Cooperative Bimetallic Radical Catalysis Enables Asymmetric Hydrogen-Atom Transfer

Achieving precise stereocontrol in asymmetric hydrogen-atom transfer (HAT) reactions is a central challenge in radical chemistry, particularly in nonenzymatic systems. Existing approaches primarily rely on carbon-centered radicals and conventional hydrogen donors with inherently weak X-H bonds, which are prone to racemic background processes and suffer from limited donor diversity. Herein, we report a new conceptual approach: cooperative bimetallic radical catalysis that enables asymmetric HAT without the formation of carbon radicals. This cooperative system employs two titanium catalysts to independently activate both the hydrogen donor and acceptor, facilitating a concerted HAT process with excellent stereochemical communication. This strategy expands the accessible scope of HAT chemistry by unlocking the use of unconventional hydrogen donors, such as imidazole, beyond constraints of weak X-H bonds. Mechanistic studies support the proposed dual activation and concerted HAT pathway. This work represents an intriguing mode in asymmetric HAT, providing a sustainable platform for stereoselective radical transformations.