Coumarins have been synthesized by microwave irradiation in solvent free reaction condition, and excellent yields of coumarins have been obtained with high purity. Pechmann method is a revere reaction which is one of the easy and forthright scheme used to produce coumarins. IR and NMR spectroscopy have been used to confirm the successful synthesis of coumarins by Pechmann reaction. Use of commercially accessible low-cost catalyst makes this procedure very fascinating from a cost-ffective point of view. An easygoing and capable microwave synthesis technique has been evolved for condensation of beta-ketoester and substituted phenol in the presence of catalytic quantity of oxalic acid at extensive temperature range to give the resultant substituted 4-methyl-2H-chromen-2-one in elevated output.