Aerobic Synthesis and Nucleophilicity of 2,3‐Dihydroindolizines

Abstract

Herein, we reported a practical and metal‐free synthesis of 2,3‐dihydroindolizines using N‐alkyl pyridinium salts and electron‐deficient alkenes with ambient air as a sole oxidant. Interestingly, a halogen bond donor (penta‐fluoroiodobenzene 20 mol %) was successfully applied to promote this partial oxidation by slowing down the undesired decomposition processes, probably because of the formation of a halogen‐bonded adduct. Moreover, the C1 position of 2,3‐dihydroindolizines was utilized as a good nucleophile for nucleophilic aromatic substitution with 4‐iodo‐1‐methylpyridin‐1‐ium trifluoromethanesulfonate as electrophile and provided a new‐type dipyridinium compound effectively.