azlactones as polymer components and intermediates

Azlactones as Polymer Components and Intermediates

Polybenzimidazoles have been extensively in~estigatedl-~ since they were first described in 1959.4 The outstanding thermal and chemical stabilities of this class of polymers have suggested broad utility in high-temperature films, laminates, adhesives, fibers, and insulating foams.

Traditionally, polybenzimidazoles have been obtained by the reaction of aromatic tetraamines with dicarboxylic acids or their derivatives at high tern~eratures.'-~ In a two stage process for the preparation of poly[2,2'-( rn-phenylene)-5,5'bibenzimidazole], the final stage involves solid state polymerization at 385°C: A useful solution polymerization method has been described by Marvel utilizing refluxing sulfolane or diphenylsulfone as solvent? More recently, polyphosphoric acid has been utilized as a solvent for the preparation of a variety of polybenzimidazoles, polybenzoxa- zoles, and polybenzothiazoles?

We recently reported' that polyamides derived from the reaction of bis(2-oxazolin-5-one)s (bisazlactones) and diamines readily cyclodehydrate thermally to produce polymers containing 2-imidazolin-5-one units. Seeking to utilize bisazlactones in the synthesis of other heterocyclic polymer systems, we considered azlactones as reagents to convert o-phenylenediamines into benzimidazoles. We now report the facile preparation of benzimidazoles from the reaction of azlactones and o-phenylenediamines, and the extension of this reaction to the preparation of poly(amide-benzimidazo1e)s.

EXPERIMENTAL

Measurements

'H- and 13C-NMR spectra were recorded using a Varian EM360L, Jeol FX100, Varian XL200, or Varian XL400 spectrometer, under the conditions noted in Tables I and 11, using tetramethyl- silane or DMSO-d, as an internal reference. Infrared spectra were obtained on a Perkin-Elmer 283B spectrophotometer. Melting point determinations were made using a Bristoline hot-stage microscope and are uncorrected. A Cannon-Ubbelohde viscometer was used to determine the inherent viscosity of polymer solutions with concentrations of 0.5 g/100 mL in DMF at 30 0.1'C.

Materials

2-Phenyl-2-oxazolin-5-one (9a),15 N-benzoyl-a-aminoisobutyric acid,',, l7 4,4-dimethyl-2-phenyl- 2-oxazolin-5-one (9b)," N, N'-terephthaloylbis(glycine),'' N, N'-terephthaloylbis( a-aminoisobutyric acid)," 2,2-p-phenylenebis(2-oxazolin-5-one) (12a)," and 2,2'-p-phenylenebls(4,4- dimethyl-2-oxazolin-5-one) (12b)" were prepared according to literature procedures. 2,2'-rn-Phenylenebis(4,4-dimethyl-2-oxazolin-5-one) (12c), mp 125-127OC (lit." mp 129OC) was prepared by procedures analogous to those in the literature." 3,3',4,4'-Tetraaminobiphenyl was purified by sublimation (0.1 torr, 220°C) as yellow crystals, mp 181OC.

Model Compounds

N-Hippuryl-o-phenylenediamine (loa): A solution of o-phenylenediamine (3.36 g, 0.031 mol) in dry DMF (8 mL) was added to a vigorously stirred solution of 2-phenyl-2-oxazolin-5-one (5.0 g, 0.03 mol) in DMF (5 mL) at room temperature. After stirring overnight, the product was filtered, dried overnight in uacm, and crystallized from ethanol to give 1 O a in 95% yield: mp 228OC; IR (CHBr,) 3440,3220,1640-1480 cm- '; 'H-NMR (DMSO-d,) ppm 4.15(d, 2H) 4.96(s, 2H), 6.43-7.33(m,4H), 7.4-8.1(m,5H), 8.91(t, lH), 9.35(s, 1H). ANAL. Calcd for C,,H,,N,&: C, 66.9%; H, 5.6%; N, 15.6%. Found: C, 66.8%; H, 5.5%; N, 15.5%. N-(a-Benzoylaminoisobutyryl)-o-phenylenediamie (lob): A solution of 4,4-dimethyl-2-

phenyl-2-oxazolin-5-one (5.68 g, 0.030 mol) in THF (10 mL) was added dropwise to a solution of

Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 27, 1781-1790 (1989) 0 1989 John Wiley & Sons, Inc. CCC 0360-6376/89/051781-10$04.00

TA

BL

E I

'H-N

MR

Spe

ctra

of M

odel

Com

poun

ds and

Pol

ymer

s ~~

~

Com

poun

d N

H

CO

NH

' C

ON

H*

Aro

mat

ics

NHZ

CHZ

CH

,

10a*b

low

Ilea

lllf

13ac

l3bd

13C=

14'

1IW

16lf

15be

16c=

lSa*

16W

17ee

17lf

7.91 (d

, J =

7.5, 2). 7.40-7.54

(m, 3).

7.20 (

d, J

= 7.5, l), 6.92

(t,

J =

7.5, 1).

6.75 (d. J

= 7.5, l), 6.57

(t, J

= 7.5, 1)

6.82-7.02

(m, 2), 6.38-6.73

(m, 2).

7.88-8.00

(m, 2). 7.44-7.58

(m. 3),

7.96-8.07

(m, 2), 7.43-7.66(m, 5

). 7.11-7.22

(m, 2)

7.85-8.00 (

m, 2), 7.29-7.63

(m, 5). 7.01-7.21

8.17 (s

, 4), 7.50-7.90 (

m, 8)

8.00 (s,4), 7.62-7.88 (

m, 8)

8.20-8.40

(m, l), 7.96-8.10

(m, 2).

7.40-7.67 (m, 5)

, 7.03-7.23 (

m, 4)

7.94 (

d, J

= 8,4), 7.40-7.95 (

m, 12)

7.96-8.12

(m), 7.69-7.78

(m), 7.42-7.64

(m)

7.40-8.18

(m), 7.11-7.22 (

m) 6.70-6.84 (

m)

7.92-8.03

(m), 7.37-7.80

(m)

8.03 (

br s), 7.23-7.80 (

m),

6.56

-6.9

6 (m

)

7.00-8.20

(m. 10)

7.96 (

d, J

= 7,2), 7.61 (

d. J

= 7.5, 2).

7.55 (t

. J

= 7.5. 1).

7.48 (

t. J

= 7.5, 2).

7.28 (t

, J

= 7.5, 2). 7.03 (

t, J

= 7.5, 1)

7.80-7.93

(m, 3). 7.35-7.51

(m. 3)

7.78-7.95

(m, 2). 7.21-7.61

(m, 4)

4.12

-

(d, J

= 5.5,2)

1.53 (s, 6)

- 4.77

(d, J

= 5,2)

-

1.80 (s, 6)

5.35

-

-

2.21 (6, 12)

(d, J

= 6

.4)

-

1.79 (s, 12)

-

1.80 (

8, 12)

5.76 (

d, J

= 5), -

4.90(d.

J =

6) -

1.47 (s), 1.57 (s),

1.82 (s)

-

1.46 (s

) 1.80 (6)

-

1.52 (s

) 1.81

(s)

4.15 (

d. J

= 6.2) -

-

1.57 (s

, 6)

- 3.85 (

d, J

= 6,2),-

3.20 (m

, 2),

2.50 (m

, 2)

2.52

1.46 (s. 6

) ..

(b

r, 2)

(t. J

= 6, 23,304 (

q, J

= 6,2)

MH

z, D

MSO

-d,.

bSpe

ctru

m ru

n at

WC.

'100

MH

z, D

MSO

-d6.

dlOO M

Hz,

TFA

-d.

'ZOO

MH

z, D

MSO

-d6.

TABL

E I1

C

-NM

R S

pect

ra of

Mod

el C

ompo

unds

and

Poly

mer

s 13

Com

poun

d 'c

=o

*c=o

C

=N

A

rom

atic

s C

C

H,

CH3

10a%

b

lob"

lla'

llb

"

13ad

13

be

13C

c

14'

lSaa

1Sb"

1Sb"

lSC

c l

ad

1W

17a

17bc

167.

8

171.

