Highly selective synthesis of 6-substituted benzothiophenes by Sc(OTf)3-catalyzed intermolecular cyclization and sulfur migration

Abstract

A series of 6-substituted benzo[b]thiophenes was efficiently synthesized using a Sc(OTf)₃-catalyzed intermolecular cyclization between para-substituted N-(arylthio)succinimides and alkynes taking advantage of a unique and selective 1,2-sulfur migration. Investigations with DFT shed light on the migration process occuring via an electrophilic ipso cyclization of a vinyl cation to a key spirocyclic thiete intermediate.