Kinetic Resolution of Heterocyclic Lactams by a Photocatalytic Cobalt-Catalyzed Dehydrogenation.

Abstract

Chiral heterocyclic lactams have been kinetically resolved in a photochemical process that involves selective hydrogen abstraction by a chiral benzophenone catalyst. Recognition of one enantiomer is achieved by a two-point hydrogen bonding interaction that directs the reactive carbonyl group of the photocatalyst to the C-H bond at the stereogenic center within the lactam. The generated radical is converted to an oxidized product in a cobaloxime-catalyzed dehydrogenation reaction. The unreactive enantiomer is retained and isolated in enantiomerically enriched form (21 examples, 31-56% yield, 90-99% ee).