7 -

-

- -

-

-

171.

6

175.

3

175.

8

173.

0 16

7.7

172.

9

169.

2 17

3.3

166.

6

165.

5

166.

7

164.

5 16

9.2

172.

4 16

5.4

166.

1

166.

3

165.

3 (p

lus o

ther

s)

165.

6

165.

8 16

6.6

166.

1

166.

5 16

5.2

-

-

152.

6

157.

7 14

9.3

157.

7 15

9.0

160.

1

153.

2

159.

9

160.

0

160.

1 -

-

-

-

142.

4, 1

33.9

, 130

.8, 1

27.8

, 126

.9,

143.

7, 1

33.5

, 130

.2, 1

27.2

, 127

.0,

134.

1, 1

31.5

, 128

.4, 1

27.6

, 121

.6

133.

6, 1

29.3

, 126

.6, 1

25.9

, 119

.6

137.

0, 1

32.1

, 130

.1, 1

29.8

, 115

.8

137.

7, 1

32.1

, 130

.3, 1

29.8

, 115

.7

134.

6, 1

29.8

, 128

.5, 1

28.4

, 127

.5,

134.

8, 1

31.2

, 128

.1, 1

27.7

, 121

.3,

136.

6, 1

35.6

,129

.7,

129.

6,12

9.5

125.

8, 1

25.4

, 122

.7, 1

16.0

, 115

.6

127.

7, 1

25.8

, 121

.6, 1

15.8

, 113

.9

118.

3, 1

11.5

126.

6, 1

25.5

, 121

.1, 1

14.4

120.

5, 1

18.4

, 116

.5, 1

11.3

, 109

.2

127.

8, 1

27.6

, 127

.5, 1

21.6

, 121

.5

115.

4, 1

12.9

11

2-14

0 (m

any

peak

s)

142.

0, 1

36.8

, 135

.2, 1

27.6

, 121

.5,

120.

8, 1

15.6

, 113

.6

112-

144

(man

y pe

aks)

13

8.9,

133

.9, 1

31.3

, 128

.6, 1

28.2

, 12

7.3,

123

.2, 1

19.1

13

9.5,

134

.6, 1

31.3

, 128

.4, 1

28.1

, 12

7.7,

123

.0, 1

20.1

13

4.0,

131.

3,12

8.2,

127.

4 13

4.0,

130

.1, 1

27.2

, 126

.6

-

55.6

-

51.6

55.2

52

.6

52.9

-

-

52.3

,54.

9 56

.5

52.8

, 55.

2

53.0

, 56.

6 -

57.0

-

55.4

43.1

-

38.0

-

37.6

-

-

-

41.6

,U.l

-

-

-

43.3

-

42.7

, 38.

4 41

.5,4

0.3

-

24.4

-

26.0

27.0

26

.9

27.5

-

-

24.4

26

.4

24.6

26

.8

25.1

, 27.4

-

25.0

-

24.2

'101

MH

z, D

MSO

-d6.

b

~p

ec

t~

ru

n at

97

0~

. '50

.3 M

Hz,

DM

SO-d

6.

d25J

MH

z, D

MSO

-d6.

el

Ol M

Hz,

TFA

-d.

1784 J. POLYM. SCI. POLYM. CHEM. ED. VOL. 27 (1989)

o-phenylenediamine (3.24 g,O.O30 mol) in THF (50 mL) at room temperature. After stimng overnight, the colorless precipitate was filtered and washed with THF and dried to give 2.1 g of lob. The filtrate was concentrated under reduced pressure to give an additional 4.8 g of product: total yield 6.9 g, 77%. Recrystallization from ethanol gave an analytical sample, mp 188-189°C.

ANAL. Calcd for C,,H,,N30,: C, 68.7; H, 6.4; N, 14.1. Found: C, 69.4; H, 6.6; N, 14.3. 2-(Benzoylaminomethyl)benzimidazole (lla): A solution of o-phenylenediamine (3.36

g, 0.031 mol) and 2-phenyl-2-oxazolin-5-one (5.0 g, 0.031 mol) in dry DMF (20 mL) was refluxed 18 h under nitrogen. The mixture was cooled to room temperature and poured into water (50 mL) to give a yellow precipitate which was filtered, washed with water, then ether, and recrystallized from acetonitrile to give l la in 96% yield: mp 236°C.

