Herein, we report a mild and efficient cascade annulation of methyl(2‐(phenylethynyl)phenyl)sulfanes and methyl(2‐(phenylethynyl)phenyl)selanes with sulfonyl chlorides under visible‐light irradiation, without the need for an external photocatalyst. This method exhibits broad substrate scope and affords a variety of 3‐sulfonated benzo b thiophenes and benzo b selenophenes in 23%–88% yields. Comprehensive mechanistic studies, including Stern–Volmer quenching, triplet‐state quenching, and radical‐trapping experiments, support a triplet energy transfer mechanism and rule out a chain‐process pathway.
Yu et al. (Mon,) studied this question.