6. 35 (s, 1H); 5.9 5.75 (m, 2H); 5.05 4.90 (m, 4H); 3 .95 3 .85 (t, 4H); 2. 1 5 2. 00 (q, 4H); 1. 5 5 1. 70 (m,4H) ; 1. 50 1. 20 (m, 12 H) 13 C NMR (75 MHz, CDCl 3 ppm): = 160. 84 13 9 08 12 2 95 11 4 84 110. 3 4, 100. 70, 68.35 3 3 87 2 8 97, 26. 10 Synthesis of 1 bromo 3,5 bis(pent 4 en 1 yloxy)benzene (36). 3g (15.9 mmol) of 5 bromobenzene 1,3 diol (30) 6.58g (47.6 mmol) of potassium carbonate, .66g (4 mmol) of potassium iodide, 4.70mL (5.91g, 39.7 mmol) of 5 bromo 1 pentene. Yield: 4.42, 85 .8% 1 H NMR (300MHz, CDCl 3 (s, 2H); 6.40 (s, 1H); 5.9 5.75 (m, 2H); 5.05 4.90 (m, 4H); 3 .95 3 .85 (t, 4H); 2.35 2.15 (q, 4H); 1.95 1.80 (m,4H) 13 C NMR (75 MHz, CDCl 3 ppm): = 160. 80 137.77, 123.00, 115.52, 110.44, 100.80, 67.61, 30.23, 28.47. General procedure for b oron ation of benyl bromide (36 38). In a flame dried 3 neck round bottom flask, 1 equivalent of phenyl bromide was dissolved in dry THF under argon. The solution was cooled to 78C and 1.1 equivalent of n butyl lithium was added slowly. The solution was a llowed to stir at 78C for 1 hour than 1.1 equivalents of triisopropyl borate was added all at once. The reaction was allowed to rise to room temperature over 2 hours, then quenched with 1M HCl. The aqueous phase was extracted three times with diethyl eth er. The organic phase was then dried over magnesium sulfated and the solvent was removed via rotary evaporation. The crude produce was then purified via silica plug, hexanes were used to remove all impurities then the product was flushed of the silica with diethyl ether. The solvent was removed, first under vacuum to remove the bulk of the ether, then under argon flow to remove the

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103 remaining ether. The resulting solid was recrystallized from hexane. This yields pure boronic acid monomer in good yields. Syn thesis of (3,5 bis(undec 10 en 1 yloxy)phenyl)boronic acid (41). 2g ( 4.0 5mmol) of 36 1.78 mL ( 4.46 mmol) n butyl lithium), .84 g ( 1.03mL, 4.46 mmol) triisopropyl borate. Yield: .98g 53% HRMS: Actual [M+H ] + =459.3654 Theory [M+ H ] + =459.3645 1 H NMR (300MHz, d6 D MSO 7.95 (bs, 2H) 6. 90 5 (s, 2H); 6.45 (s, 1H); 5. 85 5.75 (m, 2H); 5.0 0 4. 8 0 (m, 4H); 3 .95 3 .85 (t, 4H); 2. 00 1.90 (q, 4H); 1. 75 1. 60 (m,4H); 1.50 1. 2 0 (m, 24H) 13 C NMR (75 MHz, d6 DMSO 59 38 13 8 88 114.32, 11 2 10 10 2 20 6 7 35 3 3 49 31.13, 29. 14 2 8 97 2 8 90 2 8 92 2 8 67 2 8 4 5 FT IR (ATR, cm 1 ) 3333, 2920, 2849, 1586, 1350, 1165, 1026, 907, 782. Synthesis of (3,5 bis(pent 4 en 1 yloxy)phenyl)boronic acid (39). 2g (6.15mmol) of 38 2.71mL ( 6.76 mmol) n butyl lithium), 1.27g (1.56mL 6.76mmol) triisopropyl borate. Yield: 1.07g, 60% HRMS: Actual [M+H ] + =291.1769 Theory [M+ H ] + =291.1765 1 H NMR (300MHz, d6 DMSO 8.08 (bs,2H); 6. 9 0 (s, 2H); 6.4 5 (s, 1H); 5.9 5.75 (m, 2H); 5.05 4.90 (m, 4H); 3 .95 3 .85 (t, 4H); 2. 20 2.1 0 (q, 4H); 1. 80 1. 65 (m,4H) 13 C NMR (75 MHz, d6 DMSO = 159. 36 13 8 13 11 5 29 11 2 15 10 3 32 6 6 77 3 9 78 28. 07 FT IR (ATR, cm 1 ) 3294, 2936, 2872, 1586, 1351, 1162, 1061, 913, 840. Deprotection of pinacol protected boronic acid via acid/base hydrolysis. In a round bottom flask, .5g of 4,4,5,5 tetramethyl 2 (2 (undec 10 enyl)tridec 12 enyl) 1,3,2 dioxaborolane (13) was dissolved i n a 6:4 ethanol:water solution. The water portion was either 3M HCl or 3M NaOH. The reaction was refluxed with stirring

