Syntheses of heterocyclic compounds containing B-N coordinate bonds as models for thermally stable polymers

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Title:
Syntheses of heterocyclic compounds containing B-N coordinate bonds as models for thermally stable polymers
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McCormick, Charles Lewis, 1946-
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Polymers -- Thermal properties   ( lcsh )
Chemistry thesis Ph. D
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Thesis -- University of Florida.
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Bibliography: leaves 134-139.
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Typescript.
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Vita.

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5':;:T :F:.: OF H.TE: .'CYCLIC COrMPOUNDS CONTAIMNiI B--N COCRINA[E

B9C.....- AS MODELS

FOPR TI: I-.L:.Y STABLE POLYMERS











CHARLES LEWI MCCOR!ICK III









A DISSERTATION PRESENTED TO Th-E G -))ADUATF 7U0J;CEL 0, TE JNIVE-T: *F

FLOPIDA IN PASTA FULLILL T OF REQI 'L.i'' "'LT

OCR THE DEGRE OrF DOCTORR G FHIL.SuPH


t' r~; -'''




















This dissertation is dedicated in memory of

Mr. Claude Stuart

who dedicated his life to teaching chemistry

in the Greenville, Mississippi, Public School

System.

















ACKNOWLEDGEMENTS


I wish to express my gratitude and appreciation to Dr. G. B. Butler

for his patience, guidance, and understanding during the course of this

research. My appreciation is also extended to Dr. T. E. Hogen Esch, Dr.

Paul Tarrant, Dr. Martin Vala, and Dr. Henry C. Brown for serving on my

supervisory committee.

Grateful thanks are extended to my colleagues in the laboratory for

their frienship and good humor, which made work quite enjoyable.

The financial assistance received from the National Science Founda-

tion is gratefully acknowledged (grant number GH32766 and GH17926i)

I also wish to thank my parents for their support and encoragement

during my graduate studies.

A special expression of gratitude goes to my wife, Pat, for her love,

encouragement, and assistance in completion of this project.














TABLE OF CONTENTS


Page


Acknowledgements..... ... .

List of Tables .

List of Figures. .

Abstract. vi

Chapter

I. IIITF.CDUCTI .

A. Polymers Exhibiting Principles of Thermal Stability
B. Boron-Nitrogen polymers .
C. Boron-Oxygen Polymers .
D. Boron-Carbon Polymers. .. ..
E. Amine-Boranes as Hydroborating Agents .
F, Boron-Nitrogen Coordinate Bonds in Cyclic and
Bicyclic Compounds .... .
G. Statement of Problem .

II. SYNTHESES OF UNSATURATED TERTIARY ANILINES .

A. Syntneses of Para-substituted-N.N-Diallylanilines
B. Synthesis of N,N,N',N'-Tetraallyl-p-
phenylenediamine .
C. Synthesis of N,N-Di-3-butenylaniline .


III. 'FFiPAF.'iION OF BORON INTERMEDIATES .


Synthesis of Grignard Reagents
Preparation of Substituted Pbenylboronic Acids
Syntheses of Borate Esters of Substituted
PhenylDooronic Acids . .
Cyclotriboroxenes . .
Preparation of Triethyl- .- fr.-!;, Lboranes
Preparation of Pyridine-Phenylborane .













IV. SYNTHESES AND REACTIONS.OOF BORON HETEROCYCLES 31

A. Reaction of Triethylamine-Phenylborane with
N,N-Diallylaniline .. 31
B. Mechanism of Formation of Azaborolidines and
Azaborabicyclo(3.3.O.)octanes .. .35
C. Deuterium Labeling Studies 41
D. Preparation of 3-Deuteropropene by an
Alternate Method .. .. 50
E. Preparation and Reactions of p-Substituted 1,5-
Diphenyl-l-aza-5-borabicyclo(3.3.0. )cctanes 50
F. Preparation of Bic-L,L4-[L5-( 4-m-ethylphenyl.)-1-
aza-5-borabicyclo(3.3.0.)octyl]benzene and
Bis-1.,4-[5-( 4-chlorophenyl )-l-aza-5 -borabicycio-
(3.3.0.)octyl]benzene .
G. Reaction of N,N,N',N'-Tetraallyl-p-phc.ylene-
diamine with p-Phenylenediborane .. 62
H. llBoron Nuclear Magnetic Resonunc Studies .
I. Temperature Studies by Differential Scanning
Calorimetry 64
J. Synthesis of 1,6-Diphenyl-"-a.zt-6-borabic,'..-
(4 4.0.)decans .
K. Conclusions .. .

V. EXPERIMENTAL .

A. Equip,:tert and Trx:-atment: of a,t: 7-
B. Syntheses and Characterizaton 7'



2i li.ography .


Biograph ica Ske. tch


. *0i
















LIST OF TABLES


Table Page

1 Skeletal Bond Energies 4

2 Substituted 1,5-Diphenyl-l-aza-5-borabicyclo(3.3.0)octanes
and i,2-Diphenyl-1 ,2-azaborolidines 54

3 Physical Data of Substituted 1,5-Diphenyl-l-aza-5-bora-
bicyclo(3.3.0)octanes 55,56

4 Spectral Data of Substituted 1,5-Diphenyl-l-aza-5-bora-
bicyclo(3.3.0)octanes 57,58
















LIST OF FIGURES

Figure Page

1 Nmr Spectrum of 1,5-Diphenyl-1-aza--5-borabicyclo(3.3.0)-
octane 34

2 Infrared Spectrum of 3-Deuteropropene 45

3 Nmr Spectrum of 3-Deuteropropene 46

4 Infrared Spectrum of 3,7-Dideutero-l,5-diphenyl-1-aza-
5-borabicyclo(3.3.0)octane 48

5 Nmr Spectr'un of 3,7-Dideutero-l,5-diphenyl-i-aza-5-bora-
bicyclo(3.3.0)octane 49

6 Nmr Spectra of 1,5-Bis-(4-cblocropheiiyl)-i-aza-5-bo'a-
bicyclo(3.3.0)octane and 1,2-.ic-(4-chlorophenyl)-1,2-
azaboroli.dine 60


















Abstract of Dissertation Presented to the
Graduate Council of the University of Florida in Partial Fulfillment
of the Requirements for the Degree of Doctor of Philosophy

SYNTHESES OF HETEROCYCLIC COMIPCUOIOD CONTAINING B-N COORDINATE
BONDS AS MODELS
FOR THERMALLY STABLE POLYMERS

By

CHARLES LEWIS MCCORMICK III

June, 1973

Chairman: Dr. G. B. Butler
Major Department: Chemistry

The major goals of this research were to exaAine the mechanisnI of

tha reaction of triethylaimine-phernyloranrT. with NN-d- alylani.L:' i a"-

to extend this reaction to the preparation of compounds which could be

utilized for the synthesis of high molecular weight, thermally stable

pclymers.

1,5-Diphenyl-l-aza-5-borabicyclo (3.3.0) octane, 1 ,2-d.phernyl-, 2-

azaborolidine, and propene were isolated as the major products of the

reaction of triethylamine-pheny Iborane with N,N-diallylaniline. Thes-

compounds were characterized by nuclear magnetic resonance, infrared,

mass spectroscopy, and elemental analyses.

Two mechanisms were proposed for the forration of propene arnd

l,2-diphe.nyl--1,2-azaboro Lidine.

Triethylami ne-dideuterophanriyboran-;? ,a prepsard anri s'bsequelntly

reacted with N,N--diallylanilin'e to give 3,7-dideutero-i,5-diphenyi-l--aza

5-borabicyclo( 3.0) octane, 3-deutero- 2--diphieny1- 2- xa;borolidiTie,









and 3-deuteropropene. These products were consistent with one of the

proposed mechanisms, a concerted, facile elimination of propene. This

elimination mechanism was supported by model studies of the transition

states.

Triethylamine-phenylborane was reacted with N,N-di-3-butenylaniline

to give 1,2-diphenyl-l-(3-butenyl),2-hydro-azaboracyclohexane and 1,6-

diphenyl-l-aza-6-borabicyclo(4.4.0)decane. No butene gas was eliminated,

giving further support for the proposed mechanism.

Several substituted derivatives of 1,5.-diphenyl-l-aza-5-borabicyclo-

(3.3.0)octane were prepared. The B-N coordinate bonds in these compounds

were studied by nuclear magnetic resonance, 1B nuclear magnetic resonance,

infrared spectroscopy, and differential scanning calorimetly. The B

chemical shifts in these ccrapounds varied from 2.2 to 6.0 p.p.m. relative

to trimWethylborate. The B-N coordinate bonds e:xhibited absorb'inc-, near
-1
1275 cm. Temperatures for the dissociation of the boron-nitrogen coor-

dinate bond, determined by differential scanning calorimetry appeared to

be near 5200 K. The heats of dissociation of the B-N bond for bis-l,4-

[5- 4-methylphenyl)-l-aza-5-borabicyclo(3.3.0)octyl]benzeue, and bis-1,4-

[5- (4-o-'~.o ophenyl)-l-aza-5-borabicy.lo(3.3.0)octyl]benzene were calciu-

lated to 28.5 krai/m-ole and 30.3 kcal/zioli,, respectively.

Sev-eral substituted derivatives of i,5-diphenyi-i-aza-5-borabicyclo-

(.3.3.0)octane were prepared which are excellent monomer precursoTs for

condensation polymerization.


v .1i.
















Chapter I

INTRODUCTION

A. Polymers Exhibiting Principles of Thermal Stability

The demands of the space program, and more recently the garment

industry, have led to extensive research in the area of thermally stable

polymers and flame retardant polymers.

Ladder polymers, 1, or double-stranded polymers have been made

which show good thermal stability. The increased thermal stability of

these polymers was attributed to the added stability cf the ring systems.

Cleavage must occur twice within a given ring of the polymer for chain
1,2,3,4,5
degradation. i,2 ,4,5












.1

Recently, ladder polyamerrs cabls in air above '09' C and based

on ,inyJ-acetylenes, have been p -paro.

Hete.roatom pclyners show a higher resistance to oxidative degra-

d.cion at elevated telera:ture's. keletl bonds, s'nch as Al-0, Si-O,

Si-N, P-N, B-0, and 3-N, might: b cxpected to show resistance to ther-

mal oxidation, and polymers wicih r.hei:e units should be --ore inert ra

high temperature. Bon c.A is:i:, ..c:rgies arc given in Table









Polyphenyleneoxadiazoles, polyphecQylenetriazoles, polyphenylaee-

thiazoles, and polybenzimidazoles have been shown to be capable of

forming thermally stable films aid fibers.8,9,10,11 Another series of

thermally stable heterocyclic polymers, 2, was prepared by the conden-

sation of 3,3'-diaminobenzidine with tetrabutyl esters of diboronic
12
acids.





NH--/\ -\N \

I NH ./ "NH



2
13,14
butler and Stackman demonstrated the high resistanc" of

cyclic polydia.lylriphenyl silanes, 3, to thermal degr-a-atici. Po..-

atrs ;containiag bodith eteroatonm stability aid "ladder' ralili.y 'i-

been prepared by the hydrolysis of phenyltrichlorosilane in ai o.rg c ic

solvni1

Ph Ph


"' -- L .-' *- I- --
S1


0J





3

i recent yvet:s, a number of hete;o:or3 a riug and chain syyste.;s';,

sucI; as; carbazeno, 4, orazenes, 5, phosphazenes, .6, bcr~oeaes, .,

si.lo-':na"e-, n3, ad silazanes, 9, have sho.:n remarkable therial st .biity.









I \/

V./B P

"C"/ N
S4 5 I 6

S\/,S Si
0 0 0 0 NN N
I I I I

7 8 9


This stability has been interpreted in terms of resonance stabili-

zation inherent in these systems. An intensive investigation into the

possibilities of incorporating these compounds into polymers for flame
16 .17
retardance is currently of top priority in the fibers industry.

.-:trcatom polyiners containing C-N, C-0, B-N, F-C, P-N, Si--N, and Si-0

bonds have been reiewLed.

Tberaoplasti.: ccati-gs and fibers have been prepared from cyclic

polys loxanes, Methylphenylcyclotetrasiloxanes have been polym..ri:ed to

give polymers with thermal stability dependent upon phenyl substitution.

He~eroato:m pclymers containing boron have been known for Tiany years.

Boric oxide consi..-s of a three-dimensicnal network of distorted 30,

retrahedra. HexagRorna boron nitcide, _10, has a hexagonal layer struc-

ture and is som-atl n ca.ll.d ,h.ite graphite. These materials have ex-

cellent th er:i. ability 2'"h0'0C) and other useful. properties whii

bave coamnerci.ai utility. Th iey have stimulated research efforts toward
N N



.- .. ', -,

i i
















TABLE 1. SKELETAL BOND ENERGIES (kcal/m.ole)


128

106.5

106


89

86

85.,

82 .6


Bond

Si-C

C-N

Si-S
P=N

P-N
P-C

C-S

Al-C

S-N


Bond

C=N

Al-- 0

B-0
B--N

Si-O
Si-N


P-O

C--C
C--C:


S-0


D

",50

80




68

68
-'70


9,104


91i


83


E

IV78

72.8

'v70

68-76




65

61
"'6 c

,55





5



high molecular weight polymers based on boron. Certain phases of boron

chemistry also find their counterparts in the technologically important

area of silicon chemistry. Since the bond energies of boron-oxygen

(~130 kcal) and boron-nitrogen ('100 kcal) are high, there should be

high temperature applications.

Most polymeric boron compounds have not been characterized ade-

quately. Little information is available on reactivity, molecular
20,21
weights, and solubility in many cases.2



B. Boron-Nitrogen Polymers
22
Since the discovery of borazene and its stability at 500C,22

mai-y publications have appeared attempting to incorporate this com-

pound into thermally stable polymers. Reviews covering all phases

of borazene chemistry may be found in the literature. An impor-

tant aspect of borazene chemistry is the strong driving force for

formation of cyclotriborazenes from dehydrogenation of substituted

amine-borane adducts (Scheme I).

SCHEME I
-2
PNH2 + H2BR' ---- R2 N-->BH2R' --- rN-.-' '
(1) Monoborazans (2) Monoborazeac




3 \


H 2 H
R' R' -3H (4)
I I /

H A --.-3H. ()/

Cyclotriborazane R- B-R'


Cy clotri -raze
Cy clotril 2r"zene.:









The monoborazine would be electronically unstable and should form

polymers. However, the stabilizing influence of suitable bond angles

and n-bonding in the cyclic trimer favors this homologue.

Three main avenues have been investigated for the formation of
19
boron-nitrogen polymers. The first involves the opening of various

borazene rings, and the second, reactions of the unstable mcnoborazines.

The final method has been an attempt to link borazene rings in an

ordered fashion, avoiding cross-linking.

As a general rule, cyclotriborazenes do not undergo ring opening

to liear polymers, However, the polymerization of N- and/or B-methyl--,

ary]-, or triazinylcyclotriborazenes in a closed system at 3500 to

600'C, oc in the presence of catalysts, led to hard, glassy, irsolub~le

resins.' No molecular weight was given. An open-chain, low

,o.leccular weight polyiser of the structure, (PhB-NC4H9)n, where n=20 to 40

was prepared by rhhe reaction of pheny1borondichloride with isobucyi.amias."

