A mild and efficient synthesis of bis(indolyl)methane derivatives catalyzed by monoammonium salt of 12-tungstophosphoric acid

Abstract

A simple, highly rapid and efficient electophilic substitution reaction of indole with various aromatic aldehydes has been carried out using 5 wt% of monoammonium salt of 12-tungstophosphoric acid [(NH₄)H₂PW₁₂O₄₀] as a solid acid catalyst in acetonitrile to afford the corresponding bis(indolyl)methanes in excellent yields (84-95%) at room temperature. The heteropolyacid-based catalyst has the advantages of simple workup procedure, water insolubility with good activity and high yielding reaction for the synthesis of bis(indolyl)methane derivatives.