- Interaction of a chirally functionalised porphyrin derivative with chiral micellar aggregates. Construction of a system with stereoselective cytochrome-P450 biomimetic activity
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The inclusion behaviour of porphyrin derivative manganese [5-(4-(carboxyphenyl-(N-L-proline)))-10-15-20-triphenylporphyrinyl] chloride 1MnCl in micellar aggregates of sodium N-dodecanoyl-L-prolinate L-SDP and of sodium dodecylsulfate SDS has been studied by means of several spectroscopic techniques. The catalytic activity in the epoxidation reaction of some test chiral olefins has been also investigated. Comparison with the case of the related manganese[5-(4-carboxyphenyl)-10-15-20-triphenylporphyrinyl] chloride 2MnCl, gave evidence that suggests the presence of a chiral functionality on the periphery of porphyrin macrocycles affects their aggregation mode within the biomembrane models. This results in the modulation of their stereoselective Cytochrome P450 biomimetic activity.
- Cantonetti, Veronica,Monti, Donato,Venanzi, Mariano,Bombelli, Cecilia,Ceccacci, Francesca,Mancini, Giovanna
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Read Online
- Molybdenum-doped epoxy resins as catalysts for the epoxidation of alkenes
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Epoxy resins were polymerised using molybdenum ethoxide and 2-ethylhexanoate as polymerisation initiators. The thermosets thus obtained are useful epoxidation catalysts for a variety of alkenes, including propene with tert-butyl hydroperoxide as an oxidant. To investigate the long-term performance of these resins, they were used repeatedly in up to 120 reactions without any reconditioning. Compared with other catalyst systems based on organic polymers, they reveal unprecedented long-term activities over periods of months so that catalyst lifetimes of years can be expected. Di-, tri-, tetra- and oligofunctional epoxy resin monomers were used and compared. The catalytic performance of the thermosets strongly depends on the resin type and the polymerisation initiator. Promising results were obtained with monomers bearing 3 or 4 glycidyl groups in combination with Mo(OEt)5 as an initiator. Metal leaching, determined by sensitive atomic spectroscopic techniques, is extremely low. Inorganic-organic hybrid catalysts can be easily prepared by adding inorganic components such as silicagel to the liquid resins, followed by polymerisation.
- Arnold, Ulrich,Fan, Fengwen,Habicht, Wilhelm,Doering, Manfred
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Read Online
- A cyclodextrin-modified ketoester for stereoselective epoxidation of alkenes
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A β-cyclodextrin-modified ketoester 2 was prepared by covalent attachment of a reactive ketone moiety to β-cyclodextrin. Treatment of 2 with Oxone as terminal oxidant would produce CD-substituted dioxirane, which can effect stereoselective alkene epoxidation. The 2-mediated (S)-α-terpineol epoxidations proceeded to give terpineol oxides in high yields, and the stereoselectivities (i.e., cis-/trans-epoxide ratio) decreased from 2.5:1 to 1:1.2 with increasing steric bulkiness of the terpenes. This steric-dependent stereoselectivity can be understood based on different binding geometries of the 2/terpene inclusion complexes according to the 1H NMR titration and 2D ROESY experiments. Enantioselective epoxidation of styrenes has also been achieved with 2 as catalyst (20-50 mol %) in aqueous acetonitrile solution, and up to 40% ee was obtained in 4-chlorostyrene epoxidation at 0 °C. Similar enantioselectivities were also obtained for the 2-mediated epoxidation of 1,2-dihydronaphthalene (37% ee), 4-chlorostyrene (36% ee), and trans-stilbene (31% ee).
- Chan, Wing-Kei,Yu, Wing-Yiu,Che, Chi-Ming,Wong, Man-Kin
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Read Online
- Tungstenocene-grafted silica catalysts for the selective epoxidation of alkenes
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Tungstenocene(IV) dichloride was successfully deposited and grafted on the surface of a commercially-available non-ordered silica support via either a liquid-phase or a dry impregnation approach. After a high-temperature calcination step, two W(VI)-grafted silica catalysts, with a metal loading around 1.2–1.7 wt.%, were obtained. They were fully characterized by physisorption and spectroscopic techniques, which evidenced well-dispersed tungsten oxide polyoxo cluster sites, for the catalyst prepared via liquid-phase grafting, and evenly dispersed larger monoclinic tungsten(VI) oxide aggregates, for the catalyst prepared via dry impregnation, respectively. Both W/SiO2 solids showed moderate to good conversion values in the epoxidation of (R)-(+)-limonene and methyl oleate (up to 68%), in the presence of aqueous hydrogen peroxide, with good selectivity to the desired epoxides (63% and 78%, respectively). The heterogeneous character of the most interesting W/SiO2 catalyst prepared via dry impregnation was confirmed by a hot centrifugation test and by an extended recovery and reuse of the solid in six catalytic runs.
