In this research work, we report an efficient and easy method for preparation of 2-arylbenzimidazoles from o-phenylenediamines and phenoxyacetic acids under microwave condition using a Wells-Dawson heteropolyacid (H 6 P 2 W 18 O 62 Á 24H 2 O) as catalyst. The heterogeneous reaction conditions provided a very simple, environmentally friendly, clean, economical and selective protocol, for the preparation of benzimidazole derivatives. The catalyst is easily recycled and reused without loss of the catalytic activity.
Phosphotungstic acid (PTA) is used an efficient catalyst for the von Pechmann condensation reaction of phenols and b-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.
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