An SiO2/ZnBr2 mediated expeditious approach to 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one derivatives in water under microwave irradiation

Abstract

A new one-pot three-component green approach has been developed for the synthesis of a series of pyrazolone derivatives 2(a–s) from differently substituted aromatic aldehydes, ethylacetoacetate and phenylhydrazine/2,4-dinitrophenylhydrazine in excellent yields (94–98%), employing SiO₂/ZnBr₂ as a recyclable Lewis acid catalyst in water under microwave heating. The molecular structure of compounds 2a and 2d were well supported by single crystal X-ray crystallographic analysis. The present protocol bears a wide substrate tolerance and is believed to be more practical, efficient, eco-friendly and compatible as compared to existing methods.