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104 overnight, after which it was cooled to RT and neutralized. The solution was extracted three times with diethyl ether and the organic ph ase was dried with magnesium sulfate. The solvent was removed in vacuo and the residue was analyzed via NMR. No reduction in the integration of the methyl peaks associated with the pinacol protecting group was observed. Deprotection of pinacol protected b oronic acid via hydrogenation with In a Parr bomb equipped with a magnetic stir bar, 5g of 4,4,5,5 tetramethyl 2 (2 (undec 10 enyl)tridec 12 enyl) 1,3,2 dioxaborolane (13) was dissolved in approximately 30mL of toluene. 5 mol% of Wilk Parr bomb was sealed and placed under 600 PSI of hydrogen. The reaction was heated to 90C and reacted for three days. After three days the toluene was removed under vacuum and residue was analyzed via NMR. No reduction i n the integration of the methyl peaks associated with the pinacol protecting group was observed. Deprotection of pinacol protected boronic acid via hydrogenation with Pd/C. In a Parr bomb equipped with a magnetic stir bar, .5g of 4,4,5,5 tetramethyl 2 (2 (undec 10 enyl)tridec 12 enyl) 1,3,2 dioxaborolane (13) was dissolved in approximately 30mL of toluene. 5 mol% of Pd/C was added and the Parr bomb was sealed and placed under 600 PSI of hydrogen. The reaction was heated to 90C and reacted for three days. After three days the toluene was removed under vacuum and residue was analyzed via NMR. No reduction in the integration of the methyl peaks associated with the pinacol protecting group was observed. Deprotection of pinacol protected boronic acid via boron trichloride. In a flame dried three neck flask, .5g of 4,4,5,5 tetramethyl 2 (2 (undec 10 enyl)tridec 12

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1 05 enyl) 1,3,2 dioxaborolane (13) was dissolved in dry dichloromethane. 4 equiv. of boron trichloride was added drop wise to the reaction at 0C. The re action was allowed to warm up to RT and stir overnight under argon. The solvent as then removed in vacuo and the resulting residue was analyzed via NMR. No reduction in the integration of the methyl peaks associated with the pinacol protecting group was ob served. Deprotection of 4,5 diphenyl 2 (p tolyl) 1,3,2 dioxaborolane via In a Parr bomb equipped with a magnetic stir bar, .5g of 4,5 diphenyl 2 (p tolyl) 1,3,2 dioxaborolane (46) was dissolved in approximately 30m bomb was sealed and placed under 600 PSI of hydrogen. The reaction was heated to 90C and reacted for three days. After three days the toluene was removed under vacuum and residue was anal yzed via NMR. No reduction in the integration of the methyl ene pe aks associated with the protecting group were observed. Deprotection of 4,5 diphenyl 2 (p tolyl) 1,3,2 dioxaborolane via hydrogenation with Pd/C. In a Parr bomb equipped with a magnetic stir bar, .5g of 4,5 diphenyl 2 (p tolyl) 1,3,2 dioxaborolane (46) was dissolved in approximately 30mL of toluene. 5 mol% of Pd/C was added and the Parr bomb was sealed and placed under 600 PSI of hydrogen. The reaction was heated to 90C and reacted for three days. After three days the toluene was removed under vacuum and residue was analyzed via NMR. The integration of the methyl ene peaks associated with the protecting group were no longer observed. Complete deprotection was accomplished

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106 CHAPTER 5 Boroni c Acid and Ester Polymers 5.1 Background Polymeric systems containing boron centered Lewis acids have are used for a number of applications such as; polymeric Lewis acid c atalysts and catalyst support, sensors, stimuli responsive polymers and as f ilms in lithium ion batteries 89 91,112,117 120 As mentioned in the previous chapter, the Lewis acidity of the boron containing moiety can be tuned from weakly Lewis acidic boric acid to highly Lewis acidic alky, and aryl boran es J kle et al. has reported a system for synthesizing well defined polymers with a variety of boron containing Lewis acid pendant groups (Figure 5 1) 112 This method allows acc ess to a wide range of boron containing polymers via post polymerization functionalization.

