A fast and efficient bromination of isoxazoles and pyrazoles by microwave irradiation

A fast and efficient method has been developed for the bromination of isoxazoles and pyrazoles using microwave irradiation. In this method, N-bromosuccinimide was used in different acid solvents according to the reactivity of the substrates to give mono-brominated isoxazoles and pyrazoles in good yields. Trifluoroacetic acid was found to be the best solvent for highly unreactive isoxazoles and pyrazoles.