Ctross-.lin2ked polymer was formed by the pyrolysis of B-trichloro-N--tri-'

arlcyclotrlborazeues, (C6-BAr) 3, from room temperature up to 500"C."

r'y,:.oboraene rings, havpb been linked to give polymers, ,1 of high

mol.cuiar weight. Benzene solivle polymer i7as formed fhan ;yycloborazene
27
vings ware linked by :oe process:2



Me Me !

n i + 2n KC5.
.-.N -. N.-Hs- hen B..h :.
;.I Bu
n
1.1



Cvc3tr'iboraznc- : rics ,hav,, a.l.so bee :inked v react etg dio!p ithi








N-triphenylcyclotrihoraane: 28




Ph h
HBP B H -
2 I i + HO(CH2)200H -2B. 20
PhN BNPh PhN 2BNPh
H 6(CH2 )2


12


Other examples have been reported in which B,N'-dichlorocycletri-

borazenes and diamines reacted to give polymers stable up to 250-

300CC.29 Copolymers have been prepared by the free-radical poly-

merization of B-trivinyi--N-triphenylcyclotriborazene wich styrene

and methyl methacrylate.30 The reaction of aniline with an equi-

molar concentration of trimethox'-yclotriborexene was reported to
31
give a poly :er with the following structure:


OMe


S0
.B ----- N

13 h -n

High boiling diamines have been known to polymerize upon

heati'-ng with various alkylborates. For example, ethylenediamiine

reacts with tri'ethyLbcrate to givw" a polymer with the following
32
structure: -
i i
N-- --B -
S/ ,

!jn









The reaction of p-aminophenol and tripropoxyborane resulted

in the formation of a resin. The structure assigned to the poly-
33
mer was:



B NH 0- -- --NH -- --- B
j n

15



C. Boron-Oxygen Polymere

Oligomeric compounds containing boron-oxygen links have been

made by heating al ky.-- or arylboronic acids. Most of the resulting

compounds are easily hydrolyzed, although they exhibic remarkable

thermal stability. As in the borazene series, the trimers, cyclo-

triboroxenes, sec. To be the most favored thermndyaa;micaly.y Cycle.

triboroxenes have bce'n reported to have 10-20% aroima-.ic chadrcrx:e.








.23 17


35
boronic acids under !vauu',- le first ainhydrlde of phenyiboroni.

acid was prepared in 1836 Te structure of triphenycyclotri-
G 37




38
phenylboronic acid yielded th cyclic triTer:

ChOOCOPh',

D '~Ci









Cyclotriboroxenes disproportionate to boric oxide and trialkyl or
39
triaryl boranes at elevated temperatures. This fact seems to

rule out the possibility of ring-opening polymerizations of these

cyclic trimers.

Benzenediboronic acids have been prepared as starting materials

for polymerization. These acids were formed by the extension of the

synthesis of phenylboronic acid, 19.,41



-gBr (1) (CH30)3B -B(OH).
(2) H30
19

42 40
Diboronic acids were prepared by Nielsen4 and Musgrave43 by

reaction of a bis-Grignard reagent with trimethylborate in tetra-

hydrofuran. Subsequent hydrolysis yielded the diboronic acid, 20.



2(0H)B- --B(OH)2


20

Polyesters from diboronic acids have been reported, but no mo3!ecular

weights were given.4 Mixtures of boric acids with glycols gave high

molecular weight polymers. No structure det.erminations were made,

alti;'..",h cross-l-inking is inevitable in these systres. Polymeric
,'6
glycol borates and esters of borcnic acids have hben studied. A

careful steady of the condensation reactions of orthoboric aci-3l with
47 48
diols has also been made. RecenLly, Svarcs a.t al. reported th-

preparation of a copolymer, 21, of pentaerythritol and boric a.cid.


!0

I c








D. Boron-Carbon Polymars

Polymers containing only boron and carbon are rare. Tri-n-

hexylboron decomposed on heating to produce two polymeric materials.4

A dark solid was assigned the structure [-B(C6H13)BH-]nand a vis-

cous liquid [-B(C6H13)-(C6H12)-B(CHI13)-In Pyrolysis of Me2BCH2CHIa Me2
50
yielded trimethylboron and polymers with the following structures:0



B-CH-CH-B -- -CH2--CHi B / -
1, \_2 -
I n
22 23

A patent has been awarded for the synthesis of a polymer, 24, pre-

pared by reacting a boron halide or ester with the di-Grignard of
51
p-dibrotobenzrne.

-2-B

OH
IIn

24

Several other polymeric boron-carbon compounds have been re-
ported.21,52,53,54
ported.




55
The first organoboranes were synthesized in 1862 by FranklanAd

by tle reaction of diaikyl zinc compounds with Lriethylborate. He

He observed the ability of these boranes to coordinate with ammonia.

Since that time countless papers on other boron-nitrogen coordi-

nation compounds have appeared.

Koster first utilized triethylaiine-borane in 1957 in the hyiro-









boration of cyclododeca-l,5,9-triene. Hawthorne57 observed that

pyridine borane would react with olefins in diglyne at 100C to pro-

duce trialkylboranes. Nielsen58 observed that phenylborane readily
59
disprcportionated to triphenylborane and diborane. Hawthorne59 pre-

pared pyridine and triethylamine adducts of phenylborane and aryl-

substituted phenylboranes which were white crystalline materials stable

in air and had melting points from 50 to 80*C. Pyridine- and tri-

ethylamine-alkylboranes0 and -arylboranes59,61 were prepared by the

presence of the amine bases.

Hawthorne reported the reduction of substituted cyclotriboroxenes

by lithium aluminum hydride and the presence of pyridine, trimerhyl-

amine, or triethylamine to give the corresponding amine-bcranes.

Ashby64 reacted several trialkynamine-boranes with olefins to

form trialkylboranes in 78--95% yields.

The mechanism for hydrobor.ltion by amine-boariic is believed ;:o

involve the rate determining dissociation of the smine-borane. A

sufficiently high temperature is required for the dissociation of the
65
B-N bond.65 B-H addition can then proceed via the boron p-orbital

interaction with che T-elect-rcns of the olefin (Schem.e II).66

SCHEME II

:.' -R RN + RMH,




--. -
S--C--.-
tBH/2 + ..=.. ... = -- --- -- C--- C -
H ---- -H.....uuR

P,








Cyclic boranes were prepared by Koster6768 by the reactions of

trialkylamine-boranes with diolefins. Hawthorne9,70 reacted trimethyl-

amaine-t-butylborane with a number of olefins and diolefins. Reaction

with divinyl ether and divinyl silane gave corresponding heterocyclic

compounds.

The coordination compounds formed by substituted alkyl- and aryl-

borons with amines have been studied relating steric factors to B-N

bond stability. Heats of dissociation of the complexes of trimethylboron

with various amines are all about -7.26 0.21 kcal/mole.7

Aaine-boranes may undergo dehydrogenation to give monoborazenes

or aemnoboranes (Scheme I). When B-trimethylborazane, 25, was heated
72
to 2800C under 20 atm.. pressure, B-dimethylborazena, 26, was forqpd.

1his compound was further dealkylated to yield B-trimethylcyclotri.-

borazene, (HN-BMe)3, Both of the above steps required cbe eliim ati-.on

of :.ethaiv.



H3N-BMe ------- N-BMe CH
3 3 Me. 2 4 t
25 26


Further examples of elimination were the formation of B-a-llyl-
73
vonoborazenes by the following reactions:



-:B(C 3 ------.- EtN-B(C + C h

27

H3N+B(C3)3 -------- f ,2N-B(C3H5)2 + C3


Pyrol.-:. of amine--phenylborane adducts leads to aminoboranes. The









heating of diethylamine-phenylborane at 80--110C under vacuum resulted
7 Lk
in 88% yield of diethylaminoborane, 29.'




Et2NH-BH2Ph -- H2 + Et2N-BHPh

29



Several papers were presented dealing with amine-boranes and

aninoboranes at an international symposium on boron-nitrogen chemistry.7

Heteroaromatic boron-nitrogen compounds have also been reviewed in
7,75
some detail.



F. Cyclic and Bicyclic Compounds with Boron-Nitrogen Coordinate Bonds

The bicyclic ester, 30, formed by the azeotropic dehydration of an

equimolar mixture of l,l,l-trimethy.letLhane and boric acid was re-

ported in a patecrn in 1959.76 This compound upon heating yielded a

glassy polymer.
/ 0
C-- ------- Polymer

--0


Similar bicyclic compounds bad been prepared by 3rown in 1951

by the reaction of trit.anolam~ne vi.th boric acid'. 'he prodlu;:t was

a white crystalli:ne solid, m.p. 236.5-237.5C. Two possible struc-

tures were proposed:

---. -I



\ C\ \ \,i
)--B--0 C) -V--yB~-~G









In the cage structure, 31, boron maintains trigonal coplanar hybridi-

zation. In the second structure, 32, a transannular boron-nitrogen

interaction gives boron sp hybridization. Triethanolamine borate

was concluded to have structure 32 on the basis of unreactivity with
77
methyl iodide as compared to quinuclidine, 33, and triethanolamine.






H 33



Further evidence for the B-N transannular bond was found in the 11B

nuclear magnetic resonance chemical shift, relative to boron tri-

fluoride etherate, of triethanolamine borate, which is found at

higher fields (6-10.7) in aqueo'us solution than most aikyl- and aryl-

borates (6-14 to 6-19). The shift was interpreted to be due ;-o

increased sl.iel'i.g around the boron atom as a result of B-N 'r : 'ir,g

mad, therefore, increased tetrahedral character and number of bonding

electrons around the boron atom.

Later studies showed that an equilibrium could exist bet w ern

structures 31 and 32. In water and butanol the equiliibrium mixture

contained 20% of the tetrahedral species, 32, and in aprctic solvents

95% of the tetrah2dral for. Iquil.ibrium s tudics of the estr-

ification of 1:oric acid -ith triethanol.amine indicate a shift in

eq.ii.ibriu- tr ard structure 3. w0 th an -icrhesze in tefperatu-re.

Zi.merman reported the resultS off -ydril;vysis exi-erilments on bcrox-

azoldinCs." H -elated T.he -T bond stc.nc tn to rat s of hydroyivis

for several c- .'n.-i ic.itudii. aze following, 34-37:












B -- C)0
0.


R


NI
0--.B 0/


Ph --<-N---CHK-CH-- --?--Ph
/ \ 2 2
0 j0


Sf83,84,85,86 83,36,87,8,889,0
A vir.ety of boronates, b.or.inat?, >*
91,99
triisopropylamine borates 99 have been postulated to ha;-r tra;ns-

annular boron-nitrogen bonds. Syntheses directed towa-;d boron-

containing amino acids for cancer chemotherapy have led to prepa-

ration of a series of substituted trietlanolamine borates. -' i -

isopropy1-91,92 and tri-n-propylamine borates have also been s uiJ.ed.

Substituted aryl boronic acids and 2-aminoethanol were heat-6 in

toluene to give the corresponding diethanolamiine arylborate,:, 4;0.",



Ar -- B<-NH
/ \

40


Recently polymers with improved antistatic properLies and flame

resistance were prepared by addition c f B-N ircllsioan .irpcunds. Fcr


R,



R- --0
R









example, the following compound (3% by weight) was mixed with poly--
95
et0hylene:95


/ MZie -CH-2 OPh
PhOCH 2- 0 CH2Ph
\06 39


Adams and Poholsky96 prepared the first reported 1,2-aza-boro-

cycloalkane, 41, by reacting N,N'-dimethyl-allylamine with triethyl-

amine-borane in toluene. The following structure was assigned:

CH I
CH --- B N H
3




97
In 1963 White reported the synthesis of 1-methyl-2-phenyl-

1,2-azoboro.id:lne, 42_, and 2--2phenyl-!,9--azboracyc che-an.', -3-, fr.:

the reactions of triethy lamine-pher'ylboraae with N-!'.ethylailyl-n.-i

and 3-butenylaiine, respectively.



( N1

Ph___ 'B H--N 3___., f P...--- F h
P- i B











Ph h
t;12 i3

In i95o3 Statton and Butler o reported t he foni.-ation of .& ef.'j.rs

substituted aza-3-borabiryclo(3.3,0)octane
of diallyletiryJ amire with crimethylam ne-phenyhborane yielded com--

pounds with the following structures:
Ph


N"--./ k ....-- N '.








The B-N coordinate bond in the bicyclic compound, 45, was believed
-l
responsible for a strong infrared absorbance at 1266 cm. The
-l
azaborolidine, 44, showed strong peaks at 1512 cm.- which were at-

tributed to the =N bond. 11B resonance signal in the nmr spec-

trum of 44 was recorded at -23 p.p.m. and of 45 at 8.9 p.p.m. rela-

tive to trimethylborate.

In 1965 Butler and Statton99 reported the preparation of four

substituted l-aza-5-borabicyclo(3.3.0)octanes and four previously

unreported 1,2-azaborolidines. These compounds were prepared by the

reaction of triethylamine-phenylborane with tertiary diallylamines.

A mechanism for the reaction was proposed based on qualitative data

which involved the cleavage of an allylic carbon-nitrogen bond. Two

of the 1,2-azaborolidines were also prepared by the reaction of tri-

ethylaziine-phanyiborane with secondary allyla.ines. The l-aza-5-

borabicyclo(3.3.0)octanes exhibited strong infrard absorption bands

at 1250-1270 cm.-, which were assigned to the B-N coordinate bond.

A new compound, 1-phenyl-1-bora-5-azoniaspiro(4.5)decane, 46, was

prepared as well as a telomer, 4Y.



Ph 3 6
---B
,....


A new bicyclic .icoipound containing a B-P coordinate bond was
100
prepared having the following structure:



<0>P 0>)
i _.j)"' -- ,/









G. Statement of Problem

The major goals of this research were to examine the mechanism

of the reaction of triethylamine-phenylborane with N,N'-diallylaniline

and to extend this reaction to the preparation of compounds which could

be utilized in the synthesis of high molecular weight, thermally stable
101
polymers.

The first step was to prepare 1,5-diphenyl-l-aza-5-borabicyclo-

(3.3.0)octane, 49, and 1,2-diphenyl-l,2-azaborolidine, 50, (R,R'=H) to

serve as models.




k -R-~^' RB=N --(=--= N---R'


50
49

The next step wuuJd be to e.a.in; i-. ,chaaistica:!ly -h-:.- o r ncot

formation of 49 and 50 occurs in a competitive -manner, 01hvioirsly,

this reaction requires loss of three carbon units for formation of

50. Since no gaseous products or other products consistent with
S102
this three-carbon chain had been previously detected, one goal

w.is ro isolate and identify :;his product.

After i.ni:ial investigation begau, it became obvious that deu-

terium labeling st.udics would be necessary. Therefore, an idea wa.r

conceived which would differentiate between two possible mechanisms.

Ano::ber goal .a.3 pr-inarat-.on of several selected derivatives of

f9, both for -synthetic purposes and property studies. Substituents

should have ielectrcnic and stacic .ffec-:s on the re.laive yields of

49 and 50. The boron.- it.o.en coordinat-. bond could be detected









by infrared, 1B nuclear magnetic resonance, and proton magnetic

resonance. The B-N bond dissociations for the various compounds

could be followed by differential scanning calorimetry. These

studies should have important meaning when extended to polymeric

systems.

Another important objective was the study of the stability

of these compounds to various conditions necessary for introducing

functionality for monomer formation.

The ultimate objective of the boron research in these labora-

tories is the incorporation of the bicyclic structure into several

thermally stable polymeric systems, 51.




SI
(CH,) r(CH )





(CH 2x H2
'. 2,,
5_1

These polymers should have some i:tult tst'irn properties. Thermal

dissociation of the dati-re bonds along the polymer backbone could

oczur without cleavage of the polyTer chains, alliing the polym'er

chain to "breathe" or function liK bellows. This cleaavage should

result in an iLncrease in the dei-r.;- of freedom along the longUI udin-'

axis of the polymer chain, and should impart additional elasticity

to the polymer.
















Chapter II

SYNTHESES OF UI Sj'ATED TERTIARY ANILINES

A. Syntheses of Para-substituted-NN-Diallylanilines

p-Substituted-N,N-diallylanilines, 52, were prepared by the
103
method of Butler and Bunch.0 3-Bromopropene was added dropwise

to a slurry of sodium carbonate and the para-substituted-aniline

in water. The reactions were allowed to proceed at 100 C for 24

to 48 hours. The resulting organic layer was separated, dried, and

vacuum dis killed,




--H,( -:- 2 3-bromoprcpene -- X- )


52


The lol. owing compounds were prepared by the above method:

N.N--diallyla.nline, 37.6%; p-bromo-N,N-diallylariline, 74.5%;

p-.lc ro--N :::-I -.. -I l.lanil ine, 72.5% ; p-me thyl-N ,N-diallylaniline,

70 .1a; and p-methoxy-N.,.-diallylaniline, 88%

The ccrr spending se-ondar' :,onoallyian.ilnes were also ob-

t:Aine-d: fror, early .ractitns in the di.sillation.



