NiH-Catalyzed Enantio- and Regioselective Hydroarylation of Unactivated Alkenes Enabled by Outer-Sphere Electron Transfer with Diaryliodonium Salts.

Abstract

Asymmetric hydroarylation of unactivated alkenes provides a direct route to enantiomerically enriched C-C bonds in aryl-containing compounds, a key transformation in pharmaceutical and natural product synthesis. While recent advances have achieved high regio- and enantioselectivity with terminal alkenes, controlled hydroarylation of unactivated interna alkenes remains challenging. Here we report a nickel-hydride-catalyzed protocol that overcomes this limitation through a mechanistic paradigm shift. By employing diaryliodonium salts as dual-function reagents, our method achieves high enantio- and regioselectivity in the hydroarylation of both internal and terminal unactivated alkenes. These salts enable a transition from concerted to stepwise oxidative addition via dissociative single-electron transfer (DSET), generating a cationic alkyl-nickel intermediate prone to fragmentation and aryl radical addition. Mechanistic studies, including a key experiment in 1,4-dioxane yielding an enantiomerically pure solvent-functionalized product, establish migratory insertion as the enantio- and regio-determining step. This approach not only expands the scope of asymmetric hydroarylation but also provides a new mechanistic framework for selective hydrofunctionalization reactions.