Synthesis of heterocyclic containing benzoxazole moiety

Article abstract of DOI:10.1080/10426500701641262

3-Aryl-2-benzoxazol-2-yl-2-[4-oxo-5-(phenylmethylene)(1, 3-thiazolidin-2-ylidene)ethanenitrile, 3-aminothiophenes, thiazoles and 2,3-dihydro-1,3,4-thiadiazoles were synthesized from 2-benzoxazol-2-yl-2(4-oxo- 3-phenylthiadiazolidin-2-ylidene)-ethanenitril

Full text of DOI:10.1080/10426500701641262

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Synthesis of Heterocyclic
Containing Benzoxazole Moiety
A. O. Abdelhamid a , V. B. Baghos a & M. M. A. Halim
b
a Department of Chemistry, Faculty of Science ,
Cairo University , Giza, Egypt
b Hormone Department , National Research Center,
Dokki , Giza, Egypt
Published online: 04 Jun 2008.
To cite this article: A. O. Abdelhamid , V. B. Baghos & M. M. A. Halim (2008) Synthesis
of Heterocyclic Containing Benzoxazole Moiety, Phosphorus, Sulfur, and Silicon and
the Related Elements, 183:6, 1313-1322, DOI: 10.1080/10426500701641262
To link to this article: http://dx.doi.org/10.1080/10426500701641262
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Phosphorus, Sulfur, and Silicon, 183:1313–1322, 2008
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500701641262
Synthesis of Heterocyclic Containing Benzoxazole Moiety
A. O. Abdelhamid,1 V. B. Baghos,1 and M. M. A. Halim2
1Department of Chemistry, Faculty of Science, Cairo University,
Giza, Egypt
2Hormone Department, National Research Center, Dokki, Giza, Egypt
3-Aryl-2-benzoxazol-2-yl-2-[4-oxo-5-(phenylmethylene)(1,3-thiazolidin-2-ylidene)-
ethanenitrile, 3-aminothiophenes, thiazoles and 2,3-dihydro-1,3,4-thiadiazoles
were synthesized from 2-benzoxazol-2-yl-2(4-oxo-3-phenylthiadiazolidin-2-
ylidene)-ethanenitrile and the appropriate of each of halo ketones and hydrazonoyl
halides. The newly synthesized compounds were elucidated by elemental analysis,
spectral data, and alternative synthetic route whenever possible. All these
compounds expected to possess biological activity.
Keywords 2,3-Dihydrothidiazoles 3-aminothiophenes; hydrazonoyl halides; thiazo-
lidines
INTRODUCTION
Medicinal compounds derived from oxazole include the antiepilep-
tic drugs trimethadione and paramethadione,1 the sedative and
muscle-relaxant zoxazolamine, and furazolidone, which is effective
against a wide range of enteric infections. Derivatives of oxazo-
lidine show promise as appetite depressants.2 Oxazole derivatives
have attracted attention because of their potential biological ac-
tivity and their use as a versatile starting material in organic
synthetic transformations.3 We report here several heterocyclic com-
pounds expected to possess biological activity from 2-benzoxazol-2-yl-
3-(phenylamino)-3-thioxopropanenitrile.4
RESULTS AND DISCUSSION
Treatment of 2-benzoxazol-2-yl-3-(phenylamino)-3-thioxopropane-
nitrile4 (1) with each of chloroacetone and ω-bromoacetophenone
Received 5 June 2007; accepted 30 July 2007.
Address correspondence to A. O. Abdelhamid, Department of Chemistry, Faculty of
Science, Cairo University, Giza 12622, Egypt. E-mail: Abdou abdelhamid@yahoo.com
1313

