- Aerobic epoxidation of olefins by carboxylate ligand-based cobalt (II) compound: synthesis, X-ray crystallography, and catalytic exploration
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A new quinoline carboxylate-based cobalt (II) metal compound, [Co (HL1)2(H2O)4] (1) (H2L1 = 2-hydroxyquinoline-4-carboxylic acid) has been hydrothermally synthesized, and fully characterized by single-crystal X-ray diffraction, powder X-ray diffraction, Fourier-transform infrared (FT-IR), elemental and thermo-gravimetric analysis. Compound 1 shows high thermal stability up to ~300°C. Single-crystal X-ray diffraction study of 1 exhibited monomeric structure experiences further stabilized in solid state through different non-covalent interaction, for example, H-bonding and π···π stacking interaction and extended to 3D supramolecular H-bonded network. Compound 1 efficiently catalyzes epoxidation reactions of olefins under homogeneous conditions using molecular oxygen as an oxidizer. Another reported quinoline carboxylate-based nickel (II) monomer [Ni(L2)2(H2O)2] (2) (HL2 = thiazole-4-carboxylic acid) has been synthesized and characterized to compare it with compound 1 towards aerobic epoxidation reactions, where 1 comes as superior.
- Brandao, Paula,Debnath, Rakesh,Gayen, Saikat,Ghosh, Pameli,Koner, Subratanath,Lin, Zhi,Maity, Tanmay,Mal, Dasarath,Patra, Birendra Nath,Pratihar, Jahar Lal,Sepay, Nayim
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- Ni/Photoredox-Catalyzed Enantioselective Cross-Electrophile Coupling of Styrene Oxides with Aryl Iodides
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A Ni/photoredox-catalyzed enantioselective reductive coupling of styrene oxides and aryl iodides is reported. This reaction affords access to enantioenriched 2,2-diarylalcohols from racemic epoxides via a stereoconvergent mechanism. Multivariate linear regression (MVLR) analysis with 29 bioxazoline (BiOx) and biimidazoline (BiIm) ligands revealed that enantioselectivity correlates with electronic properties of the ligands, with more electron-donating ligands affording higher ee's. Experimental and computational mechanistic studies were conducted, lending support to the hypothesis that reductive elimination is enantiodetermining and the electronic character of the ligands influences the enantioselectivity by altering the position of the transition state structure along the reaction coordinate. This study demonstrates the benefits of utilizing statistical modeling as a platform for mechanistic understanding and provides new insight into an emerging class of chiral ligands for stereoconvergent Ni and Ni/photoredox cross-coupling.
- Lau, Sii Hong,Borden, Meredith A.,Steiman, Talia J.,Wang, Lucy S.,Parasram, Marvin,Doyle, Abigail G.
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supporting information
p. 15873 - 15881
(2021/10/12)
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- Kinetic resolution ofN-aryl β-amino alcoholsviaasymmetric aminations of anilines
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An efficient kinetic resolution ofN-aryl β-amino alcohols has been developedviaasymmetricpara-aminations of anilines with azodicarboxylates enabled by chiral phosphoric acid catalysis. Broad substrate scope and high kinetic resolution performances were afforded with this method. Control experiments supported the critical roles of the NH and OH group in these reactions.
- Guo, Zheng,Xie, Jinglei,Hu, Tao,Chen, Yunrong,Tao, Houchao,Yang, Xiaoyu
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supporting information
p. 9394 - 9397
(2021/09/22)
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- MeOTf/KI-catalyzed efficient synthesis of 2-arylnaphthalenesviacyclodimerization of styrene oxides
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The MeOTf/KI-catalyzed synthesis of 2-arylnaphthalene derivatives from aryl ethylene oxides in alcohol under ambient conditions is described. The present protocol has a higher atom efficiency and wider substrate applicability with excellent yields. The reaction proceeded using the aryl ethylene oxides to give 2-arylnaphthalenes either in homo-coupling or in cross-coupling. The reaction could also be carried out at the gram scale in minutes.
