Catalytic and Multicomponent Reactions for Green Synthesis of Some Pyrazolone Compounds and Evaluation as Antimicrobial Agents

[Image: see text] A green synthetic approach and facile method was developed to produce pyrazole compounds (6a–d) by the reaction of ethyl acetoacetate (1), hydrazines (2a–d), and catalytic imidazole (3) in aqueous media. 4-Dicyanomethylene-2-pyrazoline-5-one derivatives (14a–d) were synthesized through the reaction of 2-pyrazoline-5-one derivatives (6a–d) with tetracyanoethylene (TCE) (7) by using catalytic imidazole (3) in an aqueous medium. Moreover, the 4-dicyanomethylene derivative (16) was obtained via treatment of 1-phenyl-3,5-pyrazolidinedione (15) with TCE (7). The spiropyrazoleoxirane derivatives (18 and 20) were prepared by treating the precursor 4-dicyanomethylene-2-pyrazoline-5-one derivative (14b) with hydrogen peroxide in various polar solvents under alkaline conditions. The spiropyrazole oxirane derivative (18) was used as a precursor for the design of functionalized pyrazolone derivatives (24 and 27a, b). The chemical structure of the novel designed derivatives was ascertained based on elemental analyses, mp, thin-layer chromatography, and spectral analyses. Furthermore, some of the synthesized derivatives were examined against different pathogenic bacterial and fungal strains. Their results demonstrated that some of them revealed notable antimicrobial activities.