Phosphines to phosphine oxides

In general, peroxomonosulfates have fewer uses in organic chemistry than peroxodisulfates. However, the triple salt is used for oxidizing ketones (qv) to dioxiranes (7) (71,72), which in turn are useful oxidants in organic chemistry. Acetone in water is oxidized by triple salt to dimethyldioxirane, which in turn oxidizes alkenes to epoxides, polycycHc aromatic hydrocarbons to oxides and diones, amines to nitro compounds, sulfides to sulfoxides, phosphines to phosphine oxides, and alkanes to alcohols or carbonyl compounds. 

The dioxygen adduct so formed is highly reactive and will catalyse the oxidation of phosphine to phosphine oxide and isocyanide to isocyanate (77). But clearly a survey of these reactions is not within the scope of this review and is provided elsewhere (7, 77). 

Several other oxidation reactions of selenoxides and telluroxides are summarized in Fig. 23. Ley, Barton, and co-workers discovered that di-4-methoxyphenyltellur-oxide (54) could be used catalytically as an oxidant in the presence of 1,2-dibromotetrachloroethane. After reduction of the telluroxide to the telluride, the di-4-methoxyphenyltelluride (24) debrominated the 1,2-dibromotetrachloroethane to give the tellurium(IV) dibromide, which was hydrolyzed in situ to give the telluroxide 54. This process was used to oxidize phosphines to phosphine oxides and... 

Like its monomeric counterpart, the polymeric reagent is inert to simple amines, amides, alcohols and phenols, but easily oxidizes thiols to disulphides, phosphines to phosphine oxides, hydroquinone and catechol to quinones, and thioketones, thioesters and trithiocar-bonates to the corresponding 0x0 derivatives, in dichloromethane, chloroform or acetic... 

NR = nonreactive toward hydrocarbons PO = oxidation of phosphines to phosphine oxides MF — peroxometallacyclic adduct formation with cyanoalkenes NSE — nonstereoselective epoxidation SE=stereoselective epoxidation AE = asymmetric epoxidation HA- hydroxylation of alkanes HB=hydroxylation of arenes OA = oxidation of alcohols to carbonyl compounds K = ketonization of Lermina 1 alkenes SO oxidation of S02 to coordinated S04 MO = metallaozonide formation with carbonyl compounds I = oxidation of isocyanides to isocyanates. 

A large number of Group VIII metal-dioxygen complexes catalyze the oxidation of phosphine to phosphine oxide or isocyanides to isocyanates by molecular oxygen.6,12,56,140,141 146,184 However, their use as catalysts for the oxidation of alkenes generally leads to the same products as those obtained from free radical chain autoxidations.184,196-198... 

If the Rh-catalyst is stabilized by a monodentate phosphane ligand, it can be destroyed because the lifetime of the oxidation of phosphine to phosphine oxide is less than 1 h. Yet, if the catalyst is stabilized by a bidentate ligand, and the catalyst has a lifetime of 2-3 h, then it can convert into different species that have no catalytic activity. However, such a synthetic approach would suffer as a result of a short lifetime and a low TON. 

P-Oxidation. P-oxidation, a little known reaction, involves the conversion of trisub-stituted phosphines to phosphine oxides, for example, diphenylmethylphosphine to diphenylmethylphosphine oxide. Although this reaction is described as a typical CYP-dependent monooxygenation, it too is now known to be catalyzed by the FMO also. 

Ans. (a) Rhodium catalysts for hydrogenation require ligands capable of stabilizing a low oxidation state, (b) Oxygen atom donors oxidize phosphine to phosphine oxide. Also phosphines are not the best ligands to stabilize... 

This product must be purified from phosphorus before it can be used as an adhesion promoter for electronic devices. This is done by oxidising the phosphine to phosphine oxide with hydrogen peroxide or organic peroxides and by separating the products chromatographically. 

Barium manganate, BaMn04, is commercially available. The dark-blue crystals are obtained from aqueous solutions of barium chloride and potassium permanganate [552, 555]. It oxidizes alcohols, especially benzylic alcohols, to carbonyl compounds [552, 555] hydroquinone to quinone [555] benzylamines to benzaldehydes [555] aromatic amines to azo compounds [555] and phosphines to phosphine oxides [555],... 

NR s not reactive toward hydrocarbons S = stereoselective epoxidation E = epoxidation HA = hydroxylation of alkanes OA = oxidation of alcohols to carbonyl compounds PO oxidation of phosphines to phosphine oxides OC = oxidative cleavage of alkenes K= ketonization of alkenes DO = hydroxylation of alkenes to diols AO al1ylic oxidation of alkenes. 

In the absence of peroxides, MTO also catalyzes the oxidation of tertiary phosphines to phosphine oxides [3, 17]. 

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