Visible‐Light‐Mediated Eosin Y Photoredox‐Catalyzed Vicinal Thioamination of Alkynes: Radical Cascade Annulation Strategy for 2‐Substituted‐3‐sulfenylindoles

An organic dye photoredox‐catalyzed regiospecific radical cascade annulation strategy of 2‐alkynyl‐azidoarenes to generate 3‐sulfenylindoles via vicinal thioamination of alkynes at room temperature, mediated by visible light, was developed. The method requires mild conditions, including visible light as a traceless green energy source, room temperature, eosin Y organic dye as a photoredox catalyst, ambient air as oxidant, and easily available starting materials to provide a green, efficient, metal‐ and strong‐oxidant‐free synthesis of 3‐sulfenylindoles with broad substrate scope through vicinal thioamination of alkynes.