NiH‐Catalyzed Enantio‐ and Regioselective Hydroarylation of Unactivated Alkenes Enabled by Outer‐Sphere Electron Transfer with Diaryliodonium Salts
Hyung‐Joon Kang, Leejae Kim, Ju‐Yeon Lee, Sungwoo Hong
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 internal 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.