Photochemistry-Enabled Nitrogen-Assisted Organostibines as an Efficient Alkyl Radical Precursor: Mechanistic Insights...

Organostibines exhibit significant potential as functional handles for the construction of C─C-rich scaffolds owing to their orthogonal and robust reactivity features. At present, the transformation of C(sp²)/C(sp)─Sb bonds into C─C bonds has established a mature methodology. However, breakthroughs in the C(sp³)─Sb system still require systematic investigations into reaction mechanisms, catalyst design, and other aspects. In this study, we developed a novel benchtop-stable C(sp³)─Sb and C(sp³)─Bi radical reagent and described the first use of alkyl stibine and alkyl bismuthine as an alkyl radical precursor under photoredox catalysis. Combined density functional theory (DFT) calculations and cyclic voltammetry (CV) analyses reveal that the nitrogen atom in the Sb-skeleton plays unique roles: it not only enhances the stability of alkyl stibines but also boosts redox activity via the formation of a special N─Sb coordination bond. This alkyl radical generation mode has been validated to be compatible with a range of radical alkylation reactions, including hydroarylation of electron-deficient alkenes, as well as alkyl-aryl cross-coupling and the three-component arylalkylation of alkenes/alkynes under photoredox/nickel dual catalysis. Furthermore, primary alkyl radicals have also shown excellent reactivity in conjunctive cross-coupling reactions within our system, underscoring the application potential of alkyl stibines in radical chemistry.