Hydrogen peroxide—Tungstic acid

Hydrogen peroxide-Tungstic acid, H202-H2W04. 

Thiazole A-oxides may result from the direct oxidation of thiazoles with hydrogen peroxide, tungstic acid, or peracetic acid. ... 

Migration Hydrogen peroxide Tartaric acid Rismuth compounds Tungsten Tungstic acid... 

Little work has been carried out on thiazole N-oxides. These products are unstable and breakdown by autoxidation to give thiazolium-A -oxide sulfates and other decomposition products (264). They are prepared by direct oxidation with hydrogen peroxide, or by tungstic acid (264, 265) or peracetic acid (265-267). 

The kinetics of the catalytic oxidation of cyclopentene to glutaraldehyde by aqueous hydrogen peroxide and tungstic acid have been studied and a compatible mechanism was proposed, which proceeds via cyclopentene oxide and /3-hydroxycyclopentenyl hydroperoxide. " Monosubstituted heteropolytungstate-catalysed oxidation of alkenes by t-butyl hydroperoxide, iodosobenzene, and dioxygen have been studied a radical mechanism was proved for the reaction of alkenes with t-BuOOH and O2, but alkene epoxidation by iodosobenzene proceeds via oxidant coordination to the catalyst and has a heterolytic mechanism. ... 

SCHEME 81. Tungstic acid-tributyltin chloride on a charcoal catalyst in the epoxidation of alkenes with hydrogen peroxide... 

Dithiepane can be oxidized to its 1,1-dioxide by hydrogen peroxide and this is further oxidized to the 1,1,2,2-tetraoxide by hydrogen peroxide in the presence of tungstic acid. 

Sulfunes. A recent preparation of thietane 1,1-dioxide1 emphasizes the advantage of tungstic acid catalysis2 in the hydrogen peroxide oxidation of sulfides to sulfones an induction period is eliminated and the yield improved. 

Hydrogen peroxide is a mild oxidant and its use in olefin epoxidations requires the application of appropriate catalysts. The oxidation with aqueous hydrogen peroxide in the presence of tungstic acid yields the corresponding epoxides (equation 7)9. 

Of special interest are olefm epoxidation with peroxy acids at the moment of their formation from acid anhydrides and hydrogen peroxide. Among the catalysts of olefin oxide formation from olefins interacting with H202 in the presence of metal (Ti, W, V, Ta, Ge, Mo, U, Ru) oxides or acids are tungstic acid and its salts [47], Epoxidation is described by the following mechanism ... 

The -)-erythro-isomer of 2,3-dihydroxy-3-methylpentanoic acid (73) has been synthesized by Crout and Whitehouse, and shown to be identical with the naturally occurring (-)-acid obtained from strigosine.45 trans-Hydroxylation of E-3-methylpent-2-enoic acid with tungstic oxide-hydrogen peroxide gave the ( )-erythro-acid, which was resolved as the quinine salts. The absolute configuration of the (-)-erythro-ac d (73) was determined by degradation (Scheme 4). Methylation,... 

As with percarboxylic acids, hydrogen peroxide usually requires metal activation.151-154 Peroxo complexes of d° transition metals can often be used to cleave olefins. Tungstic acid cleaves olefins to the carboxylic acid using 35% m/m hydrogen peroxide.154 Sodium tungstate has also been reported to... 

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