- Phosphorus-doped macroporous carbon spheres for high efficiency selective oxidation of cyclooctene by air
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The phosphorus-doped macroporous carbon spheres (PMCS) with a high specific surface area (574.68 m2 g-1) were synthesized by a template method. A series of catalytic experiments showed that the PMCS possessed excellent catalytic ability for the selective oxidation of cyclooctene (conversion based on cyclooctene was 50.69% and the selectivity to epoxycyclooctane was 88.47%). This journal is the Partner Organisations 2014.
- Li, Chuanxi,Yang, Manman,Liu, Ruihua,Zhao, Fangfang,Huang, Hui,Liu, Yang,Kang, Zhenhui
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- Comparison between various Keggin and Wells-Dawson sandwich-type polyoxometalates in catalytic oxidation of cyclooctene and cyclohexene with hydrogen peroxide
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The catalytic performance of tetra-n-butylammonium salts of Keggin and Wells-Dawson sandwich-type polyoxotungstates, [M4 (PW9O34)2]m- and [M4(P2W15O56)2]n- (M = Mn2+, Fe3+, Co2+, Ni2+, Zn2+), in the oxidation of cyclooctene and cyclohexene with 30% hydrogen peroxide under various conditions was investigated. In comparison, Wells-Dawson sandwich-type polyoxometalates were found to be less active than Keggin ones. In both of them, those containing Zn and Fe gave higher conversions for different oxidation conditions. These catalysts showed very good reusability in the oxidation reaction.
- Farsani, Mostafa Riahi,Jalilian, Fariba,Yadollahi, Bahram,Rudbari, Hadi Amiri
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- A nickel-modified polyoxometalate towards a highly efficient catalyst for selective oxidation of hydrocarbons
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A nickel-modified polyoxometalate compound was synthesized which exhibited excellent catalytic activity (conversion: 41.63%; selectivity: 97.21%) for selective oxidation of cyclooctene using air as an oxidant without a solvent.
- Zhou, Lei,Liu, Juan,Ji, Wenbin,Huang, Hui,Hu, Hailiang,Liu, Yang,Kang, Zhenhui
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- Solvent-free selective epoxidation of cyclooctene using supported gold catalysts
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Oxidation is one of the major pathways for the synthesis of chemical intermediates. The epoxidation of alkenes by the electrophilic addition of oxygen to a carbon-carbon double bond remains one of the most significant challenges in oxidation. Of key impor
- Bawaked, Salem,Dummer, Nicholas F.,Dimitratos, Nikolaos,Bethell, Donald,He, Qian,Kiely, Christopher J.,Hutchings, Graham J.
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- Mesostructured dihydroxy-functionalized guanidinium-based polyoxometalate with enhanced heterogeneous catalytic activity in epoxidation
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A mesostructured ionic liquid-polyoxometalate (IL-POM) hybrid has been prepared through designing a new dihydroxy-tethered guanidinium-based IL, N′′-(2,3-dihydroxypropyl)-N,N,N′,N′- tetramethylguanidinium chloride, to interact with Keggin-type POM phosphotungstic acid (H3PW) in a self-assembly process. Scanning electron microscopy and transmission electron microscopy showed its special coral-shaped micromorphology. Nitrogen sorption analysis indicated the formation of a porous structure with a moderate surface area of about 30 m2 g-1 and narrowly distributed pore size located in the mesoscale. Assessed in the cis-cyclooctene epoxidation with H2O2, the mesostructured hybrid exhibited superior heterogeneous catalytic activity and steady reusability, and the conversion was more than four times that of homogeneous H3PW itself, and more than 14 times that of the nonporous analogues. On the basis of the experimental results, a unique substrate-solvent-catalyst synergistic mechanism is proposed and discussed for understanding the dramatically enhanced catalytic performance. Copyright
- Chen, Guojian,Zhou, Yu,Zhao, Pingping,Long, Zhouyang,Wang, Jun
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- Coordinate-polymerized organic ligand towards an efficient catalyst for selective hydrocarbon oxidation
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Here we show catalyst design based on an isoxazole derivative via a coordinate-polymerized strategy. Three new coordination polymers, [Co(bpp)(mpca)2] (1), [Zn(bpp)(mpca)2] (2), and [Cd(bpp)(mpca)2] (3) [bpp = 1,3-bis(4-pyridyl)propane, mpca = 5-methyl-3-phenylisoxazole-4-carboxylic acid], have been synthesized under hydrothermal conditions. Single crystal X-ray diffraction analysis reveals that, compounds 1-3 exhibit similar wave-like chains, with mpca functioning as pendant phenyl-isoxazole arms. Catalytic experiments show that all three compounds can be used as efficient heterogeneous catalysts for the selective oxidation of cyclooctene.
- Li, Kaixuan,Hu, Hailiang,Liu, Beibei,Lin, Xiaoling,Huang, Hui,Liu, Yang,Kang, Zhenhui
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- Synthesis of a pair of homochiral manganese-based coordination polymers as stable catalyst for the selective oxidation of cis-cyclooctene
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A pair of homochiral manganese-based coordination polymers [Mn(H2O)2(bpy)(L-DBTA)] (L-1) and [Mn(H2O)2(bpy)(D-DBTA)](D-1): Syntheses, crystal structures and catalytic properties for the selective oxidation of cis-cyclooctene. The homochiral manganese-based 3D supermolecule framework exhibits high catalytic activity (38.85% conversion based on cis-cyclooctene and 76.13% selectivity for epoxycyclooctane) and stability for selective oxidation of cis-cyclooctene in the absence of solvent using TBHP as radical initiator and oxygen (in the air) as oxidant at 80 °C.
- Zhang, Guangju,Shi, Yang,Wei, Ying,Zhang, Qingguo,Zhang, Yanping,Cai, Kedi,Xiu, Siqi
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- Complexation of crystal-like mesoporous phenylene-silica with Cr(CO) 3 and catalytic performance in the oxidation of cyclooctene
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Chromium carbonyl complexes were incorporated into a molecularly ordered mesoporous phenylene-silica by reaction with Cr(CO)6 in refluxing 1,2-dichloroethane (DCE). The modified material with a chromium loading of 0.07 mmol g-1 was characterised by powder X-ray diffraction, N2 adsorption, thermogravimetric analysis (TGA), FT-IR, 13C and 29Si MAS NMR spectroscopies. TGA under air indicated that thermal decarbonylation between 250 and 350 °C preceded the Cr-promoted decomposition and release of organic fragments at a lower temperature (onset ca. 380 °C) than that registered for the phenylene-silica precursor (onset ca. 550 °C). The catalytic performance of the modified phenylene-silica was evaluated in the oxidation of cis-cyclooctene at 55 °C with tert-butylhydroperoxide (TBHP) as the oxidant and DCE as the co-solvent. The main product was the epoxide, formed in 83% yield after 24 h, with 2-cycloocten-1-one being the main by-product. Although the activity of the catalyst decreased after the first recycle, possibly due to partial chromium leaching, it remained nearly the same thereafter, and leaching tests indicated that the catalytic reaction was essentially heterogeneous in nature. Tests carried out using a radical scavenger indicated that the reaction of the olefin with TBHP may involve both free radical and non-radical reaction mechanisms.
