- Mo Schiff base-tungstate ionic hybrid with enhanced heterogeneous catalytic activity for epoxidation reactions
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A novel metal Schiff base-tungstate ionic hybrid (Mo-MimAM-WO4) was prepared by anion-exchange of Mo Schiff base functionalized imidazole ionic liquid with sodium tungstate. The resulting hybrid catalyst was fully characterized by 1H NMR, FT-IR, XRD, SEM, TGA, and XPS, and its catalytic activity was studied for the epoxidation of alkenes using aqueous H2O2 as the oxidant. The catalyst was found to be highly efficient and showed higher catalytic activity than its corresponding homogeneous and heterogeneous analogues Mo-MimAM and Na2WO4. After reaction, the catalyst can be easily recovered by filtration and reused for the next run. The synergistic effect between Mo Schiff base complex and tungstate is revealed to be responsible for the catalyst's excellent performance in epoxidation.
- Fan, Weizheng,Leng, Yan,Liu, Jian,Jiang, Pingping,Zhao, Jiwei
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- Highly Regioselective 5-endo-tet Cyclization of 3,4-Epoxy Amines into 3-Hydroxypyrrolidines Catalyzed by La(OTf)3
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Highly regioselective intramolecular aminolysis of 3,4-epoxy amines has been achieved. Key features of this reaction are (1) chemoselective activation of epoxides in the presence of unprotected aliphatic amines in the same molecules by a La(OTf)3 catalyst and (2) excellent regioselectivity for anti-Baldwin 5-endo-tet cyclization. This reaction affords 3-hydroxy-2-alkylpyrrolidines stereospecifically in high yields. DFT calculations revealed that the regioselectivity might be attributed to distortion energies of epoxy amine substrates. The use of this reaction was demonstrated by the first enantioselective synthesis of an antispasmodic agent prifinium bromide.
- Hoshino, Yoshihiko,Iwabuchi, Yoshiharu,Kuriyama, Yuse,Sasano, Yusuke,Uesugi, Shun-ichiro,Yamaichi, Aoto
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supporting information
p. 1961 - 1965
(2021/01/04)
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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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- New molybdenum(II) complexes with α-diimine ligands: Synthesis, structure, and catalytic activity in olefin epoxidation
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Three new complexes [Mo(η3-C3H5)Br(CO)2{iPrN=C(R)C5H4N}], where R = H (IMP = N-isopropyl 2-iminomethylpyridine), Me, and Ph, were synthesized and characterized, and were fluxional in solution. The most interesting feature was the presence, in the crystal structure of the IMP derivative, of the two main isomers (allyl and carbonyls exo), namely the equatorial isomer with the Br trans to the allyl and the equatorial with the Br trans to one carbonyl, the position trans to the allyl being occupied by the imine nitrogen atom. For the R = Me complex, the less common axial isomer was observed in the crystal. These complexes were immobilized in MCM-41 (MCM), following functionalization of the diimine ligands with Si(OEt)3, in order to study the catalytic activity in olefin epoxidation of similar complexes as homogeneous and heterogeneous catalysts. FTIR,13C- and29Si-NMR, elemental analysis, and adsorption isotherms showed that the complexes were covalently bound to the MCM walls. The epoxidation activity was very good in both catalysts for the cis-cyclooctene and cis-hex-3-en-1-ol, but modest for the other substrates tested, and no relevant differences were found between the complexes and the Mo-containing materials as catalysts.
- Vasconcellos-Dias, Maria,Marreiros, Jo?o,Sales, Rita,Félix, Vitor,Brand?o, Paula,Nunes, Carla D.,José Calhorda, Maria
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- Asymmetric Total Synthesis of 19,20-Epoxydocosapentaenoic Acid, a Bioactive Metabolite of Docosahexaenoic Acid
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In this study, we report the first asymmetric total synthesis of 19,20-epoxydocosapentaenoic acid (19,20-EDP), a naturally occurring bioactive cytochrome P450 metabolite of docosahexaenoic acid, a major constituent of fish oil. Our strategy involves direct asymmetric epoxidation to produce an enantiopure β-epoxyaldehyde that can be appended to the rest of the skipped polyene core by Wittig condensation. Our route is step-economical and late divergent and could be an appealing method by which to synthesize EDP analogues for biological studies.
- Cinelli, Maris A.,Lee, Kin Sing Stephen
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p. 15362 - 15372
(2019/11/28)
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- Synthesis and catalytic activity of Mo(II) complexes of α-diimines intercalated in layered double hydroxides
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The two layered double hydroxides ZnAl-LDH and MgAl-LDH were functionalized with bis(4-HOOC-phenyl)-acenaphthenequinonediimine) (H2BIAN), leading to the intercalation of its dianion, which in a second step reacted with [Mo(CO)3X2(NCMe)2] (X = I, Br), affording four new materials. These materials and the two complexes [Mo(CO)3X2(H2BIAN)2] (X = I, Br) were tested in the olefin epoxidation reaction with substrates cis-cyclooctene, styrene, 1-octene, trans-hex-3-en-1-ol, and R-(+)-limonene, using tert-butylhydroperoxide (tbhp) as oxidant. The new catalysts were particularly good for cis-cyclooctene and styrene (100% conversions) and at least one heterogeneous catalyst was comparable to the homogeneous ones in the epoxidation of 1-octene and trans-hex-3-en-1-ol. The homogeneous catalysts were the best to oxidize R-(+)-limonene (higher conversions).
