- Iron(III)-substituted polyoxotungstates immobilized on silica nanoparticles: Novel oxidative heterogeneous catalysts
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Silica nanoparticles supporting polyoxometalates (POMs), namely an iron(III) mono-substituted Keggin-type polyoxotungstate of formula α-[PW11FeIII(H2O)O39] 4- and a sandwich-type tungstophosphate with the formula B-α-[(PW9O34)2FeIII 4(H2O)2]6- were synthesized. The POM/SiO2 nanocomposites were obtained by alkaline hydrolysis of tetraethoxysilane using a reverse micelle and sol-gel technique. The spectroscopic studies suggest that the POMs were successfully immobilized on the silica nanoparticles. The catalytic activity of POM/SiO2 nanomaterials was tested in the epoxidation of geraniol using H 2O2 as oxygen donor. The α-[PW11Fe III(H2O)O39]4-/SiO2 nanocomposite was the most efficient catalyst with high geraniol conversion and good regioselectivity for 2,3-epoxygeraniol.
- Sousa, Joana L.C.,Santos, Isabel C.M.S.,Sim?es, Mário M.Q.,Cavaleiro, José A.S.,Nogueira, Helena I.S.,Cavaleiro, Ana M.V.
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- New heptacoordinate tungsten(II) complexes with α-diimine ligands in the catalytic oxidation of multifunctional olefins
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New tungsten(II) and molybdenum(II) heptacoordinate complexes [MX2(CO)3(LY)] (MXLy: M = W, Mo; X = Br, I; LY = C5H4NCY = N(CH2)2CH3 with Y = H (L1), Me (L2), Ph (L3)) were synthesized and characterized by spectroscopic techniques and elemental analysis. The two tungsten complexes WXL1 (X = Br, I) were also structurally characterized by single crystal X-ray diffraction. The metal coordination environment is in both a distorted capped octahedron. The complexes with L1 and L2 ligands were grafted in MCM-41, after functionalization of the ligands with a Si(OEt)3 group. The new materials were characterized by elemental analysis, N2 adsorption isotherms, 29Si MAS and 13C MAS NMR. The tungsten(II) complexes and materials were the first examples of this type reported. All complexes and materials were tested as homogeneous and heterogeneous catalysts in the oxidation of multifunctional olefins (cis-hex-3-en-1-ol, trans-hex-3-en-1-ol, geraniol, S-limonene, and 1-octene), with tert-butyl hydroperoxide (TBHP) as oxidant. The molybdenum(II) catalyst precursors are in general very active, reaching 99% conversion and 100% selectivity in the epoxidation of trans-hex-3-en-1-ol. Their performance is comparable with that of the [Mo(η3-C3H5)X(CO)2(LY)] complexes, but it increases with immobilization. On the other hand, most of the W(II) complexes display an activity similar or inferior to that of the Mo(II) analogues and it decreases after they are supported in MCM-41. DFT calculations show that tungsten complexes and iodide ligands are more easily oxidized from M(II) to M(VI) than molybdenum ones, while the energies of relevant species in the catalytic cycle are very similar for all complexes, making the theoretical rationalization of experimental catalytic data difficult.
