NHC triggered cascade metal-free synthesis of 2,3-diarylated indoles under solvent-free conditions

A new cascade strategy to the synthesis of 2,3-disubstituted indoles via the metal-free reaction of aryl aldehyde and aryl amine triggered by N-heterocyclic carbene (NHCs) under solvent-free conditions, has been disclosed. The protocol has the advantages of easy work-up, high yields, wide application scope, and an environmentally benign procedure compared with the reported methods.