US Patent 7342126 Process for the preparation of 4-oxo-4-((4-(phenylamino)phenyl)amino)-2-butenoic acid

A process for the preparation of 4-oxo-4-((4-(phenylamino)phenyl)amino)-2-butenoic acid includes reacting p-aminodiphenyl amine and maleic anhydride in a reaction first mixture containing a volatile organic solvent under suitable reaction conditions to provide a second mixture containing 4-oxo-4-((4-(phenylamino)phenyl)amino)-2-butenoic acid product; subjecting the second mixture to vacuum distillation to remove the volatile organic solvent while simultaneously adding diluent oil to produce a dispersion of 4-oxo-4-((4-(phenylamino)phenyl)amino)-2-butenoic acid in the diluent oil.