- Bisio, Chiara,Gallo, Alessandro,Psaro, Rinaldo,Tiozzo, Cristina,Guidotti, Matteo,Carniato, Fabio
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p. 133 - 142
(2019/06/18)
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- Highly selective and efficient olefin epoxidation with pure inorganic-ligand supported iron catalysts
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Over the past two decades, there have been major developments in the transition iron-catalyzed selective oxidation of alkenes to epoxides; a common structure found in drug, isolated natural products, and fine chemicals. Many of these approaches have enabled highly efficient and selective epoxidation of alkenes via the design of specialized ligands, which facilitates to control the activity and selectivity of the reactions catalyzed by iron atom. Herein, we report the development of the olefin epoxidation with inorganic-ligand supported iron-catalysts using 30% H2O2 as an oxidant, and the mechanism is similar to iron-porphyrin type. With the catalyst 1, (NH4)3[FeMo6O18(OH)6], various aromatic and aliphatic alkenes were successfully transformed into the corresponding epoxides with excellent yields as well as chemo- and stereo-selectivity. This catalytic system possesses the advantages of being able to avoid the use of expensive, toxic, air/moisture sensitive and commercially unavailable organic ligands. The generality of this methodology is simple to operate and exhibits high catalytic activity as well as excellent stability, which gives it the potential to be used on an industrial scale, and maybe opens a way for the catalytic oxidation reaction via inorganic-ligand coordinated iron catalysis.
- Zhou, Zhuohong,Dai, Guoyong,Ru, Shi,Yu, Han,Wei, Yongge
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supporting information
p. 14201 - 14205
(2019/10/02)
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- Titanium-silica catalyst derived from defined metallic titanium cluster precursor: Synthesis and catalytic properties in selective oxidations
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A class of titanium-grafted mesoporous silica catalysts has been designed and prepared starting from molecularly defined metal clusters. The organosol mixture of zerovalent Ti13 clusters was impregnated onto the surface of ordered mesoporous silica molecular sieves (MCM-41 and MMM-2) and, after high-temperature calcination, an evenly dispersed non-single-site Ti(IV)nOx-like silica-supported catalyst was obtained. The catalytic solids, fully characterized by microscopic, spectroscopic and porosimetric techniques, showed standard performance in the liquid-phase epoxidation of a cyclic alkene, as limonene, but remarkably high selectivity values in the oxidative carboxylation of styrene, with tert-butylhydroperoxide and carbon dioxide in the presence of tetrabutylammonium bromide as a cocatalyst. Unprecedented high yields, up to 67%, in styrene carbonate were achieved after 24 h, under solvent-free conditions. The catalysts displayed also a noteworthy stability of the performance to repeated recovery and reuse cycles.
- Evangelisti, Claudio,Guidotti, Matteo,Tiozzo, Cristina,Psaro, Rinaldo,Maksimchuk, Nataliya,Ivanchikova, Irina,Shmakov, Alexandr N.,Kholdeeva, Oxana
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p. 393 - 401
(2017/10/05)
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- An Organotin Vanadate with Sodalite Topology and Catalytic Versatility in Oxidative Transformations
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The new coordination polymer formulated as [Et3SnVO3] (1) has been synthesized and shown by a combined single-crystal and synchrotron powder X-ray diffraction structural analysis, supported by solid-state NMR, to possess a three-dimensional network structure with the sodalite topology, formed by tetravanadate polyanions, [V4O12]4?, that are linked by Et3Sn+ spacers. The catalytic versatility of compound 1 for liquid phase organic reactions was demonstrated by applying it for the epoxidation of olefins, the oxidative dehydrogenation of alcohols, and the oxidation of benzyl alcohol to benzaldehyde and benzoic acid, using tert-butyl hydroperoxide (TBHP) as oxidant. Compound 1 acts a solid reservoir for soluble, catalytically active species, which promote high selectivities to the epoxide and carbonyl (aldehyde/ketone/acid) products. The epoxidation activity compares favorably with those reported for other organotin molybdate, tungstate and vanadate coordination polymers, and is superior to that displayed by the starting materials used for its synthesis (Et3SnBr and NH4VO3) and the metavanadate NBu4VO3.
- Gomes, Ana C.,Antunes, Margarida M.,Abrantes, Marta,Valente, Anabela A.,Paz, Filipe A. Almeida,Gon?alves, Isabel S.,Pillinger, Martyn
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p. 3481 - 3489
(2018/08/03)
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- Oxidation of alkenes and sulfides catalyzed by a new binuclear molybdenum bis-oxazoline complex
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A novel bis(oxazoline) ligand derived from 1,3-dicyanobenzene was prepared and applied as a ligand for the preparation of a new binuclear molybdenyl complex. This ligand was characterized by UV-Vis, mass, 1H NMR, and FT-IR spectroscopic methods, thermal and elemental analysis and X-ray diffraction. The molybdenum complex was prepared by the reaction of this ligand with MoO2(acac)2. The catalyst was also characterized by FT-IR, UV-Vis, and ICP spectroscopy, elemental and thermal analysis. This catalytic system was efficiently used for the oxidation of alkenes and sulfides in the presence of TBHP. The effect of different solvents and kind of oxygen donor was also studied in the oxidation reactions.
