Microwave‐assisted synthesis and biological evaluation of pyrazole‐4‐carbonitriles as antimicrobial agents

Abstract

Abstract An efficient microwave‐assisted method of synthesis of pyrazole‐4‐carbonitriles has been developed. Condensation of pyrazole‐4‐carbaldehydes with hydroxylamine hydrochloride followed by reaction of the resulting oximes with the Vilsmeier‐Haack reagent pre‐formed from phthaloyl dichloride and dimethylformamide under microwave irradiation afforded the corresponding pyrazole‐4‐carbonitriles in 73% to 91% yield. The operational simplicity, avoidance of toxic reagents such as POCl 3 , shorter reaction time, higher yield compared to the classical version, easy work up, and the use of the by‐product in the regeneration of phthaloyl dichloride are the advantages of this methodology. All the target compounds were tested for antimicrobial activity against Gram‐positive bacteria Bacillus cereus and Staphylococcus aureus ; Gram‐negative bacteria Escherichia coli and Yersinia enterocolitica , and the fungal species Candida albicans .