Expanding the Toolbox for Hydrogen-Atom Transfer Catalysis: Sulfides as Structurally Diverse Catalysts under Photoredox Conditions

A new class of sulfide-based catalysts that enable hydrogen atom transfer (HAT) under visible-light-driven photoredox conditions is reported. Based on the potential of indirect HAT processes, alkyl aryl sulfides that undergo single-electron oxidation to generate radical cations were designed as candidate HAT catalysts. A wide variety of alkyl aryl sulfides exhibit catalytic activity, promoting the C–H alkylation of a broad range of substrates, including alcohols, ethers, hydrocarbons, and aldehydes, in the presence of an acridinium photocatalyst. The reactions proceed under mild conditions without additional bases or additives. The structural flexibility of the sulfide scaffold allows for substrate-specific tuning. Mechanistic studies, including fluorescence quenching and deuterium labeling, indicate pathway involving radical cation intermediates. This study establishes sulfides as modular and tunable platforms for photoredox-mediated HAT catalysis.