- Marreiros, Jo?o,Diaz-Couce, Maria,Ferreira, Maria Jo?o,Vaz, Pedro D.,Calhorda, Maria José,Nunes, Carla D.
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p. 274 - 282
(2018/11/21)
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- Characterization of Carbonyl-Phenol Adducts Produced by Food Phenolic Trapping of 4-Hydroxy-2-hexenal and 4-Hydroxy-2-nonenal
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4-Hydroxy-2-alkenals disappear in the presence of food phenolics (i.e., cathechin or quercetin), and the corresponding carbonyl-phenol adducts are produced. In an attempt to identify structure(s) of formed adducts, the reactions between model phenolics (resorcinol, 2-methylresorcinol, orcinol, and 2,5-dimethylresorcinol) and hydroxyalkenals (4-hydroxy-2-hexenal and 4-hydroxy-2-nonenal) were studied and the produced adducts were isolated by column chromatography and unambiguously characterized by one- A nd two-dimensional nuclear magnetic resonance and mass spectrometry as dihydrobenzofuranols (1), chromane-2,7-diols (2), and 2H-chromen-7-ols (3). These compounds were mainly produced at slightly basic pH values and moderate temperatures. Their activation energies (Ea) of formation were a25 kJ mol-1 for adducts 1, a32 kJ mol-1 for adducts 2, and a38 kJ mol-1 for adducts 3. A reaction pathway that explains their formation is proposed. All of these results confirm that, analogously to other lipid-derived carbonyl compounds, phenolics can trap 4-hydroxy-2-alkenals in an efficient way. Obtained results provide the basis for the potential detection of carbonyl-phenol adducts derived from hydroxyalkenals in food products.
- Hidalgo, Francisco J.,Zamora, Rosario
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p. 2043 - 2051
(2019/02/26)
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- Borinic Acid-Catalyzed, Regioselective Ring Opening of 3,4-Epoxy Alcohols
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Diarylborinic acids (Ar2BOH) catalyze the C3-selective ring opening of 3,4-epoxy alcohols with aniline, dialkylamine and arenethiol nucleophiles. The regiochemical outcome is consistent with a catalytic tethering mechanism in which the borinic acid interacts with both the electrophile and the nucleophile. The rate acceleration resulting from this induced intramolecularity effect is sufficient to overcome steric biases that would otherwise favor C4-selective opening of the substituted epoxy alcohols.
- Wang, Grace,Garrett, Graham E.,Taylor, Mark S.
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supporting information
p. 5375 - 5379
(2018/09/13)
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- An Isolable and Bench-Stable Epoxidizing Reagent Based on Triazine: Triazox
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A new triazine-based oxidizing reagent, 2-hydroperoxy-4,6-diphenyl-1,3,5-triazine (Triazox), has been developed. The reagent can be synthesized from inexpensive starting materials and is a bench-stable solid that is isolable in pure form. Epoxidation of alkenes possessing acid-sensitive functionalities using Triazox proceeded in good to excellent yields. The accompanying nonacidic triazinone coproduct can be easily removed by filtration. These features indicate that Triazox is a practically useful oxidizing reagent.
- Yamada, Kohei,Igarashi, Yuki,Betsuyaku, Tatsuki,Kitamura, Masanori,Hirata, Koki,Hioki, Kazuhito,Kunishima, Munetaka
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supporting information
p. 2015 - 2019
(2018/04/16)
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- Molybdenum(II) Complexes with α-Diimines: Catalytic Activity in Organic and Ionic Liquid Solvents
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The new [MoX(η3-C3H5)(CO)2(α-diimine)] complexes with: (i) X = Br or triflate and α-diimine = 1,10-phenanthroline (phen) and dipyridophenazine (dppz); and (ii) X = Br and α-diimine = phen and dppz, with several substituents, are synthesized and characterized. The structures of [MoBr(η3-C3H5)(CO)2(Cl-phen)] and [Mo(CF3SO3)(η3-C3H5)(CO)2(dppz)] are determined by using single-crystal X-ray diffraction. These and three complexes of 2,2′-bipyridyl (bpy), and its two derivatives with Me and tBu substituents, are tested in the homogeneous catalytic epoxidation of several olefins in dichloromethane, exhibiting, in general, a good selectivity towards the respective epoxide and relatively low TOFs. For the first time, the oxidation of cis-cyclooctene with some of these catalysts is also conducted in a variety of room-temperature ionic liquids (RTILs). In the presence of [MoBr(η3-C3H5)(CO)2(phen)], the conversions, in general, increase, compared with the reactions in organic solvents. Interestingly, different chemoselectivity is found when [C6mim][Ntf2] and [C2mim][FAP] are used with diol (24–26 %). On the other hand, [MoBr(η3-C3H5)(CO)2(L)] (L = Me-phen or dppz) exhibits much lower conversions in the RTILs tested than in common organic solvents.
