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A simple, efficient, and environmentally benign protocol for the synthesis of 3-carboxycoumarins and cinnamic acids via Knoevenagel condensation has been achieved using aqueous extract of Acacia concinna pods as a naturally occurring surfactant type catalyst. We found for the first time that the aqueous extract of Acacia concinna pods could effectively catalyze the condensation of Meldrum's acid with salicyaldehyde/aromatic aldehyde to yield 3-carboxycoumarins and cinnamic acids in excellent yields under mild conditions. The low cost, easy availability of the catalyst, and simple reaction conditions suggest the possible use of the present method for large scale preparations.

A series of pyranopyrazoles, was efficiently synthesized via one-pot, four component reaction of ethyl acetoacetate, hydrazine hydrate, aldehydes and malononitrile in the presence of catalytic amount silicotungstic acid under solvent free condition. NOE experiments confirmed that the product exist exclusively in the 2H form. The present protocol offers the advantages of clean reaction, short reaction time, high yield, easy purification and economic availability of the catalyst.