- Vasconcellos-Dias, Maria,Nunes, Carla D.,Félix, Vítor,Brand?o, Paula,Calhorda, Maria José
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- Catalytic activity of molybdenum(II) complexes in homogeneous and heterogeneous conditions
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The new complexes [MoBr(η3-C3H5)(CO)2(L)2] (C1) and [MX2(CO)3(L)2] (M = Mo(II), X = I (C2); M = Mo(II), X = Br (C3); M = W(II), X = I (C4); M = W(II), X = Br (C5)) were synthesized by reaction of 2-amino-1,3,4-thiadiazole (L) with [MoBr(η3-C3H5)(CO)2(NCCH3)2] (1), [MoI2(CO)3(CH3CN)2](M = Mo (2); M = W (4)), or [MoBr2(CO)3(CH3CN)2](M = Mo (3); M = W (5)) in 2:1 ratio. The five complexes were immobilized in MCM-41, yielding the materials MCM-Cn (n = 1-5), and C1 was also immobilized in silica gel (Silica-C1) and in a polyhedral oligomeric silsesquioxane (Cube-C1). Complexes and materials were fully characterized by spectroscopic techniques and elemental analysis. DFT calculations showed that several C1 isomers should coexist. The as synthesized and supported complexes were tested as catalysts on the oxidation of geraniol, cis-hex-3-en-1-ol, trans-hex-3-en-1-ol, (S)-limonene, and 1-octene. The conversions and TOF significantly depend on the complex and the nature of the substrate. The general conclusions are (i) complex C1 has the highest activity; (ii) tungsten complexes C4 and C5 are more active than the molybdenum analogues; (iii) the immobilization of the catalysts improves the performance; and (iv) silica gel and the polyhedral oligomeric silsesquioxane supports modify the selectivity, leading to products different from the one obtained with MCM for specific substrates.
- Vasconcellos Dias, Maria,Saraiva, Marta S.,Ferreira, Paula,Calhorda, Maria José
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p. 1465 - 1478
(2015/05/13)
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- An immobilized imidazolyl manganese porphyrin for the oxidation of olefins
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A new catalytic system based on an immobilized imidazolyl manganese porphyrin for the oxidation of olefins is presented. Merrifield resin (MR) and functionalized silica gel (SG) were chosen as supports. The results indicate that the MR system shows high reaction rates, high efficiency with hydrogen peroxide as oxidant and good recyclability up to four times, without a dramatic loss in the catalytic efficiency. The catalytic behavior seems to be strongly influenced by the immobilization reaction conditions. The oxidation reactions performed for cis-cyclooctene, styrene, cyclohexene and geraniol give the corresponding epoxides, with very high selectivity, when the MR system is used. Some considerations concerning the high efficiency of the MR system are put forward.
- De Paula, Rodrigo,Santos, Isabel C.M.S.,Sim?es, Mário M.Q.,Neves, M. Gra?a P.M.S.,Cavaleiro, José A.S.
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p. 156 - 166
(2015/05/13)
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- A new halide-free efficient reaction-controlled phase-transfer catalyst based on silicotungstate of [(C18H37)2(CH 3)2N]3[SiO4H(WO5) 3] for olefin epoxidation, oxidation of sulfides and alcohols with hydrogen peroxide
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A new reaction-controlled phase-transfer catalyst based on silicotungstate of [(C18H37)2(CH3) 2N]3[SiO4H(WO5)3] for oxidation of hydrocarbons is developed. The catalyst is a new heteropoly compound with silicon as heteroatom, which is different to the previously reported reaction-controlled phase transfer catalysts that were composed of quaternary ammonium heteropolyoxotungstates of [π-C5H 5N(CH2)15CH3]3[PW 4O16] and [π-C5H5N(CH 2)15CH3]3[PW4O 32] with phosphorus as heteroatom. The oxidation of various alkenes (such as linear terminal olefins, internal olefins, cyclic olefins and unactivated alkenes) to epoxides, sulfides to sulfoxides and sulfones, alcohols to carbonyl compounds, are successfully catalyzed by this recyclable and environmentally benign catalyst using H2O2 as oxidant and ethyl acetate as solvent. This catalyst is not only capable of catalyzing homogeneous oxidation of organic substrates with unique reaction-controlled phase-transfer character, but also avoids the use of toxic solvents. The catalyst could be easily recovered and reused after reaction, and the epoxidation of cyclohexene was performed twenty times without obvious loss in activity. The fresh catalyst and the used one were characterized by ICP, IR, UV-vis, 29Si MAS NMR and 183W NMR in detail. the Partner Organisations 2014.