B. Sy z h.iofN N' -T etralyl -p- henLvenediamine

p-Pnen)ilnediaminfe was i; ic.ed ,'t:ith 4 moles of allylbromide

in a slurry of sodium carbonate in water. The resulting viscous,

syrupy siatarial. wes diluted with water and the organic layer ex-

/ r\









tracted in ether. This solution was filtered, dried over sodium

sulfate, and then distilled under vacuum yielding a pale yellow

liquid (46.5%, b.p. 138-140* C @ 0.55 mm.).



C. Synthesis of N,N-Di-3-butenylaniline

N,N-Di-3-butenylaniline was prepared using a similar proce-

dure as in preparation of the other diallylanilines. 4-Bromo-

butene was added dropwise to a slurry of aniline in sodium car-

bonate in water. The organic layer was extracted, filtered, and

vacuum distilled yielding a colorless liquid (37%, b.p. 74-75 C

@ 0.10 mm.),

















Chapter !II

PREPARATION OF BORON INTERMEDIATES

A. Syntheses of Grignard Reagents '

The boron intermediates were prepared by modifications of

procedures reported in the literature (Scheme III).

The mono-Grignard reagents of bromobenzene, p-dibromobenzene,

p-chlorobromobenzene, p-methylbromobenzene, p-methoxybromobenzene,

and p-ethoxybromobenzene were prepared by reacting the substituted

bromcbenzenes with an equimolair quantity of Ta!nesi.m in diethyl

ether, dried over zcdium. The substituted bromobenzene was added

dropwise at a rate which maintained a jow reflux.. In each reaction,

a small crystal of iodine or i d:op of ethylenabromicde was necessary

to initiate the reaction. T1.:e induction periods varied froTm 10 to

40 minute .

An attempt was made to prepare the Grignard reiaent of p-bromo-

phenylbenzyl ethei. T1'r. ether wvs prepared by reeccing p-bromophenol

with benzylch..rid.e in acetone, .'te reutin-lg p7brtiphenylbenzyl

ether was recrysta,'lized twice from hot netlhno!. It wzas then diS-

s,-Ived in diethyl ethai, distilled from lithium a.lum'-num hydride.

Initial addition of the p-braphenylbenyl, et'-he to the -.>c.;n:liun

did not result ir iny -caction.r Cystals of iodii.r : :-d ethylene

bromide were employed to initiate the reaction. However, the addition

of further p-bromophenylbenzyv ether appea're to stop tche reaction.

Entrai~nenit and heat were eiloyed,I yet tt: re-.c:iOer' c;Old not be
































: tOH
---A-


\ / H


S-0 3(OH-)3

/- 2)


t /I) LiAH4

:4 2):;NE3


ic--
/ ;


r,0
C'l


Scheme III









forced. Only a small amount of the magnesium reacted. Perhaps

another solvent, such as tetrahydrofuran, might yield better results.

The bis-Grignard reagent was prepared from p-dibromobenzene,

Tetrahydrofuran was employed as a solvent. It became necessary to

control the heat evolved in the reaction with an ice bath. The high

viscosity of the resulting Grignard reagent presented problems in

filtering and addition through the small opening in the dropping

funnel.



B. Preparation of Substituted Phenylboronic Acids

The phenylboronic, or phenylboric, acids, 53, were prepared by

the reaction of substituted phenylmagnesium bromides with trimethyl
104
borated, followed by hydrolysis.04


(CH 0)3B H 30
X-,- MgBr --- -- X- -B(OII) + 2CH^OO


53


The trimethyl borate was added to dry diethyl ether and cooled under

nitrogen to -70 C in a dry ice-isopropanol bath., The appropriate

substituted phenylmagnesiumbromide was then added s3cwl' to the stir-

ring mixture. Too fast an addition resulted in formation of sub-

stituted biphenyls from coupling reactions, The resulting white solid-

slush was hydrolyzed slowly oy dropwise addition to the reaction mix-

ture, cooled in an ice bath. Addition without the ice bath resulted

in formation of a large yield of the substittutje t-rihenylCyclo-

triboroxine, 54. The cyclotriboroxenes were probably fo-nred by the

acid catalyzed dehydration of the phenylboro-ic ;cids. 53.










+ VhX

3 X ( B(H H30 /Bo
S(OH)

XPh N 0- PhX
53 54

The crude phenylboronic acids were recrystallized from hot

water. The following boronic acids were prepared by the above

method: phenylboronic acid (m.p. 214-216 C, 88.8%), p-chloro-

phenylboronic acid (m.p. 280-281" C, 83.5%), p-bromophenylboronic

acid (m.p. 271-2720 C, 93.5%), p-methylphenylboronic acid (m.p. 255-

2570 C, 31.0%), p-methoxyphenylboronic acid (m.p. 200-202* C, 69.0%),

and p-ethoxyphenylboronic acid (m.p. 120-122 C, 68.5%).

p-Phenylenediboronic acid 0was prepared by addition of a

tetrahydrofuran solution of the bis-Grignard reagent of p-dobromo-

benzene i-o a solution of trimethyl borate in tetrahydrofuran i.lder

nitrogen and cooled to -700 C. Addition presented problems due Lo

the thick, milky texture of the Grignard reagent, The resulting

solution was hydrolyzed with 15% sulfuric acid to give p-phpnyl-

diboronic acid (m.p. >3150 C, 74.5%).



C. Syntheses of Borate Esters of Substituted Phenylboronic Acdid

The substituted phenylboronic acids were converted to the-

corresponding dierhyl esters, 5_5, by reaction with ethanol, followed
106,107
by azeotropic distillation.10


x 5-- B(5(OH)2 + EtOH + H, 0

53 55









After all water had been distilled, the remaining solvent was re-

moved from the crude esters. The esters were then distilled under

vacuum. The following esters were prepared: diethyl phenylboronate

(b.p. 68-69 C @ 0.35 mm., 90%), diethyl p-bromophenylboronate (b.p.

76-77 C @ 0.25 mm., 41%), diethyl p-chlorophenylboronate (b.p. 92-

930 C @ 0.75 mm., 65.3%), diethyl p-methylphenylboronate (b.p. 58-

590 C @ 0.15 mm., 93.2%), diethyl p-ethoxyphenylboronate (b.p. 130-

1350 C @ 1.5 mm., 40%), diethyl p-methoxyphenylboronate (b.p. 108-

1100 C @ 2.0 mm., 60%), and tetraethyl p-phenyldiboronate (b.p. 102-

104 C @ 0.35 mm., 41%). Several of these esters have not been re-

ported previously in the literature.



D. Cyclotriboroxenes

After distillation of the substituted diethyl phenylborcaate, a

whitee residue remained in the distillation flask. These residues ve:e

recrystallized and examined by nmr, ir, and analyses. The nmr speztra

showed intense aromatic resonance signals in the 6 7.0 to 6 7.3 region.

The infrared spectra showed intense absorption in the 1350-1450 cMu.

regicT. assigned to the B-0 asymmetrical stretching modes. The melting

points were extremely high. The compounds were identical to those

formed by the dehydration of the substituted phenylboronic acids under

heat and vacuum. On this basis and elemental analysis, the structures

were assigned to be the corresponding substituted triphenylcyclocri-

boroxenes, 56. The following reaction would explain product formation.
PhX

0' 0 56
3 X-( -B(OEt) --- > + 3 EtOH
'- PhX o FhX









Several cyclotriboroxenes were recovered as by-products from

the distillation of their parent esters: triphenylcycloboroxene,

tri(p-bromophenyl)cyclotriboroxene, tri(p-chlorophenyl)cyclotri-

boroxene, tri(p-methylphenyl)cyclotriboroxene, tri(p-ethoxyphenyl)-

cyclotriboroxene, and tri(p-methoxyphenyl)cyclotriboroxene.

The distillation of tetraethyl p-phenyldiboronate yielded a

tan-colored solid which did not melt and was insoluble in all

common solvents tried. In acetone nte compound swelled and even-

tually became gel-like in structure. In analogy with the formation

of cyclotriboroxenes, 56, the compound was assumed to be a poly-

meric, 3-dimensional network, 57.

r0h
/B-

r i I.
B--- Ph OP Ph
IL -' /0
i I


57
Ph

/ \\

E. Preparation of Triethllamine-Phenylbor-anes

Several new triethylamine-phenylboranes, 58, were prepared by

modification of the method of Hawthorne. The p-substituted diethyl

phenylboronates were reduced in. the presence of triethyilamine at low

temperature under nitrogen. The reactions were carried out with slow

addition of the diethy phenyiboronate to a mixture of lithium a],in-

inum hydride in diethyl ether and triethylamine. A"ter complete di-

tion, the mixture was allowed to warm to room temperature, Filrration

followed to remove the excess lithiiru alu-ninum hydride ::d other in-









soluble salts. The triethylamine-phenyiboranes were isolated by

cooling the filtrate to -70 C and quick vacuum filtration under

nitrogen.

Li-IIH 4B
X Q B(OEt)2 -, X-- -BH-2NEt3 + salts
NEt3

58

Several of the triethylamine-phenylboranes exhibited peculiar

properties on attempted filtration. For example, the triethylamine-

(p-bromo)phenyl-borane formed a solid (crystals) at -72* C in a dry

ice-isopropanol bath. On removing the ether solvent, these crystals

seemed to melt away. At room temperature only a white residue re-

mained. This reaction could possibly be a disproportionation to

p-bromotriphenylboron, iriethylamine, and diborane. Evidence

against disproportionaticn was that the residue was insoluble in

every solvent tried, and the infrared gas spectrum showed no diborane

evolved. The second possibility would be the elimination of ethane

across the boron-nitrogen coordinate bond to give the monoborazene.

This process, though, usually requires heac and vacuum conditions.

Also, no ethane gas was evolved,

The following compounds were prepared, which are relatively

stable at room temperature: triethylamine-phenylborane (m.p. 65-6b6 C,

73%), triethylamine-(p-chloro)phenylborane (m,p. 62-63 C, 75%),

triethylamine-(p-methiyl)phenylborane (m.p. S0-830 C, 869,.), triethyl-

ainine-(p-ethoxy)phenylborane (m.p. 63-64' C, 84%), and triethylamine-

(p-toethoxy)phenylborane (m.p. 63-64' C, 82%).










The triethylamine-(p-ethoxy)phenylborane and triethylamine-

(p-methoxy)phenylborane did, however, decompose after one week,

even under nitrogen. These compounds and triethylamine-(p-bromo)-

phenylborane could be kept in toluene or benzene solvents without

decomposition.



F. Preparation of Pyridine-Phenylboranes

An attempt was made to prepare the di(triethylamine)-p-

phenylenediborane, 59, by the same general method as described

above. Tetraethyl-p-phenyldiboronate was added dropwise to a cold

mixture of lithium aluminum hydride in diethyl ether and triethyl-

amine. After complete addition, the resulting mixture was allowed

to warm to room temperature and filtered. The filtrate was cooled

to -72 C in a dry ice-isopropenol bath. No crystals were foimed.

The solution was concentrated to one-half its volume and cooled once

more. Fine, white crystals formed. These crystals were found to be

unstable in nitrogen and were, therefore, kept in the solvent. The

nmr spectrum showed only one mole of triethylamine completed to the

p-phenylenediborane. The ir spectrum showed the B-H stretching ab-
-1
sorbance at 2200 to 2420 cm.


NtN HT- i --
3 2


59


It was thought that, perhaps, a different base, such as pyridine

with less face-strain, would complex more strongly with the p-phenylene-

diborane. The same general procedure was followed using pyridine as the

base. A yellow oil was obtained from the initial react:tjn.. This ol :as









crystallized from cold diethyl ether. A small amount of yellow crystals

(m.p. 60-68 C) was obtained. The crystals were unstable in air. The nmr

spectrum showed a broad multiple at 5 8.8, which was consistent with the

expected pyridinium resonance, and an aromatic resonance at 67.3. How-

ever, only one pyridine molecule was completed to the p-phenylenediborane.

A possible reason for the complexation of only a single base mole-

cule to the diborane could be a resonance or electronic effect. A signi-


B.-B B..-/ -B


60 61


ficant contribution from 60 would allow only single coordination with the

nucleophilic bases. This problem could possibly be eliminated by pre-

paring bis-boranes, 62, with insulation from electronic effects.









EtI- BI0 -32 Bp----^^
















Chapter IV

SYNTHESES AND REACTIONS OF BORON HETEROCYCLES

A. Reaction of Triethylamine-Phenylborane with N,N-Diallylaniline

Triethylamine-phenylborane was reacted with an equimolar quantity

of N,N-diallylaniline in refluxing toluene. After 12 hours, the

solvent was removed on a rotary evaporator. The residual, phospho-

rescent-green liquid was distilled under vacuum to give three fractions.

The first fraction proved to be unreacted N,N-diallylaniline. The

second fraction was identified as 1,2-diphenyl-l,2-azaborolidine; the

third was 1,5-diphenyl-l-aza-5-borabicyclo(3.3.0)octane. A gumy

residue in the distilling flask defied all attempts at purification

dile to its insolubility. These products were consistent with those
98,93
reported by Butler and Statton.9

Examination of the two major, isolated products of the above

reaction indicated that a unit of 3 carbon atoms was needed to complete

tne balanced chemical equation (Scheme IV). Statton100 had suggested

that the loss of an allyl group would give the 1,2-dipher'yl-1,2-azaboro-

lidine, 61-. However, he was unable to trap or detect any alkcne during

the course of the reactions studied.

Since ona goal included improving the yield of the bicyclic

compound, 63, over that of the monocyclic compound, 64, while studying

the mechanism of the reaction, ic became important to isolate the miss-

ing 3-carbon unit. The reaction outlined in Scheme IV was repeated.

This time, however, the apparatus was modified to include a gas outlet









Scheme TV


Toluene
reflux


-/ -


Propene


: NEt3


1-,2- Diphe:yl- ,2 ozaboro!idine

1,5 Dipheny -- zaa--boroaicyclo (3,3,0) octane









to an infrared gas cell. The triethylamine-phenylborane and N,N-

diallylaniline were dissolved in toluene in a flask equipped with

a magnetic stirrer and heater. The solution was slowly heated. Gas

samples, as well as solution samples, were taken at regular intervals

over a temperature range from 260 C to 1100 C. The boron-hydrogen
-l
bond absorbance at 2340 cm.- was monitored, and it was found that

the initial hydroboration occurred at approximately 500 C. Little

change occurred in the intensity up to 970 C. At this point, the B-H

absorbance decreased with time. The infrared gas samples gave the

best information. Only triethylamine and toluene vapors were observed

below 92 C. However, at 95 C the spectra began to show traces of
-3
propene gas. The broad, spiked peak at 910 cm. I was the most easily

followed absorbance. At 980 C large amounts of propene were being

pumped into the ir gas cell. The spectra were identical with the one

for propene given in the Sadtler Midget Edition, No. 6403.

After 12 hours, the green reaction solution was cooled, filtered,

and roto.;aced to remove the toluene. The viscous, green liquid was

transferred under nitrogen to a small, round-bottomed flask for vacuum

distillation. Again, the 1,2-diphenyl-1,2-azaborolidine, 64 (b.p. 8&-

860 C @ 0.30 imm.), was isolated. The nmr spectrum showed resoInance

signals at 67.2 (i, 10); 53.8 (t, 2); and 61.3 (n, 4), :corespc:ring

to the aromatic, carbon-5, and carbons-6 and-7, respectively (Figure 1),
-i
The infrared spectrum exhibited an absorbance at 1389 cm~-, which was

assigned to the boron-nitrogen double bond.

