- Synthesis and Applications of (Pyridyl)imine Fe(II) Complexes as Catalysts in Transfer Hydrogenation of Ketones
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Abstract: Chiral (pyridyl)imine Fe(II) complexes, [Fe(L1)3]2+[PF6?]2, (Fe1), [Fe(L2)3]2+[PF6?]2, (Fe2), [Fe(L3)3]2+[PF6?]2 (Fe3), and [Fe(L4)3]2+[PF6?]2 (Fe4) were synthesised by reactions of synthons (S-)-1-phenyl-N-(pyridine-2-yl) ethylidine)ethanamine (L1), (R-)-1-phenyl-N-(pyridine-2-yl) ethylidine) ethanamine (L2), (S)-1-phenyl-N-(pyridine-2-yl methylene) ethanamine (L3) and (S)-1-phenyl-N-(pyridine-2-yl methylene)ethanamine (L4) with the FeCl2 salt. The solid-state structure of complex Fe4 showed that the?Fe atom contains three units of bidentate bound ligand L4 to form a six-coordinate cationic compound. The Fe(II) complexes were evaluated as catalysts in asymmetric transfer hydrogenation of ketones reactions and showed moderate catalytic activities with low enantioselectivity. Catalytic activities of the respective complexes were regulated by the nature of the metal complexes, ketone substrate and reaction conditions. Mercury and sub-stoichiometric poisoning experiments implicate possible formation of both active Fe(0) nanoparticles and Fe(II) homogeneous intermediates. Graphic Abstract: [Figure not available: see fulltext.]
- Kumah, Robert T.,Vijayan, Paranthaman,Ojwach, Stephen O.
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- Nanoheterogeneous catalytic hydrogenation of arenes: Evaluation of the surfactant-stabilized aqueous ruthenium(O) colloidal suspension
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The hydrogenation of various aromatic compounds by a surfactant-stabilized aqueous ruthenium(O) colloidal suspension was investigated. The nanocatalysts in the size range of 2.5-3.5 nm were synthesized by reducing ruthenium trichloride salt with sodium borohydride and were stabilized by the highly water soluble N,N-dimethyl-N-cetyl-N-(2-hydroxyethyl)ammonium chloride salt according to our classical approach. The efficient catalytic reactions were performed at room temperature and under hydrogen pressure. The effect of the stirring, namely magnetic stir bar or gas projection impeller, was also studied. A comparison with an analogous rhodium nanocatalyst is described.
- Nowicki, Audrey,Boulaire, Virginie Le,Roucoux, Alain
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- Kinetics and intraparticle diffusion modelling of a complex multistep reaction: Hydrogenation of acetophenone over a rhodium catalyst
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In a first step the intrinsic kinetics of acetophenone hydrogenation on a Rh/C catalyst was studied in a semi-batch reactor. Tiny catalyst grains of 17 μm in average diameter were used in order to avoid any intraparticle diffusion limitation. Experiments were performed over a wide range of operating conditions and various Langmuir-Hinshelwood kinetic equations were discriminated over the complete conversion range. The model based on nondissociative adsorption of hydrogen and noncompetitive adsorption of the organic species with the gas molecules was found to fit better all the experimental data. The relevance of its optimized parameters was then discussed. In a second step the intraparticle diffusion limitations were also studied in a semi-batch reactor by varying the particle size. Two models based on the complex kinetics previously established were developed, taking into account the catalyst grain size and shape. After an additional adjustment of one of the adsorption constants ratios, they were found to provide a good representation of the data in terms of activity and selectivity.
- Bergault, Isabelle,Fouilloux, Pierre,Joly-Vuillemin, Catherine,Delmas, Henri
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- Alkyl sulfonated diphosphines-stabilized ruthenium nanoparticles as efficient nanocatalysts in hydrogenation reactions in biphasic media
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The organometallic synthesis of ruthenium nanoparticles stabilized by water-soluble alkyl sulfonated diphosphines as ligands is described for the first time. After isolation, the so-obtained nanoparticles could be easily dispersed into water giving rise to stable aqueous colloidal solutions without precipitation over the course of several months. The catalytic behaviour of these aqueous colloidal solutions has been investigated in the hydrogenation of unsaturated substrates (tetradecene, styrene and acetophenone) in biphasic liquid-liquid conditions, showing interesting results in terms of reactivity. Interestingly, small structural differences in the backbone of the diphosphine ligands influence the catalytic activity of these nanocatalysts. In addition, preliminary tests of recycling showed promising results with neither loss of activity or significant precipitation.