- Ma, Baochun,Zhao, Wei,Zhang, Fuming,Zhang, Yingshuai,Wu, Songyun,Ding, Yong
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p. 32054 - 32062
(2014/08/18)
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- New Mo(II) complexes in MCM-41 and silica: Synthesis and catalysis
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The new complexes [MoI2(CO)3(L1)] (1) and [MoI2(CO)3(L2)] (2) were prepared from reaction of [MoI2(CO)3(NCMe)2] with the ligands 2-(2′-hydroxyphenyl)imidazoline (L1), and 2-(2′- hydroxyphenyl) benzimidazole (L2). These complexes were immobilized in MCM-41 and in silica gel, by grafting (3- chloropropyl)trimethylsilane on the surface of the materials and allowing it to react with [MoI2(-CO) 3(L1)] (1) or [MoI2(CO)3(L 2)] (2). All the molybdenum derivatives were characterized by NMR and FTIR spectroscopies, which showed coordination of L1 and L 2 in neutral form. The structure of the MCM materials was analyzed by powder X-ray diffraction and nitrogen adsorption isotherms. The catalytic activity of the complexes and materials was tested in several substrates (cis-cyclooctene, styrene, 1- octene, R-(+)limonene, geraniol, cis-hex-3-en-1-ol and trans-hex-2-en-1-ol), using tert-butylhydroperoxide (TBHP) as oxidant. Complexes 1 and 2 were in general the more active catalysts and 100% selective towards the epoxide of cis-cyclooctene. Complex 1 immobilized in silica (Si-Pr-1) was the best material, showing higher conversion than 1 in the oxidation of R-(+)limonene, with comparable selectivity towards the ring epoxide.
- Saraiva, Marta S.,Fernandes, Cristina I.,Nunes, Teresa G.,Nunes, Carla D.,Calhorda, Maria José
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p. 443 - 452
(2014/03/21)
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- Mo(II) complexes of 8-aminoquinoline and their immobilization in MCM-41
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Two new Mo(II) complexes [MoBr(η3-C3H 5)(CO)2(8-aq)] (1) and [MoI2(CO) 3(8-aq)] (2) containing the bidentate 8-aminoquinoline ligand (8-aq) were synthesized and characterized. They were immobilized in MCM-41. A 3-iodopropyltrimethoxysilane spacer reacted both with the surface, through the silane, and through the other end, with the coordinated 8-aq of complexes 1 and 2, leading to an immobilized form of the complex (MCM-Pr-1,2). In an alternative route, 8-aq reacted with 3-iodopropyltrimethoxysilane to form a new ligand L1, which could be supported in the MCM-41 and then react with the metal precursors to afford (MCM-L1-1,2). The complexes and the materials were characterized using FTIR and NMR spectroscopies, and the structure of the materials was checked with powder X-ray diffraction and nitrogen adsorption isotherms. The first synthetic procedure was less efficient in terms of metal load inside the channels of the materials. The complexes and the new materials were tested as catalytic precursors in the epoxidation of cis-cycloctene, styrene, 1-octene, R-(+)limonene, geraniol, cis-3-hexene-1-ol and trans-2-hexene-1-ol, using tert-butylhydroperoxide (TBHP) as oxidant. Although almost all the catalysts were 100% selective toward the epoxide, the conversions were in general poor. The best catalyst was complex 1, but the conversions dropped after immobilization. Conversions could be a bit improved by a careful choice of reaction conditions, the most effective being the absence of added solvent (the substrate acted as solvent).
