Bifunctional N‑Heterocyclic Carbene-Catalyzed Highly Enantioselective Synthesis of Spirocyclic Oxindolo-β-lactams

The N-heterocyclic carbene-catalyzed Staudinger reaction of ketenes with isatin-derived ketimines was investigated. The bifunctional NHCs with a free hydroxyl group were demonstrated as efficient catalysts for the reaction, giving the corresponding spirocyclic oxindolo-β-lactams in high yields with excellent diastereo- and enantioselectivities.