- Coelho, Ana C.,Balula, Salete S.,Antunes, Margarida M.,Gerganova, Tsvetelina I.,Bion, Nicolas,Ferreira, Paula,Pillinger, Martyn,Valente, Anabela A.,Rocha, Jo?o,Gonalves, Isabel S.
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- Visible-Light-Enabled Allylic C-H Oxidation: Metal-free Photocatalytic Generation of Enones
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A practical and efficient method has been established for the direct oxidation of allylic C-H bonds catalyzed by visible-light-enabled photoredox agents. This protocol uses oxygen as the sole oxidant under metal-free conditions at room temperature and pro
- Liu, Chao,Liu, Hui,Zheng, Xuan,Chen, Shanyi,Lai, Qihong,Zheng, Changlong,Huang, Mingqiang,Cai, Kaicong,Cai, Zhixiong,Cai, Shunyou
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p. 1375 - 1381
(2022/02/07)
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- g-C3N4/metal halide perovskite composites as photocatalysts for singlet oxygen generation processes for the preparation of various oxidized synthons
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g-C3N4/metal halide perovskite composites were prepared and used for the first time as photocatalysts forin situ1O2generation to perform hetero Diels-Alder, ene and oxidation reactions with suitable dienes and alkenes. The standardized methodology was made applicable to a variety of olefinic substrates. The scope of the method is finely illustrated and the reactions afforded desymmetrized hydroxy-ketone derivatives, unsaturated ketones and epoxides. Some limitations were also observed, especially in the case of the alkene oxidations, and poor chemoselectivity was somewhere observed in this work which is the first application of MHP-based composites forin situ1O2generation. The experimental protocol can be used as a platform to further expand the knowledge and applicability of MHPs to organic reactions, since perovskites offer a rich variety of tuning strategies which may be explored to improve reaction yields and selectivities.
- Corti, Marco,Chiara, Rossella,Romani, Lidia,Mannucci, Barbara,Malavasi, Lorenzo,Quadrelli, Paolo
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p. 2292 - 2298
(2021/04/12)
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- New Cu(II), Co(II) and Ni(II) azo-Schiff base complexes: Synthesis, characterization, catalytic oxidation of alkenes and DFT study
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Three new complexes with general formula of ML (M = Cu (1), Co (2), Ni (3)) containing an azo-Schiff base ligand (H2L) derived from 2,3-butanediamine and 4-(benzeneazo) salicylaldehyde were synthesized by template method. Characterization of the ligand and complexes were accomplished with FT-IR, UV–Vis, and 1H NMR. The catalytic activity of the complexes (1–3) were tested for the oxidation of various alkenes (cyclooctene, cyclohexene, styrene, α-methyl styrene, and norbornene) applying tert-butyl hydroperoxide (TBHP) as an oxidizing agent, and it was found that they were acceptable catalysts. Under the optimized reaction conditions, CuL complex displayed 94% conversion for the oxidation of cyclooctene, and CoL and NiL complexes exhibited 90 and 85% conversions for oxidizing α-methyl styrene, respectively. Based on our density functional computations, diffuse functions are compulsory in the basis set for geometry optimization of these systems. Therefore, the most stable structures and the vibrational frequencies were calculated at the M06-2X/6–311++G(d,p) level. By establishing the correlation between observed and calculated frequencies, the assignment of the vibrational modes was performed. Based on natural charge analysis (NAO), the back electron transfer from ML to the TBHP breaks the O–O bond and facilitates the formation of tert-butoxyl radicals.
- Lashanizadegan, Maryam,Asna Ashari, Hadiseh,Sarkheil, Marzieh,Anafcheh, Maryam,Jahangiry, Samira
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- Synthesis, structure, magnetic and catalytic competency of a tetradentate (nnoo) schiff base mediated dimeric copper(ii) complex
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One dinuclear copper(II) complex {μ-[2,2 -{ethane-1,2-diylbis[(azanylylidene)methanylylidene]}bis(phenolato)]}-{μ-[2,2 -{ethane-1,2- diylbis[(azanylylidene)methanylylidene]}bis(phenolato)]}dicopper(II), [Cu2(salen)2] (1) [salen2- = [2,2 -{ethane-1,2-diylbis- [(azanylylidene)methanylylidene]}bis(phenolato)] has been isolated and characterized by X-ray diffraction analysis and spectroscopic studies. X-ray single crystal structure examination revealed that each Cu(II) center in the asymmetric unit of 1 adopts a distorted square planar geometry with a CuN2O2 chromophore, where two asymmetric units are attached through congregation of Salen involving Cu-O bond to form dinuclear molecular unit [Cu2(salen)2]. In crystalline state, these dinuclear entities in 1 are extended through C-H π interactions and π π interactions displaying a 3D network structure. The variable-temperature magnetic susceptibility measurement asserted a dominant antiferromagnetic interaction between the copper(II) centers through Cu-O-Cu linkage in 1 with J = -1.46 cm-1. The catalytic efficacy of complex 1 was studied in a series of solvents for the oxidation of styrene and cyclooctene using tert-butyl-hydroperoxide (TBHP) as an active oxidant under mild conditions. The catalytic reaction mixture has been analyzed by gas chromatography and it displayed that the yield of the epoxidation and its selectivity is optimum in acetonitrile medium.
- CHOWDHURY, HABIBAR,BERA, RAJESH,ADHIKARY, CHANDAN
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p. 1280 - 1286
(2021/06/09)
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- Rare earth Ce- and Nd-doped spinel nickel ferrites as effective heterogeneous catalysts in the (ep)oxidation of alkenes
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Cerium (Ce)- and neodymium (Nd)-doped spinel nickel ferrites catalysts system were synthesized using a cost-effective sol–gel route. The as-prepared nickel ferrites and its doped Ce and Nd nanomaterials were characterized in terms of Fourier transform infrared spectrophotometry, X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, selected area diffraction pattern, zeta potential and magnetism techniques. Their catalytic potential was examined in the (ep)oxidation of 1,2-cyclooctene by using hydrogen peroxide (H2O2) or tert-butylhydroperoxide (t-BuOOH). Optimization of various parameters, including solvent, oxidant and catalyst type revealed that chloroform (CHCl3) or 1,2-dichloroethane as a solvent and t-BuOOH as an oxidant were found to be the best choice for this catalytic system. The catalytic efficiency was found as Nd–NiFe2O4 > Ce–NiFe2O4 > NiFe2O4. Further, the applied nanocatalysts could be easily renovated and exhibited high catalytic reactivity for 5 times of recycling experiments with long-time durability. A reasonable discussion of the mechanism reaction reinforced the action of these spinel catalysts.
- Adam, Mohamed Shaker S.,Hafez, Aly M.,Khalaf, Mai M.