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107 Figure 5 1 Synthesis of a variety of boron containing Lewis acids via post polymerization modifi cation 112 First, a phenyl trimethyl silane monomer is polymerized using a controlled radical polymerization technique. The resulting silane polymer is then reacted w ith boron tribromide to yield polyphenyl boron dibromide By exposing the reactive boron dibromide sp ecies to any number of nucleophiles, a catalogue of boron containing Lewis acid polymers have been synthesized. Moreover, the Lewis acidic sites were shown to be accessible by nucleophiles for potential use as catalyst support. 112 By taking advantage of the unique s tability of tetraaryl boronates, highly reacti ve catalysts can be protected 121 When tetraaryl boronates are attached to the polymer the stability an d processability of the catalyst/ boronate complex is increased. One method employed to incorporated boronates onto polystyrene beads was reported by Frechet et al. 122 In this example, a polymeric system wa s functionalized with covalently bound

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108 ammonium functionality, the counter ion was [B(C 6 F 5 ) 4 ] The polymer bead was then loaded with a metallocene catalyst. The catalyst activity was maintained as demonstrated by copolymerization of ethylene and 1 hexene. Another approach is to attach the tetraaryl boronate covalently to the polymer backbone. J kle et al. have prepared several amphiphilic block copolymers; poly(styryltriphenylbor ate b polystyrene ) and poly(styryltris(pentafluor ophenyl)borate) b poly styre ne via ATRP. The polymers were loaded with [Rh(cod) (dppb)] + (OTf) (Figure 5 2). The degree of loading was approximately 85%, confirmed via 1 H NMR 123 Figure 5 2 Tetraaryl boronate polymers used as solid support for catalysts Reprinted with permission from C ui, C.; Bonder, E. M.; Jkle, F. Journal o f the American Chemical Society 2010 132 1810 2. Copyright 2013 American Chemical Society. 123 Borate containing polymers have also found use as polyelectrolytes in lithium ion batteries. The Bazan group fabricated a bilayer p n junction of poly(fluorene co phenylene) containing a pendant cationic electrolyte with a fluoride counter ion. 124 The

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109 other layer is a conjugated polymer with a neutral pendant dimesitylbora ne, which is known to bind fluoride (Figure 5 3). Figure 5 3 Boron containing Lewis acid polymer used for ion conduction the fluorine anion jumps from the quaternary ammonium t o the boron causing a flow of ions Reprin ted by permission from Macmillan Publishers Ltd: Nature Materials; Hov en, C. V; Wang, H.; Elbing, M.; Garner, L.; Winkelhaus, D.; Bazan, G. C. Nature materials 2010 9 249 52 copyright 2010 124 When a curre nt is applied to the system, th e fluoride moved from the cationic layer to the neutral layer. This device displayed superior light emitting and current rectification performance. Boronic acids have been used in a number of polymers as stimuli responsive moietie s for applications such as drug delivery and glucose sensors. 89,125 I n drug delivery applications, diblock copolymers are made via RAFT polymerization. One block

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110 is a hydrophilic poly(dimethylacrylamide) ( blue); the other block consists of a boronic acid containing repeat unit (Figure 5 4). 126 Figure 5 4 Stimuli responsive boronic acid polymers for the encapsulation and release of small molecules ; at low glucose levels micelles are formed. As the glucos e levels increase, the polymer is fully dissolved. Adapted with permission from Roy, D.; Sumerlin, B. S. ACS Macro Letters 2012 1 529 532.Copyright 2013 American Chemical Society. 126 In an aqueous solution at low glucose concentrations the boro nic acid is uncharged and hydro phobic. This causes the polymer to form micelles with poly(di methylacrylamide) block on the outside, and the hy drophobic boronic acid block inside the micelle. As the glucose level increases the boronic acid converts to the tetrahedral charged boronate species and becomes hydrophilic. This causes the polymer micelle s to disperse into free polymer chains; releasing the contents of the micelle. Other stimuli can trigger similar results such as temperature and pH 125 Gamsey et al. has demonstrated the use of boron ic acids as a glucose sensor. This is ac complished by synthesis of a polymer containing a n anionic dye and a viologen attached to a boronic acid functional group (Figure 5 5). 127

