- Metalation and DFT studies of metal organic frameworks UiO-66(Zr) with vanadium chloride as allyl alcohol epoxidation catalyst
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UiO-66(Zr)-V as metal organic framework was prepared by metalation of the UiO-66(Zr) nodes with VCl3. The characterization of the prepared catalyst was carried out using XRD, EDX, FT IR, BET, ICP, Raman, DRS, SEM and XPS techniques. The density functional theory (DFT) was used in order to find the most stable position of the vanadium of metallated UiO-66(Zr). It was found that UiO-66(Zr)-V has been generated via metalation of V(V) ions with two OH groups of Zr-based nodes. The XPS results confirmed DFT studies. The catalytic activity of UiO-66(Zr)-V for epoxidation of some allyl alcohols such as trans-2-hexene-1-ol, geraniol, 1-octene-3-ol and 3-methyl-2-buten-1-ol with 46–97% conversions and 100% selectivity is considerable.
- Geravand, Elham,Farzaneh, Faezeh,Ghiasi, Mina
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- Kinetics and mechanism of the epoxidation of alkyl-substituted alkenes by hydrogen peroxide, catalyzed by methylrhenium trioxide
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Epoxidations of alkyl-substituted alkenes, with hydrogen peroxide as the oxygen source, are catalyzed by CH3ReO3 (MTO). The kinetics of 28 such reactions were studied in 1:1 CH3CN-H2O at pH 1 and in methanol. To accommodate the different requirements of these reactions, 1H-NMR, spectrophotometric, and thermometric techniques were used to acquire kinetic data. High concentrations of hydrogen peroxide were used, so that diperoxorhenium complex CH3Re(O)(η2-O2)2(H 2O), B, was the only predominant and reactive form of the catalyst. The reactions between B and the alkenes are about 1 order of magnitude more rapid in the semiaqueous solvent than in methanol. The various trends in reactivity are medium-independent. The rate constants for B with the aliphatic alkenes correlate closely with the number of alkyl groups on the olefinic carbons. The reactions become markedly slower when electron-attracting groups, such as halo, hydroxy, cyano, and carbonyl, are present. The rate constants for catalytic epoxidations with B and those reported for the stoichiometric reactions of dimethyldioxirane show very similar trends in reactivity. These findings suggest a concerted mechanism in which the electron-rich double bond of the alkene attacks a peroxidic oxygen of B. These data, combined with those reported for the epoxidation of styrene (a term intended to include related molecules with ring and/or aliphatic substituents) by B and by the monoperoxo derivative of MTO, suggest that all of the rhenium-catalyzed epoxidations occur by a common mechanism. The geometry of the system at the transition state can be inferred from these data, which suggest a spiro arrangement.
- Al-Ajlouni, Ahmad M.,Espenson, James H.
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- Kinetics of the epoxidation of geraniol and model systems by dimethyldioxirane
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The mono-epoxidation of geraniol by dimethyldioxirane was carried out in various solvents. In all cases, the product ratios for the 2,3 and 6,7 mono-epoxides were in agreement with literature values. Kinetic studies were carried out at 23 °C in the following dried solvent systems: acetone (k 2 = 1.49 M-1s-1), carbon tetrachloride/acetone (9/1, k2=2.19 M-1s-1), and methanol/acetone (9/1, k2 = 17 M-1s-1). Individual k2 values were calculated for epoxidation of the 2,3 and 6,7 positions in geraniol. The non-conjugated diene system was modeled employing two simple independent alkenes: 2-methyl-2-pentene and 3-methyl-2-buten-1-ol by determining the respective k2 values for epoxidation in various solvents. The kinetic results for each independent alkene showed that the relative reactivity of the two epoxidation sites in geraniol as a function of solvent was not simply a summation of the independent alkene systems.
