Oxygen-containing compounds, dioxirane oxidation

Silyl enol ethers are a class of electron-rich, nonaromatic compounds that easily form reactive radical cations on one electron oxidation. The silyl enol ether functional group is closely related to the carbonyl function and consequently, syntheses of silyl enol ethers generally make use of enolates. In addition, silyl enol ethers can be described as masked enols or enolates since their reactions often yield ketones. A number of oxidation reactions of silyl enol ethers making use of oxygen or oxygen-containing reagents such as peroxides, peracids (known as Rubottom oxidation), dioxirane, osmium tetraoxide, or triphenyl phosphite ozonide have been described in the literature. In all cases either a-hydroxy-ketones or the silyl enol ether epoxides are formed. 

Since dioxiranes are electrophilic oxidants, heteroatom functionalities with lone pair electrons are among the most reactive substrates towards oxidation. Among such nucleophilic heteroatom-type substrates, those that contain a nitrogen, sulfur or phosphorus atom, or a C=X functionality (where X is N or S), have been most extensively employed, mainly in view of the usefulness of the resulting oxidation products. Some less studied heteroatoms include oxygen, selenium, halogen and the metal centers in organometallic compounds. These transformations are summarized in Scheme 10. We shall present the substrate classes separately, since the heteroatom oxidation is quite substrate-dependent. 

The chemistries of dioxiranes in general,in addition to dimethyldioxirane (DMDO), focusing on the oxidation of sulfur compounds and heterocycles containing oxygen or sulfur,have been reviewed. Alkene epoxidation by DMDO has been studied kinetically and semi-empirically AMI calculations were used to identily the transition-state structure as the spiro conformation. ... 

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