1-Carboxymethyl-3-methylimidazolium chloride {[cmmim]Cl} as an efficient catalyst for the solvent-free synthesis of bis(indolyl)methanes

1-Carboxymethyl-3-methylimidazolium chloride {[cmmim]Cl} is utilized as a highly efficient and reusable catalyst for the synthesis of bis(indolyl)methanes by the condensation reaction of indole with arylaldehydes under solvent-free conditions at room temperature. In summary, the presented method have several advantages including simplicity, low cost, generality, efficiency, clean reaction profile, high yield, short reaction time, ease of product isolation, mild reaction conditions, and good agreement with the green chemistry protocols. In this work, all aldehydes, including benzaldehyde and arylaldehydes possessing electron-withdrawing substituents, electron-releasing substituents and halogens on their aromatic ring, afforded the desired bis(indolyl)metanes in high to excellent yields and in short reaction times.