Convenient Synthesis of 3-Substituted Benzo[b]thiophenes by Iodine-Mediated Cyclization of [alpha]-Substituted 2-(1-Phenylethylthio)styrenes

A new and convenient method for the preparation of 3-substituted benzo[b]thiophenes was developed. α-Substituted 2-(1-phenylethylthio)styrenes, which could easily be prepared from 2-mercaptophenyl ketones or benzenethiols in two or three steps, respectively, underwent 5-endo cyclization on treatment with iodine in the presence of sodium hydrogencarbonate in acetonitrile at room temperature to give 3-substituted benzo[b]thiophenes in fair to good yields.