Microwave-assisted synthesis of 4-methyl-coumarin derivatives

Four 4-methyl-coumarin derivatives were synthesized from substituted phenols and ethyl acetoacetate at a molar ratio of 1∶1.5 via the Pechmann condensation reaction using NH4HSO4(12 mol%)as the catalyst under microwave radiation and solvent-free conditions.The method was simple,green and efficient,and the reaction time was shortened to 10 min with the product yield ranging from 45% to 88.4%.