Facile synthesis of substituted 5-hydroxythio-7h-thieno[3,2-g] [1]benzothiopyran-7-ones

Abstract

Lewis acid (BF 3 (OEt) 2 ) in dry diethyl ether mediated cyclization and demethylation of substituted 2-(2-methyl-3-methylsulfanyl-phenylsulfanyl)-1,2-diphenyl-ethanones (3a-e) at ambient temperature gave 7-methyl-2,3-diphenyl-6-thio-benzo[b]thiophenes (4a-e). Treatment of (4a-e) with substituted malonic acids furnishes the corresponding substituted 5-hydroxythio-7H-thieno[3,2-g][1] benzothiopyran-7-aones. These were characterized by their elemental, IR, 1 H NMR and mass spectral analysis.