- Saraiva, Marta S.,Nunes, Carla D.,Félix, Vítor,Ribeiro, Ana P. C.,de Castro, Carlos Nieto,Calhorda, Maria José
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supporting information
p. 3922 - 3932
(2018/09/10)
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- New heterogeneous catalysts with Mo(II) intercalated in layered double hydroxides
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The Mo(II) complexes [MoX2(CO)3(BDC)] (X?=?I, Br; H2BDC?=?2,2′-bipyridine-5,5′-dicarboxylic acid) were immobilized by intercalation in two layered double hydroxides (LDH), containing Zn/Al (synthesized) and Mg/Al (commercial), as shown by infrared and13C solid state NMR spectroscopies, and X-ray powder diffraction. Their catalytic activity was studied in olefin oxidation, using as oxidant tert-butylhydroperoxide (tbhp), and was compared with the activity of the related [MoX2(CO)3(bpy)] complexes (bpy?=?2,2′-bipyridine). cis-Cyclooctene, styrene, 1-octene, trans-hex-3-en-1-ol, and R-(+)-limonene were the substrates tested. All the catalyst showed in average a high selectivity toward the epoxide of each substrate (above 90%, except for styrene), with variable conversions, but none of the heterogeneous catalysts proved to be more active than the homogeneous ones. The same or higher activity in a second catalytic run, as observed in most reactions, suggests a good recycling capability.
- Diaz-Couce, Maria,Marreiros, Jo?o,Ferreira, Maria Jo?o,Vaz, Pedro D.,Nunes, Carla D.,Calhorda, Maria José
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p. 483 - 488
(2016/11/30)
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- Synthesis, characterization and catalytic application of a new organometallic oligomer based on polyhedral oligomeric silsesquioxane
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Although homogeneous catalysts provide high performance and selectivity, the difficulty of separation and recycling of these catalysts has bothered the scientific community worldwide. Therefore, the demand for heterogeneous catalysts that possess the advantages of homogeneous ones, with ease of separation and recyclability remains a topic of major impact. The oligomeric catalyst synthesized in this work was characterized using elemental analysis, Fourier transform infrared, 13C NMR, 29Si NMR and energy-dispersive X-ray spectroscopies, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and Brunauer–Emmett–Teller analysis and compared to its homogeneous counterpart [W(CO)3Br2(ATC)] in the epoxidation of 1-octene, cyclooctene, (S)-limonene, cis-3-hexen-1-ol, trans-3-hexen-1-ol and styrene. The results showed that the percentage conversion for the homogeneous species [W(CO)3Br2(ATC)] was slightly higher than for the oligomeric catalyst (POSS-ATC-[W(CO)3Br2]). Furthermore, the selectivity for epoxide of the oligomeric catalyst was greater than that of the homogeneous catalyst by about 25% when (S)-limonene was used. Great conversions (yields) of products were obtained with a wide range of substrates and the catalyst was recycled many times without any substantial loss of its catalytic activity.
- Vieira, Eduardo Guimar?es,Silva, Rafael Oliveira,Junior, Enes Furlani,Dias Filho, Newton Luiz
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- Immobilizing of oxo-molybdenum complex on cross-linked copolymer and its catalytic activity for epoxidation reactions
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This work describes the immobilization of molybdenum acetylacetonate oxygen (MoO2(acac)2) on cross-linked porous copolymer support via covalent attachment under mild conditions. The obtained solid product DVB-AA-Mo was fully characterized by FT-IR, TG, CHN elemental analysis, nitrogen adsorption/desorption, and SEM, and was tested for the epoxidation of various alkenes with tert-butyl hydroperoxide (TBHP) as the oxidant. DVB-AA-Mo was proved to be a highly efficient catalyst for epoxidation reactions, it could easily be recovered by filtration and reused for five runs without significant loss in activity.
- Fan, Weizheng,Shi, Dongyang,Feng, Bainian
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- POSS-derived mesoporous ionic copolymer-polyoxometalate catalysts with a surfactant function for epoxidation reactions
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A series of novel polyoxometalate (POM)-based stable polymeric hybrids were successfully synthesized using polyhedral oligomeric vinylsilsesquioxanes (POSS) and ionic liquids (IL) bearing hydrophobic alkyl chains as the building blocks, followed by ion exchange with Keggin-type phosphotungstic acid (PW). The obtained hybrids POSS-ILx-PW were demonstrated to be mesostructured and amphiphilic materials with good thermal stability. Catalytic tests for the H2O2-based epoxidation of cyclooctene have shown that these newly designed catalysts exhibit extraordinary catalytic activities, catalytic rates, and quite stable reusability. The unique amphiphilic property and the mesoporous structure are revealed to be responsible for the catalysts' excellent performance in epoxidation reactions with H2O2.
