Polyvinylsulfonic acid as a novel Bronsted acid catalyst for the synthesis of bis(indolyl)methanes

Polyvinylsulfonic acid as a novel, biodegradable, and efficient Bronsted acid catalyst for the reaction of indoles with aldehydes to obtain bis(indolyl)methanes has been reported. The catalyst exhibited remarkable activity, recyclability, and tolerated a wide variety of functional groups providing the desired bis(indolyl)methanes in excellent yield (64-96%) at room temperature using ethanol as a solvent. The effect of different reaction parameters like solvent, temperature, catalyst doses, and recyclability were investigated for the title reaction.