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

Abstract

A practical intramolecular C-H functionalization reaction of N-aryl enamines has been carried out with molecular iodine (I2) 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 I2-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.