Enantioselective Formal Vinylogous N–H Insertion of Secondary Aliphatic Amines Catalyzed by a High-Spin Cobalt(II) Complex

Abstract

Vinylcarbene insertion into the nitrogen-hydrogen (N-H) bond of amines allows direct access to α,β-unsaturated γ-amino acid derivatives, meeting a marked challenge in the control of regio- and enantioselectivities. Here, we report a highly γ-selective and enantioselective insertion into N-H bonds of aliphatic or aromatic secondary amines with vinyl substituted α-diazo pyrazoleamides using a high-spin chiral <i>N,N'</i>-dioxide/cobalt(II) complex catalyst. The method affords a wide variety of valuable optically active <i>Z</i>- and <i>E</i>-type vinyl γ-amino amides. Calculation reveals a spin state change from the quartet cobalt(II) complex to a doublet Co(II)-carbene species for facile <i>Z</i>-selective and enantioselective nucleophilic addition.