Process for the preparation of 2,5-di-phenylamino-terephthalic acid and its dialkyl esters
US5616779A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 2, 1995 |
| Grant date | Apr 1, 1997 |
| Priority date | — |
| Expiry date | Mar 2, 2015 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC07C227/16
- WIPO fieldOrganic fine chemistry
- WIPO sectorChemistry
Abstract
The present invention relates to a process for the preparation of 2,5-di-phenylamino-terephthalic acid and its dialkyl esters of the formula ##STR1## in which R is a hydrogen atom or a methyl or an 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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.