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p. 3237 - 3250
(2020/07/09)
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- The big effect of a small change: formation of CuO nanoparticles instead of covalently bound Cu(ii) over functionalized mesoporous silica and its impact on catalytic efficiency
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Two different heterogeneous catalysts, one with Cu(ii) covalently bonded to functionalized mesoporous silica (FMS-Cu(II)) and another with CuO nanoparticles immobilized over the same silica (FMS-CuO-np), have been synthesized by a common route but with a minor alteration in the sequence of addition of reagents. It is interesting to find that by merely changing the order of the addition of reagents Cu(ii) can be incorporated into the framework in two different forms. In one case Cu(ii) binds to the N and O donor centers present in the functionalized material whereas in the other case CuO nanoparticles are generated in situ. The materials have been thoroughly characterized by powder X-ray diffraction, nitrogen adsorption/desorption, transmission electron microscopy, thermal analysis, FT-IR spectroscopy, solid state MAS-NMR spectroscopy and atomic absorption spectrophotometric studies. The synthesized products have been examined for their catalytic efficiencies in the oxidation of olefins, as a model case. Styrene, α-methyl styrene, cyclohexene, trans-stilbene and cyclooctene have been used as substrates in the presence of tert-butyl hydroperoxide as the oxidant in acetonitrile medium under mild conditions. The products of the catalytic reactions have been identified and estimated by gas chromatography and gas chromatography-mass spectrometry. The rate of conversion of the substrates for both the catalysts is high and the selectivity is also good. But from comparative studies, it is found that FMS-CuO-np which contains CuO nanoparticles shows better efficiency than FMS-Cu(II). The catalysts have been recycled for five catalytic cycles without showing much decrease in their catalytic activity. This journal is
- Das, Trisha,Nandi, Mahasweta,Singha, Debdas
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p. 10138 - 10155
(2020/08/17)
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- Highly Selective and Catalytic Oxygenations of C?H and C=C Bonds by a Mononuclear Nonheme High-Spin Iron(III)-Alkylperoxo Species
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The reactivity of a mononuclear high-spin iron(III)-alkylperoxo intermediate [FeIII(t-BuLUrea)(OOCm)(OH2)]2+(2), generated from [FeII(t-BuLUrea)(H2O)(OTf)](OTf) (1) [t-BuLUrea=1,1′-(((pyridin-2-ylmethyl)azanediyl)bis(ethane-2,1-diyl))bis(3-(tert-butyl)urea), OTf=trifluoromethanesulfonate] with cumyl hydroperoxide (CmOOH), toward the C?H and C=C bonds of hydrocarbons is reported. 2 oxygenates the strong C?H bonds of aliphatic substrates with high chemo- and stereoselectivity in the presence of 2,6-lutidine. While 2 itself is a sluggish oxidant, 2,6-lutidine assists the heterolytic O?O bond cleavage of the metal-bound alkylperoxo, giving rise to a reactive metal-based oxidant. The roles of the urea groups on the supporting ligand, and of the base, in directing the selective and catalytic oxygenation of hydrocarbon substrates by 2 are discussed.
- Ghosh, Ivy,Banerjee, Sridhar,Paul, Satadal,Corona, Teresa,Paine, Tapan Kanti
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p. 12534 - 12539
(2019/08/07)
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- Synthetic Entry to Polyfunctionalized Molecules through the [3+2]-Cycloaddition of Thiocarbonyl Ylides
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Here we present a comprehensive study on the [3+2]-cycloaddition of thiocarbonyl ylides with a wide variety of alkenes and alkynes. The obtained dihydro- and tetrahydrothiophene products serve as exceptionally versatile intermediates providing access to thiophenes, dienes, dendralenes, and vic-quarternary carbon centers. The use of high-pressure conditions enables thermally unstable, sterically encumbered or moderately reactive substrates to undergo the cycloaddition under mild conditions, thereby increasing the yield by up to 58percent. In addition, we showcase its utility by the formal syntheses of the pharmaceuticals NGB 4420 and tenilapine.
- Habiger, Christoph,Haut, Franz-Lucas,Korber, Johannes Nepomuk,Müller, Thomas,Magauer, Thomas,Mayer, Peter,Speck, Klaus,Wurst, Klaus
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supporting information
(2019/09/06)
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- Synthesis, characterization, and catalytic oxidation of styrene, cyclohexene, allylbenzene, and cis-cyclooctene by recyclable polymer-grafted Schiff base complexes of vanadium(IV)
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Schiff base-functionalized chloromethylated polystyrenes, PS-[Ae-Eol] (I), PS-[Hy-Eda] (II) and PS-[HyP-Eda] (III), were synthesized by reacting 2-(2-aminoethoxy)ethanol (Ae-Eol), N-(2-hydroxyethyl)ethylenediamine (Hy-Eda), and N-(2-hydroxpropyl)ethylened
- Singh, Vijay Kumar,Maurya, Abhishek,Kesharwani, Neha,Kachhap, Payal,Kumari, Sweta,Mahato, Arun Kumar,Mishra, Vivek Kumar,Haldar, Chanchal
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p. 520 - 541
(2018/02/26)
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- Cobalt-Catalyzed Regioselective Olefin Isomerization under Kinetic Control
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Olefin isomerization is a significant transformation in organic synthesis, which provides a convenient synthetic route for internal olefins and remote functionalization processes. The selectivity of an olefin isomerization process is often thermodynamically controlled. Thus, to achieve selectivity under kinetic control is very challenging. Herein, we report a novel cobalt-catalyzed regioselective olefin isomerization reaction. By taking the advantage of fine-tunable NNP-pincer ligand structures, this catalytic system features high kinetic control of regioselectivity. This mild catalytic system enables the isomerization of 1,1-disubstituted olefins bearing a wide range of functional groups in excellent yields and regioselectivity. The synthetic utility of this transformation was highlighted by the highly selective preparation of a key intermediate for the total synthesis of minfiensine. Moreover, a new strategy was developed to realize the selective monoisomerization of 1-alkenes to 2-alkenes dictated by installing substituents on the γ-position of the double bonds. Mechanistic studies supported that the in situ generated Co-H species underwent migratory insertion of double bond/β-H elimination sequence to afford the isomerization product. The less hindered olefin products were always preferred in this cobalt-catalyzed olefin isomerization due to an effective ligand control of the regioselectivity for the β-H elimination step.
- Liu, Xufang,Zhang, Wei,Wang, Yujie,Zhang, Ze-Xin,Jiao, Lei,Liu, Qiang
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supporting information
p. 6873 - 6882
(2018/05/30)
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- Molybdenum(0) tricarbonyl and tetracarbonyl complexes with a cationic pyrazolylpyridine ligand: Synthesis, crystal structures and catalytic performance in olefin epoxidation
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The synthesis of molybdenum(0) tricarbonyl and tetracarbonyl complexes of the form [Mo(CO)3(ptapzpy)Br] (1) and cis-[Mo(CO)4(ptapzpy)]Br (2) is reported, where ptapzpy = 2-(1-propyltrimethylammonium-3-pyrazolyl)pyridine. Preparation of these derivatives was accomplished either through thermal replacement of CO in Mo(CO)6 (for 1) or substitution under milder conditions of piperidine ligands in the precursor cis-[Mo(CO)4(pip)2] (for 2). The crystal structures of the ligand [ptapzpy]Br and complexes 1 and 2 were determined. Thermal treatment of 2 at 125-150 °C leads to mono decarbonylation and formation of 1. On the other hand, oxidative decarbonylation of 1 and 2 by reaction with tert-butylhydroperoxide (TBHP, 10 equiv.) gives a molybdenum oxide hybrid material formulated as [Mo3O9([ptapzpy]Br)2]·nH2O (3), which was characterised by FT-IR and Raman spectroscopy, thermogravimetric analysis, and 13C{1H} CP MAS NMR spectroscopy. Compounds 1-3 were effective (pre)catalysts for the epoxidation of cis-cyclooctene at 55 °C with aqueous H2O2 or TBHP (slightly better results were obtained with the former). The characterisation of the Mo-containing solids isolated after the catalytic reaction showed that poorly soluble β-octamolybdate salts, (L)x[Mo8O26], were formed from 1-3 with TBHP and from 1 with H2O2, while soluble oxoperoxo species were formed from 3 with H2O2. These findings helped to explain the different catalytic performances obtained.
