Formation of Chiral All-Carbon Quaternary Stereocenters by Photoinduced Cobalt-Catalyzed Enantioselective Radical Coupling

Photoinduced enantioselective strategies provide an efficient
way
to access chiral all-carbon quaternary stereocenters. Compared with
the well-developed metal-catalyzed asymmetric conjugate addition of
organometallic reagents to enones, the construction of chiral all-carbon
quaternary stereocenters through a radical process still remains challenging,
especially for the acyclic enones due to their enhanced conformational
mobility. Herein, we disclose a photoinduced cobalt-catalyzed asymmetric
radical coupling of α,β-unsaturated 2-acyl
imidazoles and α-silylamines to give β,β-disubstituted γ-amino acid derivatives with acyclic quaternary
carbon stereocenters. The facile protocol shows good functional group
tolerance and a broad substrate scope. The corresponding chiral products
were obtained in generally good yields (up to 96%) with high enantioselectivities
(up to 99:1 e.r.).