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111 Figure 5 5 Use of boronic acid polymers as a glucose sensor ; under low glucose conditions the viologen can interact with the anionic dye, preventing fluorescence. However, when gluc ose binds to the boronic acid it allows the dye to fluoresce. Rep rinted with permission from Gamsey, S.; Suri, J. T.; Wessling, R. A.; Singaram, B. Langmuir : the ACS J ournal of S urfaces and C olloids 2006 22 9067 74. Copyright 20 06 American Chemical Society. 123 When the boronic acid is unbound the violo gen unit is in close enough proximity to the dye to prevent fluorescence. When bound glucose molecule, the boronic acid s becomes negatively charged and repels the anionic dye T his separates the quenching moiety from the dye allo wing the polymer to fluoresce. This has shown to be sensitive over a wide range of biologically use glucose concentration, from 2.5 20mM. All of the uses demonstrated here take advantage of the specific chemistry of boron. Many of the properties displayed by these boron containing Lewis acid polymers rely heavily on the polymer morphology. By using ADMET, precise boron containing polymers can be made. These precision polymer systems lead to unique morphol ogies which can elucidate the morphology of existing boron containing polymer systems, as well as potentially enhance their performance.

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112 5.2 Results and Discussion 5.2.1 Polymerization and Characterization of Poly( 4,4,5,5 tetramethyl 2 (4 ((tricosa 1,22 di en 12 yloxy)methyl)phenyl) 1,3,2 dioxaborolane ) (29). Monomer 29 was first polymerized with G1 using the bulk polymerization technique, but due to viscosity of the monomer and the resulting oligom ers, a M n of only 2500 was achieved. At this point ionic l iquids we investigated as a polyme rization medium (Figure 5 6). Figure 5 6 Polymerization of 4,4,5,5 tetramethyl 2 (4 ((tricosa 1,22 dien 12 yloxy)methyl)phenyl) 1,3,2 dioxaborolane ( 29 ) In this system 29 was dissolved in 1 b utyl 3 methylimidazolium hexafluorophosphate along with 1 mol% G1 The polymerization was run for a total of 96 hours. After precipitation, the polymer was analyzed via GPC resulting in a M n of 58,000 with a PDI of 1.86. This polymer was then analyzed for thermal characteristics via TGA and DSC (Figure 5 7 and Figure 5 8).

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113 Figure 5 7 P oly(4,4,5,5 tetramethyl 2 (4 ((tricosa 1,22 dien 12 yloxy)methyl)phenyl) 1,3,2 dioxaborolane) ( U PP29 ) is thermally stable up to approximately 350 C The TGA of the unsaturated polymer UPP29 demonstrates good thermal stability with no real decomposition until about 350 C followed by complete decomposition starting at about 400 C. The DSC of UPP29 disp lays a T g of about 23 C. When compared to the identically spaced phenyl phosphonic ester polymer produced by ADMET; the T g is comparable at 28 C. 47 As expected no T m was observed, this is due to the unsaturation in the backbone and the bulky non interacting pendant group.

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114 Figure 5 8 A T g for poly(4,4,5,5 tetramethyl 2 (4 ((tricosa 1,22 dien 12 yloxy)me thyl)phenyl) 1,3,2 dioxaborolane) ( UPP29 ) is observed at 23 C but no T m is seen Next the remain double bond were hydrogenated the remaining to yield a pure polyethylene backbone (Figure 5 9). While Pd/C is traditionally used for hydrogenation of the re sidual double bonds, it was avoided in this case due to its propensity to cleave the catalyst did cause cleavage of the benzylic ether pendant group This was determined v ia NMR by observing an increase in the relative number of backbone hydrogens in relation to the benzylic proton s. After this was discovered, a more tolerant non catalytic hydrogenation method was used. This method uses three equivalents of toluenesulfonylh ydrazide (TSH) and tri p ropylamine (TPA) disolved in o xylene. The reaction is attached to a bubbler and the reaction was refluxed until nitrogen was no

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115 longer observed evolving from the reaction vessel Another addition of TSH and TPA were added and reflux ed until no more nitrogen was released. The solvent was removed and the polymer was analyzed via NMR and IR to determine whether complete saturation was achieved and cleavage of the benzylic ether was avoided. The NMR showed no loss of the pendant group an d complete hydrogenation was observed. The IR however, showed there was remaining internal olefin s ( observ ed by the out of plane alkene C H bend near 967cm 1 ) 48 so the saturation was not complete. The polymer underwent several more rounds of hydrogenation but i nternal olefins were still observed, al beit in very small amount amounts Figure 5 9 Hydrogenation of poly(4,4,5,5 tetramethyl 2 (4 ((tricosa 1,22 dien 12 yloxy)methyl)phenyl) 1,3,2 dioxab orolane) ( UPP29 ) Use catalyst caused cleavage of the pe ndant group. Stoichiometric hydrogenation with TSH, however, preserved the pendant group.