- Baumstark,Franklin,Vasquez,Crow
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- Selective Epoxidation of Olefins by Oxo(V) Alkylpreoxides. On the Mechanism of the Halcon Epoxidation Process
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Novel vanadium(V) alkylperoxy complexes with the general formula VO(OOR)(R'-OPhsal-R'') (II) were synthesized and characterized by physicochemical methods.These complexes most probably have a pentagonal pyramidal structure, with an axial vanadyl group and, in the pentagonal plane, three positions occupied by the Schiff base planar ligand and two positions occupied by a bidendate alkylperoxy group which is presumably weakly coordinatively bonded to the metal by the alkoxy oxygen atom.These complexes are very effective reagents for the selective transformation of olefins into epoxides, with yields ranging from 40percent for 1-octene to 98percent for tetramethylethylene.The reactivity of olefins is sensitive to steric hindrance and increases with the olefin nucleophilicity.The epoxidation of olefins by complexes II is steroselective, inhibited by water, alcohols, and basic ligands or solvents, and accelerated in polar nondonor solvents.Kinetic studies showed that the olefin coordinates to the metal prior to the decomposition of the metal-olefin complex in the rate-determining step.Competitive epoxidation of several olefins vs. cyclohexene showed that the more strongly coordinated olefins exert an inhibiting effect on the epoxidation of the less strongly coordinated ones.These data, which are similar to those of the Halcon catalytic epoxidation process, are consistent with a pseudocyclic peroxy metalation mechanism.
- Mimoun, Hubert,Mignard, Michel,Brechot, Philippe,Saussine, Lucien
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- Experimental investigation of the low temperature oxidation of the five isomers of hexane
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The low-temperature oxidation of the five hexane isomers (n-hexane, 2-methyl-pentane, 3-methyl-pentane, 2,2-dimethylbutane, and 2,3-dimethylbutane) was studied in a jet-stirred reactor (JSR) at atmospheric pressure under stoichiometric conditions between 550 and 1000 K. The evolution of reactant and product mole fraction profiles were recorded as a function of the temperature using two analytical methods: gas chromatography and synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). Experimental data obtained with both methods were in good agreement for the five fuels. These data were used to compare the reactivity and the nature of the reaction products and their distribution. At low temperature (below 800 K), n-hexane was the most reactive isomer. The two methyl-pentane isomers have about the same reactivity, which was lower than that of n-hexane. 2,2-Dimethylbutane was less reactive than the two methyl-pentane isomers, and 2,3-dimethylbutane was the least reactive isomer. These observations are in good agreement with research octane numbers given in the literature. Cyclic ethers with rings including 3, 4, 5, and 6 atoms have been identified and quantified for the five fuels. While the cyclic ether distribution was notably more detailed than in other literature of JSR studies of branched alkane oxidation, some oxiranes were missing among the cyclic ethers expected from methyl-pentanes. Using SVUV-PIMS, the formation of C 2-C3 monocarboxylic acids, ketohydroperoxides, and species with two carbonyl groups have also been observed, supporting their possible formation from branched reactants. This is in line with what was previously experimentally demonstrated from linear fuels. Possible structures and ways of decomposition of the most probable ketohydroperoxides were discussed. Above 800 K, all five isomers have about the same reactivity, with a larger formation from branched alkanes of some unsaturated species, such as allene and propyne, which are known to be soot precursors.
- Wang, Zhandong,Herbinet, Olivier,Cheng, Zhanjun,Husson, Benoit,Fournet, Rene,Qi, Fei,Battin-Leclerc, Frederique
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p. 5573 - 5594
(2014/08/18)
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- Selective catalytic oxidation of alcohols, aldehydes, alkanes and alkenes employing manganese catalysts and hydrogen peroxide
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The manganese-containing catalytic system [MnIV,IV 2O3(tmtacn)2]2+ (1)/carboxylic acid (where tmtacn=N,N′,N′′-trimethyl-1,4,7-triazacyclononane), initially identified for the cis-dihydroxylation and epoxidation of alkenes, is applied for a wide range of oxidative transformations, including oxidation of alkanes, alcohols and aldehydes employing H2O2 as oxidant. The substrate classes examined include primary and secondary aliphatic and aromatic alcohols, aldehydes, and alkenes. The emphasis is not primarily on identifying optimum conditions for each individual substrate, but understanding the various factors that affect the reactivity of the Mn-tmtacn catalytic system and to explore which functional groups are oxidised preferentially. This catalytic system, of which the reactivity can be tuned by variation of the carboxylato ligands of the in situ formed [MnIII,III 2(O)(RCO2)2(tmtacn)2]2+ dimers, employs H2O2 in a highly atom efficient manner. In addition, several substrates containing more than one oxidation sensitive group could be oxidised selectively, in certain cases even in the absence of protecting groups. Copyright
- Saisaha, Pattama,Buettner, Lea,Van Der Meer, Margarethe,Hage, Ronald,Feringa, Ben L.,Browne, Wesley R.,De Boer, Johannes W.
