- Chemoselective hydroxylation of aliphatic sp3 C-H bonds using a ketone catalyst and aqueous H2O2
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The first ketone-catalyzed method for the oxidation of aliphatic C-H bonds is reported. The reaction conditions employ aryl trifluoromethyl ketones in catalytic amounts and hydrogen peroxide as the terminal oxidant. Hydroxylation is stereospecific and chemoselective for tertiary over secondary C-H bonds. A catalytic cycle invoking a dioxirane as the active oxidant is proposed.
- Pierce, Conor J.,Hilinski, Michael K.
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supporting information
p. 6504 - 6507
(2015/01/16)
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- Oxidations catalyzed by osmium compounds. Part 1: Efficient alkane oxidation with peroxides catalyzed by an olefin carbonyl osmium(0) complex
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A carbonyl osmium(0) complex with π-coordinated olefin, (2,3-η-1,4-diphenylbut-2-en-1,4-dione)undecacarbonyl triangulotriosmium (1), efficiently catalyzes oxygenation of alkanes (cyclohexane, cyclooctane, n-heptane, isooctane, etc.) with hydrogen peroxide, as well as with tert-butyl hydroperoxide and meta-chloroperoxybenzoic acid in acetonitrile solution. Alkanes are oxidized to corresponding alcohols, ketones (aldehydes) and alkyl hydroperoxides. Thus, heating cyclooctane with the 1-H2O2 combination at 70 °C gave products with turnover number as high as 2400 after 6 h. The maximum obtained yield of all products was equal to 20% based on cyclohexane and 30% based on H2O2. The oxidation of linear and branched alkanes exhibits very low regio- and bond-selectivity parameters and this testifies that the reaction proceeds via attack of hydroxyl radicals on C-H bonds of the alkane. The oxygenation products were not formed when the reaction was carried out under argon atmosphere and it can be thus concluded that the oxygenation occurs via the reaction between alkyl radicals and atmospheric oxygen. In summary, the Os(0) complex is much more powerful generator of hydroxyl radicals than any soluble derivative of iron (which is an analogue of osmium in the Periodic System).
- Shul'pin, Georgiy B.,Kudinov, Aleksandr R.,Shul'pina, Lidia S.,Petrovskaya, Elena A.
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p. 837 - 845
(2007/10/03)
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- Hydrogen peroxide oxygenation of alkanes including methane and ethane catalyzed by iron complexes in acetonitrile
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This paper describes an investigation of the alkane oxidation with hydrogen peroxide in acetonitrile catalyzed by iron(III) perchlorate (1), iron(III) chloride (2), iron(III) acetate (3) and a binuclear iron(III) complex with 1,4,7-triazacyclononane (4). The corresponding alkyl hydroperoxides are the main products. Nevertheless in the kinetic study of cyclohexane oxidation, the concentrations of oxygenates (cyclohexanone and cyclohexanol) were measured after reduction of the reaction solution with triphenylphosphine (which converts the cyclohexyl hydroperoxide to the cyclohexanol). Methane and ethane can be also oxidized with TONs up to 30 and 70, respectively. Chloride anions added to the oxidation solution with 1 activate the perchlorate iron derivative in acetonitrile, whereas the water as additive inactivates 2 in the H 2O2 decomposition process. Pyrazine-2-carboxylic acid (PCA) added to the reaction mixture decreases the oxidation rate if 1 or 2 are used as catalysts, whereas compounds 3 and 4 are active as catalysts only in the presence of small amount of PCA. The investigation of kinetics and selectivities of the oxidations demonstrated that the mechanisms of the reactions are different. Thus, in the oxidations catalyzed by the 1, 3+PCA and 4+ PCA systems the main oxidizing species is hydroxyl radical, and the oxidation in the presence of 2 as a catalyst has been assumed to proceed (partially) with the formation of ferryl ion, (FeIV=O)2+. In the oxidation catalyzed by the 4+PCA system (TONs attain 240) hydroxyl radicals were generated in the rate-determining step of monomolecular decomposition of the iron diperoxo adduct containing one PCA molecule. A kinetic model of the process which satisfactorily describes the whole set of experimental data was suggested. The constants of supposed equilibriums and the rate constant for the decomposition of the iron diperoxo adduct with PCA were estimated.
- Shul'pin, Georgiy B.,Nizova, Galina V.,Kozlov, Yuriy N.,Cuervo, Laura Gonzalez,Su?ss-Fink, Georg
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p. 317 - 332
(2007/10/03)
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- The first, general, highly efficient method for preparing tetrasubstituted epoxides using HOF·CH3CN
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Tetrasubstituted epoxides, and especially electron-depleted ones, generally are difficult to prepare. HOF·CH3CN complex, probably the best oxygen transfer agent known today, epoxidizes tetrasubstituted alkenes at 0 °C in a matter of minutes or less in excellent yields. HOF·CH3CN complex is very easy to prepare by bubbling diluted fluorine (commercial) through aqueous acetonitrile. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
- Rozen, Shlomo,Golan, Elizabeth
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p. 1915 - 1917
(2007/10/03)
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- A selenium catalyzed epoxidation in perfluorinated solvents with hydrogen peroxide
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The readily prepared 2,4-bisperfluorooctylphenyl butylselenide catalyzes the epoxidation of various olefins with hydrogen peroxide in a fluorous biphasic system. The catalyst is selectively soluble in perfluorinated solvents and can easily be recovered simply by phase separation. Furthermore, the catalyst can be reused several times without a decrease of yield and an increase of reaction time.
- Betzemeier, Bodo,Lhermitte, Frédéric,Knochel, Paul
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p. 489 - 491
(2007/10/03)
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