GB385605A - Process for the manufacture of indole sulphonic acids - Google Patents

Abstract

Indole and naphthindole sulphonic acids are made by condensing a hydrazine sulphonic acid of the benzene or naphthalene series with a ketone of the general formula: R<1>-CH2-CO-R<11> in which R<1> = H or alkyl and R<11> = alkyl or aryl, the condensation mixture having an acid p reaction. The hydrazine may be substituted in the aryl residue, e.g. by hydroxyl, carboxyl, alkyl, O-alkyl, halogen, or the nitro group, and in the imino group by alkyl, aralkyl or aryl. In examples (1) 1-naphthylhydrazine-7-sulphonic acid is condensed with methylethylketone or diethylketone in aqueous acetic acid solution to give respectively 2 : 3-dimethyl- and 2 - ethyl - 3 - methyl - a - naphthindole - 8 - sulphonic acids, (2) p-phenylhydrazine sulphonic acid or phenylhydrazine-2 : 5-disulphonic acid is similarly condensed with methylethylketone to give 2 : 3-dimethylindole-5-sulphonic and 4 : 7-disulphonic acids respectively, (3) m-phenylhydrazine sulphonic acid is condensed with diethylketone as in (2) yielding 2-ethyl-3-methylindole-6-sulphonic acid; the acetic acid may be omitted, (4) p-phenylhydrazine sulphonic acid is condensed with methyl-n-propylketone in aqueous oxalic acid forming 2-methyl-3-ethylindole-5-sulphonic acid, (5) 1-naphthylhydrazine-7-sulphonic acid is heated under pressure with acetophenone in presence of aqueous acetic acid to produce 2 - phenyl - a - naphthindole - 8 - sulphonic acid; using ethylphenylketone the 2-phenyl-3-methyl-a -naphthindole-8-sulphonic acid is obtained and by using methyl-a -naphthylketone the 2-naphthyl-a -naphthindole- 8 - sulphonic acid is obtained; the acetic acid may be omitted, (6) 2-naphthylhydrazine-7-sulphonic acid is heated under pressure with acetone in presence of acetic acid (10 per cent) to form 2-methyl-b -naphthindole-7-sulphonic acid, (7) 2-chloro- or 2-nitrophenylhydrazine-4-sulphonic acid is heated with methylethylketone as in (1) yielding 2 : 3-dimethyl-7-chlor- or 7-nitroindole-5-sulphonic acid respectively, (8) 2-tolylhydrazine-5-sulphonic acid is heated with diethylketone in aqueous solution yielding 2-ethyl-3 : 7-dimethylindole-5-sulphonic acid; the 2-hydroxy-, 2-methoxy and 2-carboxyphenylhydrazine-5-sulphonic acids yield respectively the 2-ethyl-3-methyl-7-hydroxy-, or 7-methoxy-, or 7-carboxyindole-5-sulphonic acids, (9) phenyl-a -benzylhydrazine-2-sulphonic acid is heated with methylethylketone as in (1) to give 1 - benzyl - 2 - methylindole - 7 - sulphonic acid, (10) 1-(a -ethyl)-naphthylhydrazine-7-sulphonic acid is condensed with diethylketone as in (1) yielding 1 : 2-diethyl-3-methyl-a -naphthindole-8-sulphonic acid. Specifications 305,174, [Class 2 (iii), Dyes &c.], and 340,619 are referred to. Phenyl-a -benzyhydrazine-2-sulphonic acid is made from the corresponding phenylbenzylamine-2-sulphonic acid, transforming the -NH group into the -N-NO group and reducing.