Facile syntheses of 3-halo and mixed 3,5-dihalo analogues of N-acetyl-l-tyrosine via sulfonic acid-catalysed regioselective monohalogenation

3-Halo and mixed-3,5-dihalo analogues of N-acetyl-l-tyrosine were obtained at ambient temperature with high yields and selectivities via p-toluenesulfonic acid-catalysed regioselective electrophilic halogenation.