Peroxide-like intermediate

No direct evidence for Mn(V) or peroxide-like intermediates have been observed yet in any native S, state. However, release of hydrogen peroxide occurs in a modified S2 state formed under a variety of conditions (removal of Cl , replacement of Cl by F and solubilization with lauryl choline chloride)(reviewed in ). These results show that the driving force for HO-OH bond formation already exists at the modified S2 oxidation level. 

It has been suggested that a (dioxygen)iron(II), or perferryl 1 complex, a likely intermediate in the autoxidation of iron(II), could abstract an allylic hydrogen and initiate lipid peroxidation [48]. Such complexes are weak oxidants at best, as has been shown before [49] and, with the exception of iron(II) edta [50], have not been observed. Constraints on the reduction potential... 

Diborane reduction of diphenylcyclopropenone followed by alkaline peroxide treatment provides" j5-phenylpropiophenone (320) and diphenylcyclopropene is a likely intermediate (equation 96). 

Besides iron-III salts, special peroxides are the most important group of oxidants, which are able to polymerize EDOT and subsequently dope PEDOT to yield highly conductive PEDOT cations (bipolarons). There are a lot of peroxidic compounds—decomposed thermally or by the catalytic action of metal cations— which, by the reaction of intermediate free oxyradicals, produce typically blue dispersions of PEDOT in water. Most of them are not sufficient to achieve optimal high conductivity. Hydrogen peroxide, alkyl hydroperoxides like tBu-OOH, and diacyl peroxides like dibenzoyl peroxide have all been described as EDOT oxidants, without becoming technically importanD i EDOT is oxidized by m-chloroperbenzoic acid to a mixture of the corresponding sulfone and 3,4-ethylenedioxy-2(5H)-thiophenone in... 

Applications of peroxide formation are underrepresented in chiral synthetic chemistry, most likely owing to the limited stability of such intermediates. Lipoxygenases, as prototype biocatalysts for such reactions, display rather limited substrate specificity. However, interesting functionalizations at allylic positions of unsaturated fatty acids can be realized in high regio- and stereoselectivity, when the enzymatic oxidation is coupled to a chemical or enzymatic reduction process. While early work focused on derivatives of arachidonic acid chemical modifications to the carboxylate moiety are possible, provided that a sufficiently hydrophilic functionality remained. By means of this strategy, chiral diendiols are accessible after hydroperoxide reduction (Scheme 9.12) [103,104]. 

A strong acceptor TCNE undergoes [2+2] rather than [4+2] cycloaddition reactions even with dienes. 1,1-Diphenylbutadiene [20] and 2,5-dimethyl-2,4-hexadiene (Scheme 5) [21] afford mainly and exclusively vinyl cyclobutane derivatives, respectively. In the reactions of 2,5-dimethyl-2,4-hexadiene (1) the observed rate constant, is greater for chloroform solvent than for a more polar solvent, acetonitrile (2) the trapping of a zwitterion intermediate by either methanol or p-toluenethiol was unsuccessful (3) radical initiators such as benzyl peroxide, or radical inhibitors like hydroquinone, have no effect on the rate (4) the entropies of activation are of... 

The latter binding mode has been observed for oxyhemocyanin (77) and in a dicopper(II) peroxide complex (78). Figure 2 illustrates structures for the peroxo intermediate which are most compatible with its spectroscopic parameters, as well as another, less likely, possibility (51). 

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