Assembly of N-Heterocyclic Carbenes and Nitroalkenes for Access to Isoxazole Derivatives

A direct isoxazole synthesis employing N-heterocyclic carbenes (NHCs) as single-carbon synthons is reported. Using imidazolium salts as carbon donors, nitroalkenes are transformed into 5-amino-substituted isoxazoles via a nucleophilic addition-cycloaddition-ring opening-hydrolysis cascade reaction. This mild process simultaneously constructs C-O and C-C bonds, accessing products that are difficult to obtain by classical methods. The proposed reaction mechanism is supported by both experimental and computational studies. Several derivatives exhibit broad-spectrum antifungal activity, highlighting their potential as fungicide leads.