- Chen, Chao,Xi, Chanjuan,Zhang, Zeyu,Zou, Song
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supporting information
p. 8559 - 8565
(2021/10/20)
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- Oxidovanadium(V) and dioxidomolybdenum(VI) Complexes of N'-(3,5-Dichloro-2-hydroxybenzylidene)-4-fluorobenzohydrazide: Synthesis, characterization, crystal structures and catalytic property
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N'-(3,5-Dichloro-2-hydroxybenzylidene)-4-fluorobenzohydrazide (H2L) was used to prepare oxidovanadium(V) complex [VOL(OEt)(MeOH)] (1) and dioxidomolybdenum(VI) complex [MoO2L(OH2)]·[MoO2L(EtOH)] (2). The complexes were characterized by IR, UV-Vis, NMR spectroscopy, and single crystal X-ray diffraction. X-ray analysis indicates that the complexes are mononuclear species with the metal atoms in octahedral coordination. The complexes were studied for catalytic oxidation property on some olefins with tert-butyl hydroperoxide as oxidant.
- Liu, Huan-Yu,Yang, Luo-Ju,Ye, Ya-Fang,Yin, Yi-Shu,Zou, Xiao-Ling
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p. 130 - 136
(2020/03/30)
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- Synthesis, Characterization and Crystal Structures of Oxidovanadium(V) and Dioxidomolybdenum(VI) Complexes Derived from 2-bromo-N'-(2-hydroxy-3-methoxybenzylidene)benzohydrazide with Catalytic Property
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Abstract: A hydrazone compound 2-bromo-N'-(2-hydroxy-3-methoxybenzylidene)benzohydrazide (H2L) was prepared and characterized by IR, UV-Vis and NMR spectra. Based on the hydrazone compound, a new oxidovanadium(V) and a new dioxidomolybdenum(VI) complexes, [VO(L)(OEt)(EtOH)] (I) and [MoO2(L)(OH2)] (II), were prepared and characterized by IR, UV-Vis, NMR spectra, and single crystal X-ray diffraction (CIF files nos. 1866755 (I) and 1866756 (II)). Complex I crystallizes as the monoclinic space group P21/c with unit cell dimensions a = 12.8733(12), b = 13.5088(13), c = 11.9262(11) ?, β = 91.765(2)°, V = 2073.0(3) ?3, Z = 4, R1 = 0.0524, wR2 = 0.1329, GOOF = 1.245. Complex II crystallizes as the monoclinic space group P21/c with unit cell dimensions a = 8.1140(9), b = 16.2975(19), c = 13.4318(15) ?, β = 106.456(2)°, V = 1703.4(3) ?3, Z = 4, R1 = 0.0296, wR2 = 0.0728, GOOF = 1.046. X-ray analysis indicates that the complexes are mononuclear species with the metal atoms in octahedral coordination. The complexes were studied for catalytic oxidation property on some olefins with tert-butyl hydrogen peroxide as oxidant.
- Liu,Zou,Yang,Ye,Yang
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p. 809 - 816
(2019/11/11)
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- Synthesis of Alkenyl Boronates from Epoxides with Di-[B(pin)]-methane via Pd-Catalyzed Dehydroboration
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A practical and broadly applicable catalytic method for the synthesis of (E)-alkenylborons is presented. Reactions are promoted by [Pd(Cl)(η3-C3H5)]2 and proceed by the dehydroboration of cyclic borates. Through
- Murray, Stephanie A.,Luc, Eugenia C. M.,Meek, Simon J.
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supporting information
p. 469 - 472
(2018/01/28)
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- Synthesis, Characterization, and Crystal Structures of Dioxomolybdenum(VI) Complexes Derived from Similar Tridentate Hydrazone Compounds with Catalytic Property
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Abstract: Two hydrazone compounds 2-chloro-N'-(2-hydroxy-4-methoxybenzylidene)benzohydrazide (H2L1) and N'-(2-hydroxy-4-methoxybenzylidene)-3-methylbenzohydrazide (H2L2) were prepared and characterized by IR, UV-Vis and 1H NMR spectra. Based on the hydrazone compounds, two new structurally similar dioxomolybdenum(VI) complexes, [MoO2L1(CH3OH)] (I) and [MoO2L2(CH3OH)] (II), were prepared and characterized by IR and UV-Vis spectra, and single crystal X-ray diffraction (CIF files nos. 1566491 (I) and 1566492 (II)). Complex I crystallizes as the triclinic space group (Formula presented.) with unit cell dimensions a = 8.0750(5), b = 10.5223(7), c = 10.8110(7) ?, α = 96.975(2)°, β = 97.909(2)°, γ = 104.497(2)°, V = 869.2(1) ?3, Z = 2, R1 = 0.0323, wR2 = 0.0620, GOOF = 1.089. Complex II crystallizes as the monoclinic space group P21/n with unit cell dimensions a = 11.680(1), b = 10.496(2), c = 14.879(2) ?, β = 98.862(2)°, V?= 1802.2(4) ?3, Z = 4, R1 = 0.0270, wR2 = 0.0675, GOOF = 1.111. X-ray analysis indicates that the complexes are mononuclear dioxomolybdenum(VI) species with the Mo atoms in octahedral coordination. The complexes were studied for their catalytic oxidation property on some olefins with tert-butyl hydrogen peroxide as oxidant.