1,5-lipheny-l-l-aza-5-borabicyclo(3.3.0)oc-ane, 63, distilled as a

light ye.liow oil (b.p. 125-130' C @ 0.30 mm.). This compound was

rccrystallized from hot ethanol, yielding white crystals (m.y, 80~-81i' C)










I0

f 11












ppm (8
Figure 1. Nmr spectrum of 1,5diphenii 1aza5orabicyclo(3.3.0)octane
r i' i















4.0 3.o 2.0 1.0 0
ppm (8) t.)
Figure 1. Nmr spectrum of 1,5-diphenyl-l-aza-5-borabicyclo(3.3.0)octane









The nmr spectrum is shown in Figure 1. The aromatic protons give

resonance signals centered at 66.85 (m, 10). The a protons give

a multiple (area 4) at 63.35. The b protons exhibit a distorted

quintet (area 4) at 62.1. The c protons are assigned to the multiple

(area 4) centered at 61.1. All chemical shifts are relative to tetra-

methylsilane in deuterochloroform. The B1 nmr spectrum showed a

chemical shift at 3.6 p.p.m. relative to trimethylborate. This chem-

ical shift value is strong evidence for the boron-nitrogen coordinate

bond since increased shielding around the boron atom would result in

an upfield shift. The chemical shift value for diethylamine-borane

is 3.1 p.p.m. and for the 3.3.0. bicycloborate esters of triethanolamine

3.4 p.p.m,1
-1
The infrared spectrum showed a strong absorbance at 1285 cm. ,

which was assigned to the boron-nitrogen coordinate bond. The mass

spectrum showed a parent peak at 263 tl. The elemental analysis for

1,5-diphenyl-l-aza-5-borabicyclo(3.3.0)octane agreed with that cal-

culated for the model compound.

Anal. Calcd. for C8 H22 N: C, 82.13; H, 8.42; 3, 4.11; and N,
-- 10 z22

5.32. Found: C, 82.15; H, 8.51; B, 4.21; and N, 5.41.



B. Mechanism of Formation of Azaborolidines and Azabo1rabicYclo-
(3.3.0)octanes

The proposed mechanism for the reaction cf triethylaaine-

phenylborane with N,N-diallylaniline is outlined in Schemes V and VI.

The triethylamine-phenylborane, 65, dissociates to give the free

phenylborane, 66, and triethylamine, One of the allyl groups of the

N,N diallylaniline, 76, undergoes a single hydroboration to give the







Scheme V


I -5
H-aE~


'/

^xCH


+ :N(Et)3


I,---.. ~ N -5
~ ~/(


67


-C4

'-^/<--.--


4,-


~-- -


~-~














Scheme VI


.7n


\69


() ri"(2)
"'i' .


/' ."`
I, s ---F;-


+ prope ne


I

\ul
~









uncoordinated intermediate, 69. This involves a four-membered

transition state, 68. In solution there is probably an equilibrium

between the uncoordinated, 69, and the coordinated, 70, intermediates.

Above 90 C in toluene, competitive pathways (Scheme VI) would lead

to formation of the final products 71 and 72 (X=H). The 1,5-diphenyl-

l-aza-5-borabicyclo(3.3.0)octane, 72, could be formed by a second

hydroboration with boron adding to the terminal end of the remaining

double bond. This might occur by either pathway 1 or pathway 2.

Brown66 proposed a four-centered transition state for the general

process of hydroboration. Following this proposal, the transition

state for the coordinated fonr, 73, would have much more strain than

that of the uncoordinated form, 74. Therefore, it seems likely that

the second hydroboration proceeds along pathway 2,

Tle foi.r-tion of the 3,2-jiphenyl-1,2-azaborolidine, 71, is

accompanied by the elimination of propene gas. Amnine-boranes have
73
been reported to dealkylate at very high temperatures under vacuum,

as discussed in the introduction. Obviously, this system is a special

one which allows for very facile propene elimination at relatively

low temperatures, atmospheric pressure, ancr mild conditions.

The coordinated intermediate, 70, is perfectly si'ited for a

concerted elimination of propene as shown below:



-X--X X-: piopene
H7 71
70 71









A six-membered transition state would allow for a relatively

strain-free addition of hydrogen to the terminal end of the double

bond of the allyl group and the ensuing electron shifts.

A second mechanism may be proposed which would lead to the

same products (Scheme VII). The triethylamine in the reaction

mixture could act as a base in abstracting a proton in the 1,5-

diphenyl-l-aza-5-borabicyclo(3.3.0)octane, 72, at either of the

two beta-carbons to the quaternary ammonium group. This is the
109
well-known Hofmann elimination.0 The resulting allylborane, 75,

then could conceivably undergo a thermal cleavage to give the aza-

borolidine, 71, and propene. Alkylboranes have been reported to

undergo this type of thermal cleavage.64

The most important aspect of the concerted mechanism (Scheme

VI) involves the cquilibri~u between structures 69 and 70. This

equilibrium must likely exist for the competetive formation of

the mcnocyclic, 71, and bicyclic, 72, products. A stronger

coordination, or shift toward intermediate 70 of the equilibrium

should favor the monocyclic product. A shift toward the un-

coordinated form should yield more of the bicyclic product. The

most obvious studies, therefore, would be directed toward deter-

mining tihe electronic effects of substituents demonstrated beicw -

/ \\ ),-,



76 77

Electron-withdrawing subscituents in the para-position should

increase the electron deficiency on boron aTd would shift the equi-










Scheme VII


75









librium toward the coordinated form of the intermediate, 76.

Electron-donating substituents would be expected to have the

opposite effect. Electron-donating substituents on the aniline

ring would increase the basicity of the amine, resulting in

stronger coordination. Again, the opposite effect would be

expected for withdrawing substituents.

The Hofmann elimination mechanism would also be expected

to show similar effects of substitution. In this case, the

elimination would be possible only if the quaternized form,

72, were present.



C. Deuterium Labeling Studies

After several syntheses of substituted l,5-diphenyl-l-aza-

'-borabicyclo (3,3.0)octanes (discussed later in t!h-is 7-r ),

it was evident that substituent effects would not give a clear-

cut distinction between the concerted rrechanism and the Hofmann

elimination. Therefore, deuterium labeling studies were proposed.

If triethylamine-dideutero-phenylborane could be prepared, it

should then be possible to distinguish quite clearly the two pro-

posed mechanisms.

The proposed concerted mechanism is shown in Scheme VIII.

The triethylamine-dideuterophenylborane, 78,would dissociate to

give the free dideuterophenylborane, 79, which would undergo an

initial deuteroboration to give intermediate 80 and the coordinated

form of the intermediate, 81, by an equilibration of the two forms.

The deuterium ends up in the 3-position on the ring. A second

deuteroboration through pathway A would lead to the dideuterated











Scheme VIII





x-< )H-B--,.B3 --- <- ( xy .... -.,NEis
f_; g-- D:))-/ D


7- --9

79


-+ ,-x .--

67


,.1


DC cr~CH --CH 2


80
IA
i,


C ~---~






Scheme IX


1'hN t3


D



A
~g,,~


82
'0


ii
Cti-5'C CFAti









bicyclic product, 84. A concerted elimination, with deuterium

adding to the terminal end of the double bond in intermediate 81

and the ensuing electron shifts, wguld yield the mono-deuterated

azaborolidine, 82, and 3-deuteropropene, 83.

The expected Hofmann elimination mechanism is shown in Scheme

IX. The triethylamine in solution would attack the dideuterated

1,5-diphenyl-l-aza-5-borabicyclo(3.3.0)octane, 84, at a hydrogen

atom or deuterium atom on the beta-carbon to the quaternary nitro-

gen. Abstraction of a proton should be slightly favored over

deuterium abstraction, due to an isotope effect. Intermediate 85

could then undergo thermal cleavage to give the mono-deuterated

azaborolidine, 82, and 2-deuteropropene. If a deuterium were

abstracted rather than a proton, propene gas would be generated.

Triethylamine-dideuterophanylborane was prepared by reducing

dicthyl phenylboronate with litbiuni aluminu~n deuteride i-: ether

with triethylamine at low temperature. The triethylamine-dideutero-

borane crystals (m.p. 64-655 C) were characterized by mass spectral,

nmr, ir, and elemental analyses. The infrared spectrum showed a
.-1
broad boron-deuterium absorbance at 1680 to 1765 cm. .

N,N-Diallylaniline was added to an equimolar quantity of the

triethylamine-dide uterophenylborane in p-xylene. The reaction

vessel was provided with a gas outlet, which was attached to an

infrared gas cell and, in turn, to a dry ice--isoprcpanol gas trap.

Several gas samples were taken at: various temperatures. Above

950 C deuteropropene gas was evolved. The infrared spectrum is
-1
given in Figure 2. The absorbance at 2175 em. was consistent:

with that expected for the alylic carbon-deuterfrm stretching







WAVE'LENGTH IN MICRONS


2.7






60
1

i-


i


L




501-

40
iO-
30 j-
LI, t


53.00


25n00


WAVENUMBER CM"

Figure 2. Infrared spectrum of 3-deuteropropene.


.j- j.u~s;r;?:.


2000


i












lei















r .'c Hl II






~ I /
I i





Ij i ii

I ..4


--lr. J~~~~~ Ic.c.: ,!.. .~~... rr-Llr-* ---~-U-r j1^I -~
E 55.; .3G -.


Figure 3. Nmr spectrum of 3-deuteropropene.


"I
,~~










frequency. The mass spectrum gave a parent peak at 43, consistent

with the molecular weight.

The nmr spectrum (Figure 3) of the gas was obtained by adding

deuterochloroform to the trapped liquid propene. Resonances were

assigned as follow: the allylic protons at 51.7 (finely split

signal, area 2); protons a and b at 65.0 (finely split triplet, 2);

and proton c at 65.8 multiplee, 1). The above spectral evidence

surely indicates that the trapped gas was 3-deuteropropene rather

than 2-deuteropropene. 2-Deuteropropene would have shown no signal

in the 65.8 region and, of course, would not have shown the 2:2:1

integration pattern.

At this point, a model gas, 1-butene, was obtained to be sure

that the chemical shift assignments for 3-deuteropropene were correct.

The only expected difference in the two nnmr spectra would be the

added splitting due to the methyl group being substituted for

deuterium. The allylic proton signal moved slightly to 62.0 and was

a slightly distorted, finely divided quintet. The signals at 65.0

and 65.8 were almost identical to those of 3-deuteropropene.

The structure of the 3-deutero-1,2-diphenyl-l,2-azaborolidine,

82, was confirmed by mass, nmr, and ir spectra

The structure of the 3,7-dideutero-l,5-dipbeinyl-l-aza-5-hora-

bicyclo(3.3.0)octane, 84, was also confirmed by spectral data and

analysis of the high-boiling fraction (b.p. 64-680 C @ 0.15 mm.).

This material was recrystallized to give white, flaky crystals

(m.p. 78-79 C). The infrared spectrum exhibited absorbances

characteristic of the dipheny3-aza-borabiryclc(..3.0)octanes. In
-1
addition, the carbcu-deuteriumn absorbance appeared a'it 2150 cm.












WAVELENGTH IN MICRONS


3000
WAVENUMBER CM'Y


Figure 4. Infrared spectrum of 3,7-dideutero-l,5-diphenyl-l-aza-
5-borabicyclo(3.3.0 )octane.


2000



















i I









.... ..-.L _. .. .*- I I I 1 I I I I *
4.0 3.0 2.0 1.0 o


Figure 5. Nmr spectrum of 3,7-dideutero-1,5-diphenyl-l-aza-5-borabicyclo(3.3.0)octane.










(Figure 4). The nmr spectrum of 72 is given in Figure 5. Resonances

occur at 61.1 (m, 2); 62.15 (broad m, 1); 63.45 (m, 2); and the aromatic

resonance at 67.0 (m, 5). The mass spectrum gave a parent peak at
j-
265 -1, corresponding to the correct molecular weight. The analysis

agreed with structural assignment.

Anal. Calcd. for C8H20D 2BN: C, 81.52; H, 7.60; D, 1.52; B, 4.08;

and N, 5.28. Found: C, 81.74; B, 4.20; and N, 5.18.



D. Preparation of 3-Deuteropropene by Alternate Method

To cast aside any lingering doubts as to the identity of the

isolated gas, 3-deuteropropene was prepared by an alternate method.

The infrared and nmr spectra were compared.

Allylmagnesium bromide was added to deuterium oxide in a small

flask equipped with a gas outlet. Gas samples were trapped it' an

infrared gas cell. Samples for the nmr were obtained by liquefying

the gas in a trap, cooled by dry ice-isopropanol, and mixing with

deuterochloroform.

The infrared and nmr spectra were identical to those of the

3-deuteropropene, 83, obtained from the reaction in Schere VIII.



E. Preparation and Reactions of -Substituted 1, .5-Diphenv1-1-aza -
5-borabicyclo(3.3.0)ocranes

The next goal was the synthesis of a series of substituted 1,5-

diphenyl-l-aza-5-borabicyclo(3.3.0) octanes which would have functional

groups in the para-positions of the phenyl rings capable of conversion

to monomers.










The most obvious approach might appear to be that of electro-

philic aromatic substitution. However, boron is, in theory, a

better leaving group than hydrogen in these substitutions. Tri-

phenylboroxene was reacted with aluminum chloride and, also,

phosphorus pentachloride to yield benzene as the only identifiable

product.110 The boron atom on triphenylboroxene, or triphenyl-

cyclotriboroxene, however, might be a better leaving group than

the coordinated structure of the 1,5-diphenyl-l-aza-5-borabicyclo-

(3.3.0)octane, 63. Li 11 reacted 63 with acetyl chloride and

aluminum chloride to give acetophenone and other unidentified





+ X
C)
.63 ACI4 4










A second approach would involve nucleophilic aromatic substi-

tut.Icn. .,o major problems present themselves in this method. Both

are due to the stre:.gt'n of the bases employed in these substitutions.

If an equilibrium exists between the coordinated, 63, and un-

coordinated, 63A, forms of the bicyclic system, different chemical re-

activity would be expected for the two forms. Strong bases would be

expected to attack the electronically-deficient boron atom in struc-

ture 63A.











BN- Q '



63 63A


Structure 63 would be susceptible to Hofmann elimination by

strong bases as shown below:
H B




0 -


63

Some experimental data support the possibility of cleavage

of the bicyclic unit by the above mechanism. The 1,5-diphenyl-

l--aza-5-borabicyclo(3.3.0)octane system was destroyed by .'

reaction with butyllithium. The starting material was not

recovered, but tne products were not identified. Trinapthyl-
112
borane was reacted with methanol to give trimethoxybcrane.112

The only feasible approach in preparing 1,5-diphenyl--azn-

5-borabicyclo(3.3.0)octane with phany! substituents was to start

with the substituted bromobenzenes and to build the desired pro-

ducts. The synthesis of trietbylaitine-phenylboranes (Scheme III)

involves Grignards, acids, lithium aluminum hydride, alcohols,

heat, and Lewis bases. The preparation of substituted NN-diailyl-

anilines involves the heating of a sodium carbonate-water solution

to reflux. The desired substituents must also be readily converted

to monomer without destroying the bicyclic structure.










Preliminary studies of the 1,5-diphenyl-l-aza-5-borabicyclo(3.3.0)-

octane showed the stability to boiling water, dilute mineral acids, tri-

ethylamine, and dilute sodium hydroxide. The compound was not stable

to peroxides in sodium hydroxide or strongly acidic conditions. Oxi-

dizing conditions with bromine in acetic acid destroyed the bicyclic

structure.

