Preparation of pyrazole-based compounds in ChCl-urea DES as green solvent

Within the framework of green chemistry, solvents occupy a strategic place. Green Chemistry aims to replace the hazardous and/or harmful solvents with more environmentally friendly alternatives.A new family of ionic fluids, so-called Deep Eutectic Solvents (DES), exhibit similar physico-chemical properties to the traditionally used ionic liquids, while being much cheaper and environmentally friendlier [1]. DESs contain large, non-symmetric ions that have low lattice energy and hence low melting points [2]. Pyrazoles are one of the most important classes of bioactive heterocycles gaining increased interest from pharmaceutical, chemical, and agricultural industries over the past decade [3]. For example dihydropyrano[2,3-c] pyrazoles play an essential role as biologically active compounds and represent an interesting template for medicinal chemistry. Many of these compounds are known for their antimicrobial,insecticidal and anti-inflammatory activities [1]. Hence, in this work we have synthsized pyrazole based compounds 3 in ChCl-urea DES in different conditions. For this purpose, the reactions were performed in two steps. In the first step, pyrazolonewas prepared from condensation of hydrazine hydrate and ethyl acetoacetate under solvent free condition. At the second step, Knovenagel condensation of pyrazolone 1 with aromatic aldehyde derivatives 2followed by Michael addition gave compounds 3(Figure1).Finally, the obtained products were purified and characterizedby x-ray crystallography and spectroscopic methods such as IR, 1H NMR, and 13C NMR.