A facile synthesis of some novel fused [1,2,4]triazolo[3,4-b][1,3,4]thiadiazol derivatives

A series of novel 3-6-(4-substituted phenyl)-1,2,4]triazolo3,4-b]1,3,4]thiadiazol-3-ylmethyl]-5,6,7,8-tetrahydro1]benzothieno2,3-d]pyrimidin-4(3H)-one derivatives (7a–7h) have been synthesized from 2-amino-4,5,6,7-tetrahydrobenzob]thiophene-3-carbonitrile (1) through a multi-step reaction sequence. The key intermediate (6) on condensation with various substituted aromatic carboxylic acids in the presence of phosphorus oxychloride afforded the series of title compounds (7a–7h). The structures of all newly synthesized compounds were established on the basis of their IR, ¹H-NMR, ¹³C-NMR and liquid chromatography mass spectrometry spectral data.