Visible-Light-Induced C-S Bond Cleavage Enables Alkyl Radical Generation from Redox-Inert Substrates

We report a visible-light-driven platform for alkyl radical generation from redox-inert substrates without external photocatalysts, based on the photoinduced excitation and cleavage of sulfur-containing intermediates formed via polar activation. Thioethers derived from simple alkenes undergo efficient homolytic C-S bond cleavage under visible-light irradiation, enabling alkyl radical formation without the need for photocatalysts or stoichiometric additives. Notably, this strategy can be extended to the direct activation of unactivated alkyl chlorides and epoxides, substrates that are typically resistant to single-electron reduction under mild conditions. The generated alkyl radicals are directly applied to carbon-carbon bond-forming reactions, exemplified by alkenylation with styrenes under metal-free conditions. Mechanistic studies indicate that sulfur-based anionic species formed in situ act as photoactive intermediates, facilitating efficient radical generation upon visible-light excitation. This work establishes sulfur-mediated photoactivation as a versatile approach to alkyl radical chemistry from readily available redox-inert substrates.