- Liu,Yang,Diao,Ye,Zou
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p. 572 - 578
(2018/09/11)
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- Stable Copper Nanoparticle Photocatalysts for Selective Epoxidation of Alkenes with Visible Light
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Selective epoxidation of various alkenes with molecular oxygen (O2) under mild conditions is a longstanding challenge in achieving syntheses of epoxides. Cu-based catalysts have been found to be catalytically active for selective epoxidations. However, the application of copper nanoparticles (CuNPs) for photocatalyzed epoxidations is encumbered by the instability of CuNPs in air. Herein we report that CuNPs supported on titanium nitride (TiN) without additional stabilizers not only are stable in air but also can catalyze selective epoxidation of various alkenes with O2 or even air as a benign oxidant under light irradiation. CuNPs remain in the metallic state due to the significant charge transfer that occurs between CuNPs and TiN. The epoxidation is driven by visible light irradiation at moderate temperatures, achieving good to high yields and excellent selectivity. The photocatalytic process is applicable to the selective epoxidation of various alkenes. In this photocatalytic system, reactant alkenes chemically adsorb on CuNPs, forming Cu-alkene surface complexes, and light irradiation can activate the complexes for reaction. The cyclic ether solvent also plays a key role, reacting with O2 on the surface of CuNPs under light irradiation, yielding oxygen adatoms. The activated surface complexes react with the adatoms, yielding the corresponding epoxides. Analysis of the influence of irradiation wavelength and intensity on the epoxidation suggests that light-excited electrons of CuNPs drive the reaction. The adatoms formed react with alkenes, producing the final product epoxides. We also observed interesting product stereoselectivity, predominantly generating the trans isomers for the epoxidation of stilbene (up to 97%). The findings reported here not only provide an effective and selective reaction system for alkene epoxidations but also are a step toward demonstrating the practical use of CuNPs as photocatalysts for various applications.
- Huang, Yiming,Liu, Zhe,Gao, Guoping,Xiao, Gang,Du, Aijun,Bottle, Steven,Sarina, Sarina,Zhu, Huaiyong
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p. 4975 - 4985
(2017/08/17)
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- Stereoselective Tandem Bis-Electrophile Couplings of Diborylmethane
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A copper-catalyzed three-component linchpin coupling method for the stereoselective union of readily available epoxides and allyl electrophiles is disclosed. Transformations employ [B(pin)]2-methane as a conjunctive reagent, resulting in the fo
- Murray, Stephanie A.,Liang, Michael Z.,Meek, Simon J.
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supporting information
p. 14061 - 14064
(2017/10/17)
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- Diastereoselective C?H Bond Amination for Disubstituted Pyrrolidines
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We report herein the improved diastereoselective synthesis of 2,5-disubstituted pyrrolidines from aliphatic azides. Experimental and theoretical studies of the C?H amination reaction mediated by the iron dipyrrinato complex (AdL)FeCl(OEt2) provided a model for diastereoinduction and allowed for systematic variation of the catalyst to enhance selectivity. Among the iron alkoxide and aryloxide catalysts evaluated, the iron phenoxide complex exhibited superior performance towards the generation of syn 2,5-disubstituted pyrrolidines with high diastereoselectivity.
- Iovan, Diana A.,Wilding, Matthew J. T.,Baek, Yunjung,Hennessy, Elisabeth T.,Betley, Theodore A.
