Alkene difunctionalization enabled by photocatalytic hydrogen atom transfer from haloalkane α-C(sp3)–H bonds

We developed a mild photocatalytic method to generate tert-butoxy radical species that can effectively achieve C(sp3)–H abstraction at halogen’s α site. Thus, the difunctionalization of aromatic alkenes could be realized by hydrogen transfer radical addition and radical polar crossover process, affording an array of haloalkane products with broad substrate scope and excellent functional group tolerance. Moreover, the transformations of haloalkanes to alkanes, haloalkenes, or heterocyclic compounds can be accomplished upon simple manipulation. The reaction mechanistic paradigm of the generated tert-butoxy radical species is supported by control experiments and Stern-Volmer analysis, and the radical polar crossover is analyzed by Hammett plotting and density functional theory (DFT) calculation. The hydrogen atom transfer on the C(sp3)–H bond of halogen’s α site induced by tert-butoxy radical species is also revealed by DFT calculations.