Carbon-boron bond cleavage has been reported to occur with n-butyl-
113
lithium, bromine, peroxides, and acetylchloride in pyridine.1

Several previously unreported, substituted 1,5-diphenyl-l-aza-5-

borabicyclo(3.3.0)octanes were prepared along with their monocyclic

by-products. These are listed in Table 2. Each synthesis involved

essentially the same procedures as were outlined for the model com-

pounds. Some modifications were, however, necessary in nearly every

case due to the new functional groups. The average time required for

synthesis and isolation of each pair of bicyclic and monocyclic cos--

pounds was approximately 4 to 5 weeks. Physical properties, nmr, ir,

mass spectra, and elemental analyses are given in Tables 3 and 4 for

the bicyclic compounds. The details of each synthesis are given in

the experimental section and will not be repeated in this chapter.

Instead, the preparation of 1,5-bis-(4-chloropbenyl)-l-aza-5-borabi-

cyclo(3.3.0)occane. 93, and 1,2-bis-(4-chlorophenyl)-1,2-azaoor-lidine,

94, will be presented to give the reader an idea of the approach to

synthesis, separation, work-up, and analysis of these compounds.

Triethylamine-(p-chloro)phenylborane was dissolved in a large

volume of toluene in a round-bottopied flask under nitrogen. The

contents were heated to 550 C, and then the p-chloro-N,N-diallyl-

aniline was added dropwise to the stirring mixture. As the reactio-.










TABLE 2
SUBSTITUTED 1,5-DIPHENYL-1-AZA-5-BORABICYCLO-
(3.3.0)OCTANES AND 1,2-DIHENYL-1,2-AZABOROLIDINES


j )- Y
-\_. ^ _T


.1,-Diphenyl-l-aza-5-borabicyclo(3.3.0.)octane

Cpd. No. X

63 H H

87 H Er

89 H Cl

91 Ci HC

U. 3 Cl Cl

95 Br H

97 Dr Br

SCHI


'OC i, OCH3

1 "C3 ,CHC CCHI3
2 0


1,2-Diphenyl-1,2-azaborolidine

Cpd. No. X Y

64 H H

88 H Br

90 H Cl

92 Cl H

94 Cl Cl

96 Br H

98 Br Br

100 CH3 CIH

104 OC23 OCH3
102 OCH3 OCH

104 OCH2CH3 OCH3
23 3










TABLE 3. PHYSICAL DATA OF SUBSTITUTED
1,5-DIPHENYL-1-AZA-5-BORABICYCLO(3.3.0.)OCTANES


Cpd. No.


Name


63 1,5-Diphenyi-l-aza-5-
borabicyclo(3.3.0.)octane

84 3,7-Dideutero-1,5-diphenyl-1-
aza-5-borabicyclo( 3.3.0. )octane


87 l-(4-Bromophenyl),5-phenyl-l-
aza-5-borabicyclo(3.3.0.)octane



S9 i-(4-Chlorophenyl),5-phenyj-1-
aza-5-borabicyclc(3.3., )octane



91 l-Phenyl,5-(4-c l--. p.eiyl)-l-
aza-5 -borabicyclo (3.3.0.)octane


93 1,5-Bis-(4-chlorophenyl)-1-
aza-5-borabicyclo(3.3.0.)octane


Formula

C18H22BN


CI8H20D2BN



C H 21ENBr





18 21




C H2i ::C1



CI8H0 BNC12
1820 2


M.P.(0C)


80-81


78-79


Analysis (Calculated, Found)

C,82.13; H,8.42; N,5.32; B,4.11
C,82.15; H,8,51; N,5.41; B,4.21


C: C,81.52;
B,4.08
F: C,81.74;


116-118 C: C,63.19;
Br,23.36
F: C,63.11;
Br,23.24


95-96


93-95


C: C,72.63;
01,11.91
F: C,72.66;
C1.12.04

C: 0,72.63;
C1,11.91
F: C,72.59;

C: C,65.08;
C1,21.36
F: C,64.97;


H,7.60; D,1.52; N,5.28;

N,5.18; B,4.20

H,6.19; N,4.09; B,3.16;

H,6.29; N,3.96; B,2.90;


H,7.11; N,4.70; B,3.64;

H,7.06; N,4.59; B,3.73;


H,7.11;

i-1,7.12;


N,4.70; B,3.64;

N,4.71; cl.12.08


H,6.07; N,4.22; B,3.26;

H,5.99; N,4.15; 01,21.13










TABLE 3 (continued)


M.P.(C)


Analysis (Calculated, Found)


97 1,5-Bis-(4-bromophenyl)-l-
aza-5-borabicyclo(3.3.0.)octane


99 1,5-Bis-(4-Tmthylphenyl)-l-
aza-5-borabicyclo(3.3.0.)octane


C18H2BNBr2


93-94


C20H26BN 107-108 C:
F:


C: C,51.35;
Br,37.96
F: C,51.89;


H,4.78; N,3.33; B,2.57;

H,4.74; Br,37.96


C,82.46; H,9.00; N,4.81; B,3.72
C,82.21; H,9.05; N,4.96; B,3.71


l,5-Bis-(4-methoxyphenyl )-1-
aza-5-borabicyclo(3.3.0. )octane


1-(4-Methoxyphenyl),5-
(-ethoxyphenyl)-l-aza-
5-borabicyclo (3.3. )octane

Bis- ,4-[5-(4-nmethylphenyl)-
l-aza-5-borabicyclo(3.3.0.)-
octyl]benzene

Bis-1,4-[5 -(4-chlorophenyi)-
l-aza-5-borabicyclo(3.3.0.)-
octyl]benzene


C20 H2 T)j'2



C2 H 2BNO2
C21H28B2N



C32"42B2N2


112-114 C: C,74.32;
0,9.90
F: C,74.19;


166-137 C:
F:


202-204 C:
F:


CoH 36B 2N2Cl2 198-200
3.0 36 i'


H,8.11; N,4.33; B,3.35;

H,8.01; N,4.16; B,3.36


C,74.79; H,8.37
C,75.23; H,8.29


C,80.69; H,8.89; N,5.88; B,4.54
C,80.39; H,8.71; N,5.70; B,4.72


C: C,69.67;
C1,13.71
F: C,64.47;
C1,14.02


H,7.02; N,5.42; B,4.18;

H,6.86; N,5.45; B,4.27;


Cpd. No.


Name


Formula


101



103



104











TABLE 4. SPECTRAL DATA OF SUBSTITUTED
1,5-DIPHENYL-1-AZA-5-BORABICYCLO(3.3.0.)OCTANES


1Be (p.p.m.)
Chemical Shift


3.6


i.9





2.8


NMR
(5) *


Chemical Shift


Compound
Number


63


Areas

9.8
4.0
4.0
4.1

10.4
4.0
2.0


6.85
3.3
2.1
1.1

7.0
3.45
2.15
1.1

6.9
3.3
2.05
1.1

7.0
3.3
2.05
1.1

7.0
3.3
2.05
1.05

7.2
3.4
2.15
1.15


IR (cm.-1)
B-N Absorbance


1275




1273


1270




1270


1280


1275


Mass Spectrum
Parent Peak


263 *1




265 1


342 1




297 1


297 +1




332 1


* Chemical shift relative to trimiethyl borate
** Chemical shift relative to tetramethylsilane


in deuterochloroform


4.0
4.2
4.0

9.0
4.0
4.2
4.0

9.1
4.0
4.0
4.1

8.2
4.0
4.0
4.0











TABLE 4 (continued)


lB* (p.p.m.)
Chemical Shift


NMR
16 .0


Chemical Shift


7.05
3.35
2.10
1.15


4.7


6.8
3.4
2.1
1.1


6.0


103


3.35
2.1
1.1

6.9
3.7
3.3
2.0
1.3


Areas


8.1
4.0
4.0
S.1


8.0
3.8
10.1
4.1


6.1
2.1
2.0
2.1

8.3
9.1

4.1
4.2


IR (cm.-1)
B-N Absorbance


1275


1275


1281


1278


Mass Spectrum
Parent Peak


421 1


291 1


323 1


337 1


Double Peak
1273 and 1286



Double Peak
1260 and 1273


Compound
Number


4.


1.05


6.9
3.2
2.1
1.1


12.2
8.0
14.1
8.2

12.3
8.0
8.0
8.1


6.90
3.23
2.05
1.05


476 1




517 1









proceeded and the temperature raised, a brilliant green color appeared.

Infrared gas samples indicated the formation of propene gas. The reac-

tion was allowed to proceed at 920 C for 24 hours. The contents were

cooled, filtered, and then the solvent was removed on a rotary evapo-

rator. The residual liquid was transferred to a small flask for dis-

tillation on a spinning band column. Several fractions were collected.

The first fraction proved to be unreacted p-chloro-N,N-diallylaniline.

The second fraction was a clear, viscous liquid (b.p. 130-135 C @ 0.20

mm.). This compound turned brown on exposure to air. The third frac-

tion was the same compound. The infrared spectrum was consistent with

the azaborolidine structure, 94, with the B=N absorbance assigned at
-i
1400 cm. -. The mass spectrum gave a parent peak at 289 1, consistent

with the molecular weight. The nmr spectrum (Figure 6) shows resonances

at 57,05 (m, 8); 63.75 (t, 2); 61.7 (m, 4) for the aromatic, a, and b.c

protons respectiialy.

Anal. Calcd. for C ,H 1BNC1 : C, 62.09; H, 4.87; N, 4.83; B, 3.73;
la 14 2
and Cl, 24.46. Found: C, 61.78; H, 5,01; and Cl, 24.45.

The fourth fraction (b.p. 170-175' C) was very viscous and solidi-

fied in the side arm. This material was recrystallized from ethanol to

give a crystalline solid (m.p. 93-950 C). The ir spectrum gave a strong

absorbance at 1275 cm.-1 which was assigned to the B-4 coordinate bond.

The mass spectrum gave a peak at 332 *1, corresponding to the correct

molecular weight. The nmr spectrum (Figure 6) showed resonances at 67.2

(m, 8); 63.4 (m, 4); 62.15 (q, 4); and 61.15 (in, 4) for the aromatic, a,

b, and c protons respectively.

Anal. Calcd. for C H 20BNCi,: C, 65.08; H, 6.07; N, 4.22; B, 3.26;

and Cl, 21.36. Found: C, 64.97; H, 5.99; N, 4.15; and Cl, 21.13.














CA C-


S-93


9Li.


-~~~ ~~ t' .r-,-. -~---- r~u --


Figure 6. Nmr spectra of 1,5-bis-(4-chlorophenyl)-l-aza-5-borabicyclo-
(3.3.0)octane and 1,2-bis-(4-chlorophenyl)- ,2-azaborolidine.


-i-r ~l-r.---+- --i ui--C----. -~- -)- -J--..rL--c--~---Lu~~- -1' C- ~ 1


LiiL/lt /*-Wy^' -.!'


?*.;*>(&


s~l
"M?~~h;-l;~lrY.Y-*~C~/










A comparison of the spectra in Figure 6 reveals some interesting

effects. A look at models gives some insight into these effects. In

the monocyclic structure, 94, the phenyl rings are far apart and the

ring must be nearly planar. As a result, the b protons are moved

upfield and the c protons are deshielded, resulting in an overlap of

the protons on carbons b and c. The a protons are also slightly

deshielded, probably due to the planar positioning of the phenyl groups

relative to the 5-membered ring. In the bicyclic structure, 93, the

a, b, and c protons give three distinct resonance absorptions. The

model of this compound shows the phenyl groups tied back, much like

butterfly wings, relative to the B-N bond axis. The two propylene

bridges are also forced back in the opposite direction to the phenyl

groups. The b_ protons are in the region expected for 5-membered,

bicyclic rings. The a and c protons are s-ielded relative to the

azaborolidine, resulting in upfield shifts of 4 co 5 p.p.m.

The B1 nmr spectrum of 93 exhibited a chemical shift of 2.2

p.p.m., relative to trimethyl borate. This compares with 3.6 p.p.m.

for the unsubstituted 1,5-diphenyl-l-aza-5-borabicyclc(3.3.0) otane.



F. Preparation of Bis- 14-15--(4-methj Lphenvl)-l-aza-5-borabicyclo-
(3.3.0)octyl]benzene and Bis-1,4- [5- (4-hioEronvl )-l-aza-5-bora-
bicyclo(333.0)oct_1 benzene

Bis-1, 4- [5- (4-me thy lphenyl)-l-aza-5-bora-bicyclo ( 3..0) oetyl] -

benzene, 104, and bis-l,4-[5-(4-chlorophenyl)-l-aza--5-bcrabicyclo-

(3.3.0)octyljbenzene, 105, were prepared by reacting N,N,N',N''-

tetraallyll--pphcnylen di a-ine with tried thy la:mine-(4-;:e thy ) phenyl-

borane and triethylamine(4-chicro)phenyiborane. These compounds,

of course, were not distillable and were purified using silica ge.i









chromatography and recrystallization. Physical and spectral data are

given in Tables 3 and 4.






CH Q ----CH3 Cl- -Cl


104 105





The high molecular weights of these compounds and their molecular

structures make them excellent models for the study of polymers with

similar structures. The boron-nitrcgen coordinate bonds in these com-

pounds exhibited double absorbances in the 7.8 to 8.0 micron region

compared to single absorbances in the 1,5-diphenyl-l-aza-5-borabicyclo-

(3.3.0)octaees. These compounds were the best models for differentiAl

scanning calorimetry studies, described later in this chapter.



G. Reaction of N,N,N',N'-Tetraallyl-p-phenylenediaamine with
p-Phenvienediborane

The relatively high yields of 104 and 105 encouraged attempts

to prepare oligomeric or polymieric products. It seemed that the

above synthesis should be extended by reacting a bis-borane com-

pound, 107, with 1,N,N',N'-tetraallyl--pphenylneediamiue, 106, to

yield a polymer, 1.08. Attempts to prepare the pure di(pyridine)-

p-phenylenediborane and di(triethylamine)-p-phenylenediborane are

described in Chapter III. The resulting crude compound, 107, was

reacted with the tetraallyl compound, 106. A viscous, brown com-

pound was obtained. This compound was insoluble in every solvent










CH2=CHCH CHCH=CH rR-
2 2,N & /z 2c R.oN

CH2=CHCH/ 2CHCH=CH2
2 2 2 107
106





108



tried, but swelled to a gel-like material in acetone after several

weeks. The material appeared to be cross-linked, as might be

expected by examination of the above equation.



H. !Boron Nuclear Magnetic Resonance Studies

11 nmr spectra were obtained for the substituted bicyclic

compounds listed in Table 4. The chemical shifts in chlorof rm

were measured in p.p.m. relative to trirethy borate by a Varian

XL-100 instrument. The chemical shift values varied from 1.9 to

5.2 p.p.m. for the compounds studied. These shifts are very close

to those given in the literature for dietbylamine-borane (3.2 p.p.m.),

pyridine-borane (4.7 p.p.m.), and for the (3.3.3)bicycloborate

ester of the triethanolainines (3.2 p.p.m.).8 The chemical shift

of these bicyclob.,rate caters to somewhat higher fields than other

alkyl borates was attributed to increased shielding around the

boron atom duep to the boron-nitrogen coordinate bond, thus increasing

the tetrahedral character and the number of bonding electrons around

the boron atoms.
11
Some of the iB cheraical shifts in Table 4 might be interpreted

in light of the above discussion. The electronic effects of the









phenyl substituents on the bicyclic structure 109 should be reflected

in the boron-nitrogen bond strength and in the tetrahedral character

of this bond. The bicyclic structure, for which both _x and y are


x 0 --y


)j 109
chlorine atoms, gives a chemical shift of 2.2 p.p.m. When x is

chlorine and y is hydrogen, the chemical shift is 5.2 p.p.m. This

may be interpreted as a result of the withdrawing effect of chlorine

increasing the electron deficiency of boron and, therefore, strength-

ening the B-N coordinate bond. If x is hydrogen and y is bromine,

the chemical shift drops to 1.9 p.p.m. This effect is consistent

with a decrease in the basicity of the amine, thus decreasing the

B-N bond strength. Less reduction is noticed when x is hydrogen and

y is chlorine; this compound, 89, gives a chemical shift of 2.8 p.p.m.

