12-Tungstophosphoric acid supported on zirconia as an efficient and heterogeneous catalyst for the synthesis of bis(indolyl)methanes and tris(indolyl)methanes

12-Tungstophosphoric: acid (TPA) supported on zirconia was employed as an efficient, heterogeneous catalyst for the liquid phase electrophilic substitution reactions of indoles with aldehydes or indole aldehyde to afford the corresponding bis(indolyl)methanes or tris(indolyl)methanes in good to high yields. The catalytic efficiency of TPA was found to increase after supporting on zirconia, which was expressed in terms of TON (turnover number) and TOF (turnover frequency, h(-1)). The catalyst was characterized by XRD, FTIR, BET surface area, elemental analysis and SEM technique and was found to be reusable without significant loss of activity. [GRAPHICS] R1 = H or CH3 R2 = H or CH3 (c) 2007 Elsevier B.V. All rights reserved.