Photoredox-Catalyzed and Copper(II) Salt-Assisted Radical Addition/Hydroxylation Reaction of Alkenes, Sulfur Ylides, and Water

A visible light-driven photoredox-catalyzed and copper(II)-assisted three-component radical addition/hydroxylation reaction of alkenes, sulfur ylides, and water is reported. This process shows broad substrate scope and high functional group tolerance, with respect to both readily available sulfur ylides and alkenes, providing high-yielding and practical access to valuable γ-hydroxy carbonyl compounds. Key to the success of the reaction is the controlled generation of α-carbonyl carbon radicals from sulfur ylides via sulfonium salts by a visible-light-driven proton-coupled electron transfer (PCET) strategy in a mixture of 2,2,2-trifluoroethanol/CH2Cl2. Addition of Cu(TFA)2·H2O helps to accelerate the radical-cation crossover to improve the reaction efficiency. Mechanistic studies suggest that the hydroxy moiety in the products stems from water. This study also builds up a platform for further investigation into the radical synthetic chemistry of sulfur ylides.