Process for preparing cationic methine dyestuffs

In the preparation of cationic methine dyestuffs of the general formula ##STR38## in which R represents an alkyl radical which has 1 to 4 C atoms and is optionally substituted by hydroxyl, alkoxy having 1 to 4 C atoms, acyloxy, halogen, cyano, carboxyl, C.sub.1 - to C.sub.4 -carbalkoxy, carboxamido or acetyl,

• R.sup.1 represents hydrogen, alkyl having 1 to 4 C atoms, halogen, alkoxy having 1 to 4 C atoms, hydroxyalkoxy having 2 to 4 C atoms, an optionally halogen-, C.sub.1 - to C.sub.4 -alkoxy- or C.sub.1 - to C.sub.4 -alkoxy-substituted phenoxy, benzyloxy or benzyl radical, carboxyl, an alkyl carboxylate having 1 to 4 C atoms, a carboxamide group which is optionally substituted by 1 or 2 C.sub.1 - to C.sub.4 -alkyl radicals, a sulphonamide group which is optionally substituted by 1 or 2 C.sub.1 - to C.sub.4 -alkyl radicals, alkylsulphonyl having 1 to 4 C atoms, phenylsulphonyl or a cyano, trifluoromethyl, acetyl or benzoyl group,
• A represents a radical of the formula ##STR39## in which the radicals R.sup.2 and R.sup.3 independently of each other represent an alkyl radical which has 1 to 4 C atoms and is optionally substituted by hydroxyl, C.sub.1 - to C.sub.4 -alkoxy, halogen, cyano, phenyl, carbalkoxy having 1 to 4 C atoms, carboxamido, acyloxy, benzyloxy, sulphonamido or acylamino,
• R.sup.2 also represents an optionally halogen-, C.sub.1 - to C.sub.4 -alkyl- or C.sub.1 - to C.sub.4 -alkoxy-substituted phenyl or benzyl radical, or together with the adjacent C atom of the benzene ring can form a 5- or 6-membered ring, and
• R.sup.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.sup.5 represents an alkyl radical having 1 to 4 C atoms, an optionally halogen-, C.sub.1 - to C.sub.4 -alkyl- or C.sub.1 - to C.sub.4 -alkoxy-substituted phenyl radical or a carbalkoxy radical having 1 to 4 C atoms,
• R.sup.6 represents hydrogen or an alkyl radical which has 1 to 4 C atoms and is optionally substituted by hydroxyl, halogen, alkoxy having 1 to 4 C atoms, cyano or acyloxy, and
• R.sup.7 represents hydrogen, halogen, C.sub.1 - to C.sub.4 -alkyl, C.sub.1 - to C.sub.4 -alkoxy, carbalkoxy having 1 to 4 C atoms, C.sub.1 - to C.sub.4 -alkylsulphonyl, phenylsulphonyl, acetyl or benzoyl,
• or a radical of the formula ##STR41## in which R.sup.8 and R.sup.9 independently of each other have the same respective meaning as R and R.sup.1,
• in which
• X denotes phenyl, phenyl substituted by 1 to 3 alkyl radicals having 1 to 4 C atoms, alkoxy radicals having 1-4C atoms, and m, n, o and p independently of one another denote 1 to 4, and, alkyl having 1-4C atoms or alkoxy having 1-4C atoms, m, n, o and p independently of one another denote 1 to 4, and
• in which
• acyloxy is acetoxy, propionyloxy, benzoyloxy or carbamoyloxy,
• by condensing a methylene compound of the formula ##STR42## or a salt of the formula ##STR43## in which R, R.sup.1, X and m have the abovementioned meaning, with a compound of the formula
• A--CHO
• in which
• A has the abovementioned meaning, and with 1-7 mols of an acid of the formula
• XSO.sub.3 H
• or of the salt with 0-6 mols of the acid the improvement which comprises homogeneously mixing the reactants as a viscous melt in the presence of up to 15% by weight of water relative to the total weight of the organic starting components, and removing substantially all water present,