Synthesis of some new benzofuran-based thiophene, 1,3-oxathiole and 1,3,4-oxa(thia)diazole derivatives

Treatment of 3-(3-methylbenzofuran-2-yl)-3-oxopropanenitrile (1) with phenyl isothiocyanate afforded the thioacetanilide derivative 3, which when reacted with alpha-haloketones, alpha-halodiketones, and hydrazonoyl chlorides gives thiophene, 1,3-oxathiole, and 1,3,4-thiadiazole derivatives 6a,b 10a,b and 14a-g, respectively. Treatment of 3-methyl-2-benzofurancarboxylic acid hydrazide (15) with benzaldehyde followed by bromine afforded the 1,3,4-oxadiazole derivative 18. Treatment of the acid hydrazide 15 with phenyl isothiocyanate gave the thiosemicarbazide 20. Compound 20 could be converted into 1,3,4-oxadiazole, 1,2,4-triazole-3-thione, and 1,3,4-thiadiazole derivatives 21, 22, and 23, respectively. (c) 2007 Wiley Periodicals, Inc.