Copper-Catalyzed Enantioconvergent Radical Deborylative Coupling of Racemic Benzylboronic Esters with Alkynes and Alkenylboronic Esters

Transition metal-catalyzed enantioconvergent deborylative C-C coupling of racemic alkylboronic esters represents a powerful tool to construct chiral C-C bonds given their availability, stability, and functional group tolerance. However, it is challenging, as the classic two-electron transmetalation occurs concertedly with stereoretention, hindering the enantioconvergent deborylative transformations. Herein, we report a radical strategy that enables the copper-catalyzed enantioconvergent deborylative C(sp³)-C(sp) coupling of benzylboronic esters with alkynes. The success of this strategy relies on two key elements: radical boron abstraction enables the enantioconvergent transformation by generating a prochiral radical; copper/chiral multidentate N,N,P-ligand catalyst promotes the desired pathways, ensuring chemo- and enantioselectivity. The strategy is orthogonal to the halide-based coupling, tolerating electron-rich aromatic rings, proceeding rapidly, and requiring low catalyst loading. We further demonstrate the generality by extending it to an enantioconvergent deborylative C(sp³)-C(sp²) coupling with alkenylboronic esters.