Oxone reaction with ketones

Recently, Crousse and coworkers reported that new fluoro ketones serve as efficient catalysts for the epoxidation reactions with Oxone in hexafluoropropan-2-ol (HFIP) (equation 46). ... 

Aromatic methyl ketones can be halogenated at the a-position with Oxone and sodium halide, however, corr5>eting halogenation of the aromatic ring is significant. Q, a-Dichloroketones can be synthesized from alkynes by reaction with Oxone in HCl/DMF (eq 83). Oxone consistently gave better results than MCPBA for this transformation. 

All the reactions were carried out at 0°C, with the substrate (1 equivalent), ketone (3 equivalents), Oxone (5 equivalents), and NaHCC>3 in CH3CN aqueous EDTA for 2 hours. High enantioselectivity can generally be obtained for trans- and trisubstituted olefins. The favored spiro and planar transition states have been proposed for ketone 130-mediated rrans-stilbene epoxidation (Scheme 4-48). 

Asymmetric epoxidation of olefins is an effective approach for the synthesis of enan-tiomerically enriched epoxides. A variety of efficient methods have been developed [1, 2], including Sharpless epoxidation of allylic alcohols [3, 4], metal-catalyzed epoxidation of unfunctionalized olefins [5-10], and nucleophilic epoxidation of electron-deficient olefins [11-14], Dioxiranes and oxazirdinium salts have been proven to be effective oxidation reagents [15-21], Chiral dioxiranes [22-28] and oxaziridinium salts [19] generated in situ with Oxone from ketones and iminium salts, respectively, have been extensively investigated in numerous laboratories and have been shown to be useful toward the asymmetric epoxidation of alkenes. In these epoxidation reactions, only a catalytic amount of ketone or iminium salt is required since they are regenerated upon epoxidation of alkenes (Scheme 1). 

Previously, some fluorocyclohexanones were used in a catalytic amount with Oxone for asymmetric epoxidation reaction, but they gave a poor ee . It was found later that chiral ketones derived from fructose work well as asymmetric epoxidation catalysts and show high enantioselectivity in reactions of /rani-disubstituted and trisubsti-tuted olefins ". Cis and terminal olefins show low ee under these reaction conditions. Interestingly, the catalytic efficiency was enhanced dramatically upon raising the pH. Another asymmetric epoxidation was also reported using Oxone with keto bile acids. ... 

A new method for conversion of oximes to the corresponding em-halonitro derivatives using NaCl or KBr with Oxone and wet basic alumina was reported (equation 64) °. When the reaction was carried out under the same conditions but by using wet neutral alumina, complex mixtures of compounds in which the parent ketone is the most abundant product (>50%), due to the oxidative deprotection of the oxime, was obtained. 

Regeneration of ketones from tosylhydrazones with Oxone in acetone has been reported. Under controlled pH (pH = 6) the reaction gave very high yield (90%) of the product. In this paper we demonstrated that the use of in situ formed dimethyldioxirane under controlled pH conditions gives better results (equation 66). 

Chiral ketone-catalyzed asymmetric epoxidation has received intensive interest since the first reported by Curci et al. in 1984. The reaction is performed with oxone (potassium peroxomonosulfate) as the primary oxidant which generates the chiral dioxirane catalytic species in situ, which in turn, transfers the oxygen... 

The use of dioxiranes (typically DMDO or methyl(trifluoromethyl)dioxirane) as the oxygen-transfer source in epoxidations provides a commonly used and powerful alternative to peracids. The dioxiranes are prepared from the corresponding ketones via reaction with an oxygen-transfer source, usually Oxone (KHSOs) or hydrogen peroxide, the ketone in principle being a catalytic species. 

Dioxiranes, prepared from acetone and other aliphatic ketones by treatment with Oxone, can accomplish oxidations that are usually not achieved by Oxone itself [210, 211], Dioxiranes can be isolated by vacuum codistillation with the respective ketones [210], or else, they may be formed in situ and applied in the same reaction vessel [210, 211]. Examples of the applications of dioxiranes are epoxidations 210] and the oxidation of primary amines to nitro compounds [211], of tertiary amines to amine oxides [210], and of sulfides to sulfoxides [210] (equation 12). 

The formal addition of an oxygen atom across the carbonyl group gives rise to dioxiranes (equation 33). In practice, this reaction is effected with Oxone, and dimethyldioxirane (30) and other dioxiranes have been generated in solutions of their parent ketones.Dioxirane (30) has been implicated in oxidations of alkenes, sulfides and iinines. The formal addition of nitrogen across a carbon-oxygen double bond to afford oxaziridines has been reviewed (equation 34).There are also many methods available for the indirect conversion of carbonyl compounds to aziridines > and thiiranes using multi-step conversions. 

Dimethyldioxirane is a relatively strong oxidant but can show good selectivity its reactivity is similar to that of a peracid but it has the advantage of producing a neutral byproduct (acetone). Methyl(trifluoromethyl)dioxirane is a more powerful oxidant which can insert oxygen into C-H bonds with retention of configuration, as shown below." Dioxiranes are obtained by reaction of ketones with OXONE NOTE Dioxiranes are explosive and are usually handled in dilute solution. 

Oxidative Cleavage of Alkenes. An alternative to the oxidative cleavage of alkenes using ozone or the Lemieux-Johnson protocol has been reported recently. Under the action of catalytic osmium tetroxide, with oxone as a reoxidant, a variety of substituted alkenes were cleaved efficiently to furnish carbonyl compounds (eq 37). Any of the aldehydes that are produced via this sequence are immediately oxidized in situ to give the corresponding acid clearly this does not happen for any ketones so produced. Even electron deficient alkenes such as o , -unsaturated carbonyl compounds could be conveniently oxidized, although the products then underwent a decarboxylation reaction to produce the corresponding diacid. 

C-H bonds. This strategy has been used in an intramolecular fashion for the oxidation of hydrocarbons (eq 49) and steroids. Fructose-derived ketone 5 has also been used for this purpose in an intermolecular reaction for the desymmetrization and kinetic resolution of 1,2-diols to a-hydroxy ketones (eq 50). There has also been a report of the direct oxidation of hydrocarbons to ketones and lactones by Mn-porph)rin complexes with Oxone. ... 

The possibility of recycling the highly hydrophobic ILs [bmim]BF4 and [Hmim]OAc used in the Baeyere-Villiger (B-V) oxidation of ketones with Oxone was also checked [Chrobok, 2010]. After the filtration of the post reaction mixture and the extraction of the product with ethyl acetate (for [bmim]BF4) or dibutyl ether (for [Hmim]OAc), the ILs were concentrated, dried under vacuum (60 °C, 5 h) and reused. Table 3 shows four cycles of the oxidation of 2-adamantanone in ILs that are recovered and reused for further B-V reactions. No significant loss of activity of these solvents was observed. Additionally, ILs were recycled three times in a model reaction without significant loss of activity [Chrobok, 2010]. 

The pioneering work by Curd offered one of the first examples of the use of chiral catalysts in the asymmetric epoxidation of alkenes with Oxone. In this early example the use of chiral ketone (-l-)-isopinocamphone (3, Figure 19.1) afforded low enantioselectivities (<15% ee) and reaction rates in a biphasic solvent system [9]. Subsequently, Yang developed a class of C2-symmetrical ketones 4 that in a monophasic (CH3CN/H2O) solvent system gave improved enantioselectivity [47% ee for the epoxidation of ( )-stilbene] [10, 11],... 

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