ANAL. Calcd for C,,H,,N,O: C, 71.7%; H, 5.2%; N, 16.7%. Found: C, 71.6%; H, 5.2%; N, 16.6%. 2-(2-Benzoylamino-2-propyl)benzimidazole (llb): Diamide (lob) (1.5 g, 0.005 mol) was sus-

pended in dry DMF (2.5 mL) and the mixture brought to reflux to produce a reddish solution. After being refluxed for 3.5 h, the mixture was cooled, diluted with water (10 mL), and the precipitate filtered, washed thoroughly with water followed by ether, and dried to give 1.10 g (78%) of the benzimidazole (llb), mp 294-294.5”C. Recrystallization from ethanol gave an analytical sample, mp 297-297.5”C.

ANAL. Calcd for C,,H,,N,O: C, 73.1; H, 6.1; N, 15.0. Found: C, 73.0; H, 6.2; N, 15.2. 1,4-Phenylenebis(carbamidomethyl-2-benzimidazole) (13a): A solution of o-phenylene-

diamine (4.32 g, 0.04 mol) in dry DMF (15 mL) was added to a solution of 2,2’-pphenylenebi42- oxazolin-5-one] (12a) (5.0 g,O.O2 mol) in DMF (20 mL) at 100°C under an inert atmosphere. The reaction mixture was stirred at this temperature for 16 h. After being cooled to room temperature, the mixture was poured into water (100 mL) to precipitate the product in 76% yield: mp 294°C (acetone/ether).

ANAL. Calcd for ~,H,,N,O,: C, 67.9%; H, 4.7%; N, 19.8%. Found: C, 67.8%; H, 4.8%; N, 19.7%. 1,4-p-Phenylenebis(carbamido-2-propyl-2(2’)-benzimidazole) (13b): 2,2‘-p-

Phenylenebis[4,4-dimethyl-2-oxazolin-5-one] (12b) (5.0 g, 0.016 mol) was reacted with o-phenylenediamine (3.45 g,O.O32 mol) in DMF (30 mL) at 140°C for 24 h under an inert atmosphere. The product was precipitated by pouring into water (100 mL), purified by dissolving in hot DMF and reprecipitating with water, then dried overnight in uucuo, the yield was 89%: mp > 360OC; IR (Nujol) 3300, 1640, 1525, 1490, 1445, 1420, 1305, 1275 cm.-’

ANAL. Calcd for C,H,N,O,: C, 69.9%; H, 5.8% N, 17.5%. Found: C, 69.8% H, 5.7%; N, 17.2%. 1,3-m-Phenylenebis(carbamido-2-propyl-2(2’)-benzimidazole) (13c): 2,2‘-m-

Phenylenebis[4,4’-dimethyl-2-oxazolin-5-one] (12c) (1.80 g, 6 mmol) was reacted with o-phenylenediamine (1.30 g, 12 mmol) in DMF (10 mL) at reflux for 24 h under an inert atmosphere. The product was precipitated by pouring into diethyl ether (200 mL), purified by dissolving in hot DMF and reprecipitating with ether, then dried in a vacuum oven for 2 days at 75°C. The yield was 75%: mp 220-223°C. MASS SPEC. Calcd for C,,H,,N,O,: m/z 480.2274. Found: m/z 480.2268. 2,2’-(2-Benzoylamino-2-propyl)-5,5,-bi-lH-benzimidazole (14): 4,4-Dimethyl-2-pheny1-2-

oxazolin-5-one (9b) (10.6 mmol), 3,3’,4,4‘-tetraaminobiphenyl (1.1 g, 5.3 mmol) and freshly fused sodium acetate (0.87 g,10.6 mmol) were heated at reflux in acetic acid (20 mL) for 4 h. The product was cooled, poured into water (80 mL), and stirred for 15 min. The precipitate was filtered, washed with water, and dried in uucuo. Recrystallization from ethanol/acetonitrile gave 14 in 76% yield, mp 276-277°C.

