GB475627A - Manufacture of new intermediate products for dyestuffs - Google Patents

Abstract

Aminohydrazine-N-sulphonic acids (or salts thereof), of the general formula NH2RNHNH SO<3>H, where R is a residue so constituted that the amino and --NHNHSO<3>H groups are both aromatically united, e.g. a benzene, diphenyl, dibenzyl, stilbene or azimidobenzene residue, which may contain substituents such as carboxylic or sulphonic acid groups, are manufactured by treating the corresponding nitrohydrazine-N-sulphonic acids in the absence of a saponifying agent with a reducing agent which converts nitro-groups into amino-groups. The products, if desired after elimination of the sulphonic acid residue, may be caused to undergo the reactions of hydrazines and of primary aromatic amines. In examples: (1) m-nitrophenylhydrazinesulphonic acid is converted into its sodium salt, which is reduced by means of iron and acetic acid to the sodium salt of m-aminophenylhydrazine sulphonic acid; the product may be acylated, e.g. benzoylated; there may be similarly treated other nitrohydrazinesulphonic acids, e.g. those derived from 1-methyl-2-amino-4- or 5-nitrobenzene or 1-amino-2-chloro-4-nitrobenzene, the products in some cases being isolated only after acylation, e.g. benzoylation; (2) 4 : 41-aminonitrostilbene-2 : 21-disulphonic acid is diazotized and treated with sodium bisulphite solution, and the product is reduced by means of iron and hydrochloric acid to 4 - hydrazino - (o - sulpho) - 41 - aminostilbene-2 : 21-disulphonic acid, which is isolated in the form of its sodium salt; (3) N-(41-nitrophenyl)-q -azimido-4-aminobenzene is diazotized and treated with sodium bisulphite lye, and the product is reduced by means of iron and acetic acid to the sodium salt of the corresponding aminohydrazine sulphonic acid. In an example of the use of the products, (4) the product of (2) is boiled with dilute hydrochloric acid to eliminate the o -sulphonic acid group, and the product is condensed in the presence of caustic soda with ethyl acetoacetate, to produce a pyrazolone; this may be coupled with diazo compounds, whilst with nitrous acid it yields an orange-brown dyestuff by diazotization and self coupling; the ethyl acetoacetate may be replaced by ethyl oxaloacetate, ethyl terephthaloyl-bis-acetate, ethyl benzoylacetate and their derivatives.