Oxygen agent

Decomposition of adducts such as triphenyl phosphite—ozone provides a convenient method for accomplishing chemical oxidations involving singlet oxygen and making it a useful oxygenating agent for synthetic and mechanistic appHcations. 

BTSP-CF3SO3H is an efficient electrophilic oxygenating agent for adamantane and diamantane. With adamantane, the major reaction product is 4-oxahomoadamantane in isolated yield in 79% through a C—C a-bond insertion with very little 1-adamantanol, the C—H insertion product (equations 57 and 58/. In the case of diamantane, two isomeric oxahomodiamantanes were obtained along with two isomeric bridgehead diamantanols corresponding to C—C and C—H a-bond insertions. 

Bis(trimethylsilyl)peroxide-triflic acid was also found to be an efficient electrophilic oxygenating agent.209 Adamantane gives 4-oxahomoadamantane obtained through C—C a-bond insertion ... 

Reduced flavins, unlike reduced nicotinamides, are reactive towards molecular oxygen, and an intermediate produced in this reaction is a more potent oxygenating agent than molecular oxygen is itself. A number of enzymes have evolved which utilize this intermediate to oxygenate certain metabolites. These reactions usually entail monooxygenation (Scheme 5). There are, however, at least two examples of dioxygenation that have been reported... 

Dioxiranes are three-membered cyclic ring peroxides that are expected to be very unstable owing to ring strain. They are effective oxygenating agents for epoxidations of olefins, allenes, polycyclic aromatic hydrocarbons, enols. and a, /i-unsaturated ketones for insertions of oxygen into X—H... 

The reaction suggests the possible employment of the nitrosyl nitro conversion for oxide ion acceptance and donation, and this in turn could play a role in the future development of nitrosyl complexes as oxygenation agents. 

Ozone has been shown to be protonated in the superacid media to ozonium ion H03+ 51 [Eq. (4.28)], which reacts with alkanes as a powerful electrophilic oxygenating agent.125 Similarly, ozone reacts with carbocations, giving alkylated ozonium ion that undergoes further cleavage reactions. These reactions are well-covered in Chapter 5. 

Iodylbenzene with catalytic amounts of 2,2-dipyridyl diselenide converted alkenes into allylic ketones directly the actual oxygenating agent was 2-pyridineseleninic anhydride, formed in situ. 

While enol acetates from saturated ketones were useful a-oxygenation substrates, the corresponding dienol acetates are not. The relatively electron-deficient alkene bearing the acetoxy group is less attractive h> elecm hilic oxygenating agents than the unsubstituted double bond. Thus, for example, peracid treatment leads to epoxidation the unfiinctionalized alkene.However, it would seem likely that re-... 

This reaction may involve the intermediacy of the radical OCF2OF, which cyclizes to generate the dioxirane. The dioxirane is a potent oxygenating agent that generates COF2 as a by-product. It is thermally stable at 20 °C at modest pressures. 

Bis(trimethylsilyl)peroxide-triflic acid and sodium percarbonate-triflic acid are also efficient electrophilic oxygenating agents. Adamantane is transformed into 4-oxahomoadamantane in good yields obtained through C-C a-bond insertion [Eq. (6.57)]. 1 -Adamantanol, the C-H insertion product, is formed in a very small amount. Isomeric oxahomodiamantanes (C-C insertion) and bridgehead diamantanols (C-H insertion) are produced from diamantane. ... 

At 250° C. this reaction occurs with the liberation of almost 20,000 calories of energy per mol. In the presence of active catalysts especially, this decomposition of carbon monoxide to form carbon dioxide and a highly reactive carbon, complicates any attempt to use it as an oxygenating agent in vapor phase reactions. Consequently, very little experimentation has been done with the direct object of reacting hydrocarbons with carbon monoxide to form oxygen containing compounds. 

Vaz, A.D.N., S.J. Pernecky, G.M. Raner, and M.J. Coon (1996). Peroxo-iron and oxenoid-iron species as alternative oxygenating agents in cytochrome P450-cataIyzed reactions Switching by threonine-302 to alanine mutagenesis of cytochrome P450 2B4. Proc. Natl. Acad. Sci. USA 93, 4644-4648. 

The proposed mechanism for these catalytic oxidations includes two catalytic redox cycles (i) initial oxidation of iodobenzene with Oxone, producing hydroxy(phenyl)iodonium ion and hydrated iodosylbenzene and (ii) the oxidation of iron(III)-porphyrin to the oxoiron(IV)-porphyrin cation-radical complex by the intermediate iodine(III) species (Scheme 4.58) [93]. The oxoiron(IV)-porphyrin cation-radical complex acts as the actual oxygenating agent toward aromatic hydrocarbons. The presence of the [PhI(OH)]+ and PhI(OH)2 species in solutions containing Phi and Oxone has been confirmed by ESI mass spectrometry [93]. 

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