Synthesis and characterization of bis(indolyl)methanes, tris(indolyl)methanes and new diindolylcarbazolylmethanes mediated by Zeokarb-225, a novel, recyclable, eco-benign heterogenous catalyst

Zeokarb-225, is a heterogenous, recyclable, eco-benign catalyst for the liquid phase electrophilic substitution reactions of indoles with aldehydes or indole aldehydes to afford the corresponding bis(indolyl)methanes or tris(indolyl)methanes in good yields. The catalyst is also effective for the synthesis of new diindolylcarbazolylmethanes in good yields. The catalyst was characterized by FT-IR and in situ DRIFT studies (pyridine adsorption). All the products were extensively characterized by NMR, FT-IR, GC-MS and CHN analyses. A mechanism for the catalytic activity is proposed. The catalyst can be recovered and reused without loss of activity. The work-up of the reaction consists of a simple filtration, followed by concentration of the crude product and purification. The effect of solvent, the effect of substituents, the influence of mole ratio, the effect of stirring speed and the recyclable use of the catalyst are also investigated. (C) 2004 Elsevier B.V. All rights reserved.