1314
A. O. Abdelhamid et al.
in N,N-dimethylformamide containing potassium hydroxide af-
forded 2-benzoxazol-2-yl-3-(2-oxopropylthio)-3-(phenylamino)prop-2-
enenitrile (2a) and 2-benzoxazol-2-yl-3-(2-oxo-2-phenylethylthio)-3-
(phenylamino)prop-2-enenitrile (2b), respectively (Scheme 1).
SCHEME 1
Structures 2a and 2b were confirmed by elemental analysis, spectral
data, and chemical behavior. IR spectra of 2a and 2b revealed bands at
1
3112 (NH), 2186 (CN) and 1675–1645 (CO). H NMR spectrum of 2a
showed signals at δ = 1.85 (s, 3H, CH3CO), 3.45 (s, 2H, CH2) and 6.85–
7.35 (m, 10 H, ArH’s, and NH). Compounds 2a and 2b were converted
to 3-aminothiophene derivatives 4a,b via its boiling under reflux in
ethanol containing catalytic amount of piperidine. IR spectra of 4a,b
1
revealed bands near 3473, 3280, 3190 (NH, NH2), and 1673 (CO). H
NMR spectrum of 4b showed signals at δ = 7.21–7.72 (m, 14H, ArH’s)
and 11.18 (s, br., 3H, NH2, and NH) exchangeable with D2O.
Treatment of the appropriate 2a and 2b with sulfuric acid or
polyphosphoric acid afforded the thiazoles 3a and 3b, respectively. The
structure of 3 was confirmed based on elemental analysis and spectral
data. Thus, IR spectra of 3(a,b) revealed bands near 2188 (CN) and no
bands between 2000-1600 due to the absence of (CO) group.5 1H NMR
spectrum of 3a showed signals at δ 1.8 (s, 3H, CH3) and 7.22–7.77 (m,
10H, Ar-H’s and thiazole C-5).
Analogously, treatment of 1 with 3-chloropentane-2,4-dione in
N, N-dimethyl-formamide containing potassium hydroxide, afforded

Heterocyclic Containing Benzoxazole Moiety
1315
3-aminothiophene 4a and thiazole 7 (Scheme 1). Structure 7 was eluci-
dated by elemental analysis and spectral data. Thus, 1H NMR spectrum
of 7 showed signals at δ = 2.25 (s, 3H, CH3CO), 2.65 (s, 3H, CH3 thiazole
C-4), and 7.22–7.85 (m, 9H, ArH’s). Its IR spectrum revealed bands near
2194 (CN), 1675 (CO) and 1602 (C N). The formation of these products
involves initial attack by one molecule of 3-chloropentane-2,4-dione to
one molecule from thioanilide 1 to give intermediate 5 which cyclized to
final products 7 via elimination of one molecule of water and 4a through
elimination of one molecule of acetic acid.
Also, ethyl 2-chloro-3-oxobutanoate reacted with thioanilide
1
in N, N-dimethylformamide containing potassium hydroxide
to afford ethyl 3-amino-4-benzoxazol-2-yl-5-(phenylamino)-thiophene-
2-carboxylate (8) and 2-(5-acetyl-4-oxo-3-phenyl(1,3-thiazolidin-2-
ylidene)-2-benzoxazol-2-ylethanenitrile (9) (Scheme 1). Structures 8
and 9 were confirmed based on elemental analysis and spectral data.
Thus, IR spectrum of 8 revealed band at 3303, 3228, 3163 (NH2 and
NH), 1658 (CO), and 1600. Its 1H NMR (δ ppm) showed signals at 1.24
(t, 3H, CH3CH2), 4.25 (q, 2H, CH2CH3), 7.28–7.81 (m, 9H, ArH’s), and
10.55 (s, br., 3H, NH2 and NH). IR spectrum of 9 revealed bands at 2194
1
(CN), 1680, 1635 (CO’s) and 1610 (C N). Its H NMR (δ ppm) showed
signals at δ = 1.85 (s, 1H, CH3), 6.35 (s, 3H, thiazole C-5), and 6.95–7.77
(m, 9H, ArH’s).
Treatment of thioanilide 1 with the appropriate hydrazonoyl halides
10a–e in presence of potassium hydroxide to give 2,3-dihydro-1,3,4-
thiadiazole derivatives 14a–e, respectively (Scheme 2). Structure 14
was confirmed by elemental analysis, spectral data, and alternative
1
method synthesis. Thus, H NMR spectrum of 14a showed signals at
δ = 1.35 (t, 3H, CH3 CH2), 4.55 (q, 2H, CH2 CH3), and 7.25 (m, 9H,
ArH’s). Its IR spectrum revealed band at 2204 (CN), 1743 (CO) and
1
1610 (C N). H NMR (δ ppm) spectrum of 14b showed signals at δ =
1.35 (t, 3H, CH3 CH2), 2.45 (s, 3H, 4-CH3C6H4), 4.45 (q, 2H, CH2 CH3),
and 7.25–7.80 (m, 8H, ArH’s). Meanwhile, the product seemed to be
one of two isomeric structures, 14a, and 14b. By M.O. calculation using
Hyper-Chem and MBI3 method indicated the isomeric 14a more stable
than isomeric 14b (Scheme 2).
The formation of product 14 can be explained via elimination of ani-
line from the cycloadduct of nitrile imide 11 (which generated in situ by
treatment of hydrazonoyl chloride 16 with base) to CS double bond of
thioanilide 1 or by stepwise path involving substitution to give a cyclic
hydrazone 16, which easy transferred to cyclic intermediate 17. The
latter gave14 via elimination of aniline (Scheme 3).
An unequivocal support for structure 14a, came from reaction of the
appropriate C-ethoxycarbonyl-N-phenylhydrazonoyl chloride 10a with

