Ammonium Peroxydisulfate

Behrman, E. J.

doi:10.1002/047084289x.ra096

Cited by 1 publication

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“…[30,31] An important developing area is the use of salts of peroxydisulfate which are soluble in organic solvents by virtue of large organic cations in place of the commercially available ammonium, sodium, or potassium salts. This approach has not yet been reported for the Elbs or Boyland-Sims oxidations.…”

Section: Future Directionsmentioning

confidence: 99%

The Elbs and Boyland-Sims peroxydisulfate oxidations

Behrman¹

2006

Beilstein J. Org. Chem.

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This paper reviews the recent literature on the title reactions and updates a 1988 review.Page 1 of (page number not for citation purposes) 10The Elbs and Boyland-Sims oxidations are shown in Scheme 1:Scheme 1: The Elbs and Boyland-Sims Oxidations.Both of these reactions, last reviewed in 1988 [1], are nucleophilic displacements on a peroxide oxygen of the peroxydisulfate ion. In the Elbs oxidation, the nucleophile is a phenolate anion (or a tautomer) and in the Boyland-Sims oxidation, it is a neutral aromatic amine. There is no radical involvement in either case (except in side reactions, see below). The products are aromatic sulfates whose orientation relative to the phenolic group is preferentially para in the Elbs oxidation and ortho in the Boyland-Sims case. These sulfates are useful in synthesis themselves or may be hydrolyzed in acid to the dihydric phenols (or aminophenols).The yields of products are typically low to moderate, but the simplicity of the reactions frequently recommends their use. Reactions are usually carried out by dissolving the phenol or amine in an alkaline aqueous medium, sometimes with the addition of a co-solvent such as pyridine, and then adding a peroxy- Page 2 of (page number not for citation purposes) 10 disulfate salt. The ammonium and sodium salts are much more soluble than the potassium salt. This low solubility may be used to advantage to ensure slow addition of the peroxydisulfate as it is established that higher yields are achieved when the phenol(amine)-peroxydisulfate ratio is large. Isolation of the product usually takes advantage of the high water solubility of the intermediate sulfate ester; acidification of the reaction mixture is followed by extraction of the unreacted starting material (in the case of phenols) by an appropriate organic solvent. The sulfate ester remains in the aqueous phase. Hydrolysis of the sulfate ester in aqueous acid produces the (usually) organic-soluble dihydric phenol. Reactions are usually run at room temperature or below to reduce the incursion of free radical reactions. The rates are rather slow with typical secondorder rate constants (at room temperature) in the range 0.1-20 L mol -1 min -1 .[1] Mechanisms of the reactionsThe mechanisms of both reactions have been clarified. In both cases this was done by synthesis of postulated intermediates. In the Boyland-Sims oxidation, the amine-O-sulfonate was the obvious choice that was supported by a number of kinetic studies. In the Elbs oxidation, since the product is preferentially the p-sulfate, the question was whether the initial attack was at the phenolate oxygen(3) followed by rearrangement to the p-sulfate(4) or whether the initial attack was by the tautomeric p-carbanion(5) (Scheme 3).Here it was possible to synthesize the first possibility by displacement of the fluoride ion from three dinitrofluorobenzenes by reaction with Caro's acid anion .[4] The key example was for 2,5-dinitrofluorobenzene(6) which offers both an ortho and a para position for the rearrangement. Fluoride 6...

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Section: Future Directionsmentioning

confidence: 99%

The Elbs and Boyland-Sims peroxydisulfate oxidations

Behrman¹

2006

Beilstein J. Org. Chem.

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Ammonium Peroxydisulfate

Cited by 1 publication

References 87 publications

The Elbs and Boyland-Sims peroxydisulfate oxidations

The Elbs and Boyland-Sims peroxydisulfate oxidations

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