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supporting information
p. 15599 - 15602
(2017/11/16)
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- The Activation of Carboxylic Acids via Self-Assembly Asymmetric Organocatalysis: A Combined Experimental and Computational Investigation
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The heterodimerizing self-assembly between a phosphoric acid catalyst and a carboxylic acid has recently been established as a new activation mode in Br?nsted acid catalysis. In this article, we present a comprehensive mechanistic investigation on this activation principle, which eventually led to its elucidation. Detailed studies are reported, including computational investigations on the supramolecular heterodimer, kinetic studies on the catalytic cycle, and a thorough analysis of transition states by DFT calculations for the rationalization of the catalyst structure-selectivity relationship. On the basis of these investigations, we developed a kinetic resolution of racemic epoxides, which proceeds with high selectivity (up to s = 93), giving the unreacted epoxides and the corresponding protected 1,2-diols in high enantiopurity. Moreover, this approach could be advanced to an unprecedented stereodivergent resolution of racemic α-chiral carboxylic acids, thus providing access to a variety of enantiopure nonsteroidal anti-inflammatory drugs and to α-amino acid derivatives.
- Monaco, Mattia Riccardo,Fazzi, Daniele,Tsuji, Nobuya,Leutzsch, Markus,Liao, Saihu,Thiel, Walter,List, Benjamin
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supporting information
p. 14740 - 14749
(2016/11/18)
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- Substrate ionization energy influences the epoxidation of m-substituted styrenes catalyzed by chloroperoxidase from Caldariomyces fumago
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Chloroperoxidase from the fungus Caldariomyces fumago is a versatile heme-peroxidase, which is able to catalyze olefin epoxidation. In this report, the epoxidation of m-substituted styrene catalyzed by chloroperoxidase was studied. The catalytic data fit
- Mu?oz-Guerrero, Fabio A.,águila, Sergio,Vazquez-Duhalt, Rafael,Campos, Cristian H.,Torres, Cecilia C.,Alderete, Joel B.
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- A Self-Assembled Molecular Cage for Substrate-Selective Epoxidation Reactions in Aqueous Media
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Encapsulation of a manganese porphyrin in a self-assembled molecular cage allows catalytic epoxidation of various substrates in 1:1 water/acetonitrile mixtures. The cage acts as a phase-transfer catalyst and creates a protective environment for the catalyst improving the stability. The encapsulated catalyst also allows discrimination between styrene derivatives of various sizes. In a direct competition experiment, the selectivity of the epoxidation reaction could be inverted with respect to a benchmark catalyst.
- Kuijpers, Petrus F.,Otte, Matthias,Dürr, Maximilian,Ivanovi?-Burmazovi?, Ivana,Reek, Joost N. H.,De Bruin, Bas
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p. 3106 - 3112
(2016/07/06)
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- Three powerful dinuclear metal-organic catalysts for converting CO2 into organic carbonates
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Developing efficient catalysts for converting carbon dioxide (CO2) into varied organic carbonates is an important scientific goal. By using the NH2-functionalized tripodal ligand 2-((bis(2-aminoethyl)amino)methyl)phenol (HL), three dinuclear metal-organic complexes [Zn(L)]2·2ClO4 (1), [Cu(L)]2·2ClO4·2H2O (2) and [Cd(L)]2·2ClO4 (3) have been successfully isolated and structurally characterized using single-crystal X-ray diffraction analyses. Considering the dinuclear metal centers and the NH2-functional groups in the structures, 1-3 were investigated as catalysts for converting CO2 into organic carbonates, and the results show that 1-3 exhibit an outstanding ability for converting CO2 into varied organic carbonates at atmospheric pressure (0.1 MPa). The catalytic system also displays a wide substrate scope and high catalytic activity, and the reaction mechanism has been proposed herein.
