Alcohols dimethyldioxirane

In general, peroxomonosulfates have fewer uses in organic chemistry than peroxodisulfates. However, the triple salt is used for oxidizing ketones (qv) to dioxiranes (7) (71,72), which in turn are useful oxidants in organic chemistry. Acetone in water is oxidized by triple salt to dimethyldioxirane, which in turn oxidizes alkenes to epoxides, polycycHc aromatic hydrocarbons to oxides and diones, amines to nitro compounds, sulfides to sulfoxides, phosphines to phosphine oxides, and alkanes to alcohols or carbonyl compounds. 

Polymer-supported permthenate has also been used in two convergent pathways for the synthesis of isoxazoUdines with each route employing different starting materials in order to create the maximum structural diversity [73]. In the first route secondary hydroxylamines, readily prepared from amines by in situ treatment with dimethyldioxirane, were oxidized directly to nitrones using polymer-supported permthenate (PSP). Alternatively, primary alcohols were used as the... 

Dinitrocubane (28) has been synthesized by Eaton and co-workers via two routes both starting from cubane-l,4-dicarboxylic acid (25). The first of these routes uses diphenylphos-phoryl azide in the presence of a base and tert-butyl alcohol to effect direct conversion of the carboxylic acid (25) to the tert-butylcarbamate (26). Hydrolysis of (26) with mineral acid, followed by direct oxidation of the diamine (27) with m-CPBA, yields 1,4-diiutrocubane (28). Initial attempts to convert cubane-l,4-dicarboxylic acid (25) to 1,4-diaminocubane (27) via a Curtins rearrangement of the corresponding diacylazide (29) were abandoned due to the extremely explosive nature of the latter. However, subsequent experiments showed that treatment of the acid chloride of cubane-l,4-dicarboxylic acid with trimethylsilyl azide allows the formation of the diisocyanate (30) without prior isolation of the dangerous diacylazide (29) from solution. Oxidation of the diisocyanate (30) to 1,4-dinitrocubane (28) was achieved with dimethyldioxirane in wet acetone. Dimethyldioxirane is also reported to oxidize both the diamine (27) and its hydrochloride salt to 1,4-dinitrocubane (28) in excellent yield. ... 

The preparation of the allene bis-epoxide 1 started with isovaleraldehyde 9. Addition of the protected propargyl alcohol 10 under the Carreira conditions led to 11 in > 95% . Mesylation followed by displacement with methyl cuprate provided the allene without loss of enantiomeric excess. Oxidation of the allene 12 with dimethyldioxirane could have led to any of the four diastereomers of the spiro bis epoxide. In the event, only two diastereomers were observed, as a 3 1 mixture. That 1 was the major diastereomer followed from its conversion to 3. The configuration of the minor diastereromer was not noted. Exposure of 1 to nucleophilic azide then gave the easily-purified 2. 

Epoxides (see also a,(3-Epoxy alcohols, etc., Glycidic acids, esters, nitriles) From alkenes by epoxidation Dimethyldioxirane, 120 Fluorine-Acetonitrile, 135 Potassium peroxomonosulfate, 259 From carbonyl compounds Alumina, 14... 

Simple allenes (209) react with dimethyldioxirane (200) to give the corresponding spiro-dioxides 210 in instances where diastereoisomeric spiro-dioxides are possible, there is usually an acceptable stereochemical preference for epoxidation to occur anti to the alkyl substituents324,325. Allenic alcohol 211 yields the highly functionalized tetrahydro-furan 212 and tetrahydropyran derivatives by intramolecular nucleophilic addition of the hydroxy group to an intermediate allene diepoxide324. 

A mixture of epoxides 483 obtained on oxidation of 482 with dimethyldioxirane, when exposed to ferric chloride provided, as the kinetically controlled product, the a-aldehyde 484, which without purification was reduced to the a-alcohol 485. The exclusive formation of 484 is believed to occur via the benzyl cation 486, generated by Lewis-acid opening of the oxirane ring, suffering a stereospecific kinetic 1,2-hydride shift The amino alcohol 487 obtained after sequential removal of O-benzyl and N-tosyl groups from 485, on treatment with triphenylphosphine and iodine in the presence of imidazole furnished the tetracyclic base 488, which was oxidised to the ketone 489. Trapping of the kinetically generated enolate of 489 as the silylether, followed by palladium diacetate oxidation yielded the enone 490. The derived... 