- Moshref Javadi, Maedeh,Moghadam, Majid,Mohammadpoor-Baltork, Iraj,Tangestaninejad, Shahram,Mirkhani, Valiollah,Kargar, Hadi,Tahir, Muhammad Nawaz
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- Convenient and mild epoxidation of alkenes using heterogeneous cobalt oxide catalysts
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A general epoxidation of aromatic and aliphatic olefins has been developed under mild conditions using heterogeneous CoxOy-N/C (x=1,3; y=1,4) catalysts and tert-butyl hydroperoxide as the terminal oxidant. Various stilbenes and aliph
- Banerjee, Debasis,Jagadeesh, Rajenahally V.,Junge, Kathrin,Pohl, Marga-Martina,Radnik, Joerg,Brueckner, Angelika,Beller, Matthias
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p. 4359 - 4363
(2014/05/06)
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- Niobium metallocenes deposited onto mesoporous silica via dry impregnation as catalysts for selective epoxidation of alkenes
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A series of niobium catalysts for the selective epoxidation was synthesised by post-synthesis modification of a commercial silica, starting from niobocene dichloride through solventless organometallic precursor dry impregnation (OM-DI) or conventional liquid-phase grafting technique. OM-DI showed to be cheaper, more versatile, less time-consuming and avoided the use of environmentally unfriendly chlorinated solvents. Nb-SiO2 catalysts displayed an excellent performance in the epoxidation of limonene, using aqueous hydrogen peroxide as oxidant. Niobium-silica catalysts were obtained via OM-DI for the first time in this occasion. They showed conversions up to 78% and chemoselectivity to epoxide of 98%. An unexpected regioselectivity to exocyclic epoxide was also observed.
- Gallo, Alessandro,Tiozzo, Cristina,Psaro, Rinaldo,Carniato, Fabio,Guidotti, Matteo
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- Synthesis, characterization and testing of a new V2O 5/Al2O3-MgO catalyst for butane dehydrogenation and limonene oxidation
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We report the synthesis and characterization of new V2O 5/Al2O3-MgO catalysts and their application in oxidative dehydrogenation and epoxidation reactions. The materials were prepared by wet impregnation under excess acid conditions. Anchoring of the desired species on the support occurs via an exchange reaction between the vanadium complex and surface hydroxyl groups. The IR and UV-Vis spectra of these catalysts indicate the presence of monomeric vanadium species at 5 wt% V 2O5 loading, along with small amounts of polymeric species at 5 and 10 wt% V2O5 loadings. Electron paramagnetic resonance (EPR) spectroscopy reveals the presence of ferromagnetic VO 2+ dimers following calcination at 773 K. The catalysts were then tested in two reactions, namely the gas phase oxidative dehydrogenation of n-butane under flow conditions at 773 K and the liquid phase epoxidation of limonene with H2O2. The dehydrogenation reaction gave butenes and 1,3-butadiene in moderate selectivity at 8-10% conversion. The epoxidation of limonene was less successful, giving 50-70% selectivity to the 1,2-epoxide at 10-20% conversion.
- Strassberger, Zea,Ramos-Fernandez, Enrique V.,Boonstra, Agnes,Jorna, Remy,Tanase, Stefania,Rothenberg, Gadi
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p. 5546 - 5553
(2013/06/05)
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- Oxidative functional group transformations with hydrogen peroxide catalyzed by a divanadium-substituted phosphotungstate
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A divanadium-substituted phosphotungstate TBA4[γ-PW 10O38V2(μ-OH)(μ-O)] (I, TBA = tetra-n-butylammonium) reacts with one equivalent H+ to form a bis-μ-hydroxo species [γ-PW10O38V 2(μ-OH)2]3- (I′) in organic media. The strong electrophilic oxidants such as [γ-PW10O 38V2(μ-OH)(μ-OOH)]3- (II) and [γ-PW10O38V2(μ-η2: η2-O2)]3- (III) are formed by the reaction of the bis-μ-hydroxo species with H2O2. In the presence of I and H+, H2O2-based oxidations such as (i) epoxidation of alkenes (17 examples including electron-deficient ones), (ii) hydroxylation of alkanes (11 examples), and (iii) oxidative bromination of alkenes, alkynes, and aromatics with Br- as a bromo source (12 examples including chlorination) chemo-, diastereo-, and regioselectively proceed to give the corresponding oxidized products in moderate to high yields with high efficiencies of H2O2 utilization.
