| 摘要 |
The present invention relates to a process for the preparation of 2,5-di-phenylamino-terephthalic acid and its dialkyl esters of the formula <IMAGE> ethyl group, by reaction of a succinic acid dialkyl ester with a sodium alcoholate in xylene, treatment of the resulting 2,5-dihydroxy-cyclohexadiene-1,4-di-carboxylic acid dialkyl ester with acid and aniline, dehydrogenation of the resulting 2,5-di-phenylamino-dihydro-(3,6)-terephthalic acid dialkyl ester by means of oxygen, if appropriate hydrolysis of the 2,5-di-phenylamino-terephthalic acid dialkyl ester formed and liberation of the 2,5-di-phenylamino-terephthalic acid from the di-sodium salt formed. The 2,5-di-phenylamino-dihydro-(3,6)-terephthalic acid dialkyl ester is reacted with pure oxygen in the presence of an alkali metal ion and/or an alkaline earth metal ion. This significantly decreases undesirable impurities.
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