- Zhao, Dan,Liu, Xiao-Hui,Shi, Zhuang-Zhi,Zhu, Chen-Dan,Zhao, Yue,Wang, Peng,Sun, Wei-Yin
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p. 14184 - 14190
(2016/11/05)
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- Efficient Epoxidation of Styrene Derivatives by a Nonheme Iron(IV)-Oxo Complex via Proton-Coupled Electron Transfer with Triflic Acid
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Styrene derivatives are not oxidized by [(N4Py)FeIV(O)]2+ (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine) in acetonitrile at 298 K, whereas epoxidation of styrene derivatives by the iron(IV)-oxo complex occurs efficiently in the presence of triflic acid (HOTf) via proton-coupled electron transfer (PCET) from styrene derivatives to the diprotonated species of [(N4Py)FeIV(O)]2+ with HOTf. Logarithms of the first-order rate constants of HOTf-promoted expoxidation of styrene derivatives with [(N4Py)FeIV(O)]2+ and PCET from electron donors to [(N4Py)FeIV(O)]2+ in the precursor complexes exhibit a remarkably unified correlation with the driving force of PCET in light of the Marcus theory of electron transfer when the differences in the formation constants of precursor complexes are taken into account. The same PCET driving force dependence is obtained for the first-order rate constants of HOTf-promoted oxygen atom transfer from thioanisols to [(N4Py)FeIV(O)]2+ and HOTf-promoted hydrogen atom transfer from toluene derivatives to [(N4Py)FeIV(O)]2+ in the precursor complexes. Thus, HOTf-promoted epoxidation of styrene derivatives by [(N4Py)FeIV(O)]2+ proceeds via the rate-determining electron transfer from styrene derivatives to the diprotonated species of [(N4Py)FeIV(O)]2+, as shown in the reactions of HOTf-promoted oxygen atom transfer from thioanisols to [(N4Py)FeIV(O)]2+ and HOTf-promoted hydrogen atom transfer from toluene derivatives to [(N4Py)FeIV(O)]2+.
- Park, Jiyun,Lee, Yong-Min,Ohkubo, Kei,Nam, Wonwoo,Fukuzumi, Shunichi
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supporting information
p. 5806 - 5812
(2015/06/25)
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- Synthesis, structure, and catalytic oxidation of a molybdenum(VI) complex [MoO2(CH3OH)L]
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A new molybdenum(VI) complex, [MoO2(CH3OH)(L)] (L = N′-(4-diethylamino-2-hydroxybenzylidene)-4-hydroxybenzohydrazide), was prepared and characterized by spectroscopy methods and single crystal X-ray diffraction (CIF file CCDC no. 1038153). The crystal of the complex, C19H23MoN3O6, crystallizes in the triclinic space group P1 with unit cell dimensions a = 6.9824(9), b = 10.206(1), c = 15.302(2) ?, α = 94.399(2)°, β = 101.877(2)°, γ = 104.062(2)°, V = 1025.9(2) ?3, Z = 2, R1 = 0.0317, wR2 = 0.0796, S = 1.060. The Mo atom in the complex is in an octahedral coordination with phenolate O, imino N, enolate O atoms of the ligand L, and one oxo O in the equatorial plane, and with one methanol O and the other oxo O in the axial sites. Crystals of the complex are stabilized by hydrogen bonds. The complex was studied for its catalytic oxidation property on some olefins, with tert-butyl hydrogen peroxide as oxidant.
- Liu,Zang,Lv
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p. 451 - 455
(2015/07/01)
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- Rhodium-catalyzed transannulation of N-sulfonyl-1,2,3-triazoles and epoxides: Regioselective synthesis of substituted 3,4-dihydro-2 H-1,4-oxazines
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Rhodium-catalyzed transannulation of 1,2,3-triazoles and ring-opening reactions of epoxides is described. A number of 3,4-dihydro-2H-1,4-oxazines are obtained in moderate yields probably involving generation of α-imino rhodium(II) carbene species.
- Ma, Xueji,Pan, Shanfei,Wang, Hangxiang,Chen, Wanzhi
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supporting information
p. 4554 - 4557
(2015/02/19)
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- 2,2′-Bipyridyl-acetylphenolato mixed ligand copper(II) complexes: Syntheses, characterizations and catalytic activity in styrene epoxidation
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Two copper(II) complexes, [Cu(bipy)(5-Br-2-hap)(ClO4)]2 (1) and [Cu(bipy)(2-hap)(ClO4)] (2) (where bipy = 2,2′-bipyridine, 5-Br-2-hap = 5-bromo-2-hydroxyacetophenone, 2-hap = 2-hydroxyacetophenone), were synthesized and characterized. The crystal structure of 1 was determined by single crystal X-ray diffraction while 2 was reported earlier. Structural characterization reveals that the presence of bromine in 5-Br-2-hap plays a structure-determining role in dimeric 1 in comparison with the mononuclear 2 where 2-hap was used. Studies of the catalytic potential toward styrene epoxidation in homogeneous system using H2O2 as oxidant reveal that 1 is more efficient than 2 with respect to epoxide selectivity.