1316
A. O. Abdelhamid et al.
SCHEME 2
SCHEME 3
2-benzoxazol-2-yl-3-methylthio-3-sulfanylprop-2-enenitrile 15, which
prepared from 2-benzoxazol-2-yl-ethanenitrile with carbon disulfide in
N,N-dimethylformamide containing potassium hydroxide followed by
addition of iodomethane, in presence of triethylamine gave product

Heterocyclic Containing Benzoxazole Moiety
1317
identical in all aspects (m.p., mixed m.p. and spectra) with 14a via
elimination of methyl mercaptan (Scheme 3).
On the other hand, treatment of the appropriate arenediazonium
chloride with 2-benzoxazol-2-yl-2(4-oxo-3-phenylthiadiazolidin-2-
ylidene)ethanenitrile4 (19) in pyridine gave 2-{5-[aza(arylamino)-
methylene]-4-oxo-3-phenylthiadiazolin-2-ylidene)}-2-benzoxazol-2-yl-
ethane-nitrile 20(a,b) (Scheme 4). Structure 20 was confirmed by
elemental analysis and spectral data. Thus, IR spectra of 20 revealed
1
bands at 2210 (CN), 1741 (CO), and 1610 (C N). H NMR spectrum
of 20b showed signals at δ 2.23 (s, 4-CH3C6H4), 7.25–7.77 (m, 13H,
ArH’s), and 13.12 (s, br., 1H, NH).
SCHEME 4
Also, treatment of 19 with (phenylmethylene)methane-1,1-dicarbo-
nitrile in ethanoic triethylamine under reflux gave 2-benzoxazol-
2-yl-2-[4-oxo-3-phenyl-5-(phenylmethylene)(1,3-thiazolidin-2-ylidene)-
ethanenitrile (22a). Structure of 22 was elucidated by elemental
analysis, spectral data, and alternative synthetic method. IR spec-
trum of 22a revealed bands at 3060 (CH, vinyl) 2216 (CN), 1708
1
(CO) and 1604 (C N). Its H NMR spectrum showed signals at δ =
7.22–7.75 (m, 9H, ArH’S) and 8.55 (s, 1H, CH ). Thus, compound
19 reacted with the benzaldehyde in ethanol containing catalytic
amount of piperidine afforded product identical in all respects (mp,
mixed m.p., and spectra) with22a. The reaction can be explained
via Michael addition between 19 and (phenylmethylene)methane-
1,1-dicarbonitrile in ethanoic triethylamine afforded intermediate
21, which readily converted to 22a via elimination of malonon-
itrile and did not give 5-amino-2-(benzoxazol-2-ylcyanomethy-
lene)-3,7-diphenyl-4H-pyran[2,3-d]1,3-thiazoline-6-carbonitrile
(23)
(Scheme 4).

