NaHS center dot nH(2)O-induced umpolung: the synthesis of 2-acyl-3-aminoindoles from aryl methyl ketones and 2-aminobenzonitriles

An efficient method for constructing 2-acyl-3-aminoindoles from methyl ketones and 2-aminobenzonitriles is described, in which NaHS center dot nH(2)O is used as a novel umpolung reagent for the first time in organic synthesis. Mechanistic studies revealed that the key step involved an Eschenmoser sulfide contraction reaction.