- Shit, Shyamapada,Yadava, Umesh,Saha, Debraj,Roland Froehlich
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- Heterogeneous catalytic epoxidation of olefin over a hydrothermally synthesized 3D phosphate bridged copper(II) framework
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A 3D copper phosphate, [Cu2(PO4)(OH)] n (1), has been synthesized hydrothermally and characterized by single-crystal X-ray diffraction analysis. In [Cu2(PO4)(OH)] n, there are two types of copper centers having distorted trigonal bipyramidal geometry and distorted octahedral geometry that are connected by the μ2-bridging of each phosphate oxygen ultimately forming a η8-PO4 bridged 3D network. The compound exhibited excellent catalytic performance in olefin epoxidation. Epoxidation of styrene and substituted styrenes, as well as bulky olefins like cycloalkenes and long-chain alkenes, is efficiently catalyzed by [Cu2(PO 4)(OH)] n using tert-butylhydroperoxide in acetonitrile. The results obtained in the heterogeneous catalytic reactions show that the olefins are converted to the respective epoxides in good yield with high selectivity. [Cu2(PO4)(OH)] n was catalytically more active and selective in comparison to simple copper(II) phosphate salt in heterogeneous medium. The catalyst can be recycled and reused several times without significant loss of activity.
- Saha, Debraj,Maity, Tanmoy,Sen, Rupam
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p. 2444 - 2454
(2013/08/23)
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- Lanthanide carboxylate frameworks: Efficient heterogeneous catalytic system for epoxidation of olefins
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Two lanthanide-based three dimensional metal-organic frameworks (MOF) viz. [Nd(HCOO)3]n (1) and [Pr(HCOO)3]n (2) have been synthesized and characterized. Both the compounds have similar structure. In this study we have demonstrated that the compounds are highly efficient in catalyzing epoxidation of various cyclic and linear olefinic substrates. MOF compounds are stable and recyclable under the reaction conditions. Notably, MOF systems are remarkably more active and selective than the corresponding lanthanide oxide in epoxidation reaction of olefins.
- Sen, Rupam,Saha, Debraj,Koner, Subratanath
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experimental part
p. 124 - 130
(2012/04/10)
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- One-dimensional chain copper(II) complex: Synthesis, X-ray crystal structure and catalytic activity in the epoxidation of styrene
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Two new copper(II) complexes, [Cu(HL1)(NO3)] (1) (H2L1 = 1-(N-ortho-hydroxyacetophenimine)-ethane-2-ol) and {[Mg(H2O)6][Cu(pydca)2]·2H 2O}n (2) (H2pydca = 2,5-pyridine dicarboxylic acid) have been synthesized and characterized. X-ray crystal structure analysis reveals that the geometry of complex 1 is square planar, where copper(II) centers are linked through a weak coordination by the nitrate O atoms occupying two axial positions, resulting a helical chain structure. Complex 1 crystallizes in the chiral space group P21. There is no chiral center in the Schiff-base ligand of 1, its helical structure develops due to the formation of a NO3- bridged chain through an asymmetric arrangement. Complex 2 is a 1D chain in which the copper(II) ions are connected by bridging carboxylato ligands. The [Mg(H2O)6]2+ moiety occupies the inter-chain space. Epoxidation reactions of styrene and substituted styrenes are homogeneously catalyzed by complexes 1 and 2 with H 2O2 as the oxidant.
- Saha, Debraj,Maity, Tanmoy,Dey, Tirthankar,Koner, Subratanath
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experimental part
p. 55 - 61
(2012/05/19)
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- Synthesis and antibacterial activities of cyclodimers of styrene oxides
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A simple synthetic procedure for preparation of 1,4-dioxanes or 1,3-dioxolanes from styrene oxides is described. Electron-donating groups on the aromatic ring of the styrene oxides were found to favour formation of 1,4-dioxanes while electron-withdrawing
- Mazimba, Ofentse,Majinda, Runner R.,Masesane, Ishmael B.
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experimental part
p. 299 - 304
(2012/05/04)
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- A biomimetic iron catalyst for the epoxidation of olefins with molecular oxygen at room temperature
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It's no sacrifice: A bio-inspired iron system, in which a β-keto ester serves as a sacrificial cosubstrate, readily epoxidizes olefins under ambient conditions with air. Aromatic olefins are oxidized in high yields with excellent chemoselectivity. Mechanistic investigations point out substantial differences to well-known radical-based autoxidations.
