Iodine/Copper Iodide-Mediated C-H Functionalization: Synthesis of Imidazo[1,2-a]pyridines and Indoles from N-Aryl Enamines

A practical intramolecular C-H functionalization reaction of N-aryl enamines has been carried out with molecular iodine (I-2) as the sole oxidant in the presence of copper iodide (CuI). The efficient and versatile synthetic method described here is compatible with both N-heteroaryl and N-aryl substituted enamines and produces diverse imidazo[1,2-a]pyridine and indole derivatives via I-2-mediated oxidative C-N and C-C bond formation, respectively. This ligand-free C-H functionalization methodology also works well with crude enamines, which allows for the sequential synthesis of the products directly from arylamines and ketones (or alkynes) without purification of the enamine intermediates.