Benzoic Acid Serves as Precursor of Catalytic HAT Reagent in a Two‐Molecule Photoredox System

The photoinduced regioselective HAT reactions of acetals, ethers, and alcohols using benzoic acids in a two‐molecule photoredox system led to the formation of new C–C bonds with alkenes under mild conditions. Aryl carboxy radicals generated from benzoic acids in a two‐molecule photoredox system can function as catalytic HAT reagents, even though an excess amount of a hydrogen donor substrate is required. Various acetals, ethers, alcohols, and alkenes can be employed in the photoreaction to provide both high yields of adducts and high recoveries of benzoic acids.