dppb and TfOH promoted cascade reaction of o-nitrophenylpropiolamides to access C2-spiro-pseudoindoxyls

Abstract

A dppb and TfOH promoted cascade reaction of o-nitrophenylpropiolamides to access C2-spiro-pseudoindoxyls under mild conditions has been developed. The desired products were obtained in high to excellent yields. A mechanism involving the formation of the key intermediate 3-indolol-2-carboxamide, which originates from an indolyl dimer intermediate is proposed. The notable advantages of this process include good functional group tolerance, excellent yields, and operational simplicity.