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supporting information
p. 2591 - 2603
(2013/10/21)
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- Epoxidation of alkenes and oxidation of alcohols with hydrogen peroxide catalyzed by a manganese(v) nitrido complex
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The manganese(v) nitrido complex (PPh4)2[Mn(N)(CN) 4] is an active catalyst for alkene epoxidation and alcohol oxidation using H2O2 as an oxidant. The catalytic oxidation is greatly enhanced by the addition of just one equivalent of acetic acid. The oxidation of ethene by this system has been studied computationally by the DFT method.
- Kwong, Hoi-Ki,Lo, Po-Kam,Lau, Kai-Chung,Lau, Tai-Chu
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supporting information; experimental part
p. 4273 - 4275
(2011/06/21)
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- Efficient epoxidation of electron-deficient alkenes with hydrogen peroxide catalyzed by [γ-PW10O38V2(μ-OH) 2]3-
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A divanadium-substituted phosphotungstate, [γ-PW10O 38V2(μ-OH)2]3- (I), showed the highest catalytic activity for the H2O2-based epoxidation of allyl acetate among vanadium and tungsten complexes with a turnover number of 210. In the presence of I, various kinds of electron-deficient alkenes with acetate, ether, carbonyl, and chloro groups at the allylic positions could chemoselectively be oxidized to the corresponding epoxides in high yields with only an equimolar amount of H2O2 with respect to the substrates. Even acrylonitrile and methacrylonitrile could be epoxidized without formation of the corresponding amides. In addition, I could rapidly (min) catalyze epoxidation of various kinds of terminal, internal, and cyclic alkenes with H;bsubesubbsubesub& under the stoichiometric conditions. The mechanistic, spectroscopic, and kinetic studies showed that the I-catalyzed epoxidation consists of the following three steps: 1) The reaction of I with H;bsubesubbsubesub& leads to reversible formation of a hydroperoxo species [I;circbsubesubbsubesubbsubesubcirccircbsupesup& (II), 2) the successive dehydration of II forms an active oxygen species with a peroxo group [ 2:2-O2)]3- (III), and 3) III reacts with alkene to form the corresponding epoxide. The kinetic studies showed that the present epoxidation proceeds via III. Catalytic activities of divanadium-substituted polyoxotungstates for epoxidation with H 2O2 were dependent on the different kinds of the heteroatoms (i.e., Si or P) in the catalyst and I was more active than [γ-SiW10O38V2(μ-OH)2] 4-. On the basis of the kinetic, spectroscopic, and computational results, including those of [γ-SiW10O38V 2(μ-OH)2]4-, the acidity of the hydroperoxo species in II would play an important role in the dehydration reactivity (i.e., k3). The largest k3 value of I leads to a significant increase in the catalytic activity of I under the more concentrated conditions. Copyright
- Kamata, Keigo,Sugahara, Kosei,Yonehara, Kazuhiro,Ishimoto, Ryo,Mizuno, Noritaka
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scheme or table
p. 7549 - 7559
(2011/08/03)
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- Manganese catalyzed cis-dihydroxylation of electron deficient alkenes with H2O2
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A practical method for the multigram scale selective cis-dihydroxylation of electron deficient alkenes such as diethyl fumarate and N-alkyl and N-aryl-maleimides using H2O2 is described. High turnovers (>1000) can be achieved with this efficient manganese based catalyst system, prepared in situ from a manganese salt, pyridine-2-carboxylic acid, a ketone and a base, under ambient conditions. Under optimized conditions, for diethyl fumarate at least 1000 turnovers could be achieved with only 1.5 equiv. of H2O2 with d/l-diethyl tartrate (cis-diol product) as the sole product. For electron rich alkenes, such as cis-cyclooctene, this catalyst provides for efficient epoxidation.