- Nogueira, Lucie S.,Neves, Patrícia,Gomes, Ana C.,Lavrador, Pedro,Cunha-Silva, Luís,Valente, Anabela A.,Gon?alves, Isabel S.,Pillinger, Martyn
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p. 16294 - 16302
(2018/05/22)
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- Copper(II) Schiff Base Complex Immobilized on Superparamagnetic Fe3O4@SiO2 as a Magnetically Separable Nanocatalyst for Oxidation of Alkenes and Alcohols
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A new heterogeneous catalyst containing a copper(II) Schiff base complex covalently immobilized on the surface of silica-coated Fe3O4 nanoparticles (Fe3O4@SiO2-Schiff base-Cu(II)) was synthesized. Characterization of this catalyst was performed using various techniques. The catalytic potential of the catalyst was investigated for the oxidation of various alkenes (styrene, α-methylstyrene, cyclooctene, cyclohexene and norbornene) and alcohols (benzyl alcohol, 3-methoxybenzyl alcohol, 3-chlorobenzyl alcohol, benzhydrol and n-butanol) using tert-butyl hydroperoxide as oxidant. The catalytic investigations revealed that Fe3O4@SiO2-Schiff base-Cu(II) was especially efficient for the oxidation of norbornene and benzyl alcohol. The results showed that norbornene epoxide and benzoic acid were obtained with 100 and 87% selectivity, respectively. Moreover, simple magnetic recovery from the reaction mixture and reuse for several times with no significant loss in catalytic activity were other advantages of this catalyst.
- Sarkheil, Marzieh,Lashanizadegan, Maryam
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- Dendritic porous yolk@ordered mesoporous shell structured heterogeneous nanocatalysts with enhanced stability
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One of the major challenges in heterogeneous catalysis is how to suppress the aggregation of thermodynamically unstable noble metal nanoparticles (NPs) and simultaneously maintain their high accessibility. Here we report the fabrication of integrated functional nanostructures consisting of a dendritic porous silica yolk with many small noble metal NPs and a protective mesoporous silica shell (MSS) with perpendicularly aligned pore channels and tunable shell thickness by using a well-controlled interfacial engineering strategy. Three-dimensional (3D) dendrimer-like superstructures with many permeable center-radial large pore channels and a highly accessible internal surface area, named dendritic porous silica spheres (DPSSs), serve as unique yolks not only because of their capability to accommodate high density ultrafine Au or Pt NPs, but also their functionality to act as robust physical barriers to separate and confine the aforementioned loaded NPs, which result in slowing down their aggregation at high temperatures due to Ostwald ripening. These integrated hierarchical structures also ensure good stability under weak basic and acidic conditions. Due to their superior structural properties, the DPSSs@noble metal NPs@MSS yolk-shell structures exhibit excellent catalytic performance in p-nitrophenol reduction, epoxidation reaction and CO oxidation. The favorable stability and high catalytic performance of these yolk-shell structures make the developed design strategy very useful for the fabrication of novel highly active and stable catalysts.
- Du, Xin,Zhao, Caixia,Luan, Yi,Zhang, Changbin,Jaroniec, Mietek,Huang, Hongwei,Zhang, Xueji,Qiao, Shi-Zhang
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p. 21560 - 21569
(2017/10/23)
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- A synergistic effect of a cobalt Schiff base complex and TiO2 nanoparticles on aerobic olefin epoxidation
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In this study, a cobalt Schiff base complex and TiO2 nanoparticles exhibited a synergistic effect on the visible-light photocatalytic activity in the aerobic oxidation of various olefins in the absence of a reducing agent. The catalyst structure was found to be well preserved after the oxidation reaction and the catalyst could be reused at least five times.
- Jafarpour, Maasoumeh,Kargar, Hossein,Rezaeifard, Abdolreza
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p. 79085 - 79089
(2016/09/09)
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- Copper(II) complex of (±)trans-1,2-cyclohexanediamine azo-linked Schiff base ligand encapsulated in the nanocavity of zeolite-Y for the catalytic oxidation of olefins
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A Schiff base ligand derived from 2-hydroxy-5-(phenylazo)-benzaldehyde and (±)trans-1,2-cyclohexanediamine (H2L) and its corresponding Cu(II) complex (CuL) were synthesized and characterized by FT-IR, UV-Vis and 1H-NMR spectroscopy. The copper Schiff base complex was encapsulated in the nanopores of zeolite-Y (CuL-Y) by the flexible ligand method and its encapsulation was confirmed by different studies. The homogeneous and the corresponding heterogeneous catalysts were used for the oxidation of different alkenes with tert-butyl hydroperoxide. Under the optimized reaction conditions, the oxidation of cyclooctene, cyclohexene, styrene and norbornene catalyzed by CuL gave 89, 63, 46 and 13 % conversion, respectively. These olefins were oxidized efficiently with 50, 96, 95 and 92 % conversion, respectively, in the presence of CuL-Y. Comparison of the catalytic behavior of CuL and CuL-Y showed the higher catalytic activity and selectivity of the heterogeneous catalyst with respect to the homogenous one.
- Lashanizadegan, Maryam,Shayegan, Sahar,Sarkheil, Marzieh
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p. 153 - 162
(2016/04/26)
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- Synthesis, characterization, DFT studies, and immobilization of cobalt(II) complex with N,N′,N″-tris(2-pyrimidinyl)dimethylentriamine on modified iron oxide as oxidation catalyst
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[Co3(PDMT)Cl6] complex, in which PDMT is N,N′,N″-tris(2-pyrimidinyl)dimethylentriamine was prepared in cyclohexanol under hydrothermal condition. At first, the crystal structure of PDMT was solved based on the Rietveld method by using laboratory X-ray powder diffraction data. The molecular geometry of the ligand and complex were optimized by B3LYP method. In order to heterogenize the prepared complex, it was immobilized on the modified Fe3O4 nanoparticles with (3-aminopropyl)trimethoxysilane (APTMS). The prepared compound designated as Fe3O4SiO2-2APTMS[Co3(PDMT)Cl6] was found to successfully catalyze the epoxidation of cyclooctene, styrene, cyclohexene, trans-stilbene as well as oxidation of fluorene, diphenylmethane, ethylbenzene, adamantane, cyclohexane, cyclooctane and norbornene with TBHP as oxidant with 25-100% conversions and 18-100% selectivities. Ligand, complex and Fe3O4SiO2-2APTMS[Co3(PDMT)Cl6] were characterized by FT-IR, TEM, XRD, Mass, UV-Vis, DSC-TGA, NMR, GC and GC-Mass techniques.
- Sharbatdaran, Masoomeh,Farzaneh, Faezeh,Larijani, Majid Mojtahedzadeh,Salimi, Alireza,Ghiasi, Mina,Ghandi, Mehdi
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p. 264 - 275
(2016/06/09)
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- Efficient photocatalytic oxygenation of alkenes by water soluble sensitizer in organic-water biphasic media
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A new green, environmentally and economically photooxygenation of olefins by molecular oxygen in the presence of 4-carboxyl tetra phenyl porphyrin (H2TCPP), Rose Bengal (RB), Methylene Blue (MB) and some metallosensitizers (MS) such as cobalt phthalocyaninesulfonate (Coph(SO3H)4), MnTCPPCl, FeTCPPCl and SbTPP(OH)2 as water-soluble sensitizers in organic-water biphasic media at room temperature under visible light was illustrated. The products were obtained with 100% conversion by H2TCPP and 100% selectivity by Coph(SO3H)4. Also in this study, singlet oxygen production as the major route for oxidation of olefins was proved.
