Novel aromatic aldehydes and process for preparing them

Abstract

Aldehydes of a 2-hydroxy-naphthalene-3-carboxylic acid arylide of the general formula ##SPC1## In which X represents a hydrogen, chlorine or bromine atom, and Ar represents a naphthyl group, a benzimidazolone, chlorobenzimidazoline, quinazolone, quinoxaline, phthalimide, phthalazine group or a phenyl group which may carry 1 to 3 lower alkyl, lower alkoxy, lower alkylsulfonyl, lower carboalkoxy, halogen, trifluoromethyl, nitro, cyano, lower alkanoylamino, benzoylamino, carboxamido or sulfonamido groups and a process for their preparation wherein the corresponding 2-hydroxynaphthalene-3-carboxylic acid arylide is reacted in a lower aliphatic carboxylic acid with hexamethylene tetramine and a mineral acid. These aldehydes are valuable intermediate products for the synthesis of optical brighteners, pharmaceuticals and, in particular, of azamethine pigments which are obtained by condensation of these aldehydes with suitable amines. The pigments thus obtained are distinguished by good fastness properties and are especially suitable for the printing of paper and the coloring of lacquers, varnishes and plastics.

Dependencies are inferred from the claim text.