In the dibromo-bicyclic compound, 97., electronic effects of the sub-.

stituents might be expected to cancel each other. The chemical shift,

3.1 p.p.m., is close to that of the unsubstituted compound, 63, at 3.6

p.p.m. The symmetrical bicyclic compounds 104 and 105 show chLem.cal

shifts of 4.4 and 4.7 p.p.m., respectively.



I. TeTrperature Studies by Differential Scanning Calorimetry

A Perkin-Elmer DSC-1B Differential Scanning Calorimeter was used

for studies of the B-N coordinate bond dissociation for all substituted

1,5-diphenyl-l-aza-5-borabicyclo(3.3.0)octanes which were prepared.

Samples were weighed and then placed in special sample holders to

reduce volitalization. Temperature scanning increments were set at 20

per minute. Melting points were easily observable and served ao









excellent calibration marks. At higher temperatures, sublimation of

the samples occurred. No decomposition peaks were observed prior to

sublimation, showing the remarkable stability of these relatively

heavy compounds. A broad endotherm appeared in all spectra beginning

at 520-540* K. This temperature seemed to be consistent with that

expected from B-N coordinate bond dissociation. However, the peak

area could not be measured due to volitalization of the sample,

beginning at a slightly higher temperature.

The bis-l,4-[5-. (4-methylphenyl)-I-aza-5-borabicyclo(3.3.0)octyl]-

benzene, 104, and the bis-l,4 -[5-(4-chlorophenyl)-l-aza-5-borabicyclo-

(3.3.0)octyl]benzene, 105, were much better models for the temperature

studies. These compounds sublimed at a much higher temperature and

allowed the observance of endotherai.s which seemed consistent with

those expected for the boron-nitrogen bond dissociation. Broad,

double peaks were observed beginning at 5320 K and ending at 6170 K

for compound 104. Similar peaks were observed for compound 105

beginning at 5410 K and ending at 6270 K. The heat of this transition

for compound 10_4 was calculated to be 60 cal./g. or 28.5 kcal./mole.

Compound 105 gave a value of 58.2 cal./g. or 30.3 kcal./mole. These

values are very close to those predicted by Butler.1



J. Synthesis of 1,6-Dipbeny-l--aza-6-borabicyclo(4.4.0)decane

The final synthetic effort in this research was an extension

of the hydroboration by triethylamine-phenylborane of N,N-di-

3-butenylaniline, 10. This reaction would be expected to yield

1,6-diphenyl-l-aza-6-borabicyclo(4.4.0)decane, 114. 1,2-Diphenyl-
















(O -NTEt3


65


i.j


110


112
i


2
V.. /
,i


\ I-


1.14


1-butene


SCHEME X


I -\
@ Oj


ill


77
<0 4. Cy


113









azaboracyclohexane, 113, should not be formed by a concerted

mechanism as was the case for the azaborolidines in our previous

studies (Scheme X). This compound could, however, conceivably be

formed by the pyrolysis of intermediate 111 at high temperature

under vacuum. The elimination could be tested, as before, by

monitoring gases produced from the reaction in p-xylene. If the

competing pathway 1 were followed at the reaction temperature,

butene gas would be detected. If only pathway 2 were followed,

the bicyclic compound should be formed in relatively higher yield.

This higher yield, obviously, would be more attractive for monomer

preparation than the yields obtained for the 1,5-dipheny-l--aza-

5-borabicyclo(3.3.0)octanes.

N,N-Di-3-butenylaniline, triechylamine-phenyiborane, and p-

xylene were slowly heated under nitrogen. Gas samples were taken

at various temperatures and time intervals. A bright green color

developed during the course of the reaction, but no butene gas was

evolved during heating. The resulting solution was filtered, roto-

vaced, and divided into two portions. The first portion was then

dissolved in benzene and passed through a neutral silica gel column.

The eluted solution was rotovaced. A white, gummy material was

obtained. This was recrystallized from ethanol to give white

crystals (m.p. 143-145 C). The compound was consistent with the

structure assigned to 1,6-diphenyl-l--aza-6-borabicyclo(4.4.0)decane.

The mass spectrum gave a parent peak at 291 tl. The infrared spectrum
--].
gave a broad absorbance at 1280 cm. consistent with that expected

for the B-N coordinate bond. The nmr spectrum exhibited resonance









signals at 60.95 (m, 4); 61.6 (m, 8); 63.5 (m, 4); and 67.3 (m, 10).

Anal. Calcd. for C20H26BN: C, 82.48; H, 9.00; B, 3.71; and

N, 4.81. Found: C, 81.98, H, 8.61; B, 3.64; and N, 4.76.

The second portion of the reaction mixture was distilled under

vacuum on a spinning band column. Several fractions were obtained.

The first fraction proved to be unreacted N,N-di-3-butenylaniline.

The second fraction (b.p. 75-78 C @ 0.50 mm.) exhibited absorbances

in the infrared spectrum and resonances in the nmr spectrum con-

sistent with the structure of 1,2-diphenyl-azacyclohexane, 113.

The third fraction (b.p. 90-95 C @ 0.50 mm.) was a pale yellow

liquid. The spectra were consistent with the assignment of 1,2-

diphenyl-l-(3-butenyl) ,2-hydro-azaboracyclohexane, 112. The nmr

spectrum showed the presence of an allyl group with resonances at

65.8 (m, 0.5); and 65.1 (m, 1). Other resonances for compound 112

occurred at 60.8 (m, 2); 61.65 (m, 6); 63.35 (m, 4); and 67.4 (m, 12).
-I
The ir spectrum showed the presence of a C=C double bond at 1645 cm.
-1
as well as the presence of a B-H bond at 2250 cm. The distillation

flask contained a gummy, brown residue, which was recrystallized from

ethanol to give a white, crystalline material. This compound was

identical to that obtained from the silica gel column chromatography.

The above results gave strong support to the mechanism proposed

for the facile, concerted elimination of propene gas in the competitive

formation of l,5-diphenyl-l-aza-5-borabicyclo(3.3.0)octanes, 72,

and 1,2-diphenyl-1,2-azaborolidine, 71 (Scheme VI).











K. Conclusions

This research has attained many of its projected goals. The

model compound, 1,5-diphenyl-l-aza-5-borabicyclo(3.3.0)octane was

prepared and its properties investigated. All of the products of

the reaction of triethylamine-phenylborane with N,N-diallylaniline

were isolated, purified, and carefully characterized by nmr, ir,

mass spectral, and elemental analyses. Propene gas was isolated

and identified as a by-product.

Mechanistic studies with deuterium labeling gave strong

support to the proposed mechanism of the facile, concerted elimi-

nation of propene. These studies ruled out a Hofmann-type elimi-

nation mechanism.

The stability of the model compou-:nd, 49, to various synthetic

conditions, such as thy;:.e necessary for iu!Icleophilic or' electro-

philic aromatic substitutions, waq deternmied. Its reactivity in

various solvents, acids, and bases was also studied.

Several substituted derivatives of 49 have been prepared which

should be excellent monomer precursors. P3relimTinary studies .sh

evidence for the formatiecn of the bis-Grignard reagt from ~ 5-

bis- ( '--bromophcnyl-l--..n. .-' -5-bor~-abi .yclc, (3.3.0 )oc.t-.::. e corra-

sponding bis.-(4- -methcx:yphenyl) compound has be-n converted to snall.

amount& of the 1,5-bis- (4-hydro;eyphenyl' --l--aa-borabi.cyclo (3.3.0)-

octarn by the reaction of lithiiml iodide in collidine. Thess two

reactions have excellent potential fir the formation of dicarboxylil

and diphenolic derivatives of -9. These compounds 1.ould be interest-

ing co-monomers for several] possible condensation pol7ym-erization











reactions. Several other compounds listed in Table IV have function-

ality which could be utilized in monomer preparation. In all, over

40 new compounds have been synthesized and characterized in this

research.

The boron-nitrogen coordinate bond has been investigated

extensively by nmr, ir, 1B nmur, and by differential scanning

calorimetry. Chemical shifts, boron-nitrogen stretching frequencies,

and heat of transition studies have given us valuable information

which has opened many avenues for future research on these hetero-

cyclic compounds and other related systems.
















Chapter V

EXPERIMENTAL

A. Equipment and Data

All temperatures are reported uncorrected in degrees centigrade.

Nuclear magnetic resonance (nmr) spectra were obtained with a Varian

A-60A Analytical NMR Spectrometer. The chemical shifts were measured

in deuterochloroform, unless otherwise specified, relative to tetra-

methylsilane.

Infrared spectra were obtained with a Beckman IR-8 Infrared

Spectrophotometer.

1IBorcn nuclear magnetic resonance spectra were obtained,

courtesy of Dr. Wallace S. Brey, with a Varian X-L 100 High Resolution

NMR Suectrometer.

Mass spectra were obtained with a Hitachi Perkin-Elmer RilU

Mass Spectrometer.

Thermal analyses were carried out on a Perkin--Elmer Differential

Scanning Calorimeter DSC-1B.

Elemental analyses were performed by Galbraith Laboratories,

Inc., Knoxville, Tennessee.









B. Syntheses and Characterization

Preparation of N,N-Diallylaniline

Aniline (186.0 g., 2.0 mol.), sodium carbonate (420.0 g., 4.0 mol.),

and 300 ml. of water were placed in a 3-liter, 3-necked, round-bottomed

flask equipped with an overhead stirrer, dropping funnel, and water-

cooled condenser. The mixture was heated to low reflux using a

heating mantle and variac. Allyl bromide (484.0 g., 4.0 mol.) was

added dropwise over a period of 4 to 5 hours with constant stirring.

The brown, syrupy liquid which resulted was stirred for 4 more hours

and then filtered into a 2-liter separatory funnel. The two resulting

layers were separated and the aqueous layer washed with 3 100 ml. por-

tions of ether. The ether was removed on a rotary evaporator. The

resulting residue was combined with the crude organic layer. This oily,

brown liquid was then added carefully to the 30% solution of sodium

hydroxide in 300 ml. of water. This solution was then transferred to

a 3-necked, 3-liter, round-bottomed flask equipped with mechanical

stirrer and addition funnel. Benzenesulfonyl chloride (100 mi.) was

added dropwise with stirring. T:.r resulting slush was cooled in a:-

ice bath and neutralized with 10% hydrochloric acid. The organic

layer was separated and dried with sodium sulfate. The crude N,,- di-

allylaniline was filtered and placed in a 1--liter, round-bottomed

flask for distillation. Using a vacuum distillation apparatus, consist-

ing of a Vifereaux column, fraction cutter, and receiving flasks, an

97.6% yield' of a clear liquid (293.0 g., b.p. 104-i06 C ( 3.5 mm.) was

obtained.-








Synthesis of p-methyl-N,N-diallylaniline

p-Toluidine (214.0 g., 2.0 mol.), sodium bicarbonate (420.0 g.),

and 1000 ml. of water were placed in a 3-liter, 3-necked, round-

bottomed flask equipped with thermometer, overhead stirrer, addition

funnel, and condenser. The mixture was heated on a heating mantle

until the temperature of the liquid reached 700 C. Allyl bromide

(581.0 g., 4.8 mol.), was added dropwise with stirring. The resulting

mixture was heated overnight. The brown liquid separated into 2 phases

on sitting. The layers were separated using a 1-liter separatory

funnel. The oily layer was washed with 3 100 ml. portions of water

and then dried over sodium sulfate. The crude p-methyl-N,N-diallyl-

aniline was filtered and then vacuum distilled yielding 262.3 g. (70.1%)

of a pale yellow liquid (b.p. 80-850 C. @ 0.350 mm.).

The infrared spectrum (ir) gave absorbances at 1520 (m), 1240 (s,

split), 800 (m), 1620 (s, split), 920 (s, split) 1340 (m), 1360 (s),

1390 (s), 1410 (m), 1425 (m), 1450 (w), 1180 (s), 990 (s), 2990 (s),

2950 (s), 3000 (s), 3020 (s), and 3110 (m) cm. .

The nmr gave resonance signals at 68.8 (m, 4); from 64.9 to 66.2

(m, 6); 63.8 (m, 4); and 62.2 (s, 3).



Synthesis of p-bromo-N ,N-diall.ylani ine

p-Bromoaniline (100 g., 0.582 mol.), sodium carbonate (126.0 g.,

1.2 mol.), and 230 ml. of water were placed in a 2-liter, 3-necked,

round-bottomed flask equipped with a mechanical stirrer, drcpi.-:n

funnel, and water-cooled condenser. The mixture was heated on a heat-

ing mantle until low reflux was obtained. Allyl bromide (146.0 g.,

1.2 mol.) was added over a 3 to 4 hour period through an addition









funnel. Stirring was continued for 12 hours, after which a syrupy,

brown liquid was obtained, along with an aqueous layer. The layers

were separated in a 1-liter separatory funnel. The aqueous layer

was washed with 2 350 ml. portions of ether. The ether was then re-

moved on a rotary evaporator and the resulting layer combined with

the crude p-bromo-N,N-diallylaniline. This crude liquid was added

dropwise to a 30% solution (100 ml.) of sodium hydroxide in water

in a 2-liter, round-bottomed flask equipped with a mechanical stirrer

and addition funnel. Benzenesulfonyl chloride (34.0 ml.) was added

dropwise. Since the reaction was exothermic, an ice bath was used

to control the temperature. The resulting cooled solution was neu-

tralized with 10% hydrochloric acid solution. The organic layer was

separated and dried with sodium sulfate. The crude product was fil-

tered and placed in a 200 ml. round-bottomed flask for vacuum distil-

lation. The distillation yielded 69.5 g. (a7.5%) of a colorless liquid

(b.p. 93-940 C @ 0.250 nm.).



Preparation of p--bromo-N,N-diallylaniline

D-Bromoaniline (200.0 g., 1.15 mol.), sodium bicarbonate (242.0 g.,

2.9 mol.), and 400 ml. of water were placed in a 2-liter, 3-necked,

round-bottomed flask equipped with stirrer, condenser, addition funnel,

and heating mari-e. The mixture was heated to low reflux. Allyl

broride (278.3 g., 2.3 mol.) was added dropwise over a two-hour period

with constant stirring. The lower, oily layer was dried with sodium

sulfate. The crude product was vacuum distilled yielding 215.3 g. (74.5%)

of a clear liquid (b.p. 113-1140 C @ 0.100 rm.).











Synthesis of p-methoxy-N,N-diallylaniline

p-Methoxyaniline (187.0 g., 1.0 mol.), sodium carbonate (210.0 g.,

2.0 mol.), and 500 ml. of water were placed in a 2-liter, 3-necked,

round-bottomed flask equipped with stirrer, addition funnel, and con-

denser. The mixture was heated to reflux on a Glas-col heating mantle.

Allyl bromide (266.0 g., 2.2 mol.) was added dropwise to the mixture.

The resulting mixture was allowed to stir at reflux overnight and was

then transferred to a 2-liter separatory funnel. The water layer was

discarded; the organic layer was dried with magnesium sulfate. The

liquid was filtered and then vacuum distilled yielding 183.4 g. (88.0%)

of a clear liquid (b.p. 87-880 C @ 0.350 mm.).

The ir spectrum showed only a small residual N-H absorbance at
-l
3420 cm.-. Other absorbances were present at 3100 (m), 2840 to 3020

(s, broad, detailed), 1840 (w, broad), 1645 (m), 1622 (w), 1580 (w),

1515 (s, broad), 1463 (m), 1442 (m), 1422 (m), 1403 (w), 1385 (w),

1360 (w), 1332 (w), 1300 (w), 1278 (w), 1240 (s, broad), 1180 (s),

1130 (m), 1040 (s), 918 (s), 815 (s), 760 (w), 712 (m) cm.-1

The nmr spectrum showed resonance signals at 66.65 (m, 4); 65.85

(m, 2); 65.1 (m, 4); and 67.1 (m, 7).



