Lactonization of C(sp2)—H Bonds in Enamides with CO2

Herein, we report a novel synthesis of 1,3‐oxazin‐6‐ones from enamides with CO₂ through C—H carboxylation and one‐pot cyclization. This transition‐metal‐free and redox‐neutral process features broad substrate scope, good functional group tolerance and facile product derivatization. The nucleophilic attack to CO₂ from the electron‐rich alkene is demonstrated for this reaction.