Herein, we report a novel synthesis of 1,3‐oxazin‐6‐onesfrom enamides with CO2 through C—H carboxylation and one‐potcyclization. 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.