ANAL. Calcd for CMH3,N602: C, 73.3%; H, 5.8%; N, 15.1%. Found: C, 73.1%; H, 5.6%; N, 14.8%. N-Hippuryl-aniline (16a): Distilled aniline (0.58 g, 60 mmol) was added to a solution of

2-phenyl-2-oxazolin-5-one (1.00 g, 60 mmol) in DMF (10 mL) and was stirred at 70°C for 48 h. After cooling to room temperature, the reaction mixture was poured into water (100 mL) and stirred for 0.5 h. The white solid was filtered off, dried in uacuo, and recrystallized from ethanol (0.6 g in 10 mL) to give 16a in 77% yield; mp 215OC.

ANAL. Calcd for C,,H,,N,O,: C, 70.8%; H, 5.5%; N, 11.0%. Found: C, 70.8%; H, 5.5%; N, 10.9%. N-Phenyl-u-benzoylaminoisobutyramide (16b): Freshly-distilled aniline (0.49 g, 53 mmol)

and 4,4-dimethyl-2-phenyl-2-oxazolin-5-one (1.00 g, 53 mmol) in dry DMF (15 mL) were stirred at room temperature for 15 h. The reaction mixture was poured into water (200 mL) and stirred for another 0.5 h. The white solid was filtered off, dried in uucuo, and recrystallized from ethanol as long needles; mp 226°C. The yield was 1.3 g (87%).

ANAL. Calcd for C,,H,,N,O?: C, 72.3%; H, 6.4%; N, 9.9%. Found: C, 72.3%; H, 6.5%; N, 9.9% N-Hippuryl-ethylenedmmm e (17a): Freshly-distilled ethylenediamine (0.37 g, 60 mmol) in

dry DMF (2 mL) was added dropwise to a solution of 2-phenyl-2-oxazolin-5-one (1.00 g, 60 mmol)

NOTES 1785

in DMF (5 mL) at 0°C and the reaction mixture was stirred for an additional 0.5 h. The cream-colored paste was poured into water (100 mL) and stirred for 0.5 h. The precipitate was filtered off, dried in vacw, and recrystallized from methanol (300 mL) to give l?a, mp 286°C. The yield was 0.9 g (66%).

ANAL. Calcd for CllH15N302: C, 59.7%; H, 6.8%; N, 18.9%. Found C, 59.6%; H, 6.8%; N, 18.7%. N~2-Aminoethyl)-a-benzoylaminoisobut~de (1%): 4,4-Dimethyl-2-phenyl-2-oxazolin-

5-one (5.0 g, 0.026 mol) in THF (25 mL) was added dropwise to a stirred solution of ethylenediamine (4.77 g, 0.080 mol) in THF (25 mL). A mild -0th- ensued. After stirring a total of 0.5 h, the colorless precipitate which had formed was filtered, washed with cold DMF, and dried. Concentration of the filtrate produced additional material which was combined with the first crop and recrystallized from THF: yield 5.04 g (76%), mp 151.5-152.5OC.

ANAL. Calcd for C13H19N303: C, 62.6; H, 7.7; N, 16.9. Found: C, 62.2; H, 7.6; N, 16.6.

Polymer Preparations

2,2’-p-Phenylenebi$2-oxazolin-5-one] (12a) and 2,2’-p-phenylenebi$4,4-dimethyl-2-oxazolin-5- one] (12b) (0.014 mol) were each condensed with 3,3’4,4’-tetraaminobiphenyl (3.0 g, 0.014 mol) by stirring in acetic acid in the presence of sodium acetate (1.15 g,0.014 mol). The reaction was carried out under a stream of nitrogen at 140°C. After 6 h, the reaction mixture was cooled to room temperature and water (200 mL) was added to precipitate the polymer which was filtered off, washed with water, and dried in vacw.

