Dioxirane oxidation

Adam, W. and Hadjiarapoglou, L. Dioxiranes Oxidation Chemistry Made Easy. 164, 45-62 (1993). 

Thioethanol -0(CH2)2S-PEGM B Dioxirane oxidation then NaOMe/MeOH 2... 

In contrast to dioxirane oxidation, the transition states for carbonyl oxide oxidation are not affected as much by RHF-UHF wave function instability problems, and there is good agreement between the MP2, MP4 and QCISD(T) barrier heights. Methyl substitution on the carbonyl oxide has very little effect on the barrier heights, but it can be anticipated that methyl substitution of the aUtene would lower the barriers significantly . The calculated changes in the barriers due to solvation are much smaller than for dioxirane oxidation, primarily because the differences between the reactant and transition state dipoles are smaller. 

SCHEME 4. Dioxirane oxidation of electron-poor alkenes... 

SCHEME 5. Dioxirane oxidation of alkenes with both electron-donor and electron-acceptor groups... 

SCHEME 10. Dioxirane oxidation of substrates with heteroatom functionaUties... 

From the aforementioned, it should be evident that the amino group is one of the most reactive functionalities towards dioxirane oxidation consequently, to achieve a chemo-selective oxidation of a multi-functionalized substrate that possesses an amino group, the latter must be protected. This may be accomplished by masking the amino substituent in the form of its ammonium salt ", or BF3 complex ", even better as an amide functionality (iV-phenylacetamide resists TFD oxidation at room temperature""). This will reduce sufficiently the oxidative reactivity of the amino group, such that another less reactive group may be selectively oxidized" ... 

A triple-bonded nitrogen functionality (a ip-hybridized nitrogen atom), namely the cyano group, is resistant towards dioxirane oxidation. The fact that acetonitrile is widely used as a solvent for dioxirane oxidations " amply substantiates the lack of oxidative reactivity of cyano compounds. 

Sulfur compounds with divalent sulfur functionalities are much more prone to dioxirane oxidation on account of their higher nucleophilicity compared to the above-presented oxygen-type nucleophiles. Examples of this type of dioxirane oxidation abound in the literature. Such a case is the oxidation of thiols, which may be quite complex and afford a complex mixture of oxidation products, e.g. sulfinic acids, sulfonic acids, disulfides, thiosulfonates and aldehydes , and is, therefore, hardly useful in synthesis. Nevertheless, the oxidation of some 9i/-purine-6-thiols in the presence of an amine nucleophile produces n >( -nucleoside analogs in useful yields (equation 19). This reaction also displays the general chemoselectivity trend that divalent sulfur functionalities are more reactive than trivalent sp -hybridized nitrogen compounds P. 

The by far more common and preparatively valuable dioxirane oxidation of divalent sulfur substrates is that of sulfides, to produce either sulfoxides or sulfones . Since sulfoxides are considerably less reactive than sulfides, the reaction outcome may be conveniently controlled by the stoichiometry of the oxidant For example, in the low-temperature oxidation of thiophene by an excess of DMD, the corresponding 1,1-dioxide (sulfone) has been obtained, albeit in low yield (equation 20). This is the first preparatively useful method for isolating this elusive sulfone, which also accentuates the importance of the neutral and anhydrous conditions under which the oxidations with the isolated DMD may be conducted. 

The enantioselective oxidation of prochiral sulfides with DMD has been achieved by using bovine serum albumin (BSA) as the chiral inductor Moderate to good enan-tioselectivities have been reported in the presence of this protein, for which a typical example is shown in equation 22 . As yet, however, no enantioselective oxidation of a prochiral sulfide has been documented by employing an optically active dioxirane. We have tried the enantioselective oxidation of methyl phenyl sulfide with the dioxirane generated from the ketone 7 (Shi s ketone), but an ee value of only ca 5% was obtained. One major hurdle that needs to be overcome with such enantioselective dioxirane oxidations is the suppression of the background oxidation of the sulfide substrate by Caroate, an unavoidable feature of the in-situ mode. 

