Synthesis of 2-benzylthio-5-phenyl-3,4-disubstituted thiophenes by intramolecular condensation of alpha-oxo ketene dibenzylthioacetals

A facile route to 2-benzylthio-5-phenyl-3,4-disubstituted thiophenes was described. Catalyzed by sodium hydroxide, the title compounds were synthesized in moderate to good yields simply from the intramolecular aldol type condensation of alpha-oxo ketene dibenzylthioacetals. The chemical selectivity for this annulation reaction was studied and discussed.