S. Renuga et al. / Tetrahedron 63 (2007) 10054–10058
10057
4. Experimental section
4.1. General methods
143.3, 169.6, 195.9. Anal. Calcd for C30H23NOS:
C, 80.87; H, 5.20; N, 3.14. Obsd: C, 81.01; H, 5.16; N,
3.10%.
The melting points are uncorrected. A domestic microwave
oven (IFB, model-electron of 750 W capacity and micro-
wave frequency of 2450 MHz) was employed for microwave
irradiation. NMR spectra were recorded at 20 ꢀC on a Bruker
4.2.2. 2-[(5Z)-5-(p-Chlorobenzylidene)-2-(p-chloro-
phenyl)-2,5-dihydro-4-phenylthiazol-2-yl]-1-phenyl-
ethanone (5b). Obtained as a colourless solid (0.750 g,
73% in method 1 and 0.392 g, 76% in method 2),
1
1
mp¼165–167 ꢀC; IR (KBr) n 1690, 1592, 1487 cmꢁ1; H
AMX 300 instrument operating at 300 MHz for H and at
75 MHz for 13C. Solutions (in CDCl3) were approximately
0.05 M and chemical shifts were referenced internally to
TMS in all cases and expressed in d scale (ppm). Two-
dimensional NMR measurements H,H-COSY, C,H-COSY
and HMBC have also been measured using the above instru-
ment. Standard Bruker software (UXNMR) was used
throughout. The single crystal X-ray data for 5b were col-
lected on an Enraf-Nonius MACH 3 four-circle diffracto-
NMR (300 MHz, CDCl3) dH 3.87 (1H, d, J¼17.7 Hz),
4.55 (1H, d, J¼17.7 Hz), 6.78 (1H, s), 7.27–7.99 (18H,
m); 13C NMR (75 MHz, CDCl3) dC 52.4, 92.6, 124.5,
128.1, 128.3, 128.5 (7), 128.5 (9), 128.6, 128.7, 129.0,
130.0, 130.1, 133.1, 133.5, 133.6, 134.4, 136.4, 140.5,
141.6, 169.6, 195.8. Anal. Calcd for C30H21Cl2NOS: C,
70.04; H, 4.11; N, 2.72. Obsd: C, 69.97; H, 4.08; N,
2.76%.
˚
meter (Mo Ka radiation, l¼0.71073 A). Elemental
analyses were performed on a Perkin–Elmer 2400 Series II
Elemental CHNS Analyser.
4.2.3. 2-[(5Z)-5-(o-Chlorobenzylidene)-2-(o-chloro-
phenyl)-2,5-dihydro-4-phenylthiazol-2-yl]-1-phenyl-
ethanone (5c). Obtained as a colourless solid (0.639 g, 62%
in method 1 and 0.408 g, 79% in method 2), mp¼166–
4.2. Synthesis of 1-aryl-2-[5(Z)-5-arylmethylidene-2,4-
diaryl-2,5-dihydrothiazol-2-yl]ethanones—general
procedure
168 ꢀC; IR (KBr) n 1693, 1612, 1463 cmꢁ1 1H NMR
;
(300 MHz, CDCl3) dH 4.17 (1H, d, J¼15.3 Hz), 4.43 (1H,
d, J¼15.3 Hz), 7.15–7.94 (19H, m); 13C NMR (75 MHz,
CDCl3) dC 48.1, 91.5, 121.6, 126.9, 127.0, 128.1, 128.3
(9), 128.4 (4), 128.6, 128.9 (6), 129.0 (4), 129.2, 129.5,
130.1, 130.9, 131.6, 132.8, 133.3, 134.2, 134.3, 137.8,
141.4, 142.6, 170.8, 195.9. Anal. Calcd for C30H21Cl2NOS:
C, 70.04; H, 4.11; N, 2.72. Obsd: C, 70.08; H, 4.14; N,
2.68%.
Method 1: by the reaction of bis(aroylmethyl) sulfide, aro-
matic aldehyde and ammonium acetate. A mixture of
bis(benzoylmethyl) sulfide (0.54 g, 2 mmol), benzaldehyde
(0.4 mL, 4 mmol) and ammonium acetate (0.154 g,
2 mmol) was taken in a glass mortar and ground to a homo-
geneous paste with a pestle. This paste was then transferred
to a borosilicate boiling tube, kept in a silica bath and placed
in a domestic microwave oven at power level 4 for 10 min.
The TLC analysis of the reaction mixture shows that the
reaction goes to completion in 10 min affording three prod-
ucts. These products were separated by column chromato-
graphy using ethyl acetate–petroleum ether [2:98 (v/v)]
mixture.
