Photoredox Catalytic Approach for Difluoroallylation of Electron-Deficient sp³ C–H Bonds

Herein, we describe a photoredox protocol for the selective difluoroallylation of electron-deficient sp3 C-H bonds with α-trifluoromethyl alkenes. The key to success is using 2,2,6,6-tetramethylpiperidine (TEMP) as an additive under metal-free conditions, thereby obviating the use of hazardous hydrogen atom transfer (HAT) reagents or oxidants in conventional sp3 C-H bond functionalization. The method features mild conditions and good functional group compatibility, and its potential is further enhanced by late-stage modification of complex molecules, scalability, and ready product transformations. Preliminary mechanistic experiments reveal α-functionalized alkyl radical species being involved.