- Zhao, Jiwei,Leng, Yan,Jiang, Pingping,Wang, Jun,Zhang, Chenjun
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p. 1022 - 1028
(2016/02/19)
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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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- Amphiphilic porous polyhedral oligomeric silsesquioxanes (POSS) incorporated polyoxometalate-paired polymeric hybrids: Interfacial catalysts for epoxidation reactions
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A new strategy to fabricate amphiphilic polyoxometalate (POM)-paired polymeric hybrids via a free radical polymerization process using polyhedral oligomeric vinylsilsesquioxanes (POSS) and ionic liquids as the building block, followed by ion exchange was designed. The obtained hybrids were demonstrated to be porous materials with excellent amphiphilic properties, and can behave as efficient interfacial catalysts for the epoxidation of alkenes with H2O2 by stabilizing Pickering emulsions. The catalysts could be recovered by centrifugation and reused with no appreciable deactivation. The unique amphiphilic porous structure is revealed to be responsible for the catalysts' excellent performances in the epoxidation reaction by accelerating the mass transfer. This journal is
- Leng, Yan,Zhao, Jiwei,Jiang, Pingping,Wang, Jun
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p. 17709 - 17715
(2015/03/04)
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- Pore size matters! Helical heterogeneous catalysts in olefin oxidation
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Helical mesoporous materials of the MCM-41 type with different pore sizes were prepared, choosing as templates myristyl (C14) or cetyl (C16) trimethyl ammonium salts, and functionalized with Mo(II) active sites based on MoI2(CO)3 (1) and MoBr(η3-C3H5)(CO)2 (2) fragments, respectively, using a pyridine-2-carbaldehyde ligand as anchor. The new materials were tested as the catalytic precursors in the epoxidation of cis-cyclooctene, styrene, R-(+)-limonene, trans-hex-2-en-1-ol, cis-3-hex-1-ol, and geraniol using tert-butylhydroperoxide (tbhp) as oxidant. All catalysts were moderately to highly selective toward the epoxide products. The materials with larger pores (C16 template) displayed a better catalytic activity, leading in general to higher conversions and selectivities, as well as faster kinetics. For instance, geraniol is epoxidized (more than 90%) with conversions above 90%. The major achievement of these catalysts, however, is the excellent product selectivity control, which is boosted when the allyl complex 1 is used, reaching 100% of the 2S, 3R species in the epoxidation of trans-hex-2-en-1-ol. The catalysts were also found to be stable through recycling experiments and truly heterogeneous with little or no leaching.
- Saraiva, Marta S.,Fernandes, Cristina I.,Nunes, Teresa G.,Calhorda, Maria José,Nunes, Carla D.
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p. 328 - 337
(2015/10/05)
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- Eu(OTf)3-Catalyzed highly regioselective nucleophilic ring opening of 2,3-epoxy alcohols: An efficient entry to 3-substituted 1,2-diol derivatives
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In our study of the total synthesis of (+)-irciniastatin A, we found a need to develop a method that enables a C3-selective nucleophilic ring opening of 2,3-epoxy alcohol by MeOH, by which we found that the use of combined catalytic amounts of Eu(OTf)3 and 2,6-di-tert-butyl-4-methylpyridine (DTBMP) enables the intended transformation to obtain 3-methoxy-1,2-diol efficiently. Promising features of a protocol that effects a highly regioselective nucleophilic ring opening of 2,3- and 3,4-epoxy alcohols using various nucleophiles including alcohols, thiols, and unprotected amines are described.
- Uesugi, Shun-Ichiro,Watanabe, Tsubasa,Imaizumi, Takamichi,Shibuya, Masatoshi,Kanoh, Naoki,Iwabuchi, Yoshiharu
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supporting information
p. 4408 - 4411
(2015/01/16)
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- Amphiphilic phosphotungstate-paired ionic copolymer as a highly efficient catalyst for triphase epoxidation of alkenes with H2O2
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A novel amphiphilic POM-paired ionic copolymer was prepared by the anion-exchange of a newly task-specific designed functionalized-ionic liquid copolymer with H3PW4O16, and characterized by FT-IR, SEM, TG, 1H NMR, and elemental analysis. This catalyst was not only capable of catalyzing the epoxidation of alkenes in a liquid-liquid-solid triphase reaction system, showing high catalytic conversions and selectivity, but also avoids the use of chlorinated solvents. After reaction, the catalyst can be conveniently recovered and steadily reused without the change of catalyst structure. The unique amphiphilic catalyst structure is revealed to be responsible for the catalyst's excellent performances in the epoxidation of alkenes with H2O2 by accelerating the mass transfer. the Partner Organisations 2014.
