Controllable atom transfer enables photoredox-catalyzed defluorinative alkylation of trifluoromethyl alkenes with polychloroalkanes

Polychloroalkanes are commonly used solvents in organic synthesis, in which dichloromethane and chloroform have been widely applied in radical-mediated alkene functionalization reactions. However, a general and mild protocol for selective activation of C-H and C-Cl bonds of polychloroalkanes via switchable atom transfer processes is still in demand. Herein, we demonstrate a conceptually distinct strategy for the formation of alkyl radicals from polychloroalkanes through hydrogen atom transfer or halogen atom transfer processes under mild photoredox conditions. Using this strategy, stoichiometric hazardous reagents and radical initiators are obviated; instead, only simple alkyl amines are used as controllable hydrogen- and halogen-atom transfer reagents. The blueprint for radical reactivity is exploited in defluorinative alkylation of α-trifluoromethyl alkenes, thereby providing access to synthetically useful polychloroalkylated gem-difluoroalkenes. Moreover, this protocol features simple catalytic systems and operation, gram-scale synthesis, modifications of complex molecules, and diverse product transformations.