The dioxirane oxidation of the C=S and N=S double bonds usually leads to the corresponding 5-oxides. In the latter case, A-oxidation may compete with 5-oxidation , and the experimental results indicate that the chemoselectivity depends on the electron density of these heteroatoms . 

There are only a few reports on the dioxirane oxidation of halogen-containing compounds. The oxidation of the chloride to the hypochlorite anion by DMD (in situ) is one... 

Of the organohahdes, only the iodides are prone to oxidation by dioxirane for example, iodobenzene is oxidized by DMD to a mixture of iodosobenzene and iodylbenzene. In contrast, alkyl iodides afford labile primary oxidation products, which eliminate the oxidized iodine functionality to result in aUcenes (equation 23). In such a dioxirane oxidation, the subsequent in-situ reaction of the alkene affords the corresponding epoxides . 

When the C—H bond to be oxidized is proximate to a functional group, as we have stated already, its reactivity depends on the type of functional group. In the case of the hydroxy group, especially in secondary alcohols, these are more prone to dioxirane oxidation than their alkane precursors and, consequently, usually carbonyl products are obtained as the final product. Primary alcohols are less reactive, but may still be converted slowly to the corresponding aldehydes or carboxylic acids (due to the facile further oxidation of aldehydes)The functional-group transformation of the alcohols to ethers or acetals reduces the oxidative reactivity " but these C—H bonds are still more reactive than unfunctionalized ones. Thus, dioxirane oxidation of benzyl ether or acetal may... 

Alkyl hydroperoxysilanes, preparation, 783 Alkyl hydrotrioxides, structural chemistry, 132 Alkyl iodides, dioxirane oxidation, 1158 Alkyl methyl sulfonates, alkyl hydroperoxide synthesis, 673... 

C-H bond unreactive to insertion, 1160 nitrile hydrolysis, 701-2 selective dioxirane oxidation, 1152 Amines... 

Chiral sulfides, dioxirane oxidation, 1156-7 Chlamydomonas reinhardtii, hydrogen peroxide determination, 646 y-Chlordene, isomers, 728 Chlorellajusca, hydrogen peroxide determination, 646... 

Hydroxyhydroperoxides, synthesis, 313-14 Hydroxylamine, dioxirane oxidation, 1151 Hydroxylation... 

Hypoiodous acid (HOI), generation in dioxirane oxidation, 1158 Hypothiocyanite, from lactoperoxidase, 612... 

Imine peroxide, analytical aspects, 744 Imines, dioxirane oxidation, 1153 Immohihzed enzymes, biosensors, 687-8 Immunoassays... 

Iodine, hydrogen peroxide titration, 627 Iodine-iodide buffer, potentiometry, 699 Iodine number, unsaturated polyolefins, 740 lodobenzene, dioxirane oxidation, 1158 lodohydrins, dioxirane oxidation, 1158 lodometry... 

Nitrobenzene chloride, sulfonylperoxy radical reactions, 1035, 1036 2-Nitrobenzenesulfinylperoxy intermediate, superoxide reactions, 1034 Nitrogen-containing compound oxidation bis(trimethylsilyl) peroxide reactions, 802-3, 804 dioxiranes, 1151-5 primary aromatic amines, 1151 A-oxidation, 531-8, 539 Nitrohpids, hpid hydroperoxides, 952-4 Nitronate ions, dioxirane oxidation, 1152-3 Nitrosation, malondialdehyde, 667 Nitroso compounds, spin trapping, 664 Nitrotyrosine, peroxynitiite determination, 740-1... 

Preservatives, pharmaceutical preparations, 623 PRESS technique, NIR spectrophotometry, 624 Primary amines, dioxirane oxidation, 1151 Primary ozonides (POZ), 716, 717 dialkyl peroxide formation, 706 IR spectroscopy, 718, 719-20 microwave spectroscopy, 721 molecular model, 750 NMR spectroscopy, 709, 723-4 octaUn ozonation, 165 ozone water disinfection, 606 7r-complexes with ozone, 732... 

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