Photoinduced Cascade Cyclization of 2‐Alkynylthioanisoles with Sulfonyl Chlorides Without an External Photocatalyst

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.