Preparation of cationic methine dyestuffs

Claim 1

In the preparation of a dyestuff of the formula ##STR38## wherein R represents an alkyl radical having 1 to 4 C atoms and which is optionally substituted by hydroxyl, alkoxy having 1 to 4 C atoms, acyloxy, halogen, cyano, carboxyl, C 1 -C 4 -carbalkoxy, carboxamido or acetyl, R 1 represents hydrogen, an alkyl radical having 1 to 4 C atoms, halogen, alkoxy having 1 to 4 C atoms, hydroxyalkoxy having 2-4 C atoms, a phenoxy radical which is optionally substituted by halogen, C 1 -C 4 -alkyl or C 1 -C 4 -alkoxy, benzyloxy, benzyl, carboxyl, an alkyl carboxylate having 1 to 4 C atoms, a carboxamide group optionally substituted by 1 or 2 C 1 -C 4 -alkyl radicals, a sulphonamide group optionally substituted by 1 or 2 C 1 -C 4 -alkyl radicals, alkylsulphonyl having 1 to 4 C atoms, phenylsulphonyl or a cyano, trifluoromethyl, acetyl or benzoyl group, and A represents a radical of the formula ##STR39## in which R 2 and R 3 independently of one another represent an alkyl radical having 1 to 4 C atoms and which is optionally substituted by hydroxyl, C 1 -C 4 -alkoxy, halogen, cyano, phenyl, carbalkoxy having 1 to 4 C atoms, carboxamide, acyloxy, benzyloxy, sulphonamido or acylamino, R 2 additionally also represents a phenyl or benzyl radical which is optionally substituted by halogen, C 1 -C 4 -alkyl or C 1 to C 4 -alkoxy or R 2 , together with the adjacent C atom of the benzene ring, can form a partially hydrogenated N- and, if appropriate, O-containing 5- or 6-ring, and R 4 denotes hydrogen, an alkyl radical having 1 to 4 C atoms, an alkoxy radical having 1 to 4 C atoms or halogen, or a radical of the formula ##STR40## in which R 5 denotes an alkyl radical having 1 to 4 C atoms, a pheny radical optionally substituted by halogen, C 1 - to C 4 -alkyl or C 1 - to C 4 -alkoxy or a carbalkoxy radical having 1 to 4 C atoms, R 6 denotes hydrogen or an alkyl radical having 1 to 4 C atoms and which is optionally substituted by hydroxyl, halogen, alkoxy having 1 to 4 C atoms, cyano or acyloxy and R 7 denotes hydrogen, halogen, C 1 - to C 4 -alkyl, C 1 - to C 4 -alkoxy, carbalkoxy having 1 to 4 C atoms, C 1 - to C 4 -alkylsulphonyl, phenylsulphonyl, acetyl or benzoyl or a radical of the formula ##STR41## wherein R 8 and R 9 independently of one another have the same meaning as R and R 1 , R 10 designates hydrogen or the cyano group, B represents a single bond or a C 1 - to C 4 -alkylene radical which is substituted by hydroxyl radicals and which is optionally substituted by one additional carboxyl group and the indices m, n, o and p independently of one another denote 1-4, by reacting a methyleneindoline compound of the formula ##STR42## with an equimolar amount of an aldehyde of the formula A--CHO and with 1 to 5 times the molar amount of a dicarboxylic or tricarboxylic acid of the formula ##STR43## wherein B is as defined above, the improvement which comprises effecting the reaction in the substantial absence of a solvent and removing water formed in the reaction.