Cascade Reactions of α-Carbonyl Radicals Enabled by Photocatalytic Hydrogen Atom Transfer for the Synthesis of Benzonaphthyridinone Derivatives.

A metal-free photocatalytic addition/cyclization of the α-carbonyl radical with N-(2-cyanophenyl)acrylamides has been developed, providing novel benzonaphthyridinone scaffolds in moderate to good yields. Arylsulfonium salt was employed as a hydrogen atom abstractor, which effectively converts various ketones into α-carbonyl radicals. This protocol has advantages including simple and mild conditions, a broad substrate scope, and remarkable tolerance toward diverse functional groups.