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 CH 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. Mechanistic studies, including fluorescence quenching and deuterium labeling, indicate a pathway involving radical cation intermediates. DFT calculations indicate that the 2‐thiazolyl structure on the sulfide enhances the catalyst activity by shifting the HAT from an S ‐centered pathway to an N ‐centered pathway. This study establishes sulfides as modular platforms for photoredox‐mediated HAT catalysis.
Sengoku et al. (Sun,) studied this question.