A new catalytic method for the preparation of bis-indolyl and tris-indolyl methanes in aqueous media

Some new metal dodecyl sulfates were prepared by the reaction of sodium dodecyl sulfate and the corresponding metal nitrates. All of the prepared salts catalyzed the condensation of indoles with aldehydes and ketones. Among of them, zirconium tetrakis(dodecyl sulfate), Zr(DS)4, was superior to others. Bis- and tris-indolyl methanes were synthesized at room temperature in high yields by using Zr(DS)4 under aqueous media. Zr(DS)4 was also recovered and reused for new runs.