Patent GB-780632-A (GB)
Title: Reduction of aromatic nitrogen compounds
Filed: 1955-08-05
Abstract: The reduction of aromatic nitrogen compounds by the action of a metal alcoholate according to the parent Specification is carried out in the presence of a reduction promoter comprising a condensed polynuclear compound containing at least 10 nuclear carbon atoms, one nucleus of which consists of an alicyclic oxygen-substituted radical having 6 nuclear carbon atoms and having the oxygen groups in quinoid relationship to each other, said oxygen substituents being oxo- or hydroxy-substituents, at least two of the carbon atoms of the alicyclic radical (other than those to which the oxygen substituents are joined) being saturated carbon atoms, and derivatives of these compounds, namely (1) polynuclear diketones as defined above and substitution products thereof wherein the substituents may, for example, be halogen, hydroxyl, nitro, mercapto, amino, cyano, sulpho, carboxyl, alkyl or alkoxy, but no carbon atom of the alycyclic radical has as a substituent more than one electronegative radical, (2) corresponding hydroxyl compounds in which one or more of the oxo groups of the diketone are replaced by hydroxy groups, (3) functional addition compounds of the diketones or hydroxyketones such as the bisulphite compounds; (4) functional derivatives of the ketones, hydroxy ketones and dihydroxy compounds such as imides, oximes, semi-carbazones, hydrazones, and esters which are saponifiable by caustic alkalis; and (5) tautomeric forms of the diketones and hydroxy ketones which are capable of isomerizing to such ketones. Specified reduction promoters include 2 : 3-dihydro1 : 4 - naphthoquinone, 4a : 5 : 8 : 8a - tetrahydro - 1 : 4 - naphthoquinone, 2 - methyl - 4a : 5 : 8 : 8a - tetrahydro - 1 : 4 - naphthoquinone - 4 - oxime, 2 : 3 : 4a : 5 : 8 : 8a - hexahydro - 1 : 4 - naphthoquinone, naphthan - 1 : 4 - dione, 2 : 4a - dimethyl - 4a : 5 : 8 : 8a - tetrahydro - 1 : 4 - naphthoquinone, 2 : 8a - dimethyl4a : 5 : 8 : 8a - tetrahydro - 1 : 4 - naphthoquinone, 2 : 3 - dichloro - 2 : 3 - dihydro - 1 : 4 - naphthoquinone, 2 : 3 - epoxy - 2 : 3 - dihydro - 1 : 4 - naphthoquinone, 6 : 7 - dimethyl - 2 - phenyl - 4a : 5 : 8 : 8a - tetrahydro - 1 : 4 - naphthoquinone, 2 : 3 - dimethyl - 2 - phenyl - 2 : 3 - dihydro - 1 : 4 - naphthoquinone, 5 : 8 - methano - 4a : 5 : 8 : 8a - tetrahydro - 1 : 4 - naphthoquinone, 5 : 8 - ethano - 4a : 5 : 8 : 8a - tetrahydro - 1 : 4 - naphthoquinone, 6 - methoxy - 4a : 5 : 8 : 8a - tetrahydro - 1 : 4 - naphthoquinone, 2 : 3 : 4a : 8a-tetrachloro-4a : 5 : 8 : 8a-tetrahydro - 1 : 4 - naphthoquinone, 1 : 2 : 3 : 4-tetrahydro - 1 : 4 - naphthalenediol, 1 - hydroxy-4 - keto - 2 - methylnaphthalene and 2 : 3 - dihydro - 1 : 4 - dihydroxynaphthalene.  The reaction is suitably carried out by adding the reducible nitrogen compound, for example nitrobenzene or a substituted nitrobenzene to a reducing mixture formed by reacting a metal hydroxide such as sodium hydroxide with an alcohol, preferably methanol, in which the reduction promoter is incorporated and heating the resulting mixture.  Examples describe the reduction of nitrobenzene, azoxybenzene and azobenzene with sodium hydroxide in methanol using as reduction promoters 2 : 3 : 4 : 5 : 8 : 8a-hexahydro - 1 : 4 - naphthoquinone, 2 : 3 - dihydro - 1 : 4 - naphthoquinone, 4a : 5 : 8 : 8a-tetrahydro - 1 : 4 - naphthoquinone and for comparative purposes 1 : 4-naphthoquinone, to give hydrazobenzene and azobenzene as the chief products with minor amounts of aniline.  Examples given for comparison wherein the reduction promoter is absent or is replaced by 1 : 4 : 4a : 9a - tetrahydro anthraquinone result in the formation of azoxybenzene as the chief product.  Polynuclear dioxo compounds.-Reduction promoters according to the invention are prepared by Diels-Alder reaction of conjugated dienes with 1 : 4-benzoquinone or 1 : 4-naphthaquinone. Specification 716,418 is referred to.