- Leng, Yan,Wu, Jianghao,Jiang, Pingping,Wang, Jun
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p. 1293 - 1300
(2014/05/06)
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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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- An efficient recyclable peroxometalate-based polymer-immobilised ionic liquid phase (PIILP) catalyst for hydrogen peroxide-mediated oxidation
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A linear cation-decorated polymeric support with tuneable surface properties and microstructure has been prepared by ring-opening metathesis polymerisation (ROMP) of a pyrrolidinium-functionalised norbornene-based monomer with cyclooctene. The derived peroxophosphotungstate-based polymer-immobilised ionic liquid phase (PIILP) catalyst is an efficient and recyclable system for the epoxidation of allylic alcohols and alkenes, with only a minor reduction in performance on successive cycles.
- Doherty, Simon,Knight, Julian G.,Ellison, Jack R.,Weekes, David,Harrington, Ross W.,Hardacre, Christopher,Manyar, Haresh
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supporting information; experimental part
p. 925 - 929
(2012/06/18)
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- Ring-opening hydrofluorination of 2,3- and 3,4-epoxy amines by HBF 4·OEt2: Application to the asymmetric synthesis of (S, S)-3-deoxy-3-fluorosafingol
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Treatment of a range of 2,3- and 3,4-epoxy amines with HBF 4·OEt2 at room temperature results in fast and efficient SN2-type ring-opening hydrofluorination to give stereodefined amino fluorohydrins. Operational simplicity, scalability, and short reaction time at ambient temperature are notable features of this method. The utility of this methodology is exemplified in a concise asymmetric synthesis of (S,S)-3-deoxy-3-fluorosafingol.
- Cresswell, Alexander J.,Davies, Stephen G.,Lee, James A.,Morris, Melloney J.,Roberts, Paul M.,Thomson, James E.
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experimental part
p. 4617 - 4627
(2011/07/30)
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- Hydrogen-bond-assisted epoxidation of homoallylic and allylic alcohols with hydrogen peroxide catalyzed by selenium-containing dinuclear peroxotungstate
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The reaction of peroxotungstates (H2WO4 + H 2O2) with H2SeO4 gave the novel seleniumcontaining dlnuclear tungsten species, (TBA)2[SeO 4{WO(O2)2}2] (I, TBA = [(n-C 4H9)4N]+), which was characterized by elemental analysis, IR, Raman, UV-vls, 77Se NMR, 183W NMR, and CSI-MS. Various kinds of homoallyllc and allyllc alcohols were efficiently epoxldlzed to the corresponding epoxy alcohols In high yields with 1 equlv. H2O2 with respect to thesubstrates. Compound I showed the highest catalytic activity for H 2O2-based epoxldatlon of homoallyllc and allyllc alcohols among selenium and tungsten complexes. The turnover frequency reachedup to 150 h-1 In a 10 mmol-scale epoxldatlon of c/s-3-hexen1 -ol and this value was the highest among those reported for the translt lon-metal catalyzed epoxldatlon of homoallyllc alcohols with H2O2. The kinetic, mechanistic, computational studies showed that the stabilization of the transition-state by the hydrogen bonding between I and the substrates results In the high reactivity for the l-catalyzed epoxldatlon of homoallyllc and allyllc alcohols. The nature of the hetero atoms In the dland tetranuclear peroxotungstates with XO 4n- ligands (X = As(V), P(V), S(VI), SI(IV), etc.) was crucial In controlling the Lewis acidity of the peroxotungstates, which significantly affects their electrophlllc oxygen transfer reactivity. Allthe data of the structural, kinetic, spectroscopic, and computational c omparison show that the dlmerlc peroxotungstate unit, {WO(O2)2} 2, In I Is activated by the SeO42- ligand.
- Kamata, Keigo,Hirano, Tomohisa,Kuzuya, Shinjiro,Mizuno, Noritaka
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supporting information; experimental part
p. 6997 - 7004
(2009/09/30)
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- Design of and mechanistic studies on a biomimetic iron-imidazole catalyst system for epoxidation of olefins with hydrogen peroxide
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Novel iron catalysts, both defined and in situ generated, for the epoxidation of aromatic and aliphatic olefins with hydrogen peroxide as terminal oxidant are described. Our catalyst approach is based on bio-inspired 1-aryl-substituted imidazoles in combination with cheap and abundant iron trichloride hexahydrate. We show that the free 2-position of the imidazole ligand motif plays a key role for catalytic activity, as substitution leads to a dramatic depletion of yield and conversion. X-ray studies, UV/Vis titrations, and NMR studies were carried out to clarify the mechanism.
