Carbamoyl Radicals via Photoredox Decarboxylation of Oxamic Acids in Aqueous Media: Access to 3,4-Dihydroquinolin-2(1H)-ones

The first visible-light-mediated photoredox oxidative approach for generating carbamoyl radicals from oxamic acids is disclosed. Reaction of the generated carbamoyl radicals with electron-deficient alkenes opens efficient access to 3,4-dihydroquinolin-2(1 H)-ones under mild conditions through a sequence of intermolecular radical addition, cyclization, and aromatization. The process is compatible with a variety of oxamic acids and electron-deficient alkenes, and a wide variety of 3,4-dihydroquinolin-2(1 H)-ones were prepared.