- Mizuno, Noritaka,Kamata, Keigo,Yamaguchi, Kazuya
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scheme or table
p. 157 - 161
(2012/06/18)
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- An Efficient Route to Selective Bio-oxidation Catalysts: an Iterative Approach Comprising Modeling, Diversification, and Screening, Based on CYP102A1
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Perillyl alcohol is the terminal hydroxylation product of the cheap and readily available terpene, limonene. It has high potential as an anti-tumor substance, but is of limited availability. In principle, cytochrome P450 monooxygenases, such as the self-sufficient CYP102A1, are promising catalysts for the oxidation of limonene or other inert hydrocarbons. The wild-type enzyme converts (4R)-limonene to four different oxidation products; however, terminal hydroxylation at the allylic C7 is not observed. Here we describe a generic strategy to engineer this widely used enzyme to hydroxylate exclusively the exposed, but chemically less reactive, primary C7 in the presence of other reactive positions. The approach presented here turns CYP102A1 into a highly selective catalyst with a shifted product spectra by successive rounds of modeling, the design of small focused libraries, and screening. In the first round a minimal CYP102A1 mutant library was rationally designed. It contained variants with improved or strongly shifted regio-, stereo- and chemoselectivity, compared to wild-type. From this library the variant with the highest perillyl alcohol ratio was fine-tuned by two additional rounds of molecular modeling, diversification, and screening. In total only 29 variants needed to be screened to identify the triple mutant A264V/A238V/L437F that converts (4R)-limonene to perillyl alcohol with a selectivity of 97%. Focusing mutagenesis on a small number of relevant positions identified by computational approaches is the key for efficient screening for enzyme selectivity. Successive rounds of modeling (MD simulations of enzyme-substrate complexes to identify hotspots for selectivity), diversification (design of minimal library) and screening of a minimal library is shown to be an efficient approach to shift and maximize regioselectivity of CYP102A1, and thus to generate the valuable oxidation product perillyl alcohol from cheap and readily available limonene.
- Seifert, Alexander,Antonovici, Mihaela,Hauer, Bernhard,Pleiss, Juergen
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experimental part
p. 1346 - 1351
(2012/05/20)
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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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- Novel polyaniline supported cobalt catalyzed aerobic oxidation of unsaturated organic compounds
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The oxidation of organic compounds with carbon-carbon double bond with molecular oxygen under atmospheric pressure in the presence of new polyaniline supported catalyst 1 has been studied. This catalyst turned out to be efficient and selective for oxidation of some unsaturated organic compounds. Oxidation of alkenes, cycloalkenes and terpenes give corresponding epoxy derivatives, whereas organic compounds with carbon carbon double bond in benzylic position give ketones as a main product. Taylor & Francis Group, LLC.
- Pielichowski, Jan,Kowalski, Grzegorz
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experimental part
p. 105 - 111
(2011/08/03)
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- Efficient epoxidation of alkenes with sodium periodate catalyzed by reusable manganese(III) salophen supported on multi-wall carbon nanotubes
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In this paper, efficient epoxidation of alkenes catalyzed by manganese(III) salophen chloride [Mn(salophen)Cl], supported on functionalized multi-wall carbon nanotubes MWCNTs, is reported. The MWCNT was modified with 1,4-diaminobenzene, 4-aminophenol and 4-aminothiophenol and [Mn(salophen)Cl] was attached to the supports via axial ligation. The prepared catalysts were used for efficient epoxidation of alkenes with NaIO4 at room temperature. These new heterogenized catalysts were characterized by elemental analysis, FT-IR spectroscopy, diffuse reflectance UV-vis spectrophotometery and scanning electron microscopy. These heterogeneous catalysts were highly reusable in the oxidation reactions and reused several times without significant loss of their catalytic activity.
- Tangestaninejad, Shahram,Moghadam, Majid,Mirkhani, Valiollah,Mohammadpoor-Baltork, Iraj,Saeedi, Mohammad Saleh
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experimental part
p. 233 - 241
(2010/08/06)
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- SOLID PHASE REACTION SYSTEM FOR OXIDATION
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A solid phase reaction system for oxidation of an organic compound, having high industrial value in which an organic solvent exerting a reverse influence on earth environments is not necessary, reuse of a catalyst is possible, and high yield can be attained, comprising a mixture of a powdery dispersion medium and a powder of a solid catalyst for the above-described oxidation reaction, and the above-described organic compound and aqueous hydrogen peroxide,wherein the above-described organic compound, the above-described solid catalyst and the above-described aqueous hydrogen peroxide are dispersed in the above-described mixture so that they get into contact mutually.