4.2.4. 2-[(5Z)-5-Benzylidene-4-(p-chlorophenyl)-2,5-di-
hydro-2-phenylthiazol-2-yl]-1-(p-chlorophenyl)ethanone
(5d). Isolated as a colourless solid (0.700 g, 68% in method 1
and 0.433 g, 84% in method 2), mp¼150–152 ꢀC; IR (KBr)
1
n 1676, 1588, 1488 cmꢁ1; H NMR (300 MHz, CDCl3) dH
3.89 (1H, d, J¼17.1 Hz), 4.47 (1H, d, J¼17.1 Hz), 6.80
(1H, s), 7.25–7.89 (18H, m); 13C NMR (75 MHz, CDCl3)
dC 52.2, 92.8, 125.7, 126.8, 127.8, 128.2 (7), 128.3 (2),
128.6, 128.8, 128.9, 129.6, 130.5, 131.8, 135.1, 135.7,
136.2, 139.7 (6), 139.7 (9), 143.2, 168.8, 194.7. Anal. Calcd
for C30H21Cl2NOS: C, 70.04; H, 4.11; N, 2.72. Obsd: C,
69.99; H, 4.09; N, 2.76%.
Among the two minor products, the one obtained in 7–
10% yields was the known compound (Z,Z)-2,20-thiobis-
(1,3-diphenylprop-2-en-1-one) 2 and the other obtained in
negligible amount was identified as 2-[(2-oxo-2-phenyl-
ethyl)sulfanyl]-1,3-diphenylprop-2-en-1-one 6. The thiazole
derivative was obtained as the major product, which was
recrystallised from chloroform–alcohol mixture.
4.2.5. 2-[(5Z)-5-(p-Chlorobenzylidene)-2,4-bis(p-chloro-
phenyl)-2,5-dihydrothiazol-2-yl]-1-(p-chlorophenyl)-
ethanone (5e). Obtained as a colourless solid (0.830 g, 71%
in method 1 and 0.480 g, 82% in method 2), mp¼158–
Method 2: by the reaction of (Z,Z)-2,20-thiobis(1,3-diaryl-
prop-2-en-1-ones) and ammonium acetate. The procedure
is the same as the one described in method 1 except that in
this method, the reactants are a mixture of (Z,Z)-2,20-thiobis-
(1,3-diarylprop-2-en-1-ones)17 (1 mmol) and ammonium
acetate (1 mmol).
160 ꢀC; IR (KBr) n 1680, 1576, 1478 cmꢁ1 1H NMR
;
(300 MHz, CDCl3) dH 3.83 (1H, d, J¼17.5 Hz), 4.44 (1H,
d, J¼17.5 Hz), 6.73 (1H, s), 7.26–7.86 (16H, m); 13C
NMR (75 MHz, CDCl3) dC 52.4, 92.6, 124.6, 128.4 (0),
128.4 (3), 128.8, 128.9, 129.0, 129.5, 130.0, 130.5, 133.8,
133.9, 134.1, 134.8, 140.1, 141.5, 168.8, 194.5. Anal. Calcd
for C30H19Cl4NOS: C, 61.77; H, 3.28; N, 2.40. Obsd: C,
61.62; H, 3.26; N, 2.43%.
4.2.1. 2-[(5Z)-5-Benzylidene-2,5-dihydro-2,4-diphenylthi-
azol-2-yl]-1-phenylethanone (5a). Obtained as a colour-
less solid (0.624 g, 70% in method 1 and 0.358 g, 80% in
method 2), mp¼176–178 ꢀC; IR (KBr) n 1695, 1586,
1
1485 cmꢁ1; H NMR (300 MHz, CDCl3) dH 3.90 (1H, d,
4.2.6. 2-[(5Z)-5-(p-Methylbenzylidene)-4-(p-chloro-
phenyl)-2,5-dihydro-2-(p-methylphenyl)thiazol-2-yl]-1-
(p-chlorophenyl)ethanone (5f). Obtained as a colourless
solid (0.684 g, 63% in method 1 and 0.441 g, 81% in method
J¼17.4 Hz), 4.57 (1H, d, J¼17.4 Hz), 6.83 (1H, s), 7.24–
7.94 (20H, m); 13C NMR (75 MHz, CDCl3) dC 52.2, 92.8,
125.6, 127.0, 127.7, 128.0, 128.1, 128.2, 128.5, 128.6,
128.9, 129.2, 129.9, 133.3, 133.5, 136.0, 136.7, 140.2,