4-Fluoro-5-((2-fluorophenyl)amino)benzo[d]oxazole-6-carboxylic acid can be reacted with halogenations reagent (such as NIS) in the presence of acid (such as trifluoroacetic acid, trifluoromethanesulfonic acid, methanesulfonic acid, formic acid, acetic acid) at ambient temperature in appropriate solvent (include aliphatic and aromatic hydrocarbon (such as pentane, hexane, heptane, cyclohexane, petroleum ether, petrol, gasoline, benzene, toluene, xylene), aliphatic and aromatic halo-hydrocarbon (such as dichloromethane, 1,2-dichloroethane, chloroform, phenixin, chlorobenzene, o-dichlorobenzene), ether (such as diethyl ether, dibutyl ether, glycol dimethyl ether, 2-methoxyethyl ether, tetrahydrofuran, dioxane), ketone (such as acetone, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone), ester (such as ethyl acetate, methyl acetate), nitrile (such as acetonitrile, propiononitrile), amide (such as N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidin-2-one), DMSO, sulfolane, HMPA, DMPU, prefer N,N-dimethylformamide and N,N-dimethylacetamide) for some time (1-12 h, prefer 3-10 h). 4-Fluoro-5-((2-fluoro-4-iodophenyl)amino)benzo[d]oxazole-6-carboxylic acid is obtained after conventional workup.