- Hajimohammadi, Mahdi,Ghasemi, Hoda
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p. 670 - 676
(2016/08/30)
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- Oxidation reactivity of a structurally and spectroscopically well-defined mononuclear peroxocarbonatoiron(III) complex
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Mononuclear peroxocarbonatoiron(III) complex [Fe-(6Me-pic)2(O2C(O)O)]- (1-O2C(O)O) with bidentate ligands (6Me-pic), prepared by the reaction of a carbonatoiron(III) complex [Fe(6Me-pic)2(CO3)]- (1-CO3) with H2O2, was fully characterized. 1-O2C(O)O showed reversible OO bond cleavage and reformation of the peroxo group under CO2 at 25 °C. 1-O2C(O)O is capable of not only oxidizing the C=C bond of cyclooctene but also the CH bond of toluene. As for cyclooctene, epoxidation is favorable under CO2 in the presence of H2O, while cis-dihydroxylation precedes under N2, indicating that the oxidation reactivity of 1-O2C(O)O toward cyclooctene can be tuned by changing the concentration of CO2 and H2O.
- Tsugawa, Tomohiro,Furutachi, Hideki,Marunaka, Megumi,Endo, Taichi,Hashimoto, Koji,Fujinami, Shuhei,Akine, Shigehisa,Sakata, Yoko,Nagatomo, Shigenori,Tosha, Takehiko,Nomura, Takashi,Kitagawa, Teizo,Ogura, Takashi,Suzuki, Masatatsu
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supporting information
p. 330 - 332
(2015/03/30)
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- Bismuth-substituted "sandwich" type polyoxometalate catalyst for activation of peroxide: Umpolung of the peroxo intermediate and change of chemoselectivity
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The epoxidation of alkenes with peroxides by WVI, MoVI, VV, and TiIV compounds is well established, and it is well accepted that the active intermediate peroxo species are electrophilic toward nucleophilic substrates. Polyoxotungstates, for example, those of the "sandwich" structure, [WZn(TM-L)2(ZnW9O34)2]q- in which TM = transition metal and L = H2O, have in the past been found to be excellent epoxidation catalysts. It has now been found that substituting the Lewis basic BiIII into the terminal position of the "sandwich" polyoxometalate structure to yield [Zn2BiIII2(ZnW9O34)2]14- leads to an apparent umpolung of the peroxo species and formation of a nucleophilic peroxo intermediate. There are two lines of evidence that support the formation of a reactive nucleophilic peroxo intermediate: (1) More electrophilic sulfoxides are more reactive than more nucleophilic sulfides, and (2) nonfunctionalized aliphatic alkenes and dienes showed ene type reactivity rather than epoxidation pointing toward "dark" formation of singlet oxygen from the nucleophilic intermediate peroxo species. Allylic alcohols reacted much faster than alkenes but showed chemoselectivity toward C-H bond activation of the alcohol and formation of aldehydes or ketones rather than epoxidation. This explained via alkoxide formation at the BiIII center followed by oxidative β-elimination.
- Amanchi, Srinivasa Rao,Khenkin, Alexander M.,Diskin-Posner, Yael,Neumann, Ronny
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p. 3336 - 3341
(2015/06/16)
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- Epoxidation of strained alkenes catalysed by (1,2-dimethyl-4(1H)pyridinone-3-olate)2MnIIICl
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The mild epoxidation of strained alkenes using (DMPO)2MnCl catalyst (DMPO = 1,2-dimethyl-4(1H)-pyridinone-3-olate) in the presence of various oxidants was studied. Hydrogen peroxide and monopersulfate were found to be the best oxidants when used with imidazole in acetonitrile at 4 °C, with up to 94% conversion. Dismutation of hydrogen peroxide was also observed when used as an oxidant. The epoxidation using hydrogen peroxide or monoperoxysulfate appears to be mild and very selective for strained alkenes. A mechanism is proposed where imidazole is required for activation of the oxidant and where a detected MnV = O species is proposed as the active species. Competitive reaction between H2O2 and the substrate for the active species is proposed and homolytic vs heterolytic scissions of the OO bond of the oxidant are discussed.
- Robinson-Miller, Adam P.,Wyatt, Mark F.,Tétard, David
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p. 376 - 390
(2015/01/30)
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- Co6(μ3-OH)6 cluster based coordination polymer as an effective heterogeneous catalyst for aerobic epoxidation of alkenes
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A new hexaprismane Co(ii)6(μ3-OH)6 cluster-based three-dimensional coordination polymer ({Co(μ3-OH) (HCOO)0.72(CH3COO)0.28}n, Co6-CP) was successfully synthesized and characterized with single-crystal XRD, IR spectra, TGA spectra and elemental analysis. Co6-CP was used as an effective heterogeneous catalyst for the aerobic epoxidation of various alkenes. For the catalytic epoxidation of trans-stilbene, the conversion and selectivity towards the epoxide reached 98.6 and 98.0%, respectively. Also, an average TOF of 22 h-1 was obtained for the reaction. The results indicated that Co6-CP displayed excellent aerobic epoxidation activity among the reported coordination polymer materials, even rivaling the traditional heterogeneous cobalt catalysts. The influence of the reaction parameters such as temperature and oxygen flow rate for the epoxidation of the trans-stilbene were also studied in detail.
- Gao, Junkuo,Bai, Linlu,Zhang, Qian,Li, Yongxin,Rakesh, Ganguly,Lee, Jong-Min,Yang, Yanhui,Zhang, Qichun
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p. 2559 - 2565
(2014/02/14)
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- Epoxidation of alkenes using inorganic polymer of silica zirconia molybdate as catalyst
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Silica zirconia sulfate was prepared by sol-gel copolymerization of the sulfated zirconium octanoxide and tetraethylorthosilicate (TEOS). Active polymer oxidation catalysts were obtained by introducing sodium molybdate into the polymer by a ligand exchange reaction. The prepared inorganic polymer designated as SZ-Mo was characterized by FT-IR, SEM, XRD, N2 sorption isotherms, and ICP techniques. It was found that SZ-Mo successfully catalyzes the epoxidation of cyclooctene, cyclohexene, trans-stilbene, and norbornene with 22-95% conversion and 60-100% selectivity. The dependence of the SZ-Mo catalytic activity to the amount of adsorbed Mo within the polymer as well as the study of catalyst stability during the course of reactions will be described in this presentation.
- Sharbatdaran,Farzaneh,Larijani
-
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- Crystal structures and catalytic performance of three new methoxy substituted salen type nickel(II) Schiff base complexes derived from meso-1,2-diphenyl-1,2-ethylenediamine
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Three new nickel(II) complexes of a series of methoxy substituted salen type Schiff base ligands were synthesized and characterized by IR, UV-Vis and 1H NMR spectroscopy and elemental analysis. The ligands were synthesized from the condensation of meso-1,2-diphenyl-1,2-ethylenediamine with n-methoxysalicylaldehyde (n = 3, 4 and 5). Crystal structures of these complexes were determined. Electrochemical behavior of the complexes was studied by means of cyclic voltammetry in DMSO solutions. Catalytic performance of the complexes was studied in the epoxidation of cyclooctene using tert-butylhydroperoxide (TBHP) as oxidant under various conditions to find the optimum operating parameters. Low catalytic activity with moderate epoxide selectivity was observed in in-solvent conditions but in the solvent-free conditions, enhanced catalytic activity with high epoxide selectivity was achieved.