1318
A. O. Abdelhamid et al.
EXPERIMENTAL
All melting points were uncorrected. IR spectra were recorded (KBr
disc) on a Shimadzu FT-IR 8201 PC Spectrophotometer. 1H-NMR spec-
tra were recorded in CDCl3or (CD3)3SO on a Varian Gemini 200
MHz Spectrometer and chemical shifts were expressed in units us-
ing TMS as an internal reference. MS spectra were recorded on a GC-
MS GP 1000 Shimadzu, Japan. Elemental analyses were carried out
at the Microanalytical Center, Cairo University, Giza, Egypt and Na-
tional Research Center. Hydrazonoyl halides6−1210a–e, 2-benzoxazol-2-
ylethanenitrile,13,14 and 14 were prepared according to previous meth-
ods in literature.
Synthesis of 2-Benzoxazol-2-yl-3-(2-oxopropylthio)-3-
(phenylamino)prop-2-enenitrile (2a) and
2-Benzoxazol-2-yl-3-(2-oxo-2-phenylethylthio)-3-(phenyl-
amino)prop-2-enenitrile (2b)
To a mixture of 2-benzoxazol-2-ylethanenitrile (1.58 g, 10 mmol), potas-
sium hydroxide (0.56 g, 10 mmol) and phenyl isothiocyanate (1.35 g, 10
mmol) in dry N, N-dimethylformamide (10 mL) was stirred for 2 h.
Chloroacetone or phenacyl bromide (10 mmol) was added and the mix-
ture was stirred for 2 h, and then diluted with water (10 mL). The solid
product was collected by filtration, washed with water, and recrystal-
lized from the proper solvent to give8a and 8b (Tables I and II).
1-[3-Amino-4-benzoxazol-2-yl-5-(phenylamino)-2-
thienyl]ethane-1-one (3a), and
1-[3-Amino-4-benzoxa-zol-2-yl-5-(phenylamino)-2-
thienyl]phenyl-1-one (3b)
A mixture of the appropriate compounds 2a or2b (10 mmol) in ethanol
(50 mL) and (5 drops) piperidine was refluxed for 2 h. The reaction
mixture was left to cool; the resulting product was collected and recrys-
tallized from the proper solvent to give 3a and 3b (Tables I and II).
2-Benzoxazol-2-yl-2-[4-methyl-3-phenylthiazolin-2-
ylidene]ethanenitrile (4a) and
2-Benzoxazol-2-yl-2-(3,4-Diphnylthiazolidin-2-ylidene
ethanenitrile (4b)
A mixture of the appropriate weight of the compound 2a (1.04 g, 3 mmol)
or 2b (1.23 g, 3 mmol)) and concentrated sulfuric acid (10 mL) was
stirred for 1 h at room temperature. The reaction mixture was poured

Heterocyclic Containing Benzoxazole Moiety
1319
TABLE I Characterization Data of the Newly Synthesized
Compound
% Analyses, calcd./found
Compd.
no.
M.p., ◦C
solvent
Yield %
color
Mol. formula
mol. wt.
C
H
N
S
2a
173–175
EtOH
156–158
EtOH
71
Colorless
55
Colorless
48
Yellow
50
Yellow
74
Pale yellow
48
Pale yellow
34
Pale yellow
31
Pale yellow
34
Pale yellow
71
Yellow
66
Yellow
64
Yellow
75
Yellow
66
Orange
48
Yellow
55
Yellow
45
C19H15N3O2S
349.40
65.30
65.50
70.03
70.20
68.86
68.57
73.25
73.10
65.30
65.60
70.05
70.00
67.54
67.00
63.30
63.50
63.98
63.90
61.52
61.08
62.36
62.10
65.89
65.90
63.32
63.10
68.23
68.24
65.85
65.62
66.51
66.30
71.24
71.60
71.70
71.60
65.86
65.60
69.16
69.09
4.32
4.00
4.96
4.60
3.95
3.72
3.84
3.72
4.32
4.30
4.16
4.40
4.04
4.06
4.51
4.40
3.49
3.30
3.61
3.80
3.98
3.78
3.45
3.20
3.35
3.50
3.34
3.31
3.45
3.30
3.79
3.50
3.58
3.80
3.93
3.91
3.09
3.00
3.79
3.65
12.02
12.40
10.21
9.91
9.17
9.30
7.80
7.70
9.67
9.63
8.14
8.21
8.80
8.80
7.79
8.00
8.58
8.60
8.45
8.44
8.54
8.80
8.21
8.11
7.91
7.82
7.32
7.19
8.89
8.70
7.58
7.50
7.31
7.10
7.08
7.00
7.60
7.50
7.36
7.50
7.03
7.04
7.10
7.00
2b
C
24H17N3O2S
411.46
3a
264–267
Benzene
275–278
Benzene
245
Dioxan
205–207
Dioxan
297–300
Dioxan
175
C
19H13N3OS
331.37
12.68
12.52
10.68
10.54
12.20
12.20
10.21
10.10
11.25
11.21
11.07
11.09
11.19
11.40
14.35
14.12
13.85
13.60
16.00
15.93
15.54
15.30
13.26
13.27
16.06
16.00
15.51
15.30
9.97
3b
C
24H15N3OS
393.45
4a
C
19H15N3O2S.
349.40
4b
C24H17N3O2S,
411.46
7
C
C
C
C
C
21H15N3O2S
373.40
20H17N3O3S
379.42
20H13N3O3S
375.39
20H14N4O3S
390.38
8
EtOH
9
220–222
Dioxan
265–267
AcOH
233–235
AcOH
314–316
AcOH
272–274
AcOH
310–312
AcOH
310–312
EtOH
305–307
EtOH
>350
EtOH
335–336
EtOH
338–340
EtOH
330–333
EtOH
14Aa
14Ab
14Ac
14Ad
14Ae
20a
20b
22a
22b
22c
22d
21H16N4O3S
404.40
C24H15N5O2S
437.44
C19H12N4O2S
360.37
C
C
C
24H14N4O2S
422.43
24H15N5O2S
437.7
25H17N5O2S
451.40
C25H15N3O2S
421.46
C26H17N3O2S
435.47
Yellow
41
Yellow
42
Yellow
42
Yellow
9.80
9.64
9.80
9.21
9.30
9.30
9.10
C
25H14N3O2SCl
455.89
C
26H17N3O3S
451.47