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116 The (mostly) hydrogenated polymer SPP29 was then analyzed via DSC (Figure 5 10). This polym er also displayed no melting temperature; however the glass transition temperature was shown to increase to about 11 C. This is consistent with the T g of the identically spaced phenyl phosphonic ester polymer. 47 The endotherm seen at 36 C is not seen in the unsaturated polymer, it is believed to be caused by the precision nature of the polymer. This allows the phenyl boronic ester penda nt groups to stack and creating their own melting endotherm. This hypothesis is supported by the work from Watson et al. 63 They report a precision polymer with a phenyl ring on every 19 th carbon displays similar behavior, presumably from the phenyl ring. Figure 5 10 A T g observed for hydrogenated poly(4,4,5,5 tetramethyl 2 (4 ((tricosa 1,22 dien 12 yloxy)methyl)phenyl) 1,3,2 dioxaborolane) ( SPP29 ) at 11 C. Another thermal transition is observed at 36 C most likely caused by the stacking from the phenyl rings

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117 5.2.2 Polymerization and Characterization of In Chain Boronic Acid Polymers (SPP39 41). While the polymer with pendant phenyl pinacol boronic ester demonstrates some unique thermal properties, the inability t o exhaustively hydrogenate t he backbone limits the precise nature of the polymer. To solve this, another polymer system was devised (Figure 5 11) Figure 5 11 Precise polymerization of in chain boronic acid monomers ( 39 41 ) The resulting polymer s were insoluble, so molecular weights could not be obtained In an attempt to characterize these polymers, FT IR with an ATR attachment was employed. Figure 5 12 compares the IR spectra of 41 and UPP41 Figure 5 12. IR of 41 (blue) and UPP41 (red).

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118 The IR of UPP41 when compared to the monomer 41 displays many similarities, however, the differences between the monomer and polymer yield insights into nature of the polymer. The first difference is the intensity of the O H peek at about 3450 CM 1 ; in the monomer this peak is fairly intense and well defined, however in the polymer this intensity and the definition of the peak is greatly reduced. This indicates that some of the boronic acids may have formed the boron anhydrides mentioned earlier. This effectively crosslinks the polymer, leading to the insolubility observed. The next difference in the polymer is the disappearance of the peak at about 800 CM 1 and the formation of the peaks at about 700 and 850 CM 1 This change indicated the reduction in terminal olefin in the compound and increase in both the cis (700 CM 1 ) and trans (850 CM 1 ) internal olefins, indicative of polymerization. Similar results were obtained from UPP39 Figure 5 13. Ther mal stability of UPP39 (blue) and UPP41 (red)

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119 The thermal stability of UPP39 and UPP41 was then examined using thermal gravimetric analysis (TGA). Both polymers demonstrate good thermal stability, maintaining 90 weight% until over 313 C and 353 C respecti vely. These decomposition temperatures are consistent with many unsaturated ADMET polymers, especially polymers containing acid and ester functionality. Figure 5 14. Thermal transitions of UPP39 (blue) and UPP41 (red) Finally, the two polymers were cha racterized via differential scanning calorimetry (DSC). UPP39 displayed no T m which is consistent with shorter ethylene spacers between functional groups and unsaturation in the backbone. The T g of the polymer was 2 C. The glass transition temperature was fairly high when compared to other ADMET polymers; however a fairly high percentage of the polymer backbone was the ridged phenyl ring which can increase the T g UPP41 displayed a significantly lower T g then UPP39 around 28 C, this was expected since th e relative concentration of phenyl ring in the back bone is much lower. In contrast to the DSC of UPP39 ; UPP41 did display a

