An Efficient Aromatization of 2-Amino-4,5,6,7-tetrahydrobenzo-[b]thiophene-3-carboxylates in Dimethyl Sulfoxide Catalyzed by p-Toluenesulfonic Acid

Abstract

A novel oxidation–aromatization of alkyl 2-amino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylates is reported. The Gewald product, obtained from three-component condensation reaction between a cyclohexanone, an alkyl cyanoacetate, and sulfur, underwent an oxidation reaction in dimethyl sulfoxide in the presence of a catalytic amount of p-toluenesulfonic acid to give the corresponding alkyl 2-aminobenzo[b]thiophene-3-carboxylate in excellent yield.