Oxidative Coupling of Benzylamines with Indoles in Aqueous Medium to Realize Bis-(Indolyl)Methanes Using a Water-Soluble Cobalt Catalyst and Air as the Oxidant.

Oxidative coupling of benzylamines with indoles to bis-(indolyl)methanes (BIMs) was achieved using an inexpensive water-soluble cobalt complex, Co(bpb). The catalyst was found to be quite effective when air was used as the oxidant and water as solvent under mild reaction conditions. Aromatic amines were successfully converted to the corresponding BIMs with yields up to 85 %. We have successfully carried out a 1 gram scale reaction, and few pharmaceutically relevant compounds were also synthesised by this method in good yields. Control experiments have also been carried out to understand the possible reaction mechanism.