Iron-catalyzed reductive cyclization reaction of 1,6-enynes for the synthesis of 3-acylbenzofurans and thiophenes

A facile synthesis of 3-acylbenzofurans and thiophenes via iron( ii )-catalyzed reductive cyclization of 1,6-enynes has been developed. A sequence involving hydrogen atom transfer (HAT)/cyclization and oxygen insertion has been proposed and confirmed by isotope experiments. This benign strategy provides a viable synthetic approach to valuable carbonylated heteroaromatic compounds using ethanol as the solvent and dioxygen as the oxidant.