MICROWAVE ASSISTED SYNTHESIS OF PYRAZOLINE-BASED COUMARIN DERIVATIVES: A COMPARATIVE STUDY

Abstract

Functionalized pyrazole-based coumarin derivatives from 3-(3-(substituted-phenyl)acryloyl)-2H-chromen-2-one through microwave assisted synthesis and under reflux. Reaction of 3-acetylcoumarin with various benzaldehyde derivatives resulted in the formation of 3-[3-acryloyl]-2H-chromen-2-one and its derivatives. The reaction of the intermediate chalcones with hydrazine hydrate was carried out using both microwave assisted method and conventional heating methods under reflux to yield 3-(5-(substituted-phenyl)-4,5-dihydro-1H-pyrazol-3-yl)- 2H-chromen-2-one moieties. The structures were confirmed by analytical data and spectroscopic methods. The microwave assisted reactions were remarkably successful and produced the target compounds in higher yields at less reaction time compared to conventional heating methods. Microwave assisted synthesis is eco-friendly as release of toxic vapors or substances was not observed. Coupled with short reaction times and atom economy, this procedure is more economical.Key words: Cyclo-addition, 2H-chromen-2-one, spectroscopy, microwave irradiation, column chromatography