Patent GB-557789-A (GB)
Title: Dioxazine dyestuffs
IPC: C09B19/02
Filed: 1942-06-01
Abstract: 557,789. Dyes. DU PONT DE NEMOURS & CO., E. 1. June 1, 1942, No. 7393. Convention date, May 14, 1941. [Classes 2 (iii) and 15 (ii)] Dioxazine dyes, having an improved affinity for cotton, on which the dyeings are fast to washing and to light, and suitable also for dyeing wool, silk, regenerated cellulose or nylon fibres, are obtained by condensing 2 mols. of an aminobenzenesulphonic acid of the general formula having at least one position oto the NH 2  group unsubstituted, wherein R represents a benzazole residue (linked to NH through the benzene ring), with 1. mol of benzoquinone or a homologue or halogen substitution product thereof, and treating the resulting N : N<SP>1</SP>- disubstituted diaminoquinone with oleum, sulphuric acid or chlorosulphonic acid. Specified benzazole residues are those of benzoxazole, benzothiazole, benzimidazole and indazole and their products of substitution in the benzene and/or the heterocyclic rings. The exhaustion of the products in the dyebath, their tinctorial strength and the fastness of their dyeings to washing may be improved by warming them in concentrated sulphuric acid containing a little sodium chloride or dry hydrogen chloride, with or without a little glacial acetic acid. In examples, (1) and (2) 5-(4<SP>1</SP>-amino-2<SP>1</SP>-sulphoanilino)-2-benzimidazolone (obtained by reducing the nitro group in the product of condensation of 5-aminobenzimidazolone with 4-nitrochlorobenzene-2-sulphonic acid) is heated under reflux for 1 hour or more with tetrachlorobenzoquinone in alcohol containing anhydrous sodium acetate and the resulting condensation product is treated with fuming sulphuric acid, sulphuric acid monohydrate, conc. sulphuric acid (93-100 per cent.) or chlorosulphonic acid; (3), (4), (5) and (6), the tetrachlorobenzoquinone is replaced by (3) toluquinone, (4) benzoquinone, (5) 2 : 5-dichlorobenzoquinone, (6) tetrabromobenzoquinone. A table is also given showing the shades obtainable on cotton with the dyestuffs similarly obtainable from chloranil and the condensation products from 4 - nitrochlorobenzene - 2 - sulphonic acid and the following aminobenzazole compounds, viz., the 3- and 5-methyl-6-amino and 5-chloro-6- amino derivatives of 2-benzimidazolone, 6 - amino - 2 - benzimidazole - thione, 6 - aminobenzimidazole and its 2-methyl, 2-phenyl, 2-ochloro-phenyl and 2-o-hydroxyphenyl derivatives, 5 - amino - 1 : 2 - dimethylbenzimidazole, 5 - amino - 1 - phenyl - 2 - methyl - benzimidazole, 2 : 6 - diaminobenzthiazole, the 6 - methyl, 6-chloro, 6-methoxy and 6-ethoxy derivatives of 2 : 5-diaminobenzthiazole, 6- amino - 2 - acetylamino - benzothiazole, 6 - aminobenzoxazolone and 5-amino-indazole and its 1-methyl derivative. The Specification as open to inspection under Sect. 91 comprises also the use as aminobenzazole compound starting materials of 6 - amino - 3 - phenyl - benzimidazole and its 21: 51 - dichloro derivative, 5 - amino - 2 - methyl - benzimidazole, 5 - amino - 2 - carboxybenzimidazole, 6 - amino - 2 - (2<SP>1</SP> - hydroxy - 3<SP>1</SP> - carboxy) phenyl - benzimidazole and 7 - amino - 4 : 6 - dimethyl - 2 - acetylamino - benzothiazole. This subject-matter does not appear in the Specification as accepted. 5- Aminobenzimidazolone is obtained by reduction of 5-nitro-benzimidazolone. The 5-methyl and 5-chloro derivatives of 6-aminobenzimidazolone are obtained by condensing the 4-methyl and 4-chloro derivatives respectively of 1 : 2-diaminobenzene with urea, nitrating the product and reducing the nitro group. 6- Amino-2-benzimidazole-thione is obtained by condensing 4-nitro-1 2-diaminobenzene with thiourea and reducing the nitro group. 6-Amino-2-methyl-benzimidazole is obtained by treating 4-nitro-1 : 2-di-acetylaminobenzene with iron and hydrochloric acid to effect simultaneous ring closure and reduction of the nitro group. 6 - Amino - 2 - o - chlorophenyl - benzimidazole and 6 - amino - 2 - o - hydroxyphenyl - benzimidazole are obtained by heating 4-nitro-1 : 2- diaminobenzene with o-chlorobenzaldehyde and salicyl aldehyde respectively and reducing the nitro group. 2 : 6-Diaminobenzothiazole is obtained by oxidizing a mixture of 4-nitroaniline and ammonium thiocyanate with bromine in acetic acid and reducing the nitro group. The 6-methyl, 6-chloro, 6-methoxy and 6-ethoxy derivatives of 2 : 5-diaminobenzothiazole are similarly obtained with replacement of the 4-nitroaniline by 2-nitro-4-aminotoluene, 4-chloro-3- nitroaniline, 2-nitro-4-aminoanisole and 2-nitro-4-aminophenetole respectively. 6 - Amino - 2 - acetylamino - benzothiazole is obtained by acetylating 2 : 6-aminonitrobenzothiazole and reducing the nitro group.