GB988121A - Production of azo dyes - Google Patents

Abstract

Trimethyl hydroquinone is prepared by converting an azo compound of the formula <FORM:0988121/C2/1> in which A denotes the radical of a diazotizable amino compound, obtainable by reacting an appropriate hydrazone and ketone in the presence of a basic condensing agent (see Division C4), into trimethylquinone by reductive cleavage and oxidation of the product followed by reduction of the quinone. The reduction may be carried out in mineral acid solution with zinc or stannous salts or in neutral or weakly alkaline solution with sodium dithionite. An example is furnished.ALSO:In a process for the production of azo compounds having the general formula <FORM:0988121/C4-C5/1> in which A denotes the radical of a diazotizable amino compound, R1, R2 and R3 may be identical or different and denote hydrogen atoms, alkyl radicals, aryl radicals or aralkyl radicals, a hydrozone having the general formula <FORM:0988121/C4-C5/2> is reacted with a ketone having the general formula <FORM:0988121/C4-C5/3> in which A, R1, R2 and R3 have the meanings given above, in the presence of a basic condensing agent. The examples relate to the preparation of azo dyes from the monophenylhydrazone of mesoxaldialdehyde and corresponding compounds substituted in the benzene ring with such substituents as chloro, nitro, benze azo-, methyl and sodium sulphonate groups and such ketones as acetone, diethyl ketone, diisobutyl ketone and dibenzyl ketone. Appropriate dyes produced by the process may be employed in the preparation of 2,3,5-trimethyl-1-aminophenol-(4) (see Division C2).