Trityl chloride as a novel and efficient organic catalyst for room temperature preparation of bis(indolyl)methanes under solvent-free conditions in neutral media

A simple, clean, and highly efficient solvent-free procedure for the preparation of bis(1H-indol-3-yl)methanes is described from the reaction of carbonyl compounds (aldehydes and ketones) with 1H-indole in the presence of trityl chloride as a catalyst. The reaction proceeds rapidly in high yields at room temperature in a neutral medium. A proposed mechanism is suggested based upon former reactions and calculated results.