Synthesis of Acylbenzo[b]thiophenes, benzofurans and indoles via intramolecular oxidative cyclization enabled by photocatalytic hydrogen atom transfer (HAT)

An efficient strategy for intramolecular oxidative cyclization of 2-alkynylthioanisoles toward 3-acylbenzo[b]thiophenes by photochemical hydrogen atom transfer catalysis has been developed. 3-Acylbenzo[b]selenophenes, benzofurans and indoles can also be prepared by this protocol. This reaction is convenient to perform at room temperature under simple conditions using air as the oxidant. Mechanistic studies revealed that the formation of α-thioalkyl radicals intermediate is crucial.