BigPatents India

A process for the preparation of compounds of formula (I) wherein n represents 0,1 or 2 M represents hydrogen. An alkali metal ion or an optionally substituted ammonium ion and X represents anilino, N-alkylamino or N,-N-dialkylamino, By reation of a compound of the formula (IV) wherein M and n have the abovementioned meaning, with 2 molar equivalents of an amine of the formula X-H ,wherein X has the abovementioned meaning , at a pH of 5-10, if appropriate in the presence of an acid-trapping agent which differs fro V, characterized in that the compound of the formula (IV) is added to an aqueous reaction medium with a temperature of at lest 400C and in that the amine of the formula (V) and, if appropriate, the acid-trapping agent are added to the aqueous reaction medium independently of one another before and/or during and/or after the addition of IV, gives compounds of the formula I which are outstandingly suitable as optical brighteners.