Visible-Light-Induced C-H Alkylation of 1,2,4-Triazine-3,5(2H,4H)-diones via Infrequent 1,2-Hydrogen-Atom Transfer.

1,2,4-Triazine-3,5(2H,4H)-diones are widely present in various drug molecules and bioactive molecules. A visible-light-driven C-H alkylation of 1,2,4-triazine-3,5(2H,4H)-diones via 1,2-hydrogen-atom transfer (1,2-HAT) of amide radicals is first reported, providing an environmentally friendly and sustainable pathway to enrich the structural and functional diversity of 1,2,4-triazine-3,5(2H,4H)-diones. This novel protocol is characterized by mild and metal-free reaction conditions, an operationally simple method, and good functional group tolerance. To our delight, other heterocycles, such as isoquinoline and coumarin, also undergo alkylation reactions to construct C(sp2)-C(sp3) bonds via infrequent 1,2-HAT under current conditions.