- Ghaffari, Abolfazl,Behzad, Mahdi,Pooyan, Mahsa,Amiri Rudbari, Hadi,Bruno, Giuseppe
-
-
- Mononuclear and dinuclear salen type copper(II) Schiff base complexes: Synthesis, characterization, crystal structures and catalytic epoxidation of cyclooctene
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A series of salen type Schiff base ligands and their mononuclear (CuL n, n = 1-4) or dinuclear Cu(II) complexes (Cu2(L 5)2) were synthesized and characterized by 1H NMR, IR and UV-Vis spectroscopy as well as elemental analyses. The ligands were synthesized from the condensation of meso-1,2-diphenyl-1,2-ethylenediamine with various salicylaldehyde derivatives (x-salicylaldehyde for H2L n, x = H (n = 1), 5-Br (n = 2), 5-Br-3-NO2 (n = 3), 3-OMe, (n = 5)) and 2′-hydroxyacetophenone (n = 4). Crystal structures of two complexes (CuL4 and Cu2(L5)2) were determined. Catalytic performance of the complexes was studied in the epoxidation of cyclooctene using tert-butylhydroperoxide (TBHP) as oxidant. Various factors including reaction temperature, solvent type, time, catalyst amount and substrate to oxidant ratio were optimized. High catalytic activity and epoxides selectivity was found. Solvent free epoxidation of cyclooctene was also studied and higher catalytic activity, epoxide selectivity and lower reaction times were observed.
- Abbasi, Zeinab,Behzad, Mahdi,Ghaffari, Abolfazl,Rudbari, Hadi Amiri,Bruno, Giuseppe
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- A polyhedral oligomeric silsesquioxane (POSS)-bridged oxo-molybdenum Schiff base complex with enhanced heterogeneous catalytic activity in epoxidation
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We have generated a new heterogeneous catalyst by bridging an oxo-molybdenum Schiff base on a polyhedral oligomeric silsesquioxane (POSS) via covalent attachment. The resulting POSS-bridged oxo-molybdenum Schiff base complex catalyst was fully characterized by 1H NMR, XRD, FT-IR, SEM, TGA, and contact angle analysis, and its catalytic potential was studied for the epoxidation of alkenes using aqueous tert-butyl hydroperoxide (TBHP) as the oxidant. The catalyst was found to be highly efficient and showed higher catalytic reactivity than the corresponding homogeneous analogues with added benefits of facile recovery and recycling of the heterogeneous catalyst. The POSS-bridged oxo-molybdenum Schiff base complex was successfully reused for four runs without significant loss in activity. The unique three dimensional network catalyst structure and the hydrophobic properties of the POSS units in the catalyst are revealed to be responsible for the catalyst's excellent performance in epoxidation reactions. This journal is the Partner Organisations 2014.
- Leng, Yan,Liu, Jian,Zhang, Chenjun,Jiang, Pingping
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p. 997 - 1004
(2014/04/03)
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- Epoxidation of cyclooctene by host (nanocavity of zeolite-Y) guest (copper(II) complexes with 16- and 17-membered diaza dioxa macrocyclic Schiff bases) nanocomposite materials
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This work reports the synthesis and characterization of macrocyclic copper(II) complexes encapsulated within the nanopores of zeolite-Y. The obtained nanoparticles entrapped in the nanopores of zeolite have been characterized by FT-IR, UV-Vis, Diffuse reflectance spectra, spectroscopic techniques, molar conductance, magnetic moment data, XRD, thermal, and elemental analysis. The complexes (neat and encapsulated) were used for the oxidation of cyclooctene with tert-butyl hydroperoxide as oxidant in different solvents. The supported Cu[L1]2+-Y exhibited a moderate 81.9% selectivity for epoxidation with 84.2% conversion. The catalytic activity and selectivity of the heterogeneous catalysts do not change after recycling five times.
- Banaei, Alireza,Rezazadeh, Behnam
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p. 2129 - 2140
(2013/08/23)
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- A cobalt-based 3D porous framework with excellent catalytic ability for the selective oxidation of cis-cyclooctene
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A 3D porous framework [Co3(μ2-OH) 4(I)2]·2H2O (I = hypoxanthine) with two types of 1D channels possess excellent catalytic ability for the selective oxidation of cis-cyclooctene. The Royal Society of Chemistry 2013.
- Zhang, Guangju,Li, Hao,Zhao, Fangfang,Hu, Hailiang,Huang, Hui,Li, Haitao,Han, Xiao,Liu, Ruihua,Dong, Huan,Liu, Yang,Kang, Zhenhui
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supporting information
p. 9423 - 9427
(2013/08/23)
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- Epoxidation of mixed bi-olefins with air over nanosized Co 3O4 assisted by ultrasonic waves
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Nanosized Co3O4 prepared by a simple method is considerably active in the ultrasonic waves assisted epoxidation of mixed bi-olefins with dry air. Both conversions and selectivities are distinctly promoted with α-methylstyrene and α-pinene mixed in the molar ratio of 1:1, as compared to α-methylstyrene or to α-pinene alone. When other alkenes are mixed with cyclooctene at 1:5 (molar ratio), different effects are observed. The mixture of styrene and cyclooctene shows almost the same increase in activity as the mixture of α-methylstyrene and α-pinene. While isophorone could assist the epoxidation of cyclooctene, by itself it could not be oxidized by molecular oxygen under the present conditions. When indene is mixed with cyclooctene, its conversion increases; however, the reactivity of cyclooctene decreases notably. UV-vis spectral analysis shows that these observations may be due to the intermolecular electron transfer which is very important for the enhancement of reactivities of bi-olefinic molecules.
- Lei,Lu,Zhang,Wei,Zhou,Xia
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p. 709 - 716
(2013/07/27)
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- Surface functionalization of supported Mn clusters to produce robust Mn catalysts for selective epoxidation
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A robust heterogeneous Mn catalyst for selective epoxidation was prepared by the attachment of a Mn4 oxonuclear complex [Mn4O 2(CH3COO)7(bipy)2](ClO 4)·3H2O (1) on SiO2 and the successive stacking of SiO2-matrix overlayers around a supported Mn cluster. The structures of supported Mn catalysts were characterized by means of FT-IR spectroscopy, diffuse-reflectance UV/vis spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and Mn K-edge X-ray absorption fine structure. A ligand exchange reaction between the CH3COO ligand of 1 and surface silanol group produced a SiO2-supported Mn cluster (2), whose coordination structure was similar to 1. Subsequent heating of 2 under vacuum yielded supported Mn clusters (3, 4) through the partial elimination of CH 3COO ligands. The surface-attached Mn clusters of 2, 3, and 4 were easily released to a reaction solution under epoxidation conditions (Mn leaching: approximately 50%), although they were active for epoxidation of trans-stilbene (the conversion of trans-stilbene, 99%, and the selectivity of trans-stilbene epoxid, 96%, for 6 h on 3). We found that the functionalization of the supported Mn cluster on 2 with surface SiO2-matrix overlayers altered the reactivity of the supported Mn cluster. Dimeric Mn species (5c) with reduced Mn oxidation state and coordination numbers was formed together with a reaction nanospace surrounded by the SiO2-matrix overlayers. By optimizing the stacking manner of the SiO2-matrix overlayers, the durability of the Mn catalyst was remarkably improved from leaching (the Mn leaching reached the minimum value of 0.01%), and active and stable epoxidation performances were successfully achieved in the heterogeneous phase (the conversion of trans-stilbene, 97%, and the selectivity of trans-stilbene epoxide, 91%, for 31 h on 5c).