- Schroeder, Kristin,Join, Benoet,Amali, Arlin Jose,Junge, Kathrin,Ribas, Xavi,Costas, Miquel,Beller, Matthias
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supporting information; experimental part
p. 1425 - 1429
(2011/04/15)
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- Nickel-catalyzed cross-coupling of styrenyl epoxides with boronic acids
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Let's get multicatalytic! A Ni0 catalyst complexed with a biaryldialkyl monophosphine ligand facilitates C-C bond formation between styrenyl epoxides and aryl boronic acids (see scheme). X-ray analysis of a catalytically active nickel/ligand complex supports a redox pathway involving C sp 3-O bond activation. A variety of α-substituted alcohols were generated with good reaction efficiency by a multicatalytic sequence. Copyright
- Nielsen, Daniel K.,Doyle, Abigail G.
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supporting information; experimental part
p. 6056 - 6059
(2011/09/13)
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- Heterogeneous catalytic epoxidation of olefins over hydrothermally synthesized lanthanide containing framework compounds
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A series of novel complexes [Ln2(N3)(nic) 2(OH)3(Hnic)(H2O)]n (Ln = Y III 1 and GdIII 2; Hnic = nicotinic acid) and [Sm 4(N3)2(nic)4(OH)6(Hnic) 2(H2O)2]n (3) have been hydrothermally synthesized and structurally characterized by single-crystal X-ray analysis. Complexes 1, 2 and 3 have similar structures and consist of [Ln2(N3)(nic)2(OH)3(Hnic)(H 2O)] units that are linked to neighboring units through end-on azido, μ2 and μ3 hydroxo, and bridging carboxylato groups to form 1D infinite chains. In all the complexes the 1D chains propagate parallel to crystallographic a-axis to give rise to a ribbon-like chain structure. All the compounds exhibit excellent catalytic performance in olefin epoxidation reactions, which is reflected in high turnover numbers. Good expoxide selectivity was obtained in the cases of cyclooctene and 1-hexene. The possibility of easy recycling makes these catalysts highly promising candidates for addressing industrial needs and environmental concerns. A series of novel compounds [Ln2(N3)(nic)2(OH) 3(Hnic)(H2O)]n (Ln = YIII 1 and GdIII 2; Hnic = nicotinic acid) and [Sm4(N 3)2(nic)4(OH)6(Hnic) 2(H2O)2]n, 3, have been hydrothermally synthesized and structurally characterized. The overall structures of complexes 1, 2 and 3 are ribbon-like 1D infinite chains. All the compounds exhibit excellent catalytic performance in olefin epoxidation reactions. Copyright
- Sen, Rupam,Koner, Subratanath,Hazra, Dipak K.,Helliwell, Madeleine,Mukherjee, Monika
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experimental part
p. 241 - 248
(2011/04/14)
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- Hydrothermal synthesis of dimeric lanthanide compounds: X-ray structure, magnetic study and heterogeneous catalytic epoxidation of olefins
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A series of dimeric lanthanide carboxylato complexes [La(5-Br-NIC) 3(H2O)2]2·H2O (1); [Gd(5-Br-NIC)3(H2O)2]2 (2), [5-Br-NIC = 5-bromonicotinate] and [Sm(NIC)3(H2O) 2]2 (3) [NIC = nicotinate], have been hydrothermally synthesized and structurally characterized by single crystal X-ray analysis. Complexes 1, 2 and 3 are of similar structure and consist of a basic unit [La(carboxylato)3(H2O)2]2. In compound 1 lanthanide cation is surrounded by one chelating 5-bromo-nicotinato ligand, two bridging oxygen atoms from 5-bromo-nicotinato and two water molecules, in which each La(III) ion is nine coordinated in a tricapped prismatic geometry. However, in compounds 2 and 3 four carboxylate groups link a pair of lanthanide atoms in the O,O′-bridging mode to generate a paddle-wheel-like centrosymmetric dimer. All the compounds exhibit excellent catalytic performance in olefin epoxidation reaction. The variable temperature magnetic susceptibility measurements showed that the magnetic interaction in [Gd(5-Br-NIC)3(H2O)2]2 (2), is antiferromagnetic (J = -0.048 cm-1), while compound [Sm(NIC) 3(H2O)2]2 (3), showed a complicated low-temperature magnetic property.