- Saisaha, Pattama,Pijper, Dirk,Van Summeren, Ruben P.,Hoen, Rob,Smit, Christian,De Boer, Johannes W.,Hage, Ronald,Alsters, Paul L.,Feringa, Ben L.,Browne, Wesley R.
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supporting information; experimental part
p. 4444 - 4450
(2010/11/05)
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- A flexible nonporous heterogeneous catalyst for size-selective oxidation through a bottom-up approach
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Size does matter: The nonporous tetra-n-butylammonium salt of silicodecatungstate, synthesized through a bottom-up approach, heterogeneously catalyzes the size-selective oxidation of various organic compounds, including olefins, sulfides, and organosilanes, with aqueous H2O2 in ethyl acetate. The catalyst can be easily separated by filtration and reused several times with retention of high catalytic activity. Copyright
- Mizuno, Noritaka,Uchida, Sayaka,Kamata, Keigo,Ishimoto, Ryo,Nojima, Susumu,Yonehara, Koji,Sumida, Yasutaka
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supporting information; experimental part
p. 9972 - 9976
(2011/03/18)
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- Olefin epoxidation with hydrogen peroxide catalyzed by lacunary polyoxometalate [γ-SiW10O34(H2O) 2]4-
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The tetra-n-butylammonium (TBA) salt of the divacant Keggin-type polyoxometalate [TBA]4[γ-SiW10O34-(H 2O)2] (I) catalyzes the oxygen-transfer reactions of olefins, allylic alcohols, and sulfides with 30% aqueous hydrogen peroxide. The negative Hammett ρ+ (-0.99) for the competitive oxidation of p-substituted styrenes and the low value of (nucleophilic oxidation)/(total oxidation), Xso = 0.04, for I-catalyzed oxidation of thianthrene 5-oxide (SSO) reveals that a strongly electrophilic oxidant species is formed on I. The preferential formation of trans-spoxide during epoxidation of 3-methyl-1-cyclohexene demonstrates the steric constraints of the active site of I. The I-catalyzed epoxidation proceeds with an induction period that disappears upon treatment of I with hydrogen peroxide. 29Si and 183W NMR spectroscopy and CSI mass spectrometry show that reaction of I with excess hydrogen peroxide leads to fast formation of a diperoxo species, [TBA]4[γ-SiW10O32(O2) 2] (II), with retention of a γ-Keggin type structure. Whereas the isolated compound II is inactive for stoichiometric epoxidation of cyclooctene, epoxidation with II does proceed in the presence of hydrogen peroxide. The reaction of II with hydrogen peroxide would form a reactive species (III), and this step corresponds to the induction period observed in the catalytic epoxidation. The steric and electronic characters of III are the same as those for the catalytic epoxidation by I. Kinetic, spectroscopic, and mechanistic investigations show that the present epoxidation proceeds via III.
- Kamata, Keigo,Kotani, Miyuki,Yamaguchi, Kazuya,Hikichi, Shiro,Mizuno, Noritaka
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p. 639 - 648
(2007/10/03)
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- Activation of hydrogen peroxide through hydrogen-bonding interaction with acidic alcohols: Epoxidation of alkenes in phenol
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(Matrix presented) Electrophilic activation of hydrogen peroxide can be achieved in acidic alcohol solvents without the need for a metal catalyst. This concept is illustrated by the epoxidation of alkenes with H2O 2 employing phenol as a solvent. It is proposed that intermolecular hydrogen bonding between H2O2 and phenol activates H 2O2 for oxygen-atom transfer. In this interaction, the role of phenol is purely catalytic.
- Wahlen, Joos,De Vos, Dirk E.,Jacobs, Pierre A.
