Mesoporous zirconium phosphate: An efficient catalyst for the synthesis of coumarin derivatives through Pechmann condensation reaction

Mesoporous zirconium phosphate (m-ZrP) is used as a solid acid catalyst for the synthesis of coumarins via Pechmann condensation reaction and gave high catalytic activity for the condensation of phenols and ethyl acetoacetate in both conventional heating as well as microwave assisted method. The condensation reaction is studied in detail by varying the reaction parameters like effect of solvent, molar ratio of the reactants, temperature, and catalyst loading. Among the substituted phenols, m-amino phenol is more reactive and 100% yield is obtained in very short time at low temperature due to the presence of ring activating amine group in meta position. The m-ZrP is also active even for simple phenol and 57% yield of 4-methyl coumarin is obtained in conventional heating method. Microwave assisted synthetic method is found to be advantageous over conventional heating for the synthesis of coumarins, as it provides improved yield in very less time. (C) 2010 Elsevier B.V. All rights reserved.