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120 T m at approximately 68 C. The peak is fairly broad indicating a variety of crystalline species that melt at slightly different temp eratures. Interestingly, the first heating cycle of UPP41 displayed a much sharper melting exotherm This could be the result of the polymer annealing for long periods of time above the T g causing rearrangement into a more thermodynamically stable conform ation. The presence of a melting temperature was unusual in an ADMET polymer wi th unsaturation in the backbone. The crystallinity in this case was presumably due to presence of free boronic acid. 5.3 Conclusions By using the monomers synthesized in chapte r 4, both boronic acid and boronic ester polymers have been formed via ADMET The boronic ester polymer was polymerized using both bulk and ionic liquid polymerization techniques. Bulk conditions resulted in very low molecular weights, however using ionic liquids; high molecular weight polymers were formed. Upon saturation of the residual double bonds in back bone of the polymer, unique thermal behavior has been demonstrated. Boronic acid polymers with 20 and 8 carbons between each functional group have al so been made. These polymers have proven to be intractable, probably due to chemical crosslinking formed by formation boron anhydrides under vacuum conditions. These polymers were characterized via FT I R. These IR spectra indicate that the repeat unit rema ined intact and the terminal olefin of the monomer disappeared and internal olefins were observed. These polymers demonstrate good thermal stability and unique thermal properties, presumably due to the boronic acid functionality. Due to the insolubility of these polymers, further characterization was not possible.

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121 5.4 Experimental 5.4.1 Materials and Instrumentation 1 Butyl 3 methylimidazolium hexafluorophosphate was purchased from AK Scientific and purified via a neutral alumina plug followed by degassing via freeze pump thaw in triplicate. All other materials were purchased from Aldrich and used without further purification unless noted. Grubbs 1 st and 2 nd generation catalyst (G1 and G2) as well as Hoveyda Grubbs 1 st and 2 nd generation catalyst (HG1 and HG2) were kindly provided by Materia, Inc. Anhydrous solvents were obtained from an anhydrous solvent system. All 1 H NMR, and 13 C NMR were obtained on a Varian Mercury 300MHz spectrometer and recorded in CDCl 3 1 H and 13 C chemical shifts were referenced to signals from CDCl 3 Mass spectrograms were carried out on a Thermo Scientific DSQ MS. Elemental analyses were carried out by Atlantic Microlab, Inc. Thermogravimetric analysis (TGA) was performed on TA Instruments TGA Q1000 Series using dynamic scans unde r nitrogen. Differential scanning calorimetry (DSC) analysis was performed using a TA Instruments Q1000 series equipped with a controlled cooling accessory (refrigerated cooling system) at 10 C/min. Differential scanning calorimetry (DSC) analysis was per formed using a TA Instruments Q1000 series equipped with a controlled cooling accessory (liquid nitrogen cooling system) at 10 C/min. Gel permeation chromatography (GPC) was performed at 40 C using a Waters Associates GPCV2000 liquid chromatography syste m with an internal differential refractive index detector and two Waters Styragel HR 5E columns (10 m PD, 7.8 mm i.d., 300 mm length) using HPLC grade THF as the mobile phase at a flow rate of 1.0 mL/min.

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122 5.4.2 Procedures General procedure for ADMET poly merization in ionic liquids. Under constant argon flow, 1 equiv. of boron containing monomer was added to flame dried Schlenk flask equipped with a magnetic stir bar. Also under constant argon flow 1.5mL of 1 b utyl 3 methylimidazolium hexafluorophosphate was added. .5 1 mol% of Grubbs 1 st generation catalyst was then added to the reaction mixture. The reaction was then placed under high vacuum and polymerized for 48 hours at 50 o C. At this time another .5 1 mol% of G1 was added to the reaction and polymeriz ed for another 24 48 hours at 50 C. After the requisite time the reaction was quenched with a solution of 2mL of ethyl vinyl ether in 10mL of toluene. The ionic liquid was extracted twice more with toluene. The organic layer was separated from the ionic l iquid via pipette and the solvent removed under vacuum. The polymer was then dissolved in a minimal amount of toluene and precipitated into 250mL of cold ethanol or methanol The polymer was filtered out and thoroughly characterized via NMR, DSC, TGA, and GPC. Polymerization of 29 in ionic liquids. .5g of 29 1mol% of G1 1.5 mL of 1 butyl 3 methylimidazoium hexaflourophophate, reacted at 50 C for 48 under vacuum. Another 1mol% of G1 was added and reacted under vacuum for another 48 hours. M n : 58000 g/mol 1 H NMR (300MHz, CDCl 3 (d, 2H); 7.40 (d, 2H); 5.40 (m, 2H) ; 4.55 (s, 2H); 3.4 (m, 1H); 2.10 2.00 (q, 4H); 1.75 1.10 (m, 44H) 13 C NMR (75 MHz, CDCl 3 ppm): = 142.67, 134.97, 130.14, 127.01, 83.84, 79.22, 70.70, 34.02, 33.99, 30.04, 29.81, 29.76, 29.69, 29.34, 29. 14, 25.17, 25.04. Hydrogenation of 29 via TSH and TPA. 1 equiv. of UPP29 was dissolved in dry o xylene in a flame dried 3 neck flask. 3 equiv. of p toluenesulfonyl hydrozine (TSH) and tripropyl amine (TPA) was then added and the reaction vessle was equipp ed with a