- Saraiva, Marta S.,Nunes, Carla D.,Nunes, Teresa G.,Calhorda, Maria José
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p. 172 - 182
(2013/05/21)
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- Catalytic performance of a boron peroxotungstate complex under homogeneous and heterogeneous conditions
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The preparation and characterization (FT-IR, FT-Raman, 11B MAS NMR, diffuse reflectance, elemental analysis) of a novel boron peroxotungstate (BTBA)4H[BW4O24] (BTBA = benzyltributylammonium) is reported, along with its use in the homogeneous oxidation of cis-cyclooctene, geraniol, linalool and (-)-carveol with H 2O2 as oxidant and acetonitrile as solvent. High catalytic activity was registered for all the substrates studied under homogeneous conditions, namely 99% of conversion of geraniol after 2 h, 93% for linalool after 5 h, 74% for cis-cyclooctene after 6 h, and 100% for (-)-carveol after 2 h of reaction. Some oxidation studies were carried out with the Venturello complex, [PW4O24]3-, in the same conditions. Furthermore, the boron peroxotungstate (BW4) was immobilized using two different strategies: (a) BW4 anchored into a functionalized silica (aptesSiO2) giving BW4@aptesSiO2 and (b) BW4 encapsulated on a metal organic framework, commonly referred as MIL-101, giving BW4@MIL-101. The catalytic activity of both heterogeneous materials was investigated for geraniol oxidation and the results were compared with those obtained with BW4 under homogeneous conditions. The encapsulated boron peroxotungstate (BW4@MIL-101) gave rise to the best results, reaching complete conversion of geraniol after 3 h of reaction and 78% selectivity for 2,3-epoxygeraniol. Additionally, this heterogeneous catalyst could be reused without appreciable loss of catalytic activity, affording similar 2,3-epoxygeraniol selectivity. The heterogeneous catalysts' stability was also investigated after the oxidation reactions by different characterization techniques.
- Santos, Isabel C.M.S.,Balula, Salete S.,Sim?es, Mário M.Q.,Cunha-Silva, Luís,Neves, M. Gra?a P.M.S.,De Castro, Baltazar,Cavaleiro, Ana M.V.,Cavaleiro, José A.S.
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- Vanadyl arsenates as catalysts for selective oxidation of organic sulfides and alkenes
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Two vanadyl arsenates templated with ethylendiamonium (EnVAs) and piperazonium (PipVAs) were evaluated as catalysts for the oxidation of thioethers and alkenes, using H2O2 and t-butyl hydroperoxide (TBHP) as oxidants. The intrinsic activity of EnVAs was higher than that of PipVAs for the oxidation of sulfides. Similar results were obtained when using either H2O2 or TBHP as oxidants. However, the sterical effects were enhanced when TBHP was used and higher selectivities towards sulfoxides were achieved with this oxidant. The catalytic activity of the V-based materials in the epoxidation of simple alkenes and allylic alcohols was assessed. Upon reuse, both materials show no significant decrease in their catalytic properties.
- Berrocal, Teresa,Larrea, Edurne S.,Iglesias, Marta,Arriortua, Maria I.
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scheme or table
p. 176 - 182
(2011/03/23)
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- Catalytic asymmetric epoxidation
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The present invention relates to the synthesis of chiral epoxides via a catalytic asymmetric oxidation of olefins. Additionally, the methodology provides a method of asymmetrically oxidizing sulfides and phosphines. This asymmetric oxidation employs a catalyst system composed of a metal and a chiral bishydroxamic acid ligand, which, in the presence of a stoichiometric oxidation reagent, serves to asymmetrically oxidize a variety of substrates.
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Page/Page column 18-19
(2010/02/12)
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- Chiral hydroperoxides as oxygen source in the catalytic stereoselective epoxidation of allylic alcohols by sandwich-type polyoxometalates: Control of enantioselectivity through a metal-coordinated template
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The epoxidation of allylic alcohols is shown to be efficiently and selectively catalyzed by the oxidatively resistant sandwich-type polyoxometalates, POMs, namely [WZnM2(ZnW9O 34)2]q- [M = OV(IV), Mn(II), Ru(III), Fe(III), Pd(II), Pt(II), Zn(II); q = 10-12], with organic hydroperoxides as oxygen source. Conspicuous is the fact that the nature of the transition metal M in the central ring of polyoxometalate affects significantly the reactivity, chemoselectivity, regioselectivity, and stereoselectivity of the allylic alcohol epoxidation. For the first time, it is demonstrated that the oxovanadium(IV)-substituted POM, namely [ZnW(VO)2(ZnW 9O34)2]12-, is a highly chemoselective, regioselective, and also stereoselective catalyst for the clean epoxidation of allylic alcohols. A high enantioselectivity (er values up to 95:5) has been achieved with [ZnW(VO)2(ZnW9O 34)2]12- and the sterically demanding TADOOL-derived hydroperoxide TADOOH as regenerative chiral oxygen source. Thus, a POM-catalyzed asymmetric epoxidation of excellent catalytic efficiency (up to 42 000 TON) has been made available for the development of sustainable oxidation processes. The high reactivity and selectivity of this unprecedented oxygen-transfer process are mechanistically rationalized in terms of a peroxy-type vanadium(V) template.