Alternatively, a solution of 3,3’4,4’-tetraaminobiphenyl (1.28 g, $01 mmol) in DMF (3 mL) was added dropwise into a solution of 2,2’-phenylenebi$4,4-dimethyl-2-oxazolin-5-one] (2.00 g, 6.01 mmol) in DMF (10 mL) under an atmosphere of nitrogen. The reaction mixture then was stirred at 145°C for 24 h. After cooling to RT, the reaction mixture was added dropwise to well-stirred water (100 mL) to give a brown precipitate which was filtered off and dried in a vacuum oven at 90°C for 24 h. Further purification by dissolving in DMF and reprecipitating with water gave polymer (15b).

Equimolar amounts of 2,2’-rn-phenylenebi$4,4-dimethyl-2-oxazolin-5-one] (12c) and 3,3’,4,4’- tetraaminobiphenyl were allowed to react by stirring in either dichlorobenzene (5 mL, 2.50 mmol scale) or dry DMF (10 mL, 8.0 mmol scale) a t reflux under an inert atmosphere. After 24 h, the reaction mixture was cooled to room temperature and added to diethyl ether in order to precipitate the polymer which was filtered off, washed with ether, and dried in vacw.

Film Casting of Polymers

Polymer films were prepared by casting polymer solutions onto a glass plate by a doctor blade technique. To ensure complete removal of solvent, the films were heated overnight a t 100°C. The films obtained in this way were brittle.

RESULTS AND DISCUSSION When the present work was started, there was no report of the reaction of any type of

oxazolone with o-phenylenediamines with the exception of the reactions of 2H-oxazol-5-ones (1) (Scheme 1) to give quinoxalones (2): In an isolated example with the isopropyl compound (1, R = iPr), the intermediate (3) could be isolated as a byproduct (20%) which readily cyclized to benzimidazole (4). However, during the course of our work, Habib et al.” described the reaction of one particular class, 2-aryl-4-arylmethylene-2-oxazolin-5-ones (5) (Scheme 2) with o-phenylenediamine and sodium acetate which they found led to either benzimidazo[2,1-elimidazoles (6), or to 2-( a-phenylcarboxamido-/3-aryl)vinylbenzimidazoles (7) depending on the reaction conditions. The intermediate aminoamides (8) could be isolated by conducting the reaction in ethanol as solvent. Additional examples of benzimidazoles have been described more recently by Harb et d.”

Formation of Benzimidazoles from Oxazolones We now find that oxazolinones of type (9) (saturated azlactones) react readily with o-phenyl-

enediamine (Scheme 3). At 25°C in DMF, the product is an amide (10); at higher temperatures ring closure into the expected benzimidazole (11) readily occurs. The two steps can conveniently be carried out in one operation by reacting in DMF at 120’C. The thermal cyclodehydration


H

- 1 2

NHCO-CH-NH-CO-CF,

H

2 4 Scheme 1.

reactions were exceptionally clean, with no evidence for cyclization to isomeric imidazolinones' being noted. In view of the good yields (60-90%) and smooth course of the reactions, we were encouraged to

apply the reaction of o-phenylenediamine with azlactones to polymer synthesis. Bis(a-carboxymethylamides) were prepared by a literature method" via the reaction of

isophthaloyl or terephthaloyl chloride with the appropriate amino acid in aqueous solution.

Ph

5

a NH2 NH2

NaOAc

HOAc. c

COPh

B

Ph

HOAc. A

ArcHal NY Ph

§ z Scheme 2.

NOTES 1787

o R O I! I II

PhCNH-C-C NHPh I

k

O I1 7 : : PhCNH- C-C -NHCH,CH,NH2

R

a) R= H; b) R= CH,

Scheme 3.

Cyclodehydration in acetic anhydride by the literature method'* gave 2,2'-phenylenebi.$2-oxazolin-5-one)i (12a-c) in 6545% yields with physical properties in good agreement with the literature.

We next proceeded with model reactions in which bis(benzimidazo1e)s were prepared. Model compounds (13a-c) were prepared by reaction of bis(azlactone)s (lZa), (12b), and (12c) respec- tively with o-phenylenediamine in DMF (Scheme 4), and were characterized by elemental analysis and NMR spectrogcopy.

a) R= H. X= p-GH,,; b) R= CH,. X= p-C& c) R= CH,. X= m-C&

Scheme 4.