Synthesis of p-chloro-N,N-diallylaniline

p-Chloroaniline (225.0 g., 2.0 mol.), sodium carbonate (420.0 g.),

and 500 ml. of water were placed in a 2-liter, 3-necked, round-bottomed

flask equipped with stirrer, addition funnel, and condenser. The

mixture was heated to reflux on a heating mantle. Allyl bromide (484.0

g., 4.0 mol.) was added dropwise with stirring. Heating and stirring








were continued overnight. The resulting liquid was poured through a

filter into a separatory funnel in which two layers formed. The lower

layer was discarded and the brown, oily layer was dried with sodium

sulfate. The crude p-chloro-N,N-diallylaniline was distilled under

vacuum yielding 300.4 g. (72.5%) of a colorless liquid (b.p. 85-860

C @ 0.350 mm.). Nmr and ir spectra agreed with the assigned structure.



Preparation of N,N-di-3-butenvlaniline

Aniline (14.0 g., 0.15 mol.), sodium carbonate (32.0 g.), and

50 ml. of water were placed in a 250 ml., 3-necked, round-bottomed

flask equipped with a mechanical stirrer, addition funnel, and cold-

water condenser. The mixture was heated to a low reflux. 4-Bromobutene

(40.5 g., 0.30 mol.) was added dropwise with constant stirring. The

reaction was allowed to proceed for 24 hours. The contents were

cooled and filtered. The amine layer was separated, dried over sodium

sulfate, and distilled under vacuum. A clear, colorless liquid (11.2

g., 37%) was obtained (b.p. 74-750 C @ 0.100 mm.).

The ir spectrum exhibited absorbances at 695 (s), 748 (s), 915

(s), 992 (s), 1040 (w), w) ), 1180 to 1220 (w, detailed), 1283 (m),

1360 (m), 1395 (w), 1420 (w), 1430 to 1460 (w, detailed), 1503 (s),
-1
1600 (s), 1640 (m), and 2950 to 3050 (s, detailed, broad) cm. .

The nmr spectrum gave resonance signals at 52.25 (quartet, 4);

63.3 (m, 4); 65.1 (m, 4); 65.8 (m, 2); and 66.8 (m, 5).



Synthesis of N,N,N',N'-tetraallyl-p-phenylenediamine

p-Phenylenediamine (125.0 g., 1.15 mol.) and sodium carbonate

(530.0 g.) were added to a 3-liter, 3-necked, round-bottomed flask

fitted with a Claisen adapter, thermometer, addition funnel, and









reflux condenser. Water (1500 ml.) was added; the mixture was heated

to reflux to dissolve the solid. The solution was then cooled to 700

C and 3-bromopropene (559.7 g., 4.63 mol.) added dropwise with stirring.

The solution was refluxed overnight before extracting the oily layer

with ether. The ether layer was then dried over sodium sulfate and

filtered. The brown, oily compound was then distilled yielding 124.6 g.

(46.5%) of a pale yellow liquid (b.p. 138-1400 C @ 0.550 mm.).



Synthesis of phenylboronic acid

A mixture of ethyl ether and magnesium (36.0 g., 1.5 g. atoms)

was placed in a 1-liter, 3-necked, round-bottomed flask equipped with

a mechanical stirrer, addition funnel, and cold-water condenser. Bromo-

benzene (157.0 g., 1.0 mol.) in 200 ml. of ether was added dropwise

with stirring. After the reaction was started, the round-bottomed

flask was cooled in ice water to control the temperature. After all

the bromobenzene had been added, the contents of the flask were allowed

to warm to room temperature, Trimethylborate (103.9 g., 1.0 mol.) and

800 ml. of diethyl ether were placed in a 3-liter, 3-necked, round-

bottomed flask equipped with a mechanical stirrer, low-temperature

thermometer, and Claisen adapter with nitrogen inlet tube and addition

funnel. The Grignard reagent was filtered through glass wool into the

addition funnel. The solution in the 3-liter flask was cooled to -700

C in a dry ice-jsopropanol bath. The Grignard reagent was added drop-

wise and the temperature was controlled between -70 and -550 C. The

mixture, after cooling overnight, was hydrolyzed with 10% sulfuric

acid. The ether layer was separated and placed in a 3-liter, 3-necked,

round-bottomed flask fitted with a Claisen distilling head, mechanical









stirrer, addition funnel, and heating mantle. The ether solution was

concentrated while adding 1000 ml. of water dropwise. At this point

the temperature at the distilling head had reached 980 C. The solu-

tion was cooled. Fluffy, white crystals were observed. These were

filtered and washed with 3 10 ml. portions of hexane yielding 108.1 g.

(88.8%) of phenyl boronic acid (m.p. 214-2160 C).



Preparation of diethyl phenylboronate

Phenylboronic acid (50.0 g., 0.41 mol.), benzene (320.0 g.), 138

g. of absolute ethanol, and 2 drops of sulfuric acid were placed in a

1-necked, 1-liter, round-bottomed flask. An azeotropic distillation

apparatus consisting of a packed column, cold-water condenser, ther-

mometer, Claisen head, drying tube, and Dean-Stark trap was assembled.

The flask was heated on a Glas-col heating mantle. A ternary azeotrope

of water, ethanol, and benzene distilled over at 640 C. fi;. layers

formed in the trap. The lower (water) layer was removed as the reaction

progressed. After 2 days, the temperature at the distilling head had

reached 680 C, indicating the reaction was complete. The binary azec-

trope of benzene and ethanol distills at this temperature. The remain-

ing solvent was distilled and the resulting liquid placed in a 100 ml.

round-bottomed flask for vacuum distillation. The distillation yielded

65.5 g. (90.1%) of a clear liquid (b.p. 68-690 C @ 0.350 mm.).



Preparation of triethylamine-phenylborane

Lithium aluminum hydride (12.0 g., 0.32 m'ol.) was added to 400 ml.

of dried diethyl ether in a 3-necked, 1-liter, round-bottomed flask

equipped with condenser and drying tube, addition funnel, low-tempera-








ture thermometer, nitrogen inlet tube, addition funnel connector,

and a mechanical stirrer. The mixture was refluxed for thirty

minutes and then cooled to -720 C in a dry ice-isopropanol bath.

Triethylamine (37.4 g., 0.37 mol.) was added with stirring. Then

a solution of diethyl phenylboronate (65.5 g., 0.37 mol.) in ether

was added dropwise with stirring, keeping the temperature below

-650 C. The solution was stirred at -720 C for another hour and

then allowed to warm to room temperature. The mixture was filtered

through a sintered-glass funnel. The filtrate was concentrated and

then cooled in a dry ice-isopropanol bath resulting in the formation

of 51.9 g. (73.0%) of white, needle-like crystals (m.p. 65-660 C).



Preparation of 1,2-diphenyl-l,2-azaborolidine and 1,5-diphenyl-l-aza-
5-bora-bicyclo(3.3.0)octane

A solution of 1.25 liters of toluene, triethylamine-phenylborane

(18.0 g., 0.094 mol.), and N,N-diallylaniline (16.3 g., 0.094 mol.)

was distilled at atmospheric pressure in a 2-liter, 1-necked, round-

bottomed flask until the temperature reached 1200 C at the distilling

head. The remaining toluene was removed on a rotary evaporator,

resulting in a phosphorescent-green solution. This solution was dis-

tilled on a spinning band distillation column yielding two major pro-

ducts. The lower boiling component, 4.10 g., was a clear liquid (b.p.

84-860 C @ 0.30 mm.). The spectral data agreed with the assignment
99
of 1,2-diphenyl-1,2-azaborolidine. The ir spectrum gave absorba.ces

at 3430 (w), 3250 (w), 3060 (s), 2950 (s), 2880 (s), 1600 (s), 1490 (s),

1400 to 1440 (s, broad), 1300 (s), 1190 (m), 1150 (w), 1080 (w), 1050

(m), 1000 (m), 750 (s), 700 (s) cm.-1









The nmr spectrum gave resonances at 67.2 (m, 10); 63.8 (t, 2);

and a broad multiple at 61.8 (n, 4). The mass spectrum showed a

peak at 220 1.

Anal. Calcd. for C15H16BN: C, 81.47; H, 7.29; N, 6.34; and

B, 4.89. Found: C, 81.42; H, 7.31; N, 6.21; and B, 5.01.

The higher boiling fraction (b.p. 125-1300 @ 0.30 mm.) was

dissolved in acetone and cooled in a dry ice-isopropanol bath after

which white crystals formed. These crystals were filtered and dried

yielding 4.47 g. (m.p. 80-810 C). The spectral data and analysis

agreed with the assignment of 1,5-diphenyl-l-aza-5-borabicyclo(3.3.0)-

octane.9 The ir spectrum showed absorbances at 3040 (m), 2900 (s),

2820 (m), 1.925 (s), 1850 (w), 1580 (s), 1420 to 1480 (s, broad), 1260

(s), 1215 (m), 1175 (s), 1150 (m), 1125 (s), 1075 (m), 1040 (m), 1020

(s), 980 (s), 950 (s), 930 (m), 880 (s), 830 (w), 810 (s), /75 (s),
--1o
745 (w), 725 (s), 670 (s), and 610 (!w) cm. .

The nmr spectrum gave resonance signals at 66.85 (m, 10); 63.3

(m, 4); 62.1 (q, 4); and 61.1 (m, 4).

The mass spectrum gave a parent peak at 262 1.

Anal. Calcd. for CSH22 BN: C, 82.13; H, 8.42; N, 5.32; and

B, L.11. Found: C, 82.15; H, 8.51; N~ 5.41; and F, 4.21.



Synthes-is of p-bLroophenylboronic acid

A mixture of magnesium (27.0 g., 1.1 g. atoms) and 100 ml. of dry

diethyl ether was placed in a 1-liter, 4-necked, round-bottomed flask

equipped with a stirrer, addition funnel, and reflux condenser. p--Di-

bromobenzena (237.0 g., 1.0 moi.) in dLethyl ether was added dropwise

with stirring after the initial reaction was started. An ice bath was









used to control the reaction rate. The reaction mixture was stirred

for an additional 30 minutes at room temperature. Trimethylborate

(103.9 g., 1.0 mol.) and 800 ml. of diethyl ether were placed in a

3-liter, 3-necked, round-bottomed flask equipped with a mechanical

stirrer, low-temperature thermometer, and Claisen adapter for an

addition funnel and nitrogen inlet tube. The Grignard reagent was

filtered through glass wool into the addition funnel. The solution

in the 3-liter flask was cooled to -700 C in a dry ice-isopropanol

bath. The system was flushed with a slow stream of nitrogen. The

Grignard reagent was added dropwise with stirring and the temperature

was kept below -650 C. The mixture was allowed to warm to room tem-

perature with continuous stirring and was hydrolyzed with 10% sulfuric

acid. The ether layer was separated and placed in a 3-necked, 3-liter,

round-bottomed flask equipped with mechanical stirrer, Claisen head,

and addition funnel. Using a heating mantle and variac, the ether was

distilled away while adding 1000 ml. of water dropwise. When the tem-

perature at the distilling head reached 980 C, the solution was trans-

ferred to a l-.liter Erlenmeyer flask and allowed to cool. White, fluffy

crystals were obtained and washed with 3 10 ml. portions of hexane.

The total yield was 187.4 g. (93.5%) of p-bromophenylboronic .aci (a:.p.

27:1-272 C).

The ir spectrum showed absorbances at 3300 (broad, s), 2400 (w),

600 (s), 1500 (m), 1435 (s), 1350 (broad, s), 1280 (w), 1185 (s), 1090

(s), 1070 (w), 1010 (broad, s), 920 (w). 760 (m), 690 (s), and 630 (s)
-1
cm.

The nmr spectrum exhibited resonance signals at 67.5 (mi, 4) and

62,75 (s, 2).









Preparation of diethyl p-bromophenylboronate

p-Bromophenylboronic acid (100.8 g., 0.5 mol.), benzene (320.0 g.),

and absolute ethanol (138.0 g.) were placed in a 2-liter, 1-necked,

round-bottomed flask. An azeotropic distilling apparatus consisting

of a packed column, Claisen head, thermometer, condenser with drying

tube, and a Dean-Stark trap was assembled. The round-tottomed flask

was heated on a Glas-col mantle until a ternary azeotrope of benzene,

ethanol, and water distilled at 640 C. The water layer that resulted

was continuously removed through the Dean-Stark trap. After all of

the water had been collected, the temperature had reached 680 C the

temperature at which the binary azeotrope of benzene and ethanol dis-

till. The remaining benzene and ethanol were distilled away and the

remaining brownish liquid placed in a 100 ml. round-bottomed flask

and vacuum distilled. The distilltion yielded 47.2 g. (41.0%) of a

clear liquid (b.p, 76-770 C @ 0.250 mm.).

The ir spectrum showed absorbances at 2995 (s), 2940 (s), 2920 (s),

1920 (w), 1650 (w), 1585 (s), 1560 (w), l1187 (s), 1470 (w), 1415 (s),

1375 (s), 1270 to 1350 (broad, s), 1255 (s), 1175 (4), 1125 (s), 1375

(s), 1100 (s), 1070 (s), 1040 (s), 1005 (s), 900 (s), 815 (s), 720 (s),
-i
650 (m), and 620 (m) cm. .

The nmr spectrum showed resonances at ~7.L5 (s, 4), 64.05 (quartet,

4), and 61.25 (t, 6).


p-Bromophenylmagnesium bromide

Magnesium (27.0 g., 1.1 g. atoms) and 500 ml. of dry diethyl ether

were placed in a flamed, 1-liter, 3-necked, round-bottomed flask

equipped with mechanical stirrer, addition funnel, and cold-water









condenser. The mixture was refluxed for 30 minutes. p-Dibromobenzene

(235.9 g., 1.0 mol.) was dissolved in dry diethyl ether and placed in

a 500 ml. addition funnel. Then the mixture was activated with a small

crystal of iodine; a few ml. of the solution were added. An ice bath

was necessary to control the reflux rate while the remainder of the di-

bromobenzene was added dropwise to the stirring mixture. The resulting

solution was filtered to remove the unreacted magnesium.



Diethyl p-bromophenylboronate

p-Bromophenylboronic acid (80.0 g., 0.4 mol.), benzene (320.0 g.),

and ethanol (138.0 g.), along with a small amount of sulfuric acid,

were placed in a 2-liter, 1-necked, round-bottomed flask. An azeotropic

distillation apparatus was assembled, consisting of a packed column.

Claisen head, thermometer, condenser with drying tube, and Dean-Stark

trap. A ternary azeotrope of benzene, water, and ethanol distilled at

640 C, forming two layers in the trap. Ths lower (water) layer was

continuously removed as the reaction proceeded. The reaction appeared

complete as the temperature at the distilling head reached 670 C-the

temperature at which the binary azeotrope of benzene and ethanol dis-

tills. Most of the remaining benzene and ethan:,l were distilled away

and the remaining liquid placed in a 200 ml. round-bottomed flask.. The

brown liquid was then distilled under vacuum yielding 77.4 g. (60%) of

a clear liquid (b.p. 94-950 C @ 0.50 mm.).

The infrared spectrum showed absorbances at 2995 (s), 2940 (s),

2920 (s), 1920 (w), 1650 (w), 1585 (s), 1560 (w), 1487 (s), 1470 (w),

1415 (s), 1375 (s), 1270 to 1350 (broad, s), 1255 (s), 1175 (w), 1125 (s),

1100 (s), 1070 (s', 1040 (s), 1o005s 0 s), 00 (s), S.S (s), 720 (s), 550

(m), and 920 (m) cm.-









The nmr spectrum exhibited resonances at 67.45 (s, 4); 64.05

(quartet, 4); and 61.25 (t, 6).



