Copper-Catalyzed Enantioselective Radical Cyanation of Allenic C(sp²)–H Bonds to Access Tri- and Tetrasubstituted Chiral Allenes

The asymmetric radical functionalization of allenic C(sp2)–H bonds represents an appealing strategy for synthesizing axially chiral allenes. This method enables us to generate the more structurally complex and highly functionalized axially chiral allenes directly by using the readily accessible and less substituted racemic allenes while concurrently achieving apparent dynamic kinetic resolution. However, compared to alkyne derivative-based approaches, the asymmetric functionalization of allenic C(sp2)–H bonds remains a challenge primarily due to the intertwined demands of chemo-, regio-, and enantioselectivity. Here, we report a copper-catalyzed asymmetric cyanation of allenic C(sp2)–H bonds by using a substituted oxazoline chiral ligand. This strategy efficiently transforms low-substituted racemic allenes into highly functionalized, axially chiral allenyl nitriles in a highly chemo-, regio-, and enantioselective manner.