1320
A. O. Abdelhamid et al.
TABLE II IR Spectra, 1HNMR Spectra and Mass Spectra of the Newly
Synthesized Compounds
Comp. no.
Spectral data
2b
IR (KBr): 2202 (CN) and 1604 (CO). 1H NMR (CDCl3): 3.6 (d, 2H, CH2),
6.8–7.7 (m, 15H, ArH’s and NH).
3b
4b
IR (KBr): 2188 (CN). 1H NMR (CDCl3): 7.22–7.77 (m, 15H, ArH’s and
thiazole C-5).
IR (KBr): 3440, 3220 (NH2) and 1604 (CO).
1H NMR (CDCl3, δ ppm): 7.21–7.38 (m, 14H, ArH’s) and 11.18 (s, br,
3H, NH2 and NH).
7
IR (KBr): 2194 (CN), 1675 (CO) and 1602 (C N).
1H NMR (CDCl3): 2.25 (s, 3H, CH3 CO), 2.65 (s, 3H, CH3, thiazolo C-4)
and 7.22–7.85 (m, 9H, ArH’s).
14Aa
14Ab
IR (KBr): 2204 (CN), 1743 (CO) and 1610 (C N).
1H NMR (CDCl3): 1.35 (t, 3H, CH3-CH2), 4.55 (q, 2H, CH2 CH3) and
7.2–7.7 (m, 9H, ArH’s).
IR (KBr): 2209 (CN), 1745 (CO) and 1610 (C N).
1H NMR (CDCl3): 1.35 (t, 3H, CH3CH2), 2.45 (s, 3H, 4CH3C6H4), 4.45
(q, 2H, CH2 CH3) and 7.25–7.80 (m, 8H, ArH’s).
IR (KBr): 2204 (CN), 1743 (C O) and 1610 (C N).
1H NMR (CDCl3): 7.28–7.90 (m, 14H, ArH’s), 11.1 (s, 1H, NH).
IR (KBr): 2204 (CN), 1743 (CO) and 1610 (C N).
1H NMR (CDCl3): ppm): 2.45 (s, 3H, CH3 CO) and 7.25 (m, 9H, ArH’s).
IR (KBr): 2202 (CN), 1645 (CO) and 1610 (C N).
1H NMR (CDCl3): 7.25–7.80 (m, 14H, ArH’s).
IR (KBr): 2210 (CN), 1741 (CO) and 1610 (C N).
1H NMR (CDCl3): 7.2–7.6 (m, 14H, ArH’s ) and 13.12 (s, 1H, NH).
IR (KBr): 2208 (CN), 1743 (CO) and 1606 (C N).
1H NMR (CDCl3): 2.23 (s, 3H, 4-CH3PH), 7.25–7.77(m, 13H, ArH’s) and
13.12 (s, br, 1H, NH).
14Ac
14Ad
14Ae
20a
20b
22b
22c
IR (KBr): 3025 (CH-vinyl), 2213 (CN), 1710 (CO).
1H NMR (CDCl3, δ ppm): 7.26–7.90 (m, 9H, ArH’s), 2.47 (s, 3H, CH3).
IR (KBr): 3025 (CH-vinyl), 2211 (CN), 1706 (CO).
1H NMR (CDCl3): 7.40–7.90 (m, 9H, ArH’s)
onto ice (50 g). The resulting solid was collected and crystallized from
benzene to give 4a and 4b, respectively (Tables I and II).
Reaction of Thionilide 1 with Ethyl 2-Chloro-3-oxobutanoate
Ethyl 2-chloro-3-oxobutanoate (1.64 g, 10 mmol) was added to a mixture
of compound 1 (2.93 g, 10 mmol) in dry N, N-dimethylformamide (10
mL) containing potassium hydroxide (0.056 g, 10 mmol). The reaction
mixture was stirred for 2 h, and then left overnight, the resulting solid
was purified via column of silica gel and ethyl acetate as eluent to give
two compounds 8 and 9, respectively (Tables I and II).