- Schroeder, Kristin,Enthaler, Stephan,Bitterlich, Bianca,Schulz, Thomas,Spannenberg, Anke,Tse, Man Kin,Junge, Kathrin,Beller, Matthias
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experimental part
p. 5471 - 5481
(2009/12/27)
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- An improved iron-catalyzed epoxidation of aromatic and aliphatic olefins with hydrogen peroxide as oxidant
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A convenient and practical method for the iron-catalyzed epoxidation of aromatic and aliphatic olefins is described. The iron catalyst system is generated in situ from iron trichloride hexahydrate, pyridine-2,6-dicarboxylic acid (H2pydic), and benzylamines. By variation of the benzylamine ligand, a variety of aliphatic and aromatic olefins were oxidized in high yield (up to 96%) and good-to-excellent selectivity in the presence of hydrogen peroxide as the terminal oxidant. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Bitterlich, Bianca,Schroeder, Kristin,Tse, Man Kin,Beller, Matthias
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scheme or table
p. 4867 - 4870
(2009/05/26)
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- Polyfluorinated quaternary ammonium salts of polyoxometalate anions: Fluorous biphasic oxidation catalysis with and without fluorous solvents
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[Matrix presented] Polyfluorinated quaternary ammonium cations, [CF 3(CF2)7(CH2)3] 3CH3N+ (RFN+), were synthesized and used as countercations for the [WZnM2(H 2O)2(ZnW9O34)2] 12- (M = Mn(II), Zn(II)) polyoxometalate. The (RFN +)12[WZnM2(H20)2 (ZnW9O34)2] compounds were fluorous biphasic catalysts for alcohol and alkenol oxidation, and alkene epoxidation with aqueous hydrogen peroxide. Reaction protocols with or without a fluorous solvent were tested. The catalytic activity and selectivity was affected by both the hydrophobicity of the solvent and the substrate.
- Maayan, Galia,Fish, Richard H.,Neumann, Ronny
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p. 3547 - 3550
(2007/10/03)
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- Epoxidation of olefins
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A method for producing an epoxide from an olefin using a mixture hydrogen peroxide, a nitrile compound and a ketone is disclosed.
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- Epoxidation of alkenes with H2O2 generated in situ from alcohols and molecular oxygen using N-hydroxyphthalimide and hexafluoroacetone as catalysts
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A new epoxidation method of olefins with hydrogen peroxide and/or α- hydroxy hydroperoxide which are generated in situ from an alcohol and molecular oxygen was developed. A variety of alkenes were smoothly epoxidized with molecular oxygen in the presence of an alcohol under the influence of hexafluoroacetone (HFA) and N-hydroxyphthalimide (NHPI) as catalysts. The reaction involves the formation of α-hydroxy hydroperoxide and/or hydrogen peroxide derived from 1-phenylethanol and dioxygen by the action of NHPI and the active oxygen transfer from these hydroperoxides to HFA, giving 2- hydroperoxyhexafluoro-2-propanol which serves as the actual epoxidizing agent.
- Iwahama, Takahiro,Sakaguchi, Satoshi,Ishii, Yasutaka
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p. 693 - 705
(2007/10/03)
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- One-pot synthesis of cycloalkane derivatives using allyl phenyl sulfone and epoxymesylate
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One-pot synthesis of cycloalkane derivatives using an anion of allyl phenyl sulfone and epoxymesylate is presented. (C) 2000 Elsevier Science Ltd.
- Miyaoka, Hiroaki,Shigemoto, Tatsuya,Shinohara, Ikuo,Suzuki, Atsushi,Yamada, Yasuji
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p. 8077 - 8081
(2007/10/03)
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- Efficient epoxidation of alkenes with aqueous hydrogen peroxide catalyzed by methyltrioxorhenium and 3-cyanopyridine
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The epoxidation of alkenes with 30% aqueous hydrogen peroxide is catalyzed efficiently by methyltrioxorhenium (MTO) in the presence of pyridine additives. The addition of 1-10 mol % of 3-cyanopyridine increases the system's efficiency for terminal and trans-disubstituted alkenes resulting in high isolated yields of the corresponding epoxides. The system allows for epoxidation of alkenes with various functional groups. Alkenes leading to acid-sensitive products are efficiently epoxidized using a mixture of pyridine and 3-cyanopyridine as additives. This method is operationally very simple and uses an environmentally benign oxidant. The effects of different pyridine additives on the alkene conversion and the catalyst lifetime are discussed.
