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.