P

PhCOHN- !qNm ?& C- P NHCOPh

I N ’ H N R H H

1l a) R= H b) R= CH,

Scheme 5.

Model compound (14) (Scheme 5) was synthesized by the reaction of two equivalents of 4,4-dimethyl-2-phenyl-2-oxamlin-5-one (9b) with one equivalent of 3,3’,4,4’-tetraaminobiphenyl (3,3’-diaminobenzidine) in the presence of sodium acetate in acetic acid solution.

hparation of Polybenzimidazoles Encouraged by these results, we turned to polymer synthesis. We found that each of the

bisoxazolinones (12a-c) reacted readily with 3,3’,4,4’-tetraaminobiphenyl to give the expected polymers (16a-c) (Scheme 6): in acetic acid solution yields of 83-89% of isolated material were achieved; in DMF or dichlorobenzene the yield was - 90%.

R R

a) R= H. X= &€J,

b) R= CH3. X= pGj& c) R= C H 3 , X= m-C&

Scheme 6.

NOTES 1789

TABLE111 Preparation and Characteristics of Poly(amidebenzimidazo1e)s

Reaction TGA Polymer Conditions IV" KJ % Cyclicb ("C)

0.12 - 60 285 15a

0.11 3840g-5140h 65 325 15b 15b 1SC 0.10 - 20 -

d d 0.10 3300' 30 290 e

e

"Inherent viscosity measured in DMF, 30°C at a concentration of 0.5 g/100 mL. bDetermined by 'H - NMR. '10 % Weight lass, N, atmosphere. dAcetic acid/ sodium acetate, reflux 6 h. "DMF, 145"C, 24 h. ' Determined by low angle laser light scattering (DMF). 'GPC (DMF + 0.1% LiBr), polystyrene standard, differential refractive index detector. hGPC (DMF + 0.1% LiBr), polystyrene standard, W detector.

Preparation conditions and some characteristics of the polmers are listed in Table 111. Inherent viscosities and GPC results indicate that these polymers are of relatively low molecular weight. In addition, NMR studies (see below) indicate that, in general, incomplete cyclization occurred under the reaction conditions. These two facts may account in part for the relatively poor TGA behavior; in fact, the increased cyclic content of polymer 15b as compared to 15b seems to result in a modest increase in thermal stability. These thermal characteristics, however, are similar to those reported by Ueda et al.,'3 for a number of polyamides derived from bisoxazolinone 12a. Higher molecular weights and degrees of cyclization must be obtained before the thermal stability of this class of polybenzimidazoles can be adequately assessed.

Model NMR Compounds

Benzoylamide derivatives (Ma, b) and (17% b) were readily prepared by mixing the appropriate oxazolinone, (9a) or (gb), and either aniline or ethylenediamine in dry DMF or THF (Scheme 3). These compounds were analyzed by l3 C-NMR spectroscopy (Table 11) as simple models for the more complex compounds we sought to make.

Structural Characterization

Our structure assignments are supported by elemental analysis and by spectroscopic data. Infrared spectra for the poly(amide-benzimidazo1e)s in general were similar to those of the benzimidazole and bisbenzimidazole model compounds although the absorption bands for the former were somewhat broader. NMR spectroscopy proved to be a much more valuable tool, however, for following initial amide formation and subsequent cyclization to benzimidazoles. 'H-NMR spectra (Table I) of the open-chain model compounds (10) exhibit two downfield absorptions due to the amido-NH groups. The first of these, due to the benzamido group, appeared either as a singlet (next to the gem-&ethyl group in lob) or as a broad triplet (next to CH, in lOa). The absorption furthest downfield, due to the alkylamido group, was replaced upon cyclization by an absorption near 12 ppm due to the benzimidazole ring NH. Cyclization also resulted in a downfield shift of the absorption peak for the CH, group in the a series compounds of about 0.8 ppm and of about 0.3-0.4 ppm for the methyl groups of the b series compounds. Further evidence for the formation of benzimidazole rather than imidazolinone derivatives comes from 13C-NMR studies (Table 11). The spectrum of N-hippuryl-o-phenylene diamine (lOa) exhibits peaks at 167.8 and 166.6 ppm, corresponding to two different amide carbonyl groups. Upon cyclization to benzimidazole derivative lla, the peak at 167.8 ppm disappeared and a new peak appeared at 152.6 ppm, which is characteristic of C=N in benzimidazole ~ompounds.'~ No peaks in the vicinity of 180 ppm characteristic of imidazolinone carbonyls* were observed. In addition, cyclization of 1Oa to l l a results in an upfield shift of the methylene carbon. While a