- Adam, Waldemar,Alsters, Paul L.,Neumann, Ronny,Saha-Moeller, Chantu R.,Seebach, Dieter,Beck, Albert K.,Zhang, Rui
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p. 8222 - 8231
(2007/10/03)
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- A highly chemoselective, diastereoselective, and regioselective epoxidation of chiral allylic alcohols with hydrogen peroxide, catalyzed by sandwich-type polyoxometalates: Enhancement of reactivity and control of selectivity by the hydroxy group through metal-alcoholate bonding
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Sandwich-type polyoxometalates (POMs), namely [VZnM2(ZnW9O34)2]q- [M = Mn(II), Ru(III), Fe(III), Pd(II), Pt(II), Zn(II); q = 10-12], are shown to catalyze selectively the epoxidation of chiral allylic alcohols with 30% hydrogen peroxide under mild conditions (ca. 20 °C) in an aqueous/organic biphasic system. The transition metals M in the central ring of polyoxometalate do not affect the reactivity, chemoselectivity, or stereoselectivity of the allylic alcohol epoxidation by hydrogen peroxide. Similar selectivities, albeit in significantly lower product yields, are observed for the lacunary Keggin POM [PW11O39]7-, in which a peroxotungstate complex has been shown to be the active oxidizing species. All these features support a tungsten peroxo complex rather than a high-valent transition-metal oxo species operates as the key intermediate in the sandwich-type POM-catalyzed epoxidations. On capping of the hydroxy functionality through acetylation or methylation, no reactivity of these hydroxy-protected substrates [1a(Ac) and 1a(Me)] is observed by these POMs. A template is proposed to account for the marked enhancement of reactivity and selectivity, in which the allylic alcohol is ligated through metal - alcoholate bonding, and the H2O2 oxygen source is activated in the form of a peroxotungsten complex. 1,3-Allylic strain promotes a high preference for the threo diastereomer and 1,2-allylic strain a high preference for the erythro diastereomer, whereas tungsten - alcoholate bonding furnishes high regioselectivity for the epoxidation of the allylic double bond. The estimated dihedral angle α of 50 - 70° for the metal - alcoholate-bonded template of the POM/H2O2 system provides the best compromise between 1,2A and 1,3A strain during the oxygen transfer. In contrast to acyclic allylic alcohols 1, the M-POM-catalyzed oxidation of the cyclic allylic alcohols 4 by H2O2 gives significant amounts of enone.
- Adam, Waldemar,Alsters, Paul L.,Neumann, Ronny,Saha-Moeller, Chantu R.,Sloboda-Rozner, Dorit,Zhang, Rui
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p. 1721 - 1728
(2007/10/03)
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- Oxidation of α-hydroxy containing monoterpenes using titanium silicate catalysts: Comments on regioselectivity and the role of acidity
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The regioselective epoxidation of monoterpenes in the liquid phase has been studied using the titanosilicates TS-1 and TiAlβ. A range of oxidants (hydrogen peroxide, tert-butyl hydroperoxide and urea-hydrogen peroxide complex) have been studied in detail. The allylic alcohols linalool and geraniol have been studied alongside the non-allylic alcohol citronellol and the diene dihydromyrcene to help determine the role of the hydroxy group in these reactions. Dihydromyrcene is selectively epoxidised at the more electron rich double bond regardless of the catalyst-oxidant-solvent system used. Geraniol can undergo allylic assisted epoxidation with TS-1-acetone-hydrogen peroxide and TiAlβ-acetonitrile-urea-hydrogen peroxide. With TiAlβ-hydrogen peroxide-methanol, the reaction shows an induction period in the conversion of geraniol which is considered to be characteristic of the autocatalytic removal of titanium from the catalyst framework. Reactions with citronellol show this titanium removal is entirely due to the presence of the allylic alcohol moiety. Finally, epoxidation of linalool and the subsequent in situ conversion of the epoxide to the furano- and pyrano-oxides were studied. The ratio of furano- and pyrano-oxides formed was considered to be due, in part, to the pore geometry and the Br?nsted acidity of the catalyst.
