Novel approach to bis(indolyl)methanes using nickel nanoparticles as a reusable catalyst under solvent-free conditions

Nano-sized nickel as a catalyst has been developed for the electrophilic substitution reactions of indole with various aromatic aldehydes under solvent-free conditions to afford the corresponding bis(indolyl)methanes in high to excellent yields. The described method has promising features, such as no hazardous organic solvents or catalysts, short reaction time, high product yields, simple work-up procedure, reusable catalyst and easy product separation without further purification with column chromatography.