Difluoroalkylation/Lactonization of Alkenes with BrCF2CO2K via Photoredox Catalysis: Access to α,α‐Difluoro‐γ‐lactones†

Comprehensive Summary Due to its unique electronic properties, the difluoromethylene group (CF 2 ) has served as a valuable unity in the design of biologically active molecules. Since γ‐lactones display a broad range of biological properties, α,α‐difluoro‐γ‐lactones may exhibit unexpected biological activities, and thus their synthesis has received increasing attention. Traditional synthetic methods suffer from tedious multi‐ step processes, and very few effective methods have been reported recently. Herein, we describe the difunctionalization of alkenes with BrCF 2 CO 2 K under photoredox catalysis with the use of a boron‐Lewis acid for the access to α,α‐difluoro‐γ‐lactones. In this transformation, the alkene substrates and the used reagents, including BrCF 2 CO 2 K and the boron‐Lewis acid, PhB(OH) 2 or BF 3 ·THF, are cheap and widely available. High efficiency and atom economy may make this protocol attractive.