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p. 1777 - 1780
(2007/10/03)
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- A CONVENIENT SYNTHESIS OF EPOXIDES FROM OLEFINS USING MOLECULAR OXYGEN IN THE ABSENCE OF METAL CATALYSTS
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The system consisting of molecular oxygen and aldehydes (e.g., isobutyraldehyde and pivalaldehyde) oxidizes various olefins to give epoxides in high yields at 40 deg C for 3-6 h.Key Words: Epoxidation, Olefin, Molecular oxygen, Aldehyde
- Kaneda, Kiyotomi,Haruna, Shigeru,Imanaka, Toshinobu,Hamamoto, Masatoshi,Nishiyama, Yutaka,Ishii, Yasutaka
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p. 6827 - 6830
(2007/10/02)
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- THE SYNTHETIC UTILITY OF DIOXYPHOSPHORANES IN ORGANIC SYNTHESIS
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Diethoxytriphenylphosphorane, DTPP, prepared by reaction of triphenylphosphine and diethyl peroxide, is a "hydrolytically active" dioxyphosphorane which promotes mild and efficient cyclodehydration of diols to cyclic ethers in neutral media.Simple 1,2-, 1,4-, and 1,5-diols afford good yields of the cyclic ethers but 1,3-propanediol and 1,6-hexanediol give mainly 3-ethoxy-1-propanol and 6-ethoxy-1-hexanol, respectively, with DTPP.Tri- and tetra-substituted 1,2-diols afford the relatively stable 1,3,2-dioxaphospholanes in the presence of DTPP and the reaction conditions dictate whether epoxides, ketones, or allylic alcohols are obtained.
- Robinson, Philip L.,Kelly, Jeffery W.,Evans, Slayton A.
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- Diethoxytriphenylphosphorane: A Mild, Regioselective Cyclodehydrating Reagent for Conversion of Diols to Cyclic Ethers. Stereochemistry, Synthetic Utility, and Scope
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Diethoxytriphenylphosphorane, Ph3P(OEt)2, prepared by reaction of triphenylphosphine and diethyl peroxide, is a "hydrolytically active" dioxyphosphorane which promotes mild cyclodehydration (40-110 deg C) of diols to cyclic ethers in neutral media.The regioselectivity in the closure of (S)-(+)-propane-1,2-diol and (R)-(-)-pentane-1,4-diol with Ph3P(OEt)2 is high (81-82 percent) while the cyclodehydration of (S)-(+)-phenylethane-1,2-diol gives racemized (+/-)-styrene oxide.Simple 1,2-, 1,4-, and 1,5-diols afford good yields of the cyclic ethers but 1,3-propanediol and 1,6-hexanediol give mainly 3-ethoxy-1-propanol and 6-ethoxy-1-hexanol, respectively with Ph3P(OEt)2.Tri- and tetra-substituted 1,2-diols afford the relatively stable 1,3,2-dioxaphospholanes (or ?-dioxyphosphoranes) in the presence of Ph3P(OEt)2, and, depending on conditions, the 1,3,2-dioxaphospholanes are selectively converted to epoxides, ketones or allylic alcohols.The carbonyl compounds arise from 1,2-hydride and 1,2-methyl migrations; the allylic alcohols are derived from thermolytic eliminations. trans-1,2-Cyclohexanediols afford essentially quantitative yields (>95 percent) of the cyclohexene oxides while cis-1,2-cyclohexanediol gives the stable 1,3,2-dioxaphospholane with Ph3P(OEt)2 which decomposes under thermal conditions to cyclohexanone (90 percent).Ph3P(OEt)2 is extremely useful for conversion of "sensitive" 1,2-diols to acidic and /or thermally labile epoxides as demonstrated by the quantitative conversion of 9,10-dihydro-trans-9,10-phenanthrenediol to 9,10-dihydrophenanthrene oxide and 2α,10-pinanediol to 2α,10-epoxypinane.
- Robinson, Philip L.,Barry, Carey N.,Kelly, Jeffery W.,Evans, Slayton A.
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p. 5210 - 5219
(2007/10/02)
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- VANADIUM(V) PEROXO COMPLEXES. NEW VERSATILE BIOMIMETIC REAGENTS FOR EXPOXIDATION OF OLEFINS AND HYDROXYLATION OF ALKANES AND AROMATIC HYDROCARBONS.