- Muratsugu, Satoshi,Weng, Zhihuan,Tada, Mizuki
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p. 2020 - 2030
(2013/09/24)
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- The cinchona primary amine-catalyzed asymmetric epoxidation and hydroperoxidation of α,β-unsaturated carbonyl compounds with hydrogen peroxide
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Using cinchona alkaloid-derived primary amines as catalysts and aqueous hydrogen peroxide as the oxidant, we have developed highly enantioselective Weitz-Scheffer-type epoxidation and hydroperoxidation reactions of α,β-unsaturated carbonyl compounds (up to 99.5:0.5 er). In this article, we present our full studies on this family of reactions, employing acyclic enones, 5-15-membered cyclic enones, and α-branched enals as substrates. In addition to an expanded scope, synthetic applications of the products are presented. We also report detailed mechanistic investigations of the catalytic intermediates, structure-activity relationships of the cinchona amine catalyst, and rationalization of the absolute stereoselectivity by NMR spectroscopic studies and DFT calculations.
- Lifchits, Olga,Mahlau, Manuel,Reisinger, Corinna M.,Lee, Anna,Fares, Christophe,Polyak, Iakov,Gopakumar, Gopinadhanpillai,Thiel, Walter,List, Benjamin
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supporting information
p. 6677 - 6693
(2013/06/05)
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- Covalent attachment of a biomimetic Ru-(terpy)(bpy) complex on silica surface: Catalytic potential
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The Ru-containing modified silica [RuII(terpy)(4′Mebpy/ 4CONH(CH2)3SiO3/2)Cl]+ m·zSiO2 has been prepared by covalent attachment on silica surface of biomimetic [RuII(terpy)(4-CO2H- 4′-Mebpy)Cl]+ complex through the formation of a pseudo-peptide bond. The catalytic ability of bio-derived silica for alkene oxidation with HOOtBu has been evaluated exhibiting significant efficiency and, in some cases, showing increased activity compared vs. the corresponding 'net' [RuII(terpy)(4-CO2H-4′-Mebpy)Cl]+ complex. The data supported that the covalently attached ruthenium complex preserves the catalytic behaviour of the 'net' ruthenium complex indicating that the presented grafting process was successful.
- Papafotiou,Karidi,Garoufis,Louloudi
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p. 634 - 638
(2013/08/14)
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- The effect of encapsulated Zn-POM on the catalytic activity of MIL-101 in the oxidation of alkenes with hydrogen peroxide
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Zinc monosubstituted Keggin heteropolyanion [PZnMo2W 9O39]5- was electrostatically bound to nanocages of MIL-101 polymer matrix. The Zn-POM@MIL-101 catalyst was characterized by XRD, N2 adsorption, atomic absorption (AAS), and FT-IR spectroscopic methods. The catalytic activity of the new composite material, Zn-POM@MIL-101, was assessed in the oxidation of alkenes using aqueous hydrogen peroxide as oxidant. Zn-POM@MIL-101/H2O2 catalytic system demonstrated good catalytic activity in the oxidation reactions. Zn-POM@MIL-101 was reusable for three catalytic cycles. While the MIL-101 matrix is an active catalyst in these oxidation reactions, the presence of Zn-POM significantly changed the selectivity and reaction times. Copyright
- Saedi, Zahra,Tangestaninejad, Shaharm,Moghadam, Majid,Mirkhani, Valiollah,Mohammadpoor-Baltork, Iraj
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scheme or table
p. 463 - 473
(2012/05/20)
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- Aerobic oxidation of cycloalkenes catalyzed by iron metal organic framework containing N-hydroxyphthalimide
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Iron metal organic framework [Fe(BTC)] loaded with N-hydroxyphthalimide (NHPI) promotes the aerobic oxidation of (cyclo)alkenes to give variable percentages of allylic oxidation products and the corresponding epoxide, dependidng on the nature of the substrate. In the case of cyclopentene and cyclohexene, aerobic oxidation catalyzed by NHPI/Fe(BTC) renders their corresponding unsaturated cyclic alcohol and ketone with 97% selectivity in 5 h at 6% and 12% conversion, respectively. Under the same experimental conditions, cyclooctene exhibited 95% selectivity toward the formation of cyclooctene oxide with 2% of cyclooctenol/one at 4 h. Cycloheptene as susbstrate exhibits an intermediate behavior, and the aerobic oxidation catalyzed by NHPI/Fe(BTC) leads to the formation of cycloheptenol/cycloheptenone with 77% selectivity, accompanied by 23% of cycloheptene oxide at 4 h. Further experiments with non-symmetric olefins exhibited also a mixture of products including epoxides and allyic products. A mechanism to explain these experimental results has been proposed.
- Dhakshinamoorthy, Amarajothi,Alvaro, Mercedes,Garcia, Hermenegildo
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experimental part
p. 259 - 265
(2012/06/01)
-
- A novel heteropolyanion-based amino-containing cross-linked ionic copolymer catalyst for epoxidation of alkenes with H2O2
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A heteropolyanion-based cross-linked ionic copolymer was prepared by the anion-exchange of a newly task-specific designed amino-containing ionic copolymer with a Keggin heteropolyacid, and characterized by FT-IR, SEM, TG, XRD, UV-vis, ESR, 1H NMR, and elemental analysis. Its catalytic activity was evaluated in the epoxidation of alkenes with aqueous H 2O2. The resultant heteropolyanion-based ionic copolymer is revealed to be a highly efficient heterogeneous catalyst for epoxidation of alkenes with H2O2, adding the advantages of convenient recovery and steady reuse.
- Leng, Yan,Zhang, Weijie,Wang, Jun,Jiang, Pingping
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p. 306 - 311
(2013/02/23)
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- Anionic iron(III) porphyrins immobilized on zinc hydroxide chloride as catalysts for heterogeneous oxidation reactions
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This work describes the immobilization of an anionic iron(III) porphyrin (FePor) family on zinc hydroxide chloride (ZHC), a layered hydroxide salt prepared by reacting an aqueous zinc chloride solution with an ammonium hydroxide solution. The FePor immobilization was performed at room temperature under magnetic stirring, under air atmosphere, of each complex ethanol solution and the ZHC solid support suspension. The materials obtained were characterized by X-ray powder diffraction (XRPD), ultraviolet-visible spectroscopy (UV-vis) (solid samples), Fourier transform infrared spectroscopy (FTIR) and electron paramagnetic resonance (EPR). The catalytic activity of the solids was investigated in cyclooctene, cyclohexane and n-heptane heterogeneous catalytic oxidation reactions with iodosylbenzene as the oxygen donor. The solid catalyst's reutilization capacity was also investigated and the heterogeneous character of the catalytic process was confirmed. The compounds and the catalytic activity of FePor-ZHC were compared with the synthesis and catalytic activity of the same FePor immobilized on zinc hydroxide nitrate (ZHN). Though the matrixes are similar, the results obtained were exactly the opposite when the selectivity was analyzed.
