Replacement of sulfo groups by nitrogen

Because aromatic sulfonic acids are readily accessible replacement of sulfo groups by other groups is often the simplest way to introduce substituents into an aromatic ring. This is of particular importance for preparation of amines in the anthraquinone series. 1- and 2-Aminoanthraquinone and 1,5-, 

1- Aminoanthraquinone 355h Potassium anthraquinone-1-sulfonate (60 g) is heated with 24% ammonia solution (120 g) and sodium /w-nitrobenzenesulfonate (21 g) in a stirring autoclave up to 170-175° during 4 h and then kept at this temperature for a further 12 h (pressure ca. 25 atm). After cooling, the precipitate is filtered off, sucked dry, washed with a little hot water, boiled with acidified (HC1) water (300 ml), filtered off again, washed with hot water, and dried at 90°. This gives the technically pure product, m.p. 238°, in about 95% yield (39 g). Recrystallization from xylene affords a 75% yield of pure 1-aminoanthraquinone, 

2- Aminoanthraquinone is obtained in exactly the same way.355h Analogous directions for preparation of l-(methylamino)anthraquinone in Organic Syntheses prescribe sodium chlorate as oxidizing agent.1197 

3-Naphthalenediamine and its derivatives are obtained by heating 4-aminonaphthalene-2-sulfonic acid with ammonia or an amine at 160-180° under pressure any sulfo groups in the other ring are unaffected. 4-Hydroxynaphthalene-2-sulfonic acid exchanges both its sulfo and its hydroxyl group.1198 

A sodamide melt can be used at atmospheric pressure but gives poorer yields.383 However, use of sodamide in boiling piperidine has proved an excellent method of preparing 1-arylpiperidines from aromatic sulfonic acids.1191 

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