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123 reflux condenser and an oil bubble. The reaction was refluxed until no nitrogen was observed being released from the bubbler, about 3 hours. Another 3 equiv. of TPA and TSH was added and refluxed. This was repeated twice more. The reaction was th en cooled, and the solvent removed. The resulting residue was then disolved in a small amount of toluene and precipitated into cold ethanol. The polymer was collected via filtration and dried under vacuum yielding SPP29 1 H NMR (300MHz, CDCl 3 80 (d, 2H); 7.40 (d, 2H) ; 4.55 (s, 2H) ; 3.4 (m, 1H); 1.75 1.10 (m, 50 H) 13 C NMR (75 MHz, CDCl 3 ppm): = 142.67, 134.97 127.01, 83 .84, 79.22, 70.70, 30.04, 29.81, 29.76, 29.69, 29.34, 29.14, 25.17, 25.04. Polymerization of 39 in ionic liquids. .25g of 39 1mol% of G1 1.5 mL of 1 butyl 3 methylimidazoium hexaflourophophate, reacted at 50 C for 48 under vacuum. Another 1mol% of G1 was added and reacted under vacuum for another 24 hours. The insoluble polymer was filtered from the reaction. FT IR ( ATR CM 1 ) : 2910, 2840, 1600, 1375, 1175, 840, 710 Polymerization of 41 in ionic liquids. .25g of 41 1mol% of G1 1.5 mL of 1 butyl 3 methylimidazoium hexaflourophophate, reacted at 50 C for 48 under vacuum. Another 1mol% of G1 was added and reacted under vacuum for another 24 hours. The insoluble polymer was filtered from the reaction. FT IR ( ATR CM 1 ) : 3450, 2920, 2800, 1600, 1325, 1140, 840, 710

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124 CHAPTER 6 Summary and Future Work 6.1 Summary The work herein displays the use of boron containing Lewis a cids in various olefin metathesis applications. Ionic liquids were also studied as new reaction medium for acyclic diene metathesis polymerization. Boron containing Lewis acids were first studied for their effect on the variou s Grubbs and Hoveyda Grubbs catalysts. Grubbs catalysts have displayed increase yields in the presence of the appropriate concentration of pinacol phenyl borate The Hoveyda Grubbs catalysts, which do not contain phosphine ligands, predictably do not display any increase in yields. S urprisingly, Hoveyda Grubbs 2 nd generation catalyst displays a decrease in conversion Since this effect is not seen with Hoveyda Grubbs 1 st generation catalyst, it is proposed that Lewis acid interacts with N heterocyclic carbine, destabilizing the cataly st. The products were also analyz ed for isomerization. The reactions run with catalysts prone to isomerization, Grubbs and Hoveyda Grubbs 2 nd generation catalysts, displayed a dramatic decrease in isomerization. This study demonstrates the utility of boron containing Lewis acids in olefin metathesis. Next the use of 1 butyl 3 methylimidazolium hexafluorophosphate was studied for application as a new reaction medium for ADMET polymerization. A concentration study found that .5 mol% catalyst loading was idea l for reaching high molecular weight polymers. By keeping the reaction in solution, maximum molecular weight s were reached in 48 hrs. Purity of the ionic liquid was found to be very important; any residual imidazole will prevent the formation of polymer A ddition of phosphoric acid however, allowed the polymerization to proceed. Addition of a boron containing Lewis acid did not

