1H NMR (300 MHz, DMSO-d6, δ ppm): 8.0 (m, 2H, Ar), 7.05 (m, 2H, Ar), 5.1 (s, 2H, CH2), 4.5 (s, FK228 cost 2H, CH2), 3.85 (s, 3H, OCH3). 115–116 °C (Ref. 19, 117–118 °C); IR (KBr, cm−1): 3001, 1757, 1668, 1510, 1224, 734. 1H NMR (300 MHz, DMSO-d6, δ ppm): 8.2 (m, 2H, Ar), 7.5 (m, 2H, Ar), 4.8 (s, 2H, CH2), 4.25 (s, 2H, CH2). Anal.
calcd. for C10H8N2O4S: C 47.61, H 3.2, N 11.11. Found: C 47.37, H 3.12, N 11.09. MS (ESI, m/z):252 (M+). Equimolar amounts of substituted aryl aldehydes and N-[p-nitro benzyl/2-(4-methoxyphenyl)-2-oxoethyl]-1,3-thiazolidine 2,4-diones (2) RNA Synthesis inhibitor were suspended in 100 ml flat bottom flask containing toluene and catalytic amount of piperidine. The flask is connected to Dean–Stark apparatus fitted with calcium guard tube and refluxed with stirring for 6 h. The product precipitated out on cooling was filtered under vacuum and washed with mixture of cold dry toluene and dry ethanol (1:1). The progression and completion of the reaction was monitored by TLC and data recorded in Table 1. 5-(Benzylidene)-N-[2-(4-methoxyphenyl)-2-oxoethyl]-1,3-thiazolidine-2,4-dione unless (3a): Pale yellow crystals, IR (KBr, cm−1): 3120, 1686, 1604, 1400, 1205, 654. 1H NMR (300 MHz, DMSO-d6, δ ppm): 7.07–8.1 (m, 9H, Ar), 8.0 (s, 1H, CH), 5.2 (s, 2H, CH2), 3.85 (s, 3H, OCH3). MS (ESI, m/z):353 (M+). Anal. calcd. for C19H15NO4S: C 64.58, H 4.28, N 3.96. Found: C 64.32, H 4.15, N 3.77. 5-(4-Chlorobenzylidene)-N-[2-(4-methoxyphenyl)-2-oxoethyl]-1,3-thiazolidine-2,4-dione (3b): Pale yellow crystals, IR (KBr, cm−1):
3088, 1741, 1602, 1323, 1194, 740, 657. 1H NMR (300 MHz, DMSO-d6, δ ppm): 7.1–8.15 (m, 8H, Ar), 7.9 (s, 1H, CH), 4.9 (s, 2H, CH2), 3.9 (s, 3H, OCH3). MS (ESI, m/z): 388 (M+). Anal. calcd. for C19H14ClNO4S: C 58.84, H 3.64, N 3.61. Found: C 58.63, H 3.41, N 3.44. N-[2-(4-Methoxyphenyl)-2-oxoethyl]-5-(4-nitrobenzylidene)-1,3-thiazolidine-2,4-dione (3c): Yellow solid, IR (KBr, cm−1): 3020, 1732, 1678, 1573, 1265, 1214, 674. 1H NMR (300 MHz, DMSO-d6, δ ppm): 7.1–8.4 (m, 8H, Ar), 8.03 (s, 1H, CH), 4.78 (s, 2H, CH2), 3.7 (s, 3H, OCH3). Anal. calcd. for C19H14N2O6S: C 57.28, H 3.54, N 7.03. Found: C 57.13, H 3.28, N 6.89. 5-(4-Methoxybenzylidene)-N-[2-(4-methoxyphenyl)-2-oxoethyl]-1,3-thiazolidine-2,4-dione (3d): Pale yellow solid, IR (KBr, cm−1): 2985, 1741, 1681, 1436, 1174, 685. 1H NMR (300 MHz, DMSO-d6, δ ppm): 7.08–8.1 (m, 8H, Ar), 7.95 (s, 1H, CH), 5.23 (s, 2H, CH2), 3.8 (s, 6H, OCH3). Anal. calcd. for C20H17NO5S: C 62.65, H 4.47, N 3.65, O 20.86.