Preparation of triethylamine-(p-bromo)phenylborane

Lithium aluminum hydride (5.5 g., 0.15 mol.) was added to 400 ml.

of diethyl ether in a 4-necked, 1-liter, round-bottomed flask equipped

with a mechanical stirrer, condenser with drying tube, addition funnel

with nitrogen inlet tube, and low temperature thermometer. The mix-

ture was refluxed for 30 minutes on a heating mantle and then cooled

to -720 C in a dry ice-isopropanol bath. Triethylamine (15.8 g., 0.192

mol.) was added with stirring. A solution of diethyl p-bromophenyl-

boronate (49.3 g., 0.192 mol.) was added dropwise with stirring, keep-

ing the temperature below -650 C. The reaction mixture was allowed to

warm to room temperature and then filtered to remove the unreacted

lithium aluminum hydride. The filtrate was cooled in a dry ice-iso-

propanol bath to -700 C. White, needle-like crystals were formed.

These were unstable and appeared to melt during filtration, even under

nitrogen. The remaining material was immediately dissolved in toluene.



Preparation of 1-(4-bromophenyl)-2-phenyl-1,2-azabcrol idine and
-( 4-bromophenyl) -5--phenyl-l-aza-5-borabicyclo. 3.3.0 )octane

Triethylamine-phenylborane (19,3 g., 0.1 mol), p-bromo-N,N--diallyl-

aniline (25.2 g., 0.1 mol.), and 1.25 liters of toluene were placed in

a 2-liter, round-bottomed flask. The toluene was slowly distilled from

the flask through a fractionating column and condenser. On initial

heating the contents of the flask turned a bright yellow-green color.

When the temperature at the distilling head reached 1200 C, the residual









green liquid was transferred to a 50 ml. round-bottomed flask and

distilled on a spinning band column. Four fractions were obtained.

The two lowest boiling fractions (7.8 g.) were clear, pale yellow,

viscous liquids (b.p. 120-1230 C @ 0.15 mm.) Nmr and ir data were

consistent with the assignment of l-(4-bromophenyl)-2-phenyl-l,2-

azaborolidine. The ir spectrum gave absorbances at 3080 (s), 3060 (s),

2950 (s), 2870 (s), 1960 (w), 1890 (w), 1820 (w), 1765 (w), 1700 (w),

1630 (w), 1590 (s), 1570 (m), 1480 (broad, s), 1425 (broad, s), 1385

(s), 1300 (broad, s), 1240 (s), 1185 (m), 1150 (m), 1140 (w), 1100 (m),

1067 (s), 1050 (s), 1030 (m), 1000 (s), 960 (w), 910 (w), 880 (m), 820
-i
(s),770 (w), 740 (s), 695 (s), and 640 (m) cm. The nmr gave

resonance signals at 67.2 (m, 9); 63.75 (t, 2); and 61.7 (broad m, 4).

Anal. Calcd. for C, H BNBr: C, 60.03; H, 5.04; N, 4.67; B,
_- 5 15
3.61; and Br, 26.65. Found: C, 60.14; H, 5.12; N, 4.59; B, 3,64;

and Br, 26.52.

The two remaining fractions (b.p. 130-1320 C @ 0.15 mm.) were

dissolved in small amounts of acetone and cooled in a dry ice-iso-

propanol bath, resulting in the formation of white crystals. These

were filtered and dried yielding 6.7 g. (m:.p. 116-1180 C).

The ir, r.mr, and mass spectra were consistent with the.assignment

of structure as (4-bromophenyl)--5-phenyl-!-aza- 5-bopabicyclo(3.3.0)--

octane. The ir spectrum showed absorbances at 3050 (m), 3010 (m),

3000 (m), 2920 (s), 2825 (s), 1950 (w), 1880 (w), 1820 (w), 1700 (w),

1475 (broad, s), 1425 (m), 1400 (m), 1350 (w), 1310 (w), 1265 (s),

1227 (s), 1190 (w), 11.70 (w), 1.155 (m), 1130 (broad, -), 1080 (m), 1050

(m), 1035 (m), 1020 (m), 1000 (s), 980 (m), 950 (m), 930 (n), 890 (m),









810 (s), 740 (s), 700 (broad, s), 675 (s) cm." The nmr showed

resonance signals at 66.9 (m, 9); 63.3 (m, 4); 62.05 (quintet, 4);

and 61.1 (m, broad, 4). The mass spectrum gave a parent peak of

342 1.

Anal. Calcd. for C18H21BNBr: C, 63.19; H, 6.19; N, 4.09;

B, 3.16; and Br, 23.24. Found: C, 63.11; H, 6.29; N, 3.96; B, 2.90;

and Br, 23.36.



Preparation of l-(4-chlorophenyl)-2-phenyl-1,2-aza-borolidine and
l-(4-chlorophenyl)-5-phenyl-l-aza-5-borabicyclo(3.3.0)octane

Triethylamine-phcnylborane (32.7 g., 0.17 mol.), p-chloro-N,N-

diallylaniline (35.3 g., 0.17 mol.), and 1.5 1. of toluene were

placed in a 2-liter, round-bottomed flask. The contents were heated

on a heating mantle. Toluene (200 ml.) was slowly distilled through

a fractionating column and condenser. The mixture was slowly re-

fluxed; then the remainder of the toluene was distilled until the

temperature at the distilling head reached 1200 C. The remaining

toluene was removed on the rotary evaporator under reduced pressure.

The gir n, phosphorescent liquid was transferred to a 50 ml. flask

and distilled on a spinning band column. Three fractions were

collected. The two lowest boiling fractions (15.6 g.) were viscous,

colorless liquids (b.p. 130-1320 C @ 0.20 mm.) which turned brown

in air. A portion of the viscous liquid was sealed under vacuum for

analysis. The ir, nmr, and mass spectra were consistent with the

structure assignment of l-(4-chlorophenyl)-2-phenyl-l,2-azaborolidine.

The infrared spectrum exhibited absorbances at 3450 (w), 30'C (m),

3060 (m), 2950 (s), 2880 (s), 1960 (w), 1390 (w), 1820 (w), 1765 (w),









1640 (w), 1595 (s), .575 (w), 1490 (broad, s), 1430 (broad, s) 1393

(s), 1315 (s), 1290 (s), 1265 (m), 1245 (m), 1185 (m), 1153 (m), 1140
-1
(w), 1093 (s), 915 (m), 925 (s), 740 (s), 720 (m), and 595 (s) cm.1

The nmr spectrum gave resonance signals at 67.1 (m, 9); 63.75 (t, 2);

62.25 (m, L). The mass spectrum gave a molecular weight of 255 1l.

Anal. Calcd. for C H5 BNC1: C, 70.48; H, 5.92; B, 4.23; and

01,13.88. Found: C, 70.57; H, 6.06; N, 5.27; B, 4.40; and Cl, 13.88.

The highest boiling fraction (b.p. 144-146 C @ 0.20 mm.) was

dissolved in a small amount of acetone and cooled in a dry ice-iso-

propanol bath, resulting in the formation of 4.6 g. of flaky, white

crystals (m.p. 95-960 C.). The ir, nmr, mass spectrum and analysis

were consistent with the structure of 1-(4-chlorophenyi)-5-phenyl-l-

aza-5-borabicyclo(3.3.0)octane. The "r spectrum showed absorbances

at 3080 (m). 3060 (m), 3040 (m), 3020 (m), 2920 (broad, s), 2837 (s),

2600 (w), 1958 (w), 1893 (w), 1823 (w), 1765 (w), 1640 (w), 595 (),

1485 (broad, s), 1450 (m), 1430 (s), 1390 (m), 1345 (n), 1330 (s), 1275

(broad, s), 1255 (w), 1230 (s), 1190 (s), 1175 (s), 1160 (s), 1132 (s),

1120 (m), 1096 (s), 1053 (s), 1038 (m), 1022 (m), 1008 (s). 980 (s),

957 (m), 933 (m), 895 (s), 860 (w), 820 (s), c10 (m), 745 (s), 700 (s),

and 648 (s) cm. The nmr spectrum exhibited resonances at 67.0 (broad

m, 9); 63.3 (m, 4); 62.05 (quintet, 4); 61.1 (broad m, 4). Th mass

spectrum gave a parent peak at 297 -3

Anal. Calcd. for C18H2,BNCI: C, 72.63; H, 7.11; N, 4.70; B, 3.64;

and Cl, 11.91. Found: C. 72.66: H, 7.06; N, 4.59; B, 3.73; and Cl,

12.04.









Synthesis of p-chloro-phenylboronic acid

Magnesium turnings (36.4 g., 1.5 g. atoms) were placed in a 2-liter,

3-necked, round-bottomed flask equipped with mechanical stirrer, con-

denser with drying tube, and a 500 ml. addition funnel. Dried diethyl

ether (50 ml.) was added and the mixture refluxed for 15 minutes. p-Bromo-

chlorobenzene (287.1 g., 1.5 mol.), dissolved in I liter of dried diethyl

ether, was added dropwise after the initial reaction had started. After

complete addition, the mixture was refluxed for an additional 30 minutes.

The resulting Grignard reagent was filtered through glass wool into a 500

ml. addition funnel. Trimethylborate (155.8 g., 1.5 mol.) and 1 liter

of dry diethyl ether were placed in a 3-liter, 3-necked. round-bottomed

flask equipped with mechanical stirrer, low-temperature thermometer, and

Claisen adapter for an addition funnel and nitrogen inlet tube. The

solution was cooled to -700 C in a dry ice-isoprcpanol bath and the

Crignard reagent added dropwise with stirring. Nitrogen flow was main-

tained throughout the system during the course of the addition. The

temperature was kept below -650 C. The solution was allowed to warm to

room temperature overnight with continuous stirring. The resulting

mixture was hydrolyzed with a 15% sulfuric acid solution. The temperature

was controlled by cooling the flask in an ice bath. The two resulting

layers were separated in a 2-liter sparatory funnel and the aqueous

layer discarded. The ether layer was then placed in a 3-liter, 3-necked,

round-bottomed flask equipped with mechanical stir.rer, addition funnel,

Claisen distilling head, condenser, and heating mantle. The ether layer

was slowly distilled while adding water dropwise. when the temTiperature

at the distilling head reached 980 C, the hot solution was transferred

to a 2-liter Erlenmeyer flask and allowed to cool. :.pFroximrately 1500









ml. of water had been added as the ether was replaced. After cooling,

filtering, and washing with 3 20 ml. portions of hexane, white, fluffy

crystals, 195.2 g. (83.5%), were obtained (m.p. 280-281 C).

The ir spectrum showed absorbances at 3200 (broad, s), 1920 (w),

1880 (w), 1800 (w), 1730 (w), 1650 (w), 1590 (s), 1560 (m), 1350 (broad,

s), 1250 (w), 1170 (m), 1080 (s), 1010 (s), 820 (s), 720 (s), 670 (s),
-!
and 640 (m) cm.-

The nmr spectrum exhibited resonance signals at 57.6; and 63.1

(s, 2).



Synthesis of p-chlcrophenylboronate

p-Chl:c.'chen lboronic acid (100.0 g., 0.64 mol.) was placed in a

2-liter, round-bottomed flask. To this, ethanol (230.0 g., 5.0 mol.)

and benzene (546.0 g.) were added. An azeotropic distillation

apparatus was constructed consisting of a fractionating column,

Claisen head, thermometer, Dean-Stark trap, and condenser with dry-

ing tube. A small amount of sulfuric acid was added. The mixture

was heated on a Glas-col mantle. A ternary azeotrope of benzene,

ethanol, and water distilled ar 64 C. Two layers formed in the

trap and the lower lave" was con tinuously removed. Approximately

23 to 24 ml. of water were collected in the trap. After the temp-

erature had stabilized at 58 C, the temperature at which the binary

azeotrope of benzene and ethanol boils, the remaining solvent was

removed on the rotary evaporator. The residual crude eCter was

placed in a 200 -m., rout:d-bottomed flask and distilled under vacuum.

A clear liquid, 60.2 g. ('44.3%), was obtained (b.p. 92-930 C @ 0.75 mmn.).









The ir spectrum showed absorbances at 3100 (w), 3050 (w), 2990

(s), 2945 (s), 2920 (s), 1920 (w), 1660 (w), 1593 (s), 1563 (m),

1487 (s), 1430 (s), 1415 (s), 1375 (s), 1325 (broad, s), 1280 (s),

1258 (s), 1175 (w), 1127 (s), 1100 (s), 1087 (s), 1040 (s), 1018 (s),
-1
904 (s), 820 (s), 725 (s), 650 (s), and 625 (s) cm.-1

The nmr spectrum showed resonances at 67.4 (quartet, 4); 64.0

(quartet, 4); and 61.24 (t, 6).



Synthesis of triethylamine-(p-chlorophenyl)borane

Lithium aluminum hydride (5.32 g., 0.14 mol.) was added to 600

ml. of dry diethyl ether in a l-liter, 4-necked, round-bottomed flask

equipped with mechanical stirrer, condenser with drying tube, addition

funnel with nitrogen inlet tube, and low-temperature thermometer. The

mixture was refluxed for 30 minutes on a heating mantle and then

cooled to -70 C in a dry ice-isopropanol bath. Triethylamine (28.6

g., 0.28 mol.) was added with stirring. The system was flushed with

nitrogen; diethyl p-chlorophenylboronate (58.9 g., 0.28 mol.) was added

dropwise. The temperature was kept below -55 C. The mixture was

then filtered through a sintered-glass funnel. A watch-glass was

placed over the funnel mouth to prevent evaporation of the ether. The

filtrate was concentrated and then cooled in a dry ice-isopropanol-bath,

resulting in the precipitation of a white cry3talline substance. The

material, 47.7 g. (75%), was filtered and dried yielding whites, needle-

like crystals (m.p. 63-64 C).

The ir spectrum exhibited absorbances at 3080 (w), 3000 (s), 2950

(s), 2980 (m), 2360 (broad, s), 1910 (w), 1798 (w), 1660 (w), 1578 (s),

1475 (s), 1450 (m), 1420 (w), 1380 (s), 1345 (m), 1300 (s), 1288 (w),









1193 (s), 1170 (s), 1150 (s), 1085 (s), 1065 (m), 1040 (m), 1013 (s),

900 (m), 860 (m), 820 (s), 775 (m), 750 (s), 720 (w), and 630 (s) cm. .

The nmr spectrum showed resonance signals at 67.3 (m, 4); 62.7

(quartet, 6); and 61.2 (t, 9).



Preparation of l-phenyl-2-(4-chlorophenyl)-1,2-azaborolidine and
l-phenyl-5-(4-chlorophenyl)-l-aza-5-borabicyclo(3.3.0)octane

Triethylamine-(p-chlorophenyl)borane (22.7 g., 0.10 mol.), N,N-

diallylaniline (17.3 g., 1.0 mol.), and 1.25 1. of dry toluene were

placed in a 2-liter, round-bottomed flask. The contents were heated

on a Glas-ccl mantle and distilled through a packed column, Claisen

head and condenser. Initial heating caused a light green coloration

of the solution. After the temperature reached 1200 C at the distill-

ing head, the remainder of the solvent was removed on a rotary evap-

orator. During the distillat.ion, several infrared samples of the

solution, distillate, and gas above the solution were obtained. Propene

gas was trapped. Confirmation of this was obtained by comparison of

the gas sample spectrum with that in the Sadtler Spectra Index. The

crude, green-brown liquid was transferred to a 50 ml. round-bottomed

flask and placed on a spinning band distillation column. Four fractions

were obtained. The lowest boiling fractions were pale yellow liquids

(b.p. 120-1210 C @ 0.10 man.). This material, 15-16 g., was unstable

in air; several samples were sealed in ampoules. The nmr, ir, mass

spectrum, and analysis were consistent with the structure assignment

of l-phenyl-2-(4-chlorophenyl)-l,2-azaborolidine. The ir spectrum ex-

hibited absorbances at 3090 (m), 3060 (m), 2960 (s), 2890 (s), 1945 (w),

1920 (w), 1875 (w), 1800 (w), 1740 (w), 1595 (s), 1.560 (m), 1500 (s),