Synthesis of 7-substituted 4-methyl coumarins by Pechmann reaction using nano-crystalline sulfated-zirconia

摘要: The nano-crystalline sulfated-zirconia catalysts, prepared by one-step as well two-step sol–gel technique, showed excellent catalytic activity with a high substrate to catalyst weight ratio for the synthesis of 7-substituted 4-methyl coumarins via solvent free Pechmann reaction. m-amino phenol was found be more reactive than m-hydroxy phenol. results 100% conversion ∼100% selectivity 7-amino coumarin at 110 ◦ C within 2 min. For 7-hydroxy coumarin, 94% yield obtained after 3 h 170 80. Slow kinetics observed in polar nitrobenzene non-polar toluene both derivatives, due slow bulk diffusion reactant molecules presence solvent. microwave assisted seems advantageous way synthesize hydroxy derivative resulting (99%) much lesser time (15 min) lower temperature (150 C) compared thermal heating. use very small amount and reusability simple activation several times similar are novel properties catalyst. © 2007 Elsevier B.V. All rights reserved.