GB701128A - Process for the reduction of aromatic nitrogen compounds - Google Patents

Abstract

Aromatic compounds containing nitrogen at a higher state of oxidation than hydrazo attached directly to the nucleus are reduced by metal alcoholates in the presence of a naphthoquinone or addition product or functional derivative thereof. Preferably the reducible nitrogen compound is added to a mixture of the other components, e.g. the naphthoquinone is mixed with the alcohol, metal hydroxide added to form the alcoholate in situ and the mixture then reacted with the nitrogen compound. The naphthoquinone may be present to the extent of 1/36th to 1/300th mol. per mol. of nitrogen compound. The preferred alcoholate is sodium methylate. In the examples, (1) nitrobenzene is reduced to azoxybenzene, azobenzene and hydrazobenzene (converted into benzidine); (2) o-nitrotoluene is reduced to o-azoxytoluene, o-azotoluene, o-hydrazotoluene and o-toluidine; (3) o-nitroanisole is reduced to o-azoxyanisole, o-azoanisole, o-hydrazoanisole (converted into o-dianisidine) and o-anisidine; (4) azobenzene is reduced to hydrazobenzene; (5) a mixture of azobenzene and azoxybenzene is reduced to azobenzene and hydrazobenzene (converted into benzidine and diphenylines); (6) a mixture of o-azotoluene and o-azoxytoluene is reduced to o-hydrazotoluene (converted into o-tolidine) and o-toluidine. Other specified products are 2:21-dichlorohydrazobenzene and 2:21-diethoxyhydrazobenzene from o-nitrochlorobenzene and o-nitrophenetole respectively. m-Nitroluene, m-nitrochlorobenzene, onitrobenzoic acid and o-nitrobenzenesulphonic acid may also be reduced. The naphthoquinone compounds used in the examples are:-1:4-naphthoquinone and its addition products with sodium bisulphite, potassium bisulphite, stannic chloride and antimony pentachloride; the addition products of 2-methyl - 1:4 - naphthoquinone with sodium bisulphite, potassium bisulphite and p antimony pentachloride; 1 : 4 - naphthoquinones, substituted in the 2-position by methylamino, anilino, ethanolamino, diethanolamino, hydroxy and sulphonic acid groups; 2:3-dichloro-1:4-naphthoquinone and its addition product with antimony pentachloride; 1:2-naphthoquinone. Other suitable naphthoquinone compounds are listed. An inert solvent may be present in the reaction mixture. Addition products of naphthoquinones with organic and inorganic bisulphites are prepared as in Specification 547,913 and U.S.A. Specification 2,331,808. Specified bisulphites are those of lithium, sodium, potassium, ammonium, calcium, methylamine, dimethylamine, trimethylamine, ethylamine, propylamine, butylamine, amylamine, hexylamine, benzylamine, ethanolamine and diethyl-e thanolamine. The reaction may take place in the presence of an alcohol such as methanol. 2-Substituted-1:4-naphthoquinones where the 2-substituent is methylamino, anilino, ethanolamino or diethanolamino are prepared by reacting 1:4-naphthoquinone with methylamine, aniline, or mono- or di-ethanolamine.