Highly ( E )‐Stereoselective Synthesis of α , β ‐Unsaturated Esters and Amides via Photocatalyst‐Free Ring‐Opening of Indolizines Under Air

We have developed a visible‐light‐driven protocol for the highly stereoselective synthesis of ( E )‐ α , β ‐unsaturated esters and amides from indolizines and alcohols/amines, without the need for external photocatalysts or additives. The reaction proceeds at room temperature under air, affording excellent ( E )‐stereoselectivity, broad substrate scope, good functional group tolerance, and scalability to gram‐scale. Various primary amines and a range of alcohols, including natural‐product‐derived alcohols, are compatible with this protocol, demonstrating its potential for late‐stage functionalization. Mechanistic investigations reveal that the reaction proceeds via singlet‐oxygen‐initiated or single‐electron‐transfer pathways, with key intermediates identified by radical trapping experiments, UV–vis spectroscopy, and LC–MS analysis. This strategy provides a green and efficient route to biologically relevant ( E )‐ α , β ‐unsaturated carboxylic acid derivatives.