Light-Controlled Switch for Divergent Coupling of Thiols to Disulfides/Thioethers over CdS Quantum Dots

Switchable divergent organic transformations represent a straightforward but challenging method to synthesize structurally varied compounds starting from the same set of raw materials. Herein, we report the divergent dehydrocoupling of thiols into tunable disulfides/thioethers and H₂ in response to the visible or ultraviolet (UV) light, over CdS quantum dots. Regulating the irradiation wavelength allows disulfides and thioethers to be synthesized in moderate to high yields with good functional group tolerance. Mechanistic studies reveal that thiols are oxidized to produce sulfur-centered radicals by photogenerated holes under visible light irradiation, which then undergo S–S coupling to form disulfides. While under UV light irradiation, the cleavage of C–S bonds in thiols occurs readily to afford aryl radicals, which interact with sulfur-centered radicals, undergoing C–S coupling to obtain thioethers. This work is expected to open an avenue of light-controlled switch to maneuver a radical conversion route for divergent synthesis of value-added fine chemicals.