Oxidation reactions Potassium nitrosodisulfonate

Uncondensed phenolic units in lignin have been estimated by a color reaction based on oxidation with potassium nitrosodisulfonate (Fremy s salt) (Adler and Lundquist 1961) as illustrated below ... 

The reaction of 148 with 10% HCl-MeOH afforded selective hydrolysis of the amide to form the 3-aminopyridine 149, in which the ring was subsequently closed after treatment with palladium(O) to give the /3-carboline 150. Friedlander condensation of 150 with 2-amino-3-benzyloxy-4-bromo-benzaldehyde (151), which was synthesized in four steps (5S), gave the 2-/3-carbolinequinoline 152. Hydrogen bromide gas debenzoylation of 152 was followed by oxidation with potassium nitrosodisulfonate (Fremy s salt) to obtain Kende s intermediate 131. 

The nitrosodisulfonate salts, particularly the dipotassium salt called Fremy s salt, are useful reagents for the selective oxidation of phenols and aromatic amines to quinones (the Teuber reaction). - Dipotassium nitrosodisulfonate has been prepared by the oxidation of a hydroxylaminedisulfonate salt with potassium permanganate, " with lead dioxide, or by electrolysis. This salt is also available commercially. The present procedure illustrates the electrolytic oxidation to form an alkaline aqueous solution of the relatively soluble disodium nitrosodisulfonate. This procedure avoids a preliminary filtration which is required to remove manganese dioxide formed when potassium permanganate is used as the oxidant. " ... 

Using chromium-based oxidants 2,4-Dimethylpentane-2,4-diol chromate(VI) diester, 122 Trimethylsilyl chlorochromate, 327 Using other oxidizing agents Bis(tributyltin) oxide, 41 Hydrogen hexachloroplatinate(IV)-Copper(II) chloride, 145 4-Methoxy-2,2,6,6-tetramethyl-1 -oxopiperidinium chloride, 183 Osmium tetroxide, 222 Potassium nitrosodisulfonate, 258 Samarium(II) iodide, 270 From alkenes by addition or cleavage reactions... 

Reduction of ketone (81) with zinc and acetic acid produced the 4-hydroxypyrazoles (87), whereas reaction with dithionite gave the corresponding 1,4-dihydroxypyrazoles (88). These compounds could be oxidized with Fremy s salt (potassium nitrosodisulfonate) to the 3,4-diazacyclopentadienone 3-oxides. 

Aldehyde 64 also was elaborated to the quinone 65 by a sequence of reactions including nitration, reduction by iron in acetic acid, and oxidation by Fremy s salt (potassium nitrosodisulfonate). 

Ellipticine (E) 1 is an indolic alkaloid with antitumor activity. Some of its phenolic derivatives as N-methyl-9-hydroxyellipticine (Celiptinium), obtained from 9-hydroxy ellipticine (9-OH E), exhibit high cytotoxicity. 38 Syntheses of 9-OH E are not satisfactory considering yields and cost, justifying the attempts at the direct conversion of E to 9-OH E via 9-oxoellipticine (9-0X0 E). Potassium nitrosodisulfonate (Fremy s salt), a valuable oxidant for the synthesis of quinone-imine from heterocyclic amines,139 was used. Under these conditions the conversion of E to 9-0X0 E was observed for the first time. Its reduction to 9-OH E is then easily achieved with ascorbic acid. The radical nature of Fremy s salt [ 0-N(S03K)2] led us to carry out the oxidation reaction under sonication in order to increase the yields via an easier electron transfer.1 1... 

Phenols don t undergo oxidation in the same way that alcohols do because they don t have a hydrogen atom on the hydroxyl-bearing carbon. Instead, oxidation of a phenol yields a cyclohexa-2,5-diene-l,4-dione, or quinone. The most commonly used oxidant is Fremy s salt [potassium nitrosodisulfonate, (KSOalaNO], and the reaction takes place through a radical mechanism. 

Phenols are aromatic counterparts of alcohols but are much more acidic (pkia 10) because their anions are resonance stabilized by delocalization of the negative charge into the aromatic ring. Phenols can he oxidized to quinones by reaction with Fremy s salt (potassium nitrosodisulfonate), and quinones can he reduced to hydroquinones by reaction with NaBH4. 

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