GB396636A - The manufacture of new isatins and indigoid dyestuffs derived therefrom - Google Patents

Abstract

Thioindigo dyestuffs are prepared by condensing hydroxythionaphthenes with dimethylalkoxyisatins or their reactive a -derivatives. Both the isatins and the dyestuffs may be halogenated. The isatins may be obtained from the corresponding dimethylalkoxyaminobenzenes by the Sandmeyer synthesis. In examples: (1) 1 : 3-dimethyl-4-hydroxy-5-nitrobenzene is methylated and reduced and then converted into the isonitrosoacetanilide by warming with hydroxylaminosulphonic acid and chloral hydrate; the 4 : 6-dimethyl-7-methoxyisatin obtained by treatment with sulphuric acid, may be chlorinated to give 5-chlor-4 : 6-dimethyl-7-methoxyisatin and brominated to give the corresponding bromine compound: dyestuffs are obtained by condensing 5-chlor-4 : 6-dimethyl - 7 - methoxy (and ethoxy) isatin-a -chloride with 4 : 7-dimethyl - 5 - chlor - 3 - oxythionaphthene: (2) 3-chlor - 1 : 4 - dimethyl - 2 - methoxy - 5 - aminobenzene, prepared from 1 : 4-dimethyl-2-methoxy-5-aminobenzene by acetylation, chlorination and saponification, is converted to 6-chlor-4 : 7-dimethyl-5-methoxyisatin by the Sandmeyer synthesis and the latter, after treatment with phosphorus pentachloride condensed with 5 : 6 : 7 - trichlor - 3 - oxythionaphthene: (3) 5 - methoxy - 6 : 7 - dimethyl - isatin and 4-chlor-5-methoxy - 6 : 7 - dimethyl - isatin are prepared from 1-amino-2 : 3-dimethyl 4-methoxybenzene and 1-amino-2 : 3-dimethyl-4-methoxy-5-chlorbenzene respectively: dyestuffs are prepared by condensing 5-methoxy-6 : 7 - dimethylisatin with 2 : 1 - naphthoxy - thiophen and 5-methoxy-6 : 7-dimethylisatin-a -chloride with 5 : 6 : 7 - trichlor - 3 - oxythionaphthene: (4) 7 - brom - 4 : 6 - dimethyl - 5 - methoxyisatin and the corresponding 7-chlor compound are prepared by bromination or chlorination of 1 : 3 - dimethyl - 5 - amino - 2 - methoxybenzene and subjecting the products to the Sandmeyer synthesis: dyestuffs are obtained by condensing 7-brom-4 : 6-dimethyl 5 - methoxyisatin - a - chloride (or anilide) with 4 : 7 - dimethyl - 5 - chlor - 3 - oxythionaphthene, 4 - methyl - 6 - chlor - 3 - oxythionaphthene or 1 - chlor - 2 : 3 - naphthoxythiophene and by condensing 7-chlor-4 : 6 - dimethyl - 5 - methoxy-isatin - a - chloride with 5 : 6 : 7 - trichlor - 3 - oxythionaphthene: by using the base without halogenating, 4 : 6-dimethyl-5-methoxyisatin is obtained which may be condensed with 4 : 7-dimethyl - 5 - chlor-3-oxythionaphthene: (5) 1 -amino - 2 : 5 - dimethyl - 3 - methoxy - 4 - chlorbenzene obtained from 1-amino-2 : 5-dimethyl-3-methoxy benzene by chlorination of the corresponding urea and subsequent saponification, is converted into 4 : 7-dimethyl-5-chlor-6-methoxyisatin by condensation with mesoxalic ester (Martinet's method): the isatin may be condensed with 5 : 6 : 7-trichlor-3-oxythionaphthene.