- PROCESS FOR THE ISOMERIZATION OF 2,2,4,4-TETRAALKYLCYCLOBUTANE-1,3-DIOLS
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Disclosed is a process for the isomerization of 2,2,4,4-tetraalkylcyclobutane-1,3-diols, such as 2,2,4,4-tetramethylcyclobutane-1,3-diol, by contacting the diol with a supported ruthenium catalyst in the presence of hydrogen at elevated pressures and temperatures. The process is carried under conditions in which there is no net production of 2,2,4,4-tetraalkylcyclobutane-1,3-diol. The process may be carried out in the presence or absence of a solvent and in the liquid or vapor phase.
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Page/Page column 7
(2012/06/18)
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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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- Alkane oxygenation with H2O2 catalysed by FeCl 3 and 2,2′-bipyridine
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The H2O2-FeCl3-bipy system in acetonitrile efficiently oxidises alkanes predominantly to alkyl hydroperoxides. Turnover numbers attain 400 after 1 h at 60°C. It has been assumed that bipy facilitates proton abstraction from a H2O2 molecule coordinated to the iron ion (these reactions are stages in the catalytic cycle generating hydroxyl radicals from the hydrogen peroxide). Hydroxyl radicals then attack alkane molecules finally yielding the alkyl hydroperoxide.
- Shul'pin, Georgiy B.,Golfeto, Camilla C.,Süss-Fink, Georg,Shul'pina, Lidia S.,Mandelli, Dalmo
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p. 4563 - 4567
(2007/10/03)
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- Hydrocarbon Oxidations with Hydrogen Peroxide Catalyzed by a Soluble Polymer-Bound Manganese(IV) Complex with 1,4,7-Triazacyclononane
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Soluble manganese(IV) complexes with polymer-bound 1,4,7-triazacyclononanes as ligands (compound 2) catalyze the oxidation of alkanes by hydrogen peroxide in acetonitrile at room and lower temperatures. The corresponding alkyl hydroperoxides are the main products. The presence of a relatively small amount of acetic acid is obligatory for this reaction. The oxidation of alkanes and olefins exhibits some features (kinetic isotope effect, bond selectivities) that distinguish this system from an analogous one based on the dinuclear Mn(IV) complex 1.
- Nizova, Galina V.,Bolm, Carsten,Ceccarelli, Simona,Pavan, Chiara,Shul'pin, Georgiy B.
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p. 899 - 905
(2007/10/03)
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- Alkane Functionalization on a Preparative Scale by Mercury-Photosensitized Cross-Dehydrodimerization
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Alkanes can be functionalized with high conversions and in high chemical and quantum yields on a multigram scale by mercury-photosensitized reaction between an alkane and alcohols, ethers, or silanes to give homodimers and cross-dehydrodimers.The separation of the product mixtures is often particulary easy because of a great difference in polarity of the homodimers and cross-dimers.It is also possible to bias the product composition when the ratio of the components in the vapor phase is adjusted by altering the liquid composition.This is useful either to maximize chemical yield or to ease separation by favoring the formation of the most easily separated pair of compounds.The mechanistic basis of the reaction is discussed and a number of specific types of syntheses, for example of 2,2-disubstituted carbinols, are described in detail.The selectivity of cross-dimerization is shown to exceed that for homodimerization and reasons are discussed.Relative reactivities of different compounds and classes of compound are MeOHp-dioxanecyclohexane1,3,5-trioxacyclohexaneethanolisobutaneTHFEt3SiH.The observed selectivities generally parallel those for homodimerization, reported in the preceding paper, but certain differences are noted, and reasons for the differences are proposed.The bond-dissociation energy of Et3SiH is estimated from the reactivity data to be 90 kcal/mol.Eleven new carbinols are synthesized.
- Brown, Stephen H.,Crabtree, Robert H.
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p. 2946 - 2953
(2007/10/02)
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