- Adolfsson,Coperet,Chiang,Yudin
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p. 8651 - 8658
(2007/10/03)
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- The nickel-substituted quasi-Wells-Dawson-type polyfluoroxometalate, [NiII(H2O)H2F6NaW17O 55]9-, as a uniquely active nickel-based catalyst for the activation of hydrogen peroxide and the epoxidation of alkenes and alkenols
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A series of transition metal substituted polyfluorooxometalates (PFOM) [M(L)H2F6NaW17O55]q-, M = Zn2+, Co2+, Mn2+, Fe2+, Ru2+, Ni2+ and V5+ and L = H2O, O2-, of quasi-Wells -Dawson structure, was synthesized. In the series prepared, only the nickel-substituted polyfluorooxometalate was capable of catalytic activation of hydrogen peroxide in biphasic reaction media, the reaction leading mainly to the selective epoxidation of alkenes and alkenols. The manganese-, cobalt-, ruthenium-, iron-, vanadium-, and zinc-substituted polyfluorooxometalates were catalytically inactive, although, except for the zinc polyfluorooxometalate, very significant catalase activity was observed. Oxidation of thianthrene showed that sulfoxides were oxidized more easily than sulfides. Kinetic profiles of cyclooctene epoxidation showed that the reaction was zero order in both cyclooctene and hydrogen peroxide. Hydrogen peroxide was consumed at a rate 40% higher than the rate of epoxidation of cyclooctene. The reaction appears to proceed through an intermediate peroxo/hydroperoxo species that was observed in the IR spectrum. Atomic absorption, IR and 19F NMR spectroscopy indicated that the [Ni(H2O)-H2F6NaW17O 55]9- compound was stable under reaction conditions.
- Ben-Daniel, Revital,Khenkin, Alexander M.,Neumann, Ronny
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p. 3722 - 3728
(2007/10/03)
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- Selective epoxidation in dense phase carbon dioxide
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Selective epoxidations with transition metal catalysts (V, Ti, Mo) and ButOOH proceed with high conversions and high selectivity in dense phase carbon dioxide.
- Pesiri, David R.,Morita, David K.,Glaze, William,Tumas, William
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p. 1015 - 1016
(2007/10/03)
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- Blue fluorescence generated during lipid oxidation of rat liver microsomes cannot be derived from malonaldehyde but can be from other aldehyde species
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Generation of blue fluorescence together with phospholipid hydroperoxides and aldehyde species in rat liver microsomes during oxidation with FeCl2-ADP-ascorbic acid was monitored, and the kind of lipid oxidation products participating in the formation of blue fluorescence was investigated. Contents of phospholipid hydroperoxides were increased in an early stage of oxidation, and were decreased in an advanced stage of oxidation. Contents of components that liberated malonaldehyde, 4- hydroxyalkenals and other unsaturated aldehydes under the acidic assay conditions were increased in the advanced stage of oxidation. Water-soluble blue fluorescence with a maximum at 440-450 nm determined after separation through gel filtration accumulated in the advanced stage of oxidation, and was characterized as resistant to borohydride treatment and to be little dependent on pH values of the solvent. Wavelength of the maximum fluorescence and characteristics of the fluorescence were similar to those of fluorescence with maxima at 440-450 nm formed by reaction of unoxidized microsomes, bovine serum albumin or methylamine with alkenals, and different from those of fluorescence with maxima at above 460 nm obtained by the reaction with a mixture containing malonaldehyde. Hence, blue fluorescence accumulated in oxidized microsomes cannot be derived from free malonaldehyde but can be from other aldehyde species including alkenals.
- Inoue, Tadamichi,Kikugawa, Kiyomi
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p. 319 - 325
(2007/10/03)
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- Diastereoselective epoxidation of allylic alcohols by t-Butyl hydroperoxide/zeolites system
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Commercial zeolites promotes the epoxidation of unsaturated alcohols in chemo- and diastereoselective way.
- Palombi, Laura,Bonadies, Francesco,Scettri, Arrigo
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p. 11369 - 11376
(2007/10/03)
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- Regioselective nucleophilic ring opening of epoxides and aziridines derived from homoallylic alcohols
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The regioselectivity of nuclcopbilic ring opening of some 3,4-epoxy and 3,4-aziridino alcohols has been studied. The nucleophiles chosen were complex hydrides (LiAlH4, Red-Al and DIBAL) and Lipshutz- or Gilman-type organocuprate reagents. The C-4 substituent in the substrates was varied in order to study steric and electronic effects on the ring opening reactions. For alkyl substituents at C-4, most of the results can be explained on the basis of intramolecular delivery of the nucleophile to C-3 via a six-membered transition state, leading to 1,4-diols or 1,4-amine alcohol derivatives. In general, the epoxy alcohols gave poorer regioselectivity than the N-tosyl aziridino alcohols, for which selectivities of >95:5 were routinely obtained. The activating effect of a phenyl group at C-4 led to a switch in regiochemistry, with the 1,3-diol or 1,3-amino alcohol derivative as the major product.
- Tanner, David,Groth, Thomas
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p. 16139 - 16146
(2007/10/03)
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- Chemical, photochemical and enzymatic approach to furylhydroperoxides
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Furylhydroperoxides are accessible by three different methodologies. In the enzymatic approach, lypoxygenase is employed on non lipid-like substrates. Transition metal catalyzed epoxidation of allylic alcohols is strongly dependent on the structure of the involved hydroperoxide.