- Guerrero,Roucoux,Denicourt-Nowicki,Bricout,Monflier,Collire,Fajerwerg,Philippot
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- Tuning the structure and catalytic activity of Ru nanoparticle catalysts by single 3d transition-metal atoms in Ru12-metalloporphyrin precursors
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Ru nanoparticle catalysts were prepared from Ru12-metalloporphyrin complex precursors containing 3d transition-metal atoms attached to SiO2 surfaces. The single 3d metal atoms at the central position of the Ru12-metalloporphyrin complex precursors exerted a significant influence on the structures and hydrogenation performance of the Ru nanoparticles on the SiO2 surfaces. The Ru12-Cu-porphyrin complex afforded positively charged Ru nanoparticles, which would provide high activity toward aromatic hydrogenation.
- Muratsugu, Satoshi,Yamaguchi, Atsuki,Yokota, Gen-Ichi,Maeno, Tomoaki,Tada, Mizuki
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- Group 6 Metal Carbonyl Complexes Supported by a Bidentate PN Ligand: Syntheses, Characterization, and Catalytic Hydrogenation Activity
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We report on the preparation of a series of phosphorus-nitrogen donor ligand complexes [M(CO)4(PN)], where M = Cr, Mo, W and PN is 2-(diphenylphosphino)ethylamine. The organometallic compounds were readily obtained upon reacting the respective metal hexacarbonyls with equimolar amounts of the pertinent ligand in the presence of tetraethylammonium bromide. The PN-ligated metal carbonyls were fully characterized by standard spectroscopic techniques and X-ray crystallography. The ability of the title compounds to function as homogeneous hydrogenation catalysts was probed in the reduction of acetophenone and benzaldehyde derivatives to yield the corresponding alcohols. The reaction setup was easily assembled by simply combining the components in the autoclave on the bench outside an inert-gas-operated glovebox system.
- Faust, Kirill,Topf, Christoph,Vielhaber, Thomas
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- Heterogeneous Enantioselective Hydrogenation of Aromatic Ketones Catalyzed by Rh Nanoparticles Immobilized in Ionic Liquid
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Rhodium nanoparticles (Rh NPs) stabilized by natural cinchona alkaloids were synthesized in imidazolium-based ionic liquids using H2 as the reductant. Characterization showed well-dispersed Rh NPs of about 1.96?nm (TEM and HRTEM) and confirmed the ionic liquid and cinchona alkaloid stabilization to the Rh(0) NPs (XPS). When modified by chiral diamine, including (1R,2R)-diphenylethylenediamine ((1R,2R)-DPEN) or cinchona alkaloid derivatives, the Rh NPs catalysts exhibited good activity, chemoselectivity and enantioselectivity in the heterogeneous enantioselective hydrogenation of aromatic ketones. Synergistic effect between (1R,2R)-DPEN and cinchonidine was also observed, which significantly accelerated the reaction rate and enhanced the enantioselectivity. 63.0% enantioselectivity and 98.9% chemoselectivity could be achieved in the acetophenone enantioselective hydrogenation; up to 70.2% enantioselectivity and 100% chemoselectivity was obtained in the isobutyrylbenzene catalytic enantioselective hydrogenation. Catalytic system could be reused several times without significant loss in activity, chemoselectivity as well as enantioselectivity. This catalytic protocol opens the door to heterogeneous enantioselective hydrogenation of aromatic ketones with metal Rh NPs immobilized in ionic liquid. Graphical Abstract: [Figure not available: see fulltext.].
- Jiang, He-yan,Cheng, Hong-mei,Bian, Feng-xia
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- Water-soluble carbene complexes as catalysts for the hydrogenation of acetophenone under hydrogen pressure
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The synthesis of water-soluble Rh(I), Ir(I), and Ru(II) N-heterocyclic carbene complexes is described. These complexes are applied as catalysts for aqueous phase hydrogenation reactions. Good hydrogenation activities under ca. 40 atm pressure H2/sub
- Syska, Hitrisia,Herrmann, Wolfgang A.,Kühn, Fritz E.
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- Preparation and characterization of RuCl3 - Diamine group functionalized polymer
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Gel-type resin with diamine functional groups, FCN, was used as a matrix for immobilization of ruthenium complexes. By reacting of RuCl3 with swollen matrix of FCN polymer a series of Ru/FCN composites with various Ru loading (1%, 2%, and 4%) w
- Duraczynska,Drelinkiewicz,Serwicka,Rutkowska-Zbik,Bielańska,Socha,Bukowska,Bukowski
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- Active hydrogenation Rh nanocatalysts protected by new self-assembled supramolecular complexes of cyclodextrins and surfactants in water
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The stability of inclusion complexes between randomly methylated β-cyclodextrin (RaMeCD) or its leucine-grafted analogue (RaMeCDLeu) with two hydroxylated ammonium surfactants was investigated. The binding isotherms and complexation constants were measured using the Isothermal Titration Calorimetry (ITC) technique. These host-guest inclusion complexes were used as protective agents during the formation of rhodium(0) nanoparticles by chemical reduction of rhodium trichloride in water. The amount of protective agent was adjusted in order to ensure both stability and reactivity of the rhodium nanocatalysts under the catalytic conditions. The size and dispersion of air-stable and water-soluble rhodium suspensions were determined by Transmission Electron Microscopy (TEM) analyses. These spherical nanoparticles, with sizes between 1.20 to 1.50 nm according to the nature of inclusion complexes, were evaluated in the biphasic hydrogenation of various reducible compounds (olefins, linear or aromatic ketones), showing promising results in terms of activity and selectivity.