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Page/Page column 7
(2010/05/13)
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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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- Biomimetic alkene epoxidation and alkane hydroxylation with sodium periodate catalyzed by Mn(III)-salen supported on amberlite IRA-200
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The Mn(III)-salen, containing phosphonium groups at the 5,5′-positions of the salen ligand supported on Amberlite IRA-200 via electrostatic binding was used for the oxidation of alkenes and alkanes with sodium periodate at room temperature in the presence of imidazoles as axial ligands, and the effect of solvent, different axial ligands, and various oxygen donors was investigated. This heterogenized catalyst shows high catalytic activity in alkene epoxidation and alkane hydroxylation. It showed high selectivity in the epoxidation of stilbenes, α-pinene, and (R)-(+)-limonene, and exhibits a particular ability to epoxidize linear alkenes. The stability and reusability of this new heterogenized metallo-salen complex was also investigated. The catalyst was characterized by FTIR, UV-Vis, SEM, and thermal analysis.
- Mirkhani, Valiollah,Moghadam, Majid,Tangestaninejad, Shahram,Bahramian, Bahram
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p. 1303 - 1308
(2008/09/17)
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- Studies on the cohalogenation of limonene with N-halosuccinimides and N-halosaccharins in water. A chemo- and stereoselective preparation of (1S, 2R, 4R)-1,2-epoxylimonene
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Cohalogenation of (R)-limonene with N-halosuccinimides and N-halosaccharins followed by base treatment (Na2CO3/EtOH/H2O) of the resulting halohydrins produced stereoselectively (1S, 2R, 4R)-1,2-epoxylimonene (trans-1,2-epo
- De Mattos, Marcio C.S.,Bernini, Rafael Berrelho
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p. 411 - 414
(2008/02/10)
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- [γ-1,2-H2SiV2W10O40] immobilized on surface-modified SiO2 as a heterogeneous catalyst for liquid-phase oxidation with H2O2
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An organic-inorganic hybrid support has been synthesized by covalently anchoring an N-octyldihydroimidazolium cation fragment onto SiO2 (denoted as 1-SiO2). This modified support was characterized by solid-state 13C, 29Si, and 31P NMR spectroscopy, IR spectroscopy, and elemental analysis. The results showed that the structure of the dihydroimidazolium skeleton is preserved on the surface of SiO2. The modified support can act as a good anion exchanger, which allows the catalytically active polyoxometalate anion [γ-1,2-H 2SiV2W10O40]4- (I) to be immobilized onto the support by a stoichiometric anion exchange (denoted as I/1-SiO2). The structure of anion I is preserved after the anion exchange, as confirmed by IR and 51V NMR spectroscopy. The catalytic performance for the oxidation of olefins and sulfides, with hydrogen peroxide (only one equivalent with respect to substrate) as the sole oxidant, was investigated with I/1-SiO2. This supported catalyst shows a high stereospecificity, diastereoselectivity, regioselectivity, and a high efficiency of hydrogen peroxide utilization for the oxidation of various olefins and sulfides without any loss of the intrinsic catalytic nature of the corresponding homogeneous analogue of I (i.e., the tetra-n-butylammonium salt of I, TBA-I), although the rates decreased to about half that with TBA-I. The oxidation can be stopped immediately by removal of the solid catalyst, and vanadium and tungsten species' can hardly be found in the filtrate after removal of the catalyst. These results rule out any contribution to the observed catalysis from vanadium and tungsten species that leach into the reaction solution, which means that the observed catalysis is truly heterogeneous in nature. In addition, the catalyst is reusable for both epoxidation and sulfoxidation without any loss of catalytic performance.
- Kasai, Jun,Nakagawa, Yoshinao,Uchida, Sayaka,Yamaguchi, Kazuya,Mizuno, Noritaka
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p. 4176 - 4184
(2007/10/03)
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- Chemoselective formation of 8,9-epoxy-limonene
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We present here a synthetic path to produce, exclusively, 8,9-epoxylimonene in 75% overall yields. We developed a three step synthetic route. First, the 1,2-double bond of limonene was protected by the formation of the bromo-methylether by cohalogenation
- Almeida, Queli A.R.,Jones Jr., Joel
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p. 1285 - 1290
(2007/10/03)
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- Polyoxovanadometalate-catalyzed selective epoxidation of alkenes with hydrogen peroxide
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The bis(μ-hydroxo)-bridged dioxovanadium site in [γ-1,2-H 2SiV2W10O40]4 catalyzes the epoxidation of alkenes in the presence of only one equivalent of H 2O2 with a high yield of epoxide, high efficiency of H2O2 utilization, unusual regioselectivity, and unprecedented diastereoselectivity (see picture). (Chemical Equation Presented)
- Nakagawa, Yoshinao,Kamata, Keigo,Kotani, Miyuki,Yamaguchi, Kazuya,Mizuno, Noritaka
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p. 5136 - 5141
(2007/10/03)
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- Polymer-supported manganese porphyrin catalysts - Peptide-linker promoted chemoselectivity
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Manganese porphyrin catalysts were tethered to polymer-supports via peptide linkers. The reactivity and chemoselectivity of the catalysts were assessed in the epoxidation of limonene. It was found that the inclusion of a peptide linker incorporating a donor heteroatom which could act as an axial ligand led to a supported manganese porphyrin catalyst with unprecedented selectivity and stability. The Royal Society of Chemistry 2005.