similar shift of the quaternary carbon of lob is seen upon cyclization to benzimidazole (llb) (Table 11), the absorption peak for the methyl carbons shifts downfield by about 2 ppm. Absorptions corresponding to those of the model compounds are readily observed in the spectra of the polymers (16), thus allowing estimation of the relative amounts of open-chain and cyclic structures in these polymers.

References

1. J. P. Critchley, G. J. Knight, and W. W. Wright, Heat-Resistant Polymers, Plenum, New

2. P. E. Cassidy, T h e d y Stable Polymers, Dekker, New York, 1980, pp. 163-173. 3. H. H. Levine, in Encyclopedia of Polymer Science and Technology, H. F. Mark, N. Gaylor,

4. K. C. Brinker, and I. M. Robinson, U.S. Pat. 2,895,948 (1959); Chem. Abstr., 53, 18552f

5. A. B. Conciatori, and E. C. Chenevey, Macromol. Synth., 3, 24-28 (1968). 6. F. L. Hedberg, and C. S. Marvel, J. Polym. Sci. Polym. Chem. Ed., 12, 1823-1828 (1974). 7. R. C. Evers, F. E. Arnold, and T. E. Helminiak, Macromolecules, 14, 925-930 (1981). 8. J. K. Rasmusren, S. M. Heilmann, L. R. Krepski, H. K. Smith 11, A. R. Katritzky, and

9. F. Weygand, W. Steglich, and H. Tanner, Justus Liebigs Ann. Chem., 658, 128 (1962).

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10. H. M. Hassan, M. S. El-Husseni, and 0. M. 0. Habib, J. Prakt. Chemie, 325, 685 (1983). 11. A. A. Harb, S. E. Zayed, A. M. El-Maghraby, and S. A. Metwally, Heterocycles, 24, 1873

12. C. S. Cleaver and B. C. Pratt, J. Am. Chem. SOC., 77, 1544 (1955). 13. M. Ueda, K. Kino, K. Yamaki, and Y. Imai, J. Polym, Sci. Polym. Chem. Ed., 16, 155

14. V. A. Lopyrev, L. I. Larina, T. I. Vakul'skaya, M. F. Larin, 0 B. Nefedova, E. F. Shibanova,

15. M. Crawford and W. T. Little, J. Chem. SOC., Part 1,729 (1959). 16. R. E. Steiger, J. Org. Chem., 9, 396 (1944). 17. G. Heller and H. Lauth, Chem. Ber., 52, Part 2, 295 (1919). 18. H. Rodriguez, C. Chuaqui, S. Atala, and A. Marquez, Tetrahedron, 27,2425 (1971). 19. H. Humbert, G. Fuchs, and D. Pirck, Ger. Pat. 2,522,192; Chem. Abstr., 86, 18524j (1977). 20. H. .A. Vogel and C. S. Marvel, J. Polym. Sci. A-1, 1531 (1963).

(1986).

(1978).

and M. G. Voronkov, Org. Mag. Reson., 15(3), 219 (1981).

ALAN R. UTRITZKY* KUMAFS SAKIZADEH JOEL SWINSON

Department of Chemistry University of Florida Gainsville, Florida 32611

3M Company Corporate Research Laboratories 3 M Center St. Paul, Minnesota 55144

Received August 12,1987 Accepted June 1, 1988

STEVEN M. HEILMANN JERALD K. RASMUSSEN LARRY R. KREPSKI D. M. MOREN H. K. SMITH I1 . SADANAND V. PATHRE

'To whom all correspondence should be addressed.

azlactones as polymer components and intermediates

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