A Solvent-Free Synthesis of Coumarins Using Phosphotungstic Acid as Catalyst

Phosphotungstic acid (PTA) is used an efficient catalyst for the von Pechmann condensation reaction of phenols and beta-keto esters under solvent-free conditions. This method was compared with those of the reactions in the different solvents and catalysts. The methodology presented offers significant improvements for the synthesis of coumarins with regard to yield of products, simplicity in operation and green aspects by avoiding toxic conventional catalysts and solvents.