Preparation of cationic triarylmethane dyestuffs

Abstract

To synthesize triarylmethane dyestuffs of the general formula ##STR1## in which R.sup.1 and R.sup.2 represent optionally substituted alkyl, aryl or aralkyl or R.sup.1 and R.sup.2, together or with the ortho-position of the phenyl ring, form a heterocyclic ring and R.sup.1 can additionally represent hydrogen, R.sup.3 and R.sup.4 denote hydrogen or non-ionic substituents, n represents an integer from 1 to 4 and X.sup.- denotes an anion, by a one-pot process, an aldehyde of the general formula ##STR2## in which R.sup.4 and n have the abovementioned meaning, is subjected to a condensation reaction with an aromatic amine of the general formula ##STR3## in which R.sup.1, R.sup.2, R.sup.3 and n have the abovementioned meaning, if appropriate in the presence of urea, and the reaction mixture thus obtained is oxidized with oxygen in the presence of catalytic amounts of benzoquinones substituted by halogen or cyano or of phenanthrenequinones substituted by nitro, and in the presence of catalytic amounts of nitrogen oxides--with the exception of dinitrogen monoxide--or of substances which produce such nitrogen oxides under the reaction conditions.

Dependencies are inferred from the claim text.