- Sen, Rupam,Hazra, Dipak K.,Koner, Subratanath,Helliwell, Madeleine,Mukherjee, Monika,Bhattacharjee, Ashis
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experimental part
p. 3183 - 3191
(2011/02/18)
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- Highly efficient and metal-free oxidation of olefins by molecular oxygen under mild conditions
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Highly efficient and metal-free aerobic oxidations of cyclohexene and styrene were successfully performed under mild conditions in the presence of 1,4-diamino-2,3-dichloro-anthraquinone and N-hydroxyphthalimide. When cyclohexene was oxidized, an 89% conversion and 71% selectivity for 2-cyclohexen-1-one was obtained under 0.3 MPa at 80 °C for 5 h. In the oxidation of styrene, a 77% conversion and 69% selectivity for benzaldehyde was obtained for 10 h. Furthermore, more olefins were efficiently oxidized to corresponding oxygenated products under mild conditions. All kinds of factors that affected cyclohexene oxidation were well investigated, and the possible reaction mechanism was provided.
- Tong, Xinli,Xu, Jie,Miao, Hong,Yang, Guanyu,Ma, Hong,Zhang, Qiaohong
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p. 7634 - 7639
(2008/02/07)
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- Bacterial monooxygenase mediated preparation of nonracemic chiral oxiranes: Study of the effects of substituent nature and position
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Monooxygenation of styrene derivatives using recombinant E. coli biocatalyst is an efficient way to prepare the corresponding oxiranes. The electronic and geometric effects of the ring substituents are described and show the relaxed specificity of the enzyme and its high stereoselectivity.
- Bernasconi, Silvana,Orsini, Fulvia,Sello, Guido,Di Gennaro, Patrizia
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p. 1603 - 1606
(2007/10/03)
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- Studies on cognitive enhancing agents. II. Antiamnestic and antihypoxic activities of 1-aryl-2-(2-aminoethoxy)ethanols
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A series of 2-(2-aminoethoxy)-1-phenylethanols having a variety of N- and phenyl-substitution patterns as well as 5- and 6-membered heteroaryl counterparts of our prototype compound 1 (2-(2-dimethylaminoethoxy)-1- phenylethanol) have been prepared and evaluated for antiamnestic and antihypoxic activities. Compound 3b, the 3-methylphenyl analogue of 1, proved to be significantly more potent than I in reversing electroconvulsive shock- induced amnesia as well as CO2-induced learning-impairment in mice. It exhibited low acute toxicity in mice and afforded a greater brain/serum concentration ratio than 1 after oral administration to rats.
- Ono,Yamafuji,Chaki,Morita,Todo,Maekawa,Kitamura,Tai,Narita
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p. 1488 - 1491
(2007/10/03)
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- Epoxidation of styrenes by hydrogen peroxide as catalyzed by methylrhenium trioxide
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Methylrhenium trioxide, CH3ReO3, catalyzes the oxidation of styrenes by hydrogen peroxide. Kinetic studies by three methods were carried out in acidic CH3CN/H2O (1:1 v/v) solutions. The catalytically-active species are the mono-peroxide, CH3Re(O)2(C2), A, and the bis-peroxide, CH3Re(O)(O2)2, B, which epoxidize a given styrene at a similar rate. The rate constants are relatively insensitive to steric hindrance, but increase with the nucleophilicity of the styrene, electron-donating groups on the olefinic carbons or on the aromatic ring enhancing the rate. The rate constants for meta- and para-substituted styrenes follow a linear Hammett relationship; correlation with σ+ gave ρ + -0.93 ± 0.05. In CD3CN, epoxides were observed by 1H NMR spectroscopy. ais-β-Methylstyrene and transβ-methylstyrene led to the cis epoxide and the trans epoxide, respectively. In acidic CH3CN/H2O, the major products were 1,2-diols. In some cases C-C bond cleavage products were also observed, the extreme case being β-methoxystyrene where the C-C bond was completely cleaved to yield benzaldehyde, formaldehyde, and methanol.
- Al-Ajlouni, Ahmad M.,Espenson, James H.
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p. 9243 - 9250
(2007/10/03)
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