- Brule, Emilie,Hii, King Kuok,De Miguel, Yolanda R.
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p. 1971 - 1976
(2007/10/03)
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- Chemoselective epoxidation of dienes using polymer-supported manganese porphyrin catalysts
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Manganese porphyrin catalysts supported on different polymer resins were assessed in the selective epoxidation of three dienes. The recyclability of the catalysts was examined.
- Brulé, Emile,De Miguel, Yolanda R.,Hii, King Kuok
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p. 5913 - 5918
(2007/10/03)
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- Steric and electronic effects in catalytic epoxidation of cis(trans)-stilbenes and R-limonene with Mn(porphyrin)OAc-NaIO4 systems
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Effect of imidazole on conversion, stereoselectivity, and regioselectivity of epoxidation of cis(trans) stilbenes and R-limonene has been investigated with NaIO4 in the presence of Mn(TPP)OAc (TPP= meso-tetraphenylporphyrin dianion) and the sterically hindered Mn(TMP)OAc (TMP= meso-tetramesitylporphyrin dianion) catalysts in a two-phase (CH2Cl2-H2O) medium at 24+2 °C. A significant decrease has been observed in cis/trans epoxides ratio and 1,2-/8,9-epoxides ratio in the oxidation of cis-stilbene and R-limonene, respectively, in the presence of imidazole.
- Tayebee, Reza
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p. 2190 - 2193
(2007/10/03)
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- Hydrogen-peroxide epoxidation of natural olefins catalyzed by a dinuclear manganese complex
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The complex of Mn(IV) with the macrocyclic N-containing ligand 1,4,7-trimethyl-1,4,7-triazacyclononane (L) [L2Mn2O 3](PF6)2 catalyzes epoxidation of (+)-limonene in CH3CN solution at room temperature. Adding CH3COOH accelerates the reaction. The products are isomers of limonene epoxide with predominance of that with an epoxified ring double bond. Epoxidation of α- and β-pinene by this system is less effective, apparently due to extensive steric shielding of the double bonds in the pinenes.
- Mandelli,Voitiski,Schuchardt,Shul'pin
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p. 243 - 245
(2007/10/03)
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- Mn (Br8TPPS) supported on Amberlite IRA-400 as a robust and efficient catalyst for alkene epoxidation and alkane hydroxylation
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Manganese (III) meso-tetrakis(p-sulfonatophenyl)-β-octabromoporphyrin (supported on Amberlite IRA-400 [Mn(Br8TPPS)-Ad-400] is a robust and efficient catalyst for epoxidation of alkenes and hydroxylation of alkanes with sodium periodate at room temperature.
- Tangestaninejad,Habibi,Mirkhani,Moghadam
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p. 264 - 270
(2007/10/03)
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- Manganese(III) porphyrin supported on polystyrene as a heterogeneous alkene epoxidation and alkane hydroxylation catalyst
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Carboxymethylated crosslinked polystyrene resin [poly(4-styrylmethylacylchloride) (PSA)] support have been used to covalently attach manganese(III) tetrakis(4-aminophenyl)-porphyrin. This catalyst was found to be efficient for alkene epoxidation and alkane hydroxylation by sodium periodate. This new hydrogenised catalyst is of high stability and reusability.
- Tangestaninejad,Habibi,Mirkhani,Moghadam
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p. 3331 - 3337
(2007/10/03)
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- Preparation of an insoluble polymer-supported Mn (III) porphyrin and its use as a new alkene epoxidation and alkane hydroxylation catalyst
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An easy and effective method to prepare a new supported Mn(III)-porphyrin by immobilisation of Mn(III)-5,10,15, 20-Tetrakis(p-sulfonatophenyl)porphyrin, [Mn(TPPS)], on poly(4-styrylmethyl)pyridinium chloride (PSMP) is reported. This catalyst was found to be efficient for catalysing alkene epoxidation and alkane hydroxylation with sodium periodate. This new heterogenised metalloporphyrin catalyst is of high stability and reusability.
