Organophotoredox-Catalyzed Trifluoromethylative Cyclization of Alkenoic Thioesters

We report the visible-light-induced trifluoromethylative cyclization of alkenoic thioesters, enabling the synthesis of CF₃-substituted sulfur heterocycles without metals. Organophotocatalysts promote efficient radical cyclization with a broad substrate scope and high diastereoselectivity. Mechanistic studies indicate an oxidative quenching pathway initiated by photocatalyst-reagent interactions, and theoretical calculations reveal that the conformational bias of the carbocation intermediate governs the stereoselectivity. This strategy for synthesizing fluorinated sulfur heterocycles expands the synthetic utility of alkenyl thioesters in photoredox catalysis.