Diversity-oriented synthesis of benzo[b]thiophenes fused to medium-sized N-heterocycles via Friedel–Crafts cyclization processes

Abstract

An efficient access to benzo [b]thiophene-fused or -bridged to medium-sized N-heterocycles e.g. azocinones, azoninones and azecinones, is described. The process involves cyclization of benzo[b]thiophene carboxylic ester precursors, mediated by Lewis and Brønsted acids under suitable conditions. The ring closure precursors were assembled starting from 2-acetylbenzo[b]thiophene. The developed strategy allows control of ring size and offers easy access to fused benzo[b]thiophene polycycles of promising biological importance in moderate to good yields.