Dioxiranes as oxidizing agents

This was also accomplished with BaRu(0)2(OH)3. The same type of conversion, with lower yields (20-30%), has been achieved with the Gif system There are several variations. One consists of pyridine-acetic acid, with H2O2 as oxidizing agent and tris(picolinato)iron(III) as catalyst. Other Gif systems use O2 as oxidizing agent and zinc as a reductant. The selectivity of the Gif systems toward alkyl carbons is CH2 > CH > CH3, which is unusual, and shows that a simple free-radical mechanism (see p. 899) is not involved. ° Another reagent that can oxidize the CH2 of an alkane is methyl(trifluoromethyl)dioxirane, but this produces CH—OH more often than C=0 (see 14-4). ... 

Numerous variations of this method were developed170-173. In general, 0.1-0.8 molar solutions of dioxiranes were prepared and used as oxidizing agents. These solutions can be stored in a refrigerator. Epoxidation of many ketones has been carried out in the above way, and the dioxiranes (7-14) thus prepared were characterized spectroscopically and also by chemical methods. 

Wong M-K, T-C Chan, W-Y Chan, W-K Chan, LLP Vrijmoed, DK O Toole, C-M Che (2006) Dioxiranes generated in situ from pyruvates and oxone as environmentally friendly oxidizing agents for disinfection. Environ Sci Technol 40 625-630. 

The oxidation of organic substances by cyclic peroxides has been intensively studied over the last decades , from both the synthetic and mechanistic points of view. The earliest mechanistic studies have been carried out with cyclic peroxides such as phthaloyl peroxide , and more recently with a-methylene S-peroxy lactones and 1,2-dioxetanes . During the last 20 years, the dioxiranes (remarkable three-membered-ring cyclic peroxides) have acquired invaluable importance as powerful and mild oxidants, especially the epoxidation of electron-rich as well as electron-poor alkenes, heteroatom oxidation and CH insertions into alkanes (cf. the chapter by Adam and Zhao in this volume). The broad scope and general applicability of dioxiranes has rendered them as indispensable oxidizing agents in synthetic chemistry this is amply manifested by their intensive use, most prominently in the oxyfunctionalization of olefinic substrates. 

It is important to underline in this introduction that the importance of oxaziridines as special oxidizing agents is expected to diminish in some fields due to the use of dioxiranes. Their importance, however, is indisputable since oxaziridines as chiral oxidizing agents201,202 offer greater possibilities than dioxiranes. 

Many attempts have been made to use hydrogen peroxide as the final oxidizing agent in ketone-catalyzed epoxidations. Because hydrogen peroxide itself does not convert ketones to dioxiranes, in-situ activation of the oxidant is necessary. Shi et al. have achieved this goal by using acetonitrile as a component of the solvent mixture... 

Whereas the chiral TEMPO analog 87 was used to resolve racemic secondary alcohols, the D-fructose-derived ketone 88 [137] proved useful for oxidative resolution of racemic diols (Table 10.13) [138, 139], Persulfate in the form of Oxone, Curox, etc., served as the final oxidizing agent, and the dioxirane generated from the ketone 88 is the chiral active species. Because of the relatively low conversions (except for unsubstituted dihydrobenzoin) at which the ee stated were achieved, the method currently seems to be of less practical value. Furthermore, typically 3 equiv. ketone 88 had to be employed [138, 139]. 

Dioxiranes, of which DMD is the simplest member, are powerful electrophilic oxidizing agents, able to transfer oxygen to aromatic rings and double bonds. DMD was identified by Ragauskas [113] and Lee and coworkers [114] as a very effective bleaching agent for chemical pulps. It can be added directly to pulps or prepared in situ from acetone and PMS. 

An oxidizing agent up to 7000 times more reactive than 9a is methyl(trifluoromethyl)-dioxirane (9b), which not only hydroxylates tertiary C-H positions (Table 1) but also converts secondary C-H groups into carbonyl functions. As an illustration, the oxidation of cyclohexane at -22 °C afforded cyclohexa-... 

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