Process for preparing pure substituted 2,5-diarylaminoterephthalates and the corresponding free acids

Abstract From the Canadian patent

2,5-diarylamino terephthalates are obtained in good yields and excellent purity when the aromatic nitro compound used for oxidizing the corresponding dihydro-2,5-diarylamino terephthalate contains the aromatic radical of said diarylamino groups, i.e. when the amine formed during the oxidation is that from which said diarylamino groups derive. The products yield vary pure quinacridone pigments and allow the sythesis of only one isomer of substituted quinacridones.