Heteropolyacid (H3PW12O40) supported MCM-41: An efficient solid acid catalyst for the green synthesis of xanthenedione derivatives

HPWA/MCM-41 mesoporous molecular sieves of appropriate ratios were prepared by loading HPWA on siliceous MCM-41 by the wet impregnation method. The prepared HPWA/MCM-41 materials were characterized by X-ray diffraction analysis (XRD) and BET surface area and FT-IR measurements. The morphology of mesoporous materials was studied by TEM observation. The catalytic activity of the above materials was tested for the condensation of dimedone (active methylene carbonyl compound) and various aromatic aldehyes under liquid phase conditions at 90 degrees C. The products were confirmed by FT-IR, H-1 NMR and C-13 NMR studies. HPWA supported MCM-41 catalysts catalyses efficiently the condensation of dimedone and aromatic aldehydes in ethanol and other solvents under liquid phase conditions to afford the corresponding xanthenedione derivatives. Activities of the catalysts follow the order: HPWA/MCM-41(20 wt.%) > HPWA/MCM-41(30 wt.%) > H3PW12O40 center dot nH(2)O > HPWA/MCM-41 (10 wt.%) > HPWA/SiO2 (20 wt.%) > HM (12) > H beta (8) > Al-MCM-41 (50). Various advantages associated with these protocols include simple workup procedure, short reaction times, high product yields and easy recovery and reusability of the catalyst. (C) 2009 Elsevier B.V. All rights reserved.