Research in the isoxazole series

The bromination of phenylisoxazoles in 85% acetic acid is a second-order reaction. The ratios of the rate constants for the bromination of benzene and the investigated compounds are 1∶100–10,000. The maximum reaction rate was observed when a twofold excess of the heterocycles was present, and this constitutes evidence for the intermediate formation of complexes of isoxazoles with bromine.