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Novel covalent vandium(V) oxo peroxo complexes of general formula VO(O//2)(O-N)LL prime and anionic complexes with the general formula left bracket VO(O//2)(Pic)//2 right bracket ** minus A** plus L were synthesized and characterized by physicochemical methods and X-ray crystallography. The crystal structure of VO(O//2)(Pic) multiplied by (times) 2H//2O (Ia) revealed a pentagonal-bipyramidal environment, with a significant hydrogen bonding between the peroxo moiety and the equatorial water molecule. Protonated type II complexes (A** plus equals H** plus ) are dissociated in an aqueous solution and have an acidic nature (pK//a equals 1. 8) but are undissociated in a nonprotic solution, with a presumably peracid-like oxohydroperoxo structure. It is shown that vanadium peroxo complexes are effective oxidants in nonprotic solvents under mild conditions. They transform olefins to epoxides and cleavage products in a nonsteoroselective fashion (cis-2-butene gave a mixture of cis and trans epoxides). More interestingly, they hydroxylate aromatic hydrocarbons to phenols and alkanes to alcohols and ketones.
- Mimoun,Saussine,Daire,Postel,Fischer,Weiss
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p. 3101 - 3110
(2007/12/18)
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- PEROXO AND ALKYLPEROXIDIC MOLYBDENUM(VI) COMPLEXES AS INTERMEDIATES IN THE EPOXIDATION OF OLEFINS BY ALKYL HYDROPEROXIDES
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Novel oxoperoxomolybdenum(VI) complexes with the general formula MoO(O2)L2X2 (III, L = DMF, HMPT) and MoO(O2)Cl(O-N)L(IV, O-N = pyridin-2-carboxylate (Pic), 8-hydroxyquinolinate (Quin)) were prepared from the reaction of Ph3COOH or H2O2 with the corresponding cis-dioxo complexes.In the reaction with Ph3COOH both oxygen atoms of the peroxo moiety were found, by 18O labeling experiments, to come from the hydroperoxide.The X-ray crystal structure of MoO(O2)Cl(Pic)(HMPT) revealed a bipyramidal pentagonal surrounding with a rather short O-O distance (1.41 Angstroem).Complexes III were found to be more reactive than MoO(O2)2,HMPT for the epoxidation of olefins (oxidative cleavage products are consecutively formed) but react by the same cyclic peroxymetalation mechanism.The absence of reaction in the case of complexes IV illustrates the necessity for the metal to possess an equatorial releasable coordination site adjacent to the peroxo group for the oxygen transfer to occur.Catalytic oxidation of olefins using Ph3COOH gave a selectivity in oxygenated products very different from that using t-BuOOH, and 18O labeling studies showed that alkyl-peroxidic rather than peroxo species are intermediates in this latter reaction.The mechanism of epoxidation of olefins by alkyl hydroperoxides catalyzed by d0 metal complexes is discussed.
- Chaumette, Patrick,Mimoun, Hubert,Saussine, Lucien,Fischer, Jean,Mitschler, Andre
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p. 291 - 310
(2007/10/02)
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- Studies on the Autoxidation of Branched-chain Olefins. I. Autoxidation of 2-Methylalk-1-enes and 2-Methylalk-2-enes
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The products of the autoxidation of 2-methylpent-1-ene, 2-methylpent-2-ene, 2-methylhex-1-ene, 2-methylhex-2-ene, 2,4,4-trimethylpent-1-ene, and 2,4,4-trimethylpent-2-ene were analyzed by gas chromatography.The identification of the products corresponding to the individual peaks was possible by comparison with authentic substances or by preparative gaschromatographic separation and n.m.r.-spectroscopy of the isolated samples.In this way not only the epoxides and the products of the oxidative cleavage of the C=C double bond but also the allylic alcohols formed by LiAlH4-reduction of the oxidation mixtures could be identified and analyzed.From the results the compositions of the original oxidation mixtures were calculated.
- Bilas, W.,Hoebold, W.,Pritzkow, W.
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p. 125 - 141
(2007/10/02)
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- EPOXIDATION OF OLEFINS BY HYDROGEN PEROXIDE IN THE PRESENCE OF TETRACHLOROACETONE
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1,1,3,3-Tetrachloroacetone, an inexpensive, commercially available material, has been shown to be effective in mediating the hydrogen peroxide oxidation of a variety of olefins to epoxides.The chloroacetone is readily recovered for re-use.
- Stark, Charles J.
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p. 2089 - 2092
(2007/10/02)
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