Visible-Light Promoted Regioselective Oxygenation of Quinoxalin-2(1<i>H</i>)‑ones Using O₂ as an Oxidant

A visible-light-mediated sustainable approach for metal-free oxygenation of quinoxalin-2­(1H)-one by employing Mes-Acr-MeClO4 as a photocatalyst without using any additive or cocatalyst is reported here. O2 served as the eco-friendly and green oxidant source for this conversion. In addition, the protocol exhibited high regioselectivity and tolerance toward a broad spectrum of functional groups to furnish quinoxaline-2,3-diones in good to excellent yields.