- Schofield, Lee J.,Kerton, Owain J.,McMorn, Paul,Bethell, Donald,Ellwood, Simon,Hutchings, Graham J.
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p. 1475 - 1481
(2007/10/03)
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- Solvent effects in the regio- and diastereselective epoxidations of acyclic allylic alcohols by dimethyldioxirane: hydrogen bonding as evidence for a dipolar transition state
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A mechanistically significant solvent effect is observed in the regioselectivity of the geraniol epoxidation by dimethyldioxirane.In hydrogen bonding solvents (MeOH), the 6,7-epoxide is preferred over the 2,3-epoxide (74:26), which reveals that the more nucleophilic 6,7 double bond (the 2,3 double bond is inductively deactivated by the allylic hydroxy group) is preferentially attacked by the electrophilic dimethyldioxirane.In MeOH, both regioisomeric dipolar transition states are equally well stabilized by interaction through intermolecular hydrogen bonding with solvent molecules.In the nonpolar CCl4, intramolecular hydrogen bonding with the allylic hydroxy functionality favors attack at the 2,3-double bond and proportionally more 2,3-epoxide is formed.Similarly, also the ?-facial selectivity in the dimethyldioxirane epoxidation of methyl-substituted cchiral acyclic allylic alcohols is controlled by intermolecular versus intramolecular hydrogen bonding.Thus, higher threo selectivities are obtained in the nonpolar CCl4 by stabilization of the diastereomeric transition state with minimal allylic strain through intramolecular hydrogen bonding with the allylic hydroxy group.The geometry of the dipolar transition state for the dimethyldioxirane epoxidations is similar to that of m-CPBA, but with apparently a slightly larger (ca. 130 deg) dihedral angle α to relieve 1,2-allylic strain.
- Adam, Waldemar,Smerz, Alexander K.
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p. 3506 - 3510
(2007/10/03)
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- Oxidation of Alkenes and Sulfides with Transition Metal Catalysts
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Alkenes and sulfides were oxidized with transition-metal catalysts.The oxidant sources include molecular dioxygen, air and iodosylbenzene.The metal ions Mn(III), Fe(III), Co(II) and Ni(II) were used.The catalysts 1-18 of 1,3-dioxo-, β-ketoimine- or salen-types were prepared and their efficacy was examined. 1,2-Dihydronaphthalene is most efficiently epoxidized with O2/Me2CHCHO or PhIO in the presence of Mn(III)-salen catalysts.The Ni(II)-, Co(II)- and Fe(III)-catalysts of either β-ketoimine- or salen-types are useful for epoxidation of styrene, (E)-stilbene and (E)-benzalacetone in the O2/Me2CHCHO system; these epoxidations are stereospecific without formation of corresponding diastereomeric epoxides.Oxidation of methyl p-totyl sulfide with O2/Me2CHCHO is facilitated by the 1,3-dioxo-catalyst Co(II)-1.Monooxidation is achieved with Me2CHCHO in equimolar proportions to give the corresponding sulfoxide, whereas overoxidation is realized with excess Me2CHCHO to give the sulfone.These epoxidation and sulfide oxidations all occur at 25 deg C and are complete in less than a day.Key Words: Oxidation; Transition metals; Alkenes; Sulfides; 1,3-Diketone; β-Ketoimine; Salen.
