A practical and efficient synthesis of bis(indolyl)methanes in water, and synthesis of di-, tri-, and tetra(bis-indolyl)methanes under thermal conditions catalyzed by oxalic acid dihydrate.

A simple, clean, and highly efficient green protocol has been developed for synthesis of bis(indolyl), di(bis-indolyl), and tris-indolyl methanes by the reaction of indole with aldehydes and ketones in the presence of oxalic acid dihydrate [(CO(2)H)(2).2H(2)O] and N-cetyl-N, N, N-trimethylammonium bromide (CTAB) in water. Also, tri(bis-indolyl) and tetra(bis-indolyl)methanes as new bis(indolyl)methanes were prepared under thermal conditions.