Access to Tetrahydropyrido[1,2‑a]indol-6-one Derivatives via NHC-Catalyzed Radical Dearomatization of Indoles

Tetrahydropyrido[1,2-a]indol-6-one is a significant motif that is widely present in natural bioactive alkaloids. Herein, a facile and efficient access to the tetrahydropyrido[1,2-a]indol-6-one skeleton via NHC (N-heterocyclic carbene)-catalyzed radical relay dearomatization of indoles has been developed. This protocol exhibits metal-free, mild reaction conditions, a broad substrate scope, high efficiency, and excellent diastereoselectivity (30 examples, up to 89% yield and >20:1 dr).