Visible-light-induced Radical–Radical Cross-coupling:Alkenes C(sp~2)-N Bonds Formations

Nitrogen-containing compounds with important biological activities and unique structural reactivities are widely found in drug molecules,natural products and functional materials.The construction of C-N bond is a key step in the synthesis of nitrogen compounds with important research value.As the aim of carbon neutrality and emission peak are proposed,the development and application of green energy becomes increasingly important.How to achieve the construction of C-N bond efficiently and environmentally under mild conditions has attracted attention of organic chemists.Visible light energy has the advantages of pollution-free and cheap,C-H bond and N-H bond could be activated by visible light irradiation through electron transfer to generate corresponding radicals or radical ions.Therefore,visible-light-induced radical-radical cross-coupling has become an effective way to construct C-N bonds,which has attracted wide attention.As the basic structural of organic compounds,alkenes are extremely important reaction intermediates in organic synthesis.However,there are relatively few reports of radical cross-coupling based on C(sp~2)-N of alkenes.Therefore,the novel and effective radical activation modes need to be developed.Radica-radical coupling reaction is a kind of novel method of bonds forming,requires the generation of two radical species at the same time,the control of radical selectivity is relatively difficult.In recent years,with the development of organic photochemistry,visible-light-induced radical-radical cross-coupling reactions have been reported,providing a new way for construction of carbon-carbon bonds and carbon-hetero bonds.In this paper,a visible-light-induced radical-radical cross-coupling reaction of alkene C(sp~2)-N was studied.The C(sp~2)-N bond between polarized alkene ketene dithioacetal compounds and azole compounds was constructed in the synergistic catalysis of Acr-Mes photosensitizer and cobalt catalyst.In addition,the gram-scale production reaction and sunlight reaction have great practicability.This work not only realized the radical-radical cross-coupling reaction of alkene C(sp~2)-H/N-H,but also obtained a deeper understanding of radical chemistry and ketene dithioacetals chemistry through detailed study of the mechanisms.