Process for the preparation of substituted 4,4'-diaminostilbene-2,2'-disulphonic acids

US6025490A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Ulrich Feldhues · Bensberg, DE
• Rolf Brockmann · Bensberg, DE
• Udo Eckstein · Cologne, DE
• Detlef Szeymies · Kürten, DE

Key dates

• Filing date: Feb 11, 1998
• Grant date: Feb 15, 2000
• Expiry date: Feb 11, 2018

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07D251/68
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

A process for the preparation of compounds of the formula (I) ##STR1## wherein n represents 0-2; PA1 M represents H, alkali metal ion or optionally substituted ammonium ion; and PA1 X represents anilino, N- or N,N-alkylamino; by reaction of a compound of the formula (IV) ##STR2## with 2 molar equivalents of an amnine of the formula X--H, at a pH of 5-10, optionally in the presence of an acid-trapping agent which differs from X--H, wherein the compound of the formula (IV) is added to an aqueous reaction medium with a temperature of at least 40.degree. C. and the amine of the formula X--H and, optionally, the acid-trapping agent are added to the aqueous reaction medium independently of one another and/or during and/or after the addition of IV. The compounds of the formula I which are outstandingly suitable as optical brighteners.