- Tangestaninejad,Habib,Mirkhani,Moghadam
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p. 444 - 445
(2007/10/03)
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- A novel epoxidation reaction of olefins using a combination of chloramine-M, benzaldehyde, and benzyltriethylammonium chloride
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A combination of Chloramine-M (CH3SO2NClNa), benzaldehyde, and benzyltriethylammonium chloride (BTEAC) was found to epoxidize a wide range of olefins. While epoxidation of trans-olefins provided exclusively trans- epoxides, cis-olefins (cis-stilbene, cis-β-methylstyrene, and 4-cis-octene) gave trans-epoxides as major products. Good to excellent diastereoselectivities were obtained for epoxidation of two substituted cyclohexenes. Chloramine-T was found to give a slower reaction than Chloramine-M. cis-N-Sulfonyloxaziridine D is proposed to be the epoxidizing agent in this novel epoxidation reaction on the basis of the mechanistic studies.
- Yang, Dan,Zhang, Chi,Wang, Xue-Chao
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p. 4039 - 4043
(2007/10/03)
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- Steel-promoted oxidation of olefins in supercritical carbon dioxide using dioxygen in the presence of aldehydes
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Oxidation of olefins occurs effectively in supercritical carbon dioxide as the reaction medium with dioxygen as the primary oxidant and aldehydes as sacrificial co-oxidants. No catalyst is required, but the reaction is promoted by the stainless steel of the reactor walls. Depending on the substrate, vinylic oxidation or epoxidation can be the prevailing pathway. Epoxidation is particularly effective for substrates with internal double bonds and for long-chain terminal olefins.
- Loeker, Frank,Leitner, Walter
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p. 2011 - 2015
(2007/10/03)
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- Polystyrene-bound Manganese(III) Porphyrin as a Heterogeneous Catalyst for Alkene Epoxidation
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The manganese(III) complex of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin covalently bound to crosslinked chloromethylated polystyrene can act as an efficient heterogeneous catalyst for alkene epoxidation by sodium periodate.
- Tangestaninejad, Shahram,Mirkhani, Valiollah
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p. 788 - 789
(2007/10/03)
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- Efficient olefin epoxidation and alkane hydroxylation using sulfonated manganese(III) porphyrin supported on IRA-900 ion-exchange resin
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Sulfonated manganese(III) tetraphenylporphyrin supported on Amberlite IRA-900 ion exchange resin (MnTPPS-Ad) has been found to be a highly active and stable catalyst for olefin epoxidation and alkane hydroxylation by sodium periodate.
- Tangestaninejad,Moghadam
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p. 427 - 432
(2007/10/03)
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- Efficient and selective epoxidation of alkenes with sodium periodate using supported manganese porphyrins under ultrasonic irradiation
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Epoxides are readily obtained in high yields and good selectivities by ultrasonic irradiation of alkenes and sodium periodate in the presence of catalytic amounts of manganese porphyrins supported on polyvinylpyridine and IRA-900 ion-exchange resin.
- Tangestaninejad, Shahram,Mirkhani, Valiollah
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p. 1265 - 1266
(2007/10/03)
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- Stoichiometric enantioselective alkene epoxidation with a chiral dioxoruthenium(VI) D4-porphyrinato complex
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A dioxoruthenium(VI) complex containing a D4-porphyrinato ligand por* {H2por* = 5,10,15,20-tetrakis-[(1S,4R,5R,8S)-1,2,3,4,5,6,7,8-octahydro-1,4:5,8- dimethanoanthracen-9-yl]porphyrin} has been prepared by oxidation of its ruthenium(II) carbonyl precursor with m-chloroperoxybenzoic acid and characterised by spectroscopic methods. The [RuVI(por*)O2] complex undergoes enantioselective epoxidation of alkenes and the highest enantiomeric excess (ee) attainable is 77%. In the presence of pyrazole the complex transforms to [RuIV(por*)(pz)2] when reacting with alkenes. The kinetics of the epoxidation of para-substituted styrenes has been studied. The experimental rate law is - d[RuVI]/dt = k2[RuVI][alkene]. The second order rate constants k2 at 25°C fall in a narrow range, 2.1 × 10-3-9.7 × 10-3 dm3 mol-1 s-1. Comparison of the Hammett plot (log krel vs. σ*) with those for achiral analogues [RuVI(tpp)O2] (H2tpp = 5,10,15,20-tetraphenylporphyrin) and [RuVI(oep)O2] (H2oep = 2,3,7,8,12,13,17,18-octaethylporphyrin) suggests the formation of a radical intermediate for the alkene epoxidations. Both [RuII(por*)(CO)(EtOH)] and [RuVI(por*)O2] were examined for enantioselective catalysis. Enantioselectivities of the stoichiometric and catalytic reactions showed good correlation. There is no solvent dependence on enantioselectivity when changing the solvent from dichloromethane to benzene.
