Anilines oxidations, potassium nitrosodisulfonate

Quinones can he prepared hy the oxidation of phenols, dihydroxy-henzenes, dimethoxyhenzenes and anilines. For example, 1,4-dihydroxy-henzene (hydroquinone) can he oxidized in good yield using sodium chlorate in dilute sulfuric acid in the presence of vanadium pentoxide and also hy manganese dioxide and sulfuric acid and hy chromic acid. Other reagents which convert hydroquinones to quinones include Fremy s salt [potassium nitrosodisulfonate, (KS03)2N0] and cerium(IV) ammonium nitrate [CAN, Ce(NH4)2(N03)J. 

The presence of an amino group on an aromatic ring often results in oxidation of the ring to a quinone. The classical and industrial method is the treatment of anilines with potassium dichromate and sulfuric acid. Thus, aniline at room temperature is converted into p-benzoquinone in 86% yield [647], and 2,5-dimethylaniline at 80 °C gives a 55% yield of p-xyloquinone [648. A specific reagent for such oxidations is the Fremy salt, potassium nitrosodisulfonate (equation 528) [490. The oxidation of the amino group takes place even if it is acylated (equation 529) [1190. ... 

Oxidation of phenols or anilines to quinones by means of potassium nitrosodisulfonate (Fremy s salt) (see 1st edition). 

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See also in sourсe #XX -- [ ]

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