Catalytic Asymmetric Synthesis of α‐Quaternary Proline Derivatives by 1,3‐Dipolar Cycloaddition of α‐Silylimines

Going pro: The title reaction between α-silylimines and activated olefins proceeds in the presence of a CuI/DTBM-Segphos catalyst system with excellent diastereoselectivity and enantioselectivity. This process provides straightforward access to highly enantioenriched 5-unsubstituted α-quaternary proline derivatives. TMS=trimethylsilyl, DTBM-Segphos=5,5′-bis[di(3,5-di-tert-butyl-4-methoxyphenyl)phosphino]-4,4′-bi-1,3-benzodioxole.