Heterocyclic Containing Benzoxazole Moiety
1321
Reaction of Thionilide 1 with 3-Chloropentane-2,4-dione
A mixture of equimolar amount of compound1, potassium hy-
droxide and 3-chloropentane-2,4-dione (5 mmol each) in N, N-
dimethylformamide (20 mL) was stirred for 2 h and left overnight. The
resulting solid was collected and crystallized from dioxan to give 4 (Ta-
bles I and II). The second fraction, which did not dissolve in hot dioxan,
was crystallized from acetic acid to give product identical in all aspects
(m.p., mixed m.p., and spectra) with compound 3a.
Synthesis of 2,3-Dihydro-1,3,4-thiadiazole Derivatives 14a-e
Method A
A mixture of benzoxazol-2-ylethanenitrile (1.58 g, 10 mmol), carbon
disulfide (0.7 g, 10 mmol) and potassium hydroxide (0.56 g, 10 mmol) in
N, N-dimethylformamide (15 mL) was stirred at room temperature for
1 hr. Iodomethane (1.4 g, 0.62 mL, 10 mmol) was added to the mixture.
The reaction mixture was stirred for 2 h. The appropriate of hydrazonyl
halides 10a-e (10 mmol) and triethylamine (1.5 mL, 10 mmol) were
added to the above mixture, and then the reaction mixture was stirred
for 2 h. The resulting solid was collected and crystallized to give 14a-e,
respectively (Tables I and II).
Method B
A mixture of 2-benzoxazol-2-ylethanenitrile (1.56 g, 10 mmol), potas-
sium hydroxide (0.56 g, 10 mmol) and phenyl isothiocyanate (1.35 g, 10
mmol) in dry N, N-dimethylformamide (10 ml) was stirred for 6 h, then
add the appropriate hydrazonoyl halides 10a-e (10 mmol) and stirring
was continued for 2 h. The reaction mixture was left overnight then di-
luted with water (10 mL). The solid was collected by filtration, washed
with water, dried, and crystallized from acetic acid to give products were
identical in all respects that (m.p., mixed m.p. and spectra) with 14a-e
that were obtained from Method A.
Synthesis of 5-Aza-2-benzoxazol-2-yl-(4-oxo-3-phenyl)-5-
phenylamino(3-thiazolidine-2-ylidine)ethanenitrile (20a) and
5-Aza-2-benzoxazol-2-yl-(4-oxo-3-phenyl)-5-
methylphenylamino(3-thiazolidine-2-ylidine)ethanenitrile
(20b)
To a cold solution of 2-benzoxazol-2-yl-(4-oxo-3-phenyl)-3-thiazolidine-
2-ylidine)ethanenitrile (19) (1.66 g, 5 mmol) in pyridine (20 mL)-
sodium hydroxide (0.2 g) solution The appropriate diazonium chloride

1322
A. O. Abdelhamid et al.
[prepared by adding sodium nitrite (0.35 g, 5 mmol in water) to a cold
solution of the appropriate aromatic amine (5 mmol) was added while
stirring for 1 h. The resulting solid was collected and recrystallized from
ethanol to give compounds 20(a,b) (Tables I and II).
2-Benzoxazol-2-yl-2-[4-oxo-3-phenyl-5-(arylmethylene)-
(1,3-thiazolidin-2-ylidine)-ethanenitrile (22a-d)
Method A
A mixture of 2-benzoxazol-2-yl-(4-oxo-3-phenyl)-3-thiazolidine-2-
ylidine)ethanenitrile (19) (1.66 g, 5 mmol) and the appropriate of alde-
hyde (5 mmol) in ethanol (20 mL). Sodium ethoxide solution was added
to the above mixture while stirring. The resulting solid was collected
and recrystallized to give 22a-d (Tables I and II).
Method B
A mixture of 19 (1.66 g, 5 mmol) and the appropriate of 1-cyano-2-
arylacrylonitrie (5 mmol) in ethanol (20 mL) and few drops of triethy-
lamine was heated under reflux for 3 h. The resulting solid was collected
and recrystallized to give product identical in all respects (m.p., mixed
m.p., and spectra) with products obtained in Method A.
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