GB868361A - Process for manufacture of intermediates for pigments and dyestuffs - Google Patents

Abstract

2,5-Bis-(arylamino)-terephthalic esters are prepared by treating a 3,6-dihydro-2,5-bis-arylamino-terephthalic ester which in one of its tautomeric forms has the formula: <FORM:0868361/IV (b)/1> where R represents a carboxylic or heterocyclic aromatic residue which may be substituted or which may form part of a polycyclic structure and R1 represents an alkyl group containing up to 5 carbon atoms, with a quinone. The dehydrogenation may be effected by refluxing a mixture of the reactants in a solvent such as ethyl or amyl alcohol, ethylene glycol; dimethyl formamide or mono or odichlorobenzene. In a modified form of the process the dehydrogenation is carried out using less than the chemically equivalent amount of the quinone, e.g. 0,01 equivs., and a current of air or oxygen is passed through the reaction mixture. The group R may be a phenyl, naphthyl, pyrenyl, pyridyl, carbazyl or dibenzyfuranyl radical and may be substituted by groups such as chloro, bromo, methyl, ethyl, trifluoromethyl, phenyl, p-tolyl, anilino, acetylamino, benzoylamino, p-toluenesulphonamido, methoxy, ethoxy, b -hydroxyethoxy, phenoxy or cresoxy groups. The reaction is preferably carried out using chloranil but other quinones such as benzoquinone, naphthoquinone, anthraquinone, bromanil, 2,5-dihydroxy-benzoquinone, 2,3-di-cyano-5,6-dichloro-benzoquinone, 2,6-dihydroxy-anthraquinone and acenaphthenequinone, may also be used. Examples describe the preparation of dimethyl and diethyl esters where the group R is a phenyl, 2,4- and 2,5-dichloropheny, 2-and 4-methoxyphenyl, 4-acetylaminophenyl, 4-phenylaminophenyl, 2-naphthyl and 2-pyridyl radical. Many other products are specified. 3,6-dihydro-2,5-bis(arylamino) terephthalic esters used in the above examples are prepared by condensing dimethyl or diethyl succino-succinate with the appropriate amine.