Epoxidation of glycals can be effected in almost quantitative yield by dimethyldioxirane in acetone at 0°. In the case of nonparticipating protecting groups, the a-epoxide is formed almost exclusively. These a-l,2-anhydro sugars react with alcohols with clean inversion to form P-glycosides.5... 

Deoxygenation of pyridine A-oxides has been achieved using dimethyldioxiran <95CC1831> and palladium with sodium hypophosphite <95GCI(124)385>. Pyridine A-oxides, with ruthenium porphyrin catalysts, have been used as an oxidant of aromatic compounds <95JA(117)8879> or olefins, alcohols, sulfides and alkanes <95FI(40)867>. 

Activation of 26 with AgBF, led to the intermediate 1,2-A-sulfonylaziridinc, which reacted with the tributyltin ether glycal 27 to afford the dimer 28. The second glycal was activated with dimethyldioxirane (DMDO) to supply the intermediate epoxide that was treated with ZnCl2 and allyl alcohol to afford compound 29. 

Epoxidation of oxonine 93 with dimethyldioxirane, followed by reduction with diisobutylaluminium hydride (DIBAL-H), resulted in a separable mixture of alcohols 95 and 96, and the side product 94 (Scheme 16). Each of the isomers was submitted to Swern oxidation and sequential stereoselective reduction with L-selectride to achieve desired stereochemistry of the products 97 and 98. Formation of the side product 94 was explained by Lewis acidity of DIBAL-H and confirmed by treatment of oxirane derived from 93 with another Lewis acid, AlMe3, to produce oxocine aldehyde 99 in 35% isolated yield <1997CL665>. Similar oxidative synthetic sequence was utilized for the synthesis of functionalized oxonines as precursors of (-l-)-obtusenyne <1999JOG2616>. 

The diastereoselectivity of the dimethyldioxirane-mediated epoxidation of allylic alcohols resembles that of the peracid epoxidation4. 

WL Adam, A. K. Smerz, Solvent effects in the regio- aird diastereoselective epoxidations of acyclic allylic alcohols by dimethyldioxirane Hydrogen bonding as evidence for a dipolar transition state, J. Org. Chem. 61 (1996) 3506. 

The validity of the approach was first demonstrated by the synthesis of a linear tetrasaccharide [22] and a hexasaccharide 13 [23] as outlined in Scheme 3. Polymer-bound galactal 5 was converted to the 1,2-anhydro sugar 6 by epoxidation with 3,3-dimethyldioxirane [24], Polymer-bound 6 acted as a glycosyl donor when reacted with a solution of 7 in the presence of zinc chloride, resulting in the formation of disaccharide 8a. Upon repetition, this glycosylation procedure accommodated the secondary alcohol glycosyl acceptor 10 as well as disaccharide acceptor 12. Huor-idolysis with tetrabutylammonium fluoride (TBAF) was used to cleave the desired products from the polymeric support and furnish hexasaccharide 13 in 29% overall yield from 5 [16]. 

The general features of reactivity and selectivity of this novel oxidant are displayed in Table 3. It is significant that the fluoro derivative, i.e. methyl-(trifluormethyl)dioxirane [6], is at least 1000-fold more reactive than dimethyldioxirane. As a consequence, the fluorinated dioxirane oxidizes alkanes to the corresponding alcohols and/or ketones within minutes even at subambient temperatures [7]. 

While ethers react only slowly with dimethyldioxirane, they are efficiently hydroxylated by methyl(trifluoromethyl)dioxirane even at low temperatures. Thus r-butyl methyl ether [32] was converted to f-butyl alcohol through its hemiacetal. On the other hand, tetrahydrofuran gave butyrolactone [32] in which presumably the intermediary cyclic hemiacetal was oxidized to the lactone by an additional C —H insertion. The ketal was degraded into 2-butanone and the orthoformate into diethyl carbonate [32]. The latter transformation may serve useful for deketalation under neutral conditions. 

Dimethyldioxirane converts A(Wdimethylhydrazones to the corresponding nitriles in 94-98% yields in 2-3 min.272 It has also been used to convert cycloctatetraene to tetraepox-ides.273 A dioxirane analogue, a perfluorinated dialkylox-aziridine, has been used to oxidize alcohols to ketones.274... 

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