| 摘要 |
A process for the preparation of unsymmetrically substituted optical brighteners of the general formula <IMAGE> I where X and Y independently of one another are hydrogen, fluorine, chlorine, cyano, C1-C10-alkoxycarbonyl, unsubstituted or substituted carbamyl or sulfamyl, a sulfonic acid aryl ester group, C1-C10-alkylsulfonyl or phenylsulfonyl, and at least one of X and Y is not hydrogen, and of mixtures of such optical brighteners, wherein terephthalaldehyde is reacted successively with a compound of the general formula IIa <IMAGE> IIa and a compound of the general formula IIb <IMAGE> IIb where X and Y have the above meanings and alkyl is preferably C1-C4-alkyl, in the presence of an alkali, in a solvent from which the monocondensation product precipitates. |
