An efficient green procedure for the synthesis of bis (indolyl)

In this work, a green, simple and highly efficient procedure for the synthesis of bis(indolyl)methanes is described. the condensation of indoles with carbonyl compounds catalyzed by citric acid in water affords bis(indolyl)methanes in high yields and relatively short reaction times. the advantages of this method are using of water as a low cost solvent and efficient recyclability of the catalyst.