Pyrazole-tethered isoxazoles: hypervalent iodine-mediated, metal-free synthesis and biological evaluation

In the present work, a hypervalent iodine-mediated, metal-free route for the synthesis of a series of di- and tri-substituted pyrazole-tethered isoxazole derivatives has been utilized via [3+2]-cycloaddition reaction of nitrile oxides with alkynes. All the synthesized isoxazole derivatives were characterized by FTIR, ¹H NMR, ¹³C NMR, and HRMS data. The structure of one of the products, ethyl-3-(1,3-diphenyl-1H-pyrazol-4-yl)-5-phenylisoxazole-4-carboxylate, was confirmed by X-ray analysis. All synthesized compounds were screened for antimicrobial activity and compared to the standard drug, Amoxicillin. Some of the compounds exhibited antibacterial activity comparable to or higher than Amoxicillin. Moreover, the synthesized compounds exhibited moderate to excellent antioxidant activity. The cytotoxicity of all products was investigated against the mouse fibroblast (animal) and plant seed germination cell line (Vigna radiata).