A Unique Blend of Water, DES and Ultrasound for One‐Pot Knorr Pyrazole Synthesis and Knoevenagel‐Michael Addition Reaction

Abstract

Abstract A simple and convenient method for the tandem synthesis of 4, 4‐(arylmethylene)‐bis‐(3‐methyl‐1‐phenyl‐1H‐pyrazol‐5‐ol)s via 3‐methyl‐1‐phenyl‐5‐pyrazolone from aldehyde, phenyl hydrazine and ethyl acetoacetate using combination of Deep Eutectic Solvent (DES) and ultrasound in water is described. Shorter reaction time, easy work up and comparably good yield of desired product are crucial features. One pot Knorr synthesis and Knovenagel‐Michael reaction and use of water as solvent make this methodology an alternative to the other approaches. The advantage of applying ultrasound is, it reduces required time and temperature for reaction with improved yield. The DES and water used here recycled five times without considerable loss of activity.