- Lai, Tat-Shing,Kwong, Hoi-Lun,Zhang, Rui,Che, Chi-Ming
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p. 3559 - 3564
(2007/10/03)
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- Probing for steric and electronic effects in diastereoselective dioxirane epoxidations compared to the oxygen transfer by peroxy acids
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The spiro transition state for the oxygen transfer by dioxiranes is substantiated by the fact that no enhanced steric effects are observed when dioxiranes with alkyl groups of different size are employed, as manifested by the same (within the experimental error) diastereoselectivities in the epoxidation of 2-menthene and 1,3-dimethylcyclohexene for different dioxiranes. The π-facial selectivity (anti attack) in the epoxidation of the acetate and the methyl and trimethylsilyl ether derivatives of 2-cyclohexenol derives from steric interactions, whereas a pronounced electronic effect (electrostatic repulsion) is held responsible for the high anti selectivity of peroxides such as ascaridol and 3-hydroperoxycyclohexene. Quite generally, dioxiranes display only slightly higher diastereoselectivities than mCPBA in sterically controlled epoxidations of cycloalkenes. VCH Verlagsgesellschaft mbH, 1997.
- Adam, Waldemar,Paredes, Rodrigo,Smerz, Alexander K.,Veloza, L. Angela
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p. 547 - 551
(2007/10/03)
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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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p. 3969 - 3976
(2007/10/03)
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- A New Titanium-Silica Catalyst for the Epoxidation of Non-functionalized Alkenes and Allylic Alcohols
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Silica treated with Ti(OPri)4 is an efficient catalyst for the tert-butyl hydroperoxide epoxidation of nonfunctionalized alkenes and allylic alcohols at room temperature; the reactivity of the olefinic substrate depends on the structure, which allows the selective epoxidation of compounds containing different types of double bonds; 1H and 13C CP-MAS NMR shows the presence of isopropoxide groups in the catalyst.
- Fraile, Jose M.,Garcia, Jose I.,Mayoral, Jose A.,Menorval, Louis C. de,Rachdi, Ferid
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p. 539 - 540
(2007/10/02)
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- Regioselectivity in Epoxidation of Dienes on PW11CoO395- by Molecular Oxygen in the Presence of Aldehyde
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The regioselectivity comparable to those on moderately hindered Mn(TTMPP)Cl with NaOCl was found for the epoxidation of (R)-(+)-limonene, 4-vinyl-1-cyclohexene, and 1-methyl-1,4-cyclohexadiene on mono-cobalt-substituted Keggin-type heteropolytungstate by molecular oxygen in the presence of aldehydes.
- Mizuno, Noritaka,Tateishi, Masaki,Hirose, To-oru,Iwamoto, Masakazu
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p. 1985 - 1986
(2007/10/02)
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- Monooxygenase-like Oxidation of Hydrocarbons by H2O2 Catalyzed by Manganese Pophyrins and Imidazole: Selection of the Best Catalytic System and Nature of the Active Oxygen Species
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Fe and Mn porphyrins alone are almost unable to catalyze cyclooctene epoxidation or cyclooctane hydroxylation by H2O2.In the presence of imidazole, Mn(III) porphyrins, and particularly Mn(TDCPP)Cl, are much better catalysts than Fe porphyrins for oxygen-atom transfer from H2O2 to hydrocarbons.From a study of various Mn porphyrin catalysts and nitrogen base cocatalysts, the most efficient system that has been selected involves Mn(TDCPP)Cl in the presence of 10 - 20 equiv of imidazole.This system leads to high yields of alkene epoxidation (90 - 100 percent in less than 1 h at room temperature).Epoxidation of 1,2-dialkylethylenes is stereospecific and corresponds to a syn addition of an oxygen atom to the double bond.This system also leads to the oxidation by H2O2 of various alkanes such as cyclohexane, cyclooctane, adamantane, ethylbenzene, or tetralin, with formation of the corresponding alcohols and ketones in yields between 40 and 80 percent.The Mn(TDCPP)Cl-imidazole-PhIO and Mn(TDCPP)Cl-imidazole-H2O2 systems exhibit the following: (i) identical stereospecificities for the epoxidation of stilbene and hex-2-ene, (ii) identical regioselectivities for the epoxidation of iosoprene and limonene as well as for the hydroxylation of n-heptane, and (iii) almost identical chemoselectivities for the oxidation of cyclohexene and of mixtures of cyclooctane and cyclooctene.This indicates that very similar, if not identical, high-valent Mn-oxo intermediates are the active oxygenating species in both systems.Thus, thanks to the presence of imidazole, it is possible to perform efficient biomimetic monooxygenations of hydrocarbons by using the Mn(TDCPP)Cl catalyst and H2O2 instead of PhIO as the oxygen-atom donor.
- Battioni, P.,Renaud, J. P..,Bartoli, J. F.,Reina-Artiles, M.,Fort, M.,Mansuy, D.
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p. 8462 - 8470
(2007/10/02)
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