- MacHado, Guilherme Sippel,Wypych, Fernando,Nakagaki, Shirley
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experimental part
p. 94 - 102
(2012/03/27)
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- L-Proline-derived ligands to mimic the '2-His-1-carboxylate' triad of the non-haem iron oxidase active site
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Non-haem iron(II) oxidases (NHIOs) catalyse a variety of oxidative transformations in biology. The iron-binding environment of the NHIO active site typically incorporates a '2-His-1-carboxylate' facial triad of amino acid side-chains, a motif that has emerged as a defining feature of the enzyme family. Towards the goal of biomimetic, iron-mediated C-H activation we have synthesized a series of peptidomimetic ligands from l-proline. By coupling l-proline to 2,6-bis(bromomethyl)pyridine, 2-(bromomethyl)-6-((tert- butyldimethylsilyloxy)methyl)pyridine and picolinic acid, we have generated several new ligand architectures designed to complex with iron(II) and mimic the NHIO active site. The resulting iron complexes promote modest levels of alkene dihydroxylation and allylic oxidation using hydrogen peroxide as oxidant.
- Dungan, Victoria J.,Wong, Shwo Mun,Barry, Sarah M.,Rutledge, Peter J.
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experimental part
p. 3231 - 3236
(2012/06/01)
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- Synthesis of cyclic enones via direct palladium-catalyzed aerobic dehydrogenation of ketones
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α,β-Unsaturated carbonyl compounds are versatile intermediates in the synthesis of pharmaceuticals and biologically active compounds. Here, we report the discovery and application of Pd(DMSO)2(TFA)2 as a catalyst for direct dehydrogenation of cyclohexanones and other cyclic ketones to the corresponding enones, using O2 as the oxidant. The substrate scope includes heterocyclic ketones and several natural-product precursors.
- Diao, Tianning,Stahl, Shannon S.
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supporting information; experimental part
p. 14566 - 14569
(2011/10/17)
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- Synthesis, characterization, and catalytic activity of a polymer-supported copper(II) complex with a thiosemicarbazone ligand
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A thiosemicarbazone Cu(II) complex anchored to a polystyrene framework has been synthesized and characterized by analytical and spectroscopic techniques. The complex was found to be a highly active catalyst for the oxidation of various organic substrates including alkenes and alcohols using H 2O2 as oxidant. The reaction conditions were optimized with respect to temperature, solvent, oxidant, catalyst amount, and substrate to peroxide ratio. The heterogeneous catalyst was reused five times without significant loss of activity. A comparison between the catalytic activities of this polymer-supported Cu(II) complex and its homogeneous analogue was carried out.
- Islam, Manirul,Hossain, Dildar,Mondal, Paramita,Tuhina, Kazi,Roy, Anupam Singha,Mondal, Sanchita,Mobarak, Manir
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experimental part
p. 223 - 230
(2012/04/17)
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- Photooxygenation of alkenes by molecular oxygen in the presence of porphyrins and chlorin sensitizers under visible light irradiation
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Photooxidation of alkenes by molecular oxygen and visible light in the presence of tetraphenylporphyrin (H2TPP), tetramesitylporphyrin (H2TMP), tetrakis pentafluorophenylporphyrin (H2TPFPP) and tetrakis(2,3-dimetoxyphenyl)porphyrin T(2,3-OMeP)P and metalloporphyrins such as ClFeTPP, ClMnTMP, ClMnTPP, ClMnTPFPP, ClCoTPP and ZnTPP has been performed. Photooxidation of alkenes with tetraphenylchlorin (H2TPC) as the sensitizer with visible light has also been studied. The conversion rates for alkene oxidation were in the order of free-base porphyrins > chlorin > metalloporphyrins. In the presence of NaN3/Na2SO 3 the yield of oxidation products and conversion percentage is considerably reduced, confirming involvement of 1O2 in the mechanism.
- Hajimohammadi, Mahdi,Safari, Nasser
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experimental part
p. 639 - 645
(2011/10/04)
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- Selective oxidation of olefins catalyzed by polymer-anchored nickel(II) complex in water medium
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Selective oxidation of olefins has been carried out in water medium with tert-butylhydroperoxide (TBHP, 70% aqueous) as an oxidant using polymer-anchored Ni(II) complex as a catalyst. Several parameters were varied to optimize the reaction conditions. Under the optimized reaction conditions olefins gave selectively allylic oxidation products. The present polymer anchored Ni(II) complex can be recycled five times without any appreciable loss in catalytic activity.
- Islam, Manirul,Hossain, Dildar,Mondal, Paramita,Roy, Anupam Singha,Mondal, Sanchita,Mobarak, Manir
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scheme or table
p. 3765 - 3770
(2011/09/21)
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- Photoinduced electron transfer from enol silyl ethers to quinone. Part 1. Pronounced effects of solvent polarity and added salt on the formation of α-enones
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The enol silyl ethers (ESE) of various ketones are efficiently oxidized to the corresponding α, β-unsaturated enones (E) when a dichloromethane solution containing equimolar amounts of chloranil is irradiated with filtered light (λexc > 380 nm). The 1:1 adduct (A) of enol silyl ether and quinone is a byproduct, the structure of which is established by X-ray crystallography. Solvent polarity and added salts play a major role in establishing the product distribution between E and A. Such a medium effect, coupled with the ready isomerization of the kinetic-thermodynamic isomers derived from the silylation of 2-methylcyclohexanone, points to the cation radical of the enol silyl ether (ESE.+) as the reactive intermediate. A radical-ion pair mechanism involving the rapid one-electron oxidation of enol silyl ethers by photoactivated chloranil is discussed.
- Bockman, T. Michael,Shukla,Kochi, Jay K.
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p. 1623 - 1632
(2007/10/03)
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- Photoinduced electron transfer from enol silyl ethers to quinone. Part 2. Direct observation of ion-pair dynamics by time-resolved spectroscopy
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Time-resolved spectroscopy in two time domains (encompassing picoseconds and nanoseconds/microseconds) allows all the reactive intermediates involved in the photooxidation of enol silyl ethers (ESE) by chloranil (CA) to be identified, and each step in their temporal evolution to α-enone (E) and adduct (A) to be delineated.Thus, the radical-ion pair is the common intermediate formed in unit quantum yield via the highly efficient quenching of triplet chloranil by enol silyl ethers in both dichloromethane and acetonitrile.In the context of the Fuoss-Winstein formulation, the first-formed is a contact ion-pair, which in a non-polar solvent, such as dichloro-methane, predominantly suffers an initial ion-pair collapse (internal return) by β-proton transfer, and the resultant radical pair ultimately leads to α-enone (E).The contact ion-pair formed in the polar solvent undergoes diffusive separation, and the free ion ESE cation radical suffers desilylation by acetonitrile and ultimately leads to adduct (A).Added electrolyte to dichloromethane solutions modulates the ion-pair behaviour via the 'special salt effect' to divert the enone pathway to adduct formation.
- Bockman, T. Michael,Kochi, Jay K.
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p. 1633 - 1644
(2007/10/03)
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