Room-Temperature Synthesis of Diindolylmethanes Using Silica-Supported Sulfuric Acid as a Reusable Catalyst Under Solvent-Free Conditions

[image omitted] Efficient electrophilic substitution reactions of indoles with various aromatic and aliphatic aldehydes were carried out using a catalytic amount of H2SO4 center dot SiO2 under solvent-free conditions to afford the corresponding bis(indolyl)methanes in excellent yields.