Copper‐Catalyzed Asymmetric Hydroboration of Alkynes to C‐N Axially Chiral Azaborines via Dynamic Kinetic Resolution

Despite the substantial application potential of C–N axially chiral motifs across diverse fields, and the growing interest in azaborine frameworks owing to their distinctive physicochemical properties, the direct catalytic synthesis of C–N axially chiral azaborines has remained elusive, significantly impeding the practical deployment of these promising molecular scaffolds. Herein, we disclose a copper‐catalyzed asymmetric hydroboration reaction of alkynes with N‐arylazaborines under mild reaction conditions, which enables the efficient access to C–N axially chiral azaborine products in high yields, accompanied by excellent regioselectivity, Z ‐stereoselectivity, and enantioselectivity. Mechanistic experiments and density functional theory calculations reveal that a dynamic kinetic resolution process is involved in this reaction. Specifically, the two enantiomers of racemic N‐arylazaborines can undergo racemization via a dearomative tetracoordinate boron intermediate under the action of NaO t Bu.