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125 prevent imidazole from shutting down the polymerization, but did increase molecular weights when added to the polymerization under other conditions. Solubility of the monomer in the ionic liquids plays an important role, when the monomer is only minimally soluble low molecular weights are obtained. However, at higher temperatures, above the monomers melting point, high molecular weig hts are obtained. Syntheses of boronic acid monomers have proven to be a challenge. First alkyl boronic acid monomers were attempted, however, due to instability of the monomer, this approach was abandoned. Next a variety of aryl boronic acid monomer synt heses were attempted. Using this approach a variety of boronic acid and ester monomers ha ve been synthesized. Deprotection of boronic acid was also studied. The pinacol protecting group has proven difficult to remove, however, benzylic protecting groups we re observed to cleave under hydrogenation conditions using Pd/C. Using the precision monomer s synthesized above, precision polymers were then made. The pendant phenyl b oronic este r polymer was polymerized using Grubbs 1 st generation catalyst and molecular weights of 58000 were obtained. Upon hydrogenation, the glass transition temperature was increased, also a n endotherm associated with the pendant phenyl ring was observed. 6.2 Future Work 6.2.1 Analysis of B oronic A cid P olymers via X ray S cattering Now t hat the precise boronic acid polymers have been synthesized they can be studied to determine their morphology. As mentioned previously, both the precision carboxylic acid and phosphonic acid polymers have shown unique morphologies only seen in the precisi on polymers. Carboxylic acid polymers pK a of about 4.75, demonstrated a hydrogen bonded layered morphology, while the phosphonic acid

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126 polymer pK a of about 1, demonstrate d more ionic character. Since boronic acid polymers are the least acidic, their morph ology should be different still. This work will be carried out by our collaborators in Karen Winey group at University of Pennsylvania 6 .2.2 Synthesis of other B oron C ontaining Lewis A cid M onomers A variety of other precision boron conta ining Lewis a cid monomers can be synthesized (Figure 6 1 ). These polymers display a wide range of Lewis acidities, boronic acid being the lowest, pinacol boronic ester in the middle, and triphenyl borane being the most acidic. The morphology of precise acid polymers demonstrates a dependence on the acid pKa, ranging from ionic aggregates to hydrogen bonded dimers. Is this true for aprotic Lewis acids? The purpose of this study is to determine how the morphology of a polymer is affected by the Lewis acidity of the pend ant group Figure 6 1. Synthesis of boron containing Lewis acid monomers ( 42, 44 ) Two other monomers are proposed to be synthesized, the boronic ester and diphenyl borate monomers. The synthesis of these monomers woul d be largely the

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127 same as the synthesis for the boronic acid monomers ( 39 41 ) Lithiation could then be conducted using the isopropoxyboronic acid pinacol ester instead of the tripropyl borate for the boronic ester monomer. T he diphenyl borate monomer could be synthesized by conducting the lithiation with diphen ylboronic anhydride ( 43 ) as the boron ating agent. Figure 6 2. Precise polymerization and hydrogenation of 2 (3,5 bis(undec 10 en 1 yloxy)phenyl) 4,4,5,5 tetrameth yl 1,3,2 dioxaborolane ( 42 ) Once these monomers are synthesized they can be polymeri zed using ADMET polymerization, followed by hydrogenation of the double bonds (Figure 6 2 and 6 3). The morphology can be studied using X ray diffractio n and the therm al properties can be analyzed Figure 6 3 Precise polymerization and hydrogenation of (3,5 bis(undec 10 en 1 yloxy)phenyl)diphenylborane ( 44 )

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136 BIOGRAPHICAL SKETCH Chester (Chet) Kent Simocko was born in Bar Mills, Maine in 1986. He is the son of Gertrude Kent and Robert Chris Simocko. After graduating from Bonny Eagle High School, he began studying chemistry as Rensselaer Polytechnic Institute (RPI) in Troy, New York He studied the use of waste cellulose for new green polymers under Prof. James Moore for 2.5 years and synthesized fluorescent displacer for use in displ acement chromatography under Prof. Steven Cramer for 1 year. In 2008 he graduated from RPI with a Bachelors of Science in c hemistry and move to the University of Florida (UF) to pursue a PhD in chemistry. He decided to join the Wagener group and pick up work with the acid project, synthesizing precision boronic acid polymers. T his project is done in collaboration with Dr. Karen Winey at University of Pennsylvania. During his time at UF he developed a collaboration with Dr. Timothy Swager at the Massachus etts Institute of Technology (MIT) studying the use of ionic liquids on olefin metathesis. He enjoy s cycling, having twice completed the Horse Farm Hundred Century ride, as well as home brewing and is a member of the Hogtown Brewers. He has won numerous aw ards in homebrew competitions from all over the state of Florida.