- Scettri, Arrigo,Bonadies, Francesco,Lattanzi, Alessandra,Palombi, Laura,Pesci, Silvia
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p. 17139 - 17150
(2007/10/03)
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- Diastereoselective epoxidation of olefins by organo sulfonic peracids, II
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We have investigated the behaviour of sulfonic peracids 2 in situ generated towards olefins 7a, 7b, 9, 11, 14, 16, 18, allylic acid and homoallylic alcohols 20, 22, 24, 26, 28, 30, 33 and α,β-unsaturated ketones 35, 37, 39. Generally, the epoxidation proceeds in a peracid-like manner with greater diastereoselectivity than those by common oxidants. In particular, the epoxidation of Δ4 3-ketosteroids 39a-i led to 4α,5α-epoxides 40a-i with remarkable high de-values. Enhanced α-selectivity was also found in the epoxidation of cholesterol 28b. Due to the mild reaction conditions, even acid sensitive epoxides 8a, 8b, 10, 12, 13, 15, 17, 19 were obtained in good yields.
- Kluge,Schulz,Liebsch
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p. 2957 - 2976
(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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- 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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- Regiochemical control of the ring opening of 1:2-epoxides by means of chelating processes. 10. Synthesis and ring opening reactions of mono- and difunctionalized cis and trans aliphatic oxirane systems
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The regiochemical outcome of the ring opening of 1:2-epoxides through chelation processes assisted by metal ions, was verified in mono- and difunctionalized aliphatic oxirane systems bearing the heterofunctionality (OR) in an homoallylic and/or allylic relationship to the oxirane ring. The effect of the distance of the OR functionality from the oxirane ring and of the type of protective group on the regiochemical outcome of these systems is examined. In some cases, the use of LiClO4 or Mg(ClO4)2 as the promoting metal salt makes it possible the obtainment of a nice regioalternating process.
- Azzena, Francesca,Calvani, Federico,Crotti, Paolo,Gardelli, Cristina,Macchia, Franco,Pineschi, Mauro
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p. 10601 - 10626
(2007/10/02)
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- Sharpless epoxidation by in situ generation of furylhydroperoxides
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The compatibility of the generation of furylhydroperoxides by a radical chain process with the presence of oxygen acceptors and transition metal catalysts allows the achievement of a modified Sharpless procedure for the epoxidation of allylic alcohols and oxidation of sulphides to sulphoxides.
- Antonioletti,Bonadies,Lattanzi,Monteagudo,Scettri
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p. 5433 - 5436
(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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- Aerobic Epoxidation of Olefinic Compounds Catalyzed by Tris(1,3-diketonato)iron(III)
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Trisiron(III) (Fe(dmp)3) was found to be an excellent catalyst for oxygenation of a number of olefinic compounds including styrene analogues and olefinic alcohols into the corresponding epoxides in good to quantitative yields with combined use of molecular oxygen and an aldehyde at room temperature.
- Takai, Toshihiro,Hata, Eiichiro,Yamada, Tohru,Mukaiyama, Teruaki
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p. 2513 - 2518
(2007/10/02)
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- Asymetric Epoxidation of Homoallylic Alcohols Using Zirconium Tetrapropoxide, Dicyclohexyltartramide, and t-Butyl Hydroperoxide System
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In the asymmetric epoxidation of homoallylic alcohols, a combination of zirconium tetrapropoxide, dicyclohexyltartramide, and t-butyl hydroperoxide was found to give good enatiometric selectivities ( up to 77percent ee) especially for (Z)-homoallylic substrates.
- Ikegami, Satoru,Katsuki, Tsutomu,Yamaguchi, Masaru
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- EPOXIDATION WITH 30percent HYDROGEN PEROXIDE CATALYZED BY TUNGSTIC ACID IN BUFFERED MEDIA
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The scope of the tungstic acid catalyzed hydrogen peroxide epoxidation of olefinic alcohols is examined at room temperature, in buffered protic media.Epoxidation occurs with complete retention of configuration for both cis and trans alkenes.Chemoselectivity is discussed with respect to the olefinic alcohol structure and olefin substituents.
- Prat, Denis,Lett, Robert
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p. 707 - 710
(2007/10/02)
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- Regio- and Stereocontrolled Synthesis of Epoxy Alcohols and Triols from Allylic and Homoallylic Alcohols via Iodo Carbonates
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The regio- and stereoselective synthesis of cyclic iodo carbonates 1-10, resulting from allylic and homoallylic alcohols was investigated.These useful intermediates were easily hydrolyzed to epoxy alcohols 11-20 or triols 21-30, depending on the polymeric reagent employed (Amberlyst A 26 in the OH- or CO32- form, respectively).Stereochemical assignments were carried out by 13C NMR or 1H NMR correlations and by conversion of the compounds to products of known stereostructures.
- Bongini, Alessandro,Cardillo, Giuliana,Orena, Mario,Porzi, Gianni,Sandri, Sergio
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p. 4626 - 4633
(2007/10/02)
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