Cyclization and <i>N</i>‑Iodosuccinimide-Induced Electrophilic Iodocyclization of 3‑Aza-1,5-enynes To Synthesize 1,2-Dihydropyridines and 3‑Iodo-1,2-dihydropyridines

Metal-free cyclization and N-iodosuccinimide-induced electrophilic iodocyclization of readily available 3-aza-1,5-enynes have been developed. The reactions selectively give 1,2-dihydropyridines and 3-iodo-1,2-dihydropyridines involving an aza-Claisen rearrangement and a 6π-electrocyclization step. Furthermore, the reaction could be carried out in 10 g scale for the synthesis of 1,2-dihydropyridines.