Peroxy acid oxidations

Peroxy acid oxidation of (17) gave sulfoxide (18) whose F NMR spectrum showed equivalent CF3 groups even at —95 °C (76JA4325). Tlie rate ratio for the sulfur walk in (18/17) is an astounding 10 ° at 25 "C theoretical reasons for the difference have been discussed (80JA286i). 

Functional groups that stabilize radicals would be expected to increase susceptibility to autoxidation. This is illustrated by two cases that have been relatively well studied. Aldehydes, in which abstraction of the aldehyde hydrogen is fecile, are easily autoxidized. The autoxidation initially forms a peroxycarboxylic acid, but usually the corresponding carboxylic acid is isolated because the peroxy acid oxidizes additional aldehyde in a... 

Peroxy acid oxidation of alkenes (Sections 6.18 and 16.9) Peroxy acids transfer oxygen to alkenes to yield epoxides. Stereospecific syn addition is observed. 

Oxetanones have been obtained from peroxy acid oxidation of f-butyl substituted allenes to form the allene diepoxide, which then either rearranged spontaneously, or upon addition of acid, to the 3-oxetanone in about 30% yield (equation 113). Thus the insertion of the ring oxygen between the ends of the allene system comes about indirectly. 

Mention should be made, lastly, of occasional rearrangement encountered when peroxy acid oxidation is attempted on Hubtinnu containing reactive centers suitably disposed in the molecule. As an example may be cited the recent report by Mouaseron and Levaliois 1 of an unexpected cydization presumably taking place by wav <>l carbonium ion, as shown in Eq. (55). 

Excellent reviews by Swem167 M7f have already been cited in connexion with epoxide synthesis by peroxy acid oxidation of oIMuim (see Motiiat 1111,4.). These papers are equally useful in connexion with the present topic, and should be consulted for many details that cannot be discussed here. 

The tertiary amine bridge of 9 is preferentially eliminated by peroxy acid oxidation to give 1,2,3,4-tetrafluoronaphthalenc (10) 22° no epoxidation of the C = C bond in the starting compound is observed. Almost the same yields are achieved when using 30% hydrogen peroxide in refluxing methanol.220... 

Mechanistic studies on the peroxy acid oxidations of isotopically labelled but-2-enes have been reported291. 

Aromatic and aliphatic primary amines can be oxidized to the corresponding nitro compounds by peroxy acids and by a number of other reagents. The peroxy acid oxidations probably go by way of intermediate hydroxylamines and nitroso compounds (Scheme 2). Various side reactions can therefore take place, the nature of which depends upon the structure of the starting amine and the reaction conditions. For example, aromatic amines can give azoxy compounds by reaction of nitroso compounds with hy-droxylamine intermediates aliphatic amines can give nitroso dimers or oximes formed by acid-catalyz rearrangement of the intermediate nitrosoalkanes (Scheme 3). 

In shaip contrast to peroxy acid oxidation the oxidation of sulfoxides to sulfones with various transi tion metal salts proceeds much faster than that of sulfides to sulfoxides and consequently sulfoxides may be selectively oxidized to sulfones in the presence of sulfides. 

Meifaylenecyclopropanes undwgo oxidative ring expansion in a two-step sequence peroxy acid oxidation K> an oxaspiropentane followed by lithium i de induced rearrangement yields a cyclobutanone in moderate yield, as illustrated in equation (49). Cyclobutanone is a minor product from the reaction of... 

Silverstein and coworicers have used the peroxy acid oxidation of exo-alkylidene cycloalkanones as a route to keto acids (Scheme 23). Oxidation of pulegone (72) and hydrolysis of the derived enol lactone led to the keto acid (73). 

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