- Liao, Jen-Hai,Cheng, Kuang-Yuan,Fang, Jim-Min,Cheng, Ming-Chu,Wang, Yu
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p. 847 - 860
(2007/10/03)
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- Tetracyanoethylene-hydrogen peroxide, a mild epoxidation system of olefins
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A reagent combination system, tetracyanoethylene-30% hydrogen peroxide, was found to epoxidize olefins efficiently in acetonitrile at room temperature in a stereospecific manner with retention of the configuration of the double bond.
- Masaki,Miura,Mukai,Iwata,Oda,Itoh
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p. 686 - 688
(2007/10/03)
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- Epoxidation of olefins with formamide - Hydrogen peroxide
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Olefins are converted to epoxides in aqueous medium using formamide-hydrogen peroxide as oxidant.
- Chen, Yuanwei
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p. 4015 - 4018
(2007/10/02)
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- Oxidation of allylic alcohols by dimethyldioxirane: Competition reaction between epoxidation and C-H insertion
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Epoxidation of allylic alcohols with dimethyldioxirane is accompanied by oxidation of the hydroxy functionality; thus enone formation increases with decreasing substitution at the C-C double bond; nonetheless, selective epoxidation can be obtained by acylation of the alcohol functionality.
- Adam, Waldemar,Prechtl, Frank,Richter, Markus J.,Smerz, Alexander K.
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p. 8427 - 8430
(2007/10/02)
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- A VERY SIMPLE OXIDATION OF OLEFINS AND KETONES WITH UHP - MALEIC ANHYDRIDE
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The oxidation of olefins and ketones to oxiranes and esters, respectively, is carried out with the UHP(urea-hydrogen peroxide complex) - maleic anhydride system in a mild and very simple procedure.
- Astudillo, Luis,Galindo, Antonio,Gonzalez, Antonio G.,Mansilla, Horacio
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p. 1075 - 1080
(2007/10/02)
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- Ethyl Cyanoformate/Hydrogen Peroxide and Related Combination Systems, Novel Epoxidizing Systems of Olefins
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A combination system of ethyl cyanoformate and hydrogen peroxide was found to epoxidize olefins in a stereospecific manner at room temperature.Asymmetric epoxidation was observed with menthyl cyanoformate/hydrogen peroxide system.
- Masaki, Yukio,Miura, Tsuyoshi,Mukai, Isao,Itoh, Akichika,Oda, Hirohisa
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p. 1937 - 1940
(2007/10/02)
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- EPOXIDATION OF OLEFINS BY HYDROGEN PEROXIDE CATALYZED BY PHOSPHONOTUNGSTIC COMPLEXES
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The highest turnovers reported so far in the epoxidation of olefins with hydrogen peroxide are obtained under homogeneous conditions with trioctylmethylammonium tungstate complexed by lipophilic neutral or anionic phosphorus ligands containing the P=O subunit.
- Quenard, M.,Bonmarin, V.,Gelbard, G.
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p. 2237 - 2238
(2007/10/02)
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- POLYMER-ANCHORED VANADIUM(V) AND MOLYBDENUM(VI) CATALYSTS FOR THE REGIOSELECTIVE EPOXIDATION OF (E)-GERANIOL WITH t-BUTYL HYDROPEROXIDE
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The reaction of (E)-geraniol with t-BuOOH in the presence of polymer-anchored VV or MoVI complexes gave 2,3-epoxygeraniol in high yields.The conversion and the selectivity by the MR-type polymer catalysts containing VV were comparable to those given by homogeneous catalyst based on VO(acac)2.The present catalysts can be used repeatedly without causing significant decrease in catalytic activity.
- Yokoyama, Toshiro,Nishizawa, Masato,Kimura, Tetsuo,Suzuki, Toshishige M.
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p. 1703 - 1706
(2007/10/02)
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