Synthesis of Pyrazolone Derivatives by Grinding, Microwave, and Conventional Techniques and Their Antimicrobial Activity

Abstract

Abstract: 4-(Arylmethylidene)-5-methyl-2,4-dihydro-3H-pyrazol-3-ones were prepared via one-pot reaction of ethyl acetoacetate, hydrazine hydrate, and aromatic aldehydes using mechanical grinding, microwave irradia­tion, and conventional techniques. These compounds were reacted with ethyl cyanoacetate, urea, hydrazine hydrate, phenylhydrazine, thiosemicarbazide, and POCl3/PCl5 to afford pyranopyrazole, pyrazolopyrimidine, 4-(α-hydrazinylbenzyl)pyrazolone, pyrazolopyrazole, and 4-(arylmethylidene)-3-chloro-5-methyl-4H-pyrazole derivatives, respectively. Reactions of the latter with aromatic amines and hydrazine hydrate gave the corre­sponding 3-anilino- and 3-hydrazinylpyrazoles, respectively. Reactions of 4-(arylmethylidene)-3-hydrazinyl-5-methyl-4H-pyrazoles with acetophenone, ethyl acetoacetate, acetylacetone, diethyl malonate, ethyl cyano­acetate, and chloroacetyl chloride were also studied. The yield economy, atom economy, optimum efficiency, and reaction mass efficiency were used to compare the three synthetic techniques. The new compounds were evaluated for their in vitro antibacterial and antifungal activities, and some of them showed very strong antimicrobial activity.