Synthesis of 7-hydroxy-4-methylcoumarin via the Pechmann reaction with PVP-supported phosphotungstic acid catalyst

A novel method for synthesis of 7-hydroxy-4-methylcoumarin from resorcinol and ethyl acetoacetate via the Pechmann reaction with polyvinylpyrrolidone-supported phosphotungstic acid (PVP-HPW) catalyst is developed. The catalysts were characterized by FTIR, TGA, elemental analysis, UV-vis and a Hammet acidity function test. HPW protonated PVP to form polymeric cations. The polymeric cations interacted strongly with phosphotungstic anions, leading to an ionic liquid structure. The performance of the PVP-HPW were compared with other catalysts such as HPW, NMP-H2SO4 and PVP-H2SO4. For PVP-HPW dosage of 9% based on the weight of resorcinol, the yield of 7-hydroxy-4-methylcoumarin reached 96.73% after two hours reflux reaction at 110 degrees C, which exhibited much higher value than other catalysts. The PVP-HPW can be easily separated from the reaction mixture and retains the activity during recycling. (C) 2016 Elsevier B.V. All rights reserved.