- Thanh Chau, Nguyet Trang,Menuel, Stéphane,Colombel-Rouen, Sophie,Guerrero, Miguel,Monflier, Eric,Philippot, Karine,Denicourt-Nowicki, Audrey,Roucoux, Alain
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p. 108125 - 108131
(2016)
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- Hydrogenation of acetophenone in the presence of Ru catalysts supported on amine groups functionalized polymer
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Liquid phase hydrogenation of acetophenone (ACT) is studied over ruthenium catalysts (1-4 wt% Ru) supported on gel-type methacrylate-styrene resin (FCN) functionalized with C=O, -NH, and -NH2 groups. Microscopic studies (SEM, STEM) show that th
- Duraczynska, Dorota,Drelinkiewicz, Alicja,Bielanska, Elzbieta,Serwicka, Ewa M.,Litynska-Dobrzynska, Lidia
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- Aromatic ring hydrogenation catalysed by nanoporous montmorillonite supported Ir(0)-nanoparticle composites under solvent free conditions
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Ir(0)-nanoparticles (Ir-NPs) were synthesized into the nanopores of modified montmorillonite clay by incipient wetness impregnation of IrCl3 followed by reduction with ethylene glycol. The activation of the montmorillonite clay was carried out by treatment with HCl under controlled conditions to increase the surface area by generating nanopores which act as host for the metal nanoparticles. The synthesized Ir-NP-montmorillonite composites were characterized by N2-sorption, powder XRD, SEM, EDS, TEM, XPS, etc. The composites exhibit high surface area of 327 m2 g-1 and the Ir-NPs with size around 4 nm are uniformly distributed on the support. The Ir-NPs show efficient catalytic activity in aromatic ring hydrogenation under solvent free conditions with maximum conversion up to 100% and Turn Over Frequency (TOF) up to 79 h-1. The catalyst can be easily separated by simple filtration and remained active for several runs without significant loss of catalytic efficiency.
- Das, Prabin,Sarmah, Podma Pollov,Borah, Bibek Jyoti,Saikia, Lakshi,Dutta, Dipak Kumar
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- Mn(I) and Fe(II)/PN(H)P Catalysts for the Hydrogenation of Ketones: A Comparison by Experiment and Calculation
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The P-stereogenic PN(H)P tridentate ligand HN(CH2CH2)2P(Me)R (R=Cy, 1 a; R=tBu, 1 b) gives the Mn(I) complexes [Mn(CO)3(PN(H)P)]Br, which were tested in the asymmetric H2 hydrogenation of ketones. The amido species [Mn(CO)2(PNP)], hydrides [MnH(CO)2(PN(H)P)], and the alkoxide complex (Formula presented.) were detected by NMR spectroscopy. The manganese(I) derivative [Mn(CO)3(1 a)]Br was compared to its iron(II) analogue [FeHBr(CO)(1 a)] by kinetic and DFT studies. The DFT study suggests that both Mn(I) and Fe(II) operate via a bifunctional mechanism for H+/H? transfer with structurally similar enantiodetermining transition states and hence comparable enantioselectivity. The Mn(I) catalyst is less active than its Fe(II) analogue (k(Fe)/k(Mn)=ca. 30), which we attribute to the higher stability of the Mn(I) resting species, the off-cycle alkoxo complex [Mn(OCH(Me)Ph))(CO)2(1 a)] that follows from the larger π delocalization onto the additional CO ligand as compared to [FeH(OCH(Me)Ph))(CO)(1 a)]. (Figure presented.).
- Passera, Alessandro,Mezzetti, Antonio
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- Synthesis, characterization, and reactivity of Cp*Rh(III) complexes having functional N,O chelate ligands
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Cp*Rh(III) complexes 1a and 1b (Cp* = 1, 2, 3, 4, 5-pentamethylcyclopentadienyl) having functional N,O chelate ligands have been synthesized and characterized by 1H, 13C{1H} NMR spectroscopy, elemental analysis, IR spectroscopy and X-ray diffraction. Reactivity of these complexes has been investigated towards dehydrogenation of alcohols and hydrogenation of ketones. It was found that these compounds are precursors to the formation of Rh nanoparticles which serve as catalysts, as evidenced by mercury poisoning of the catalysis and direct observation of the particles by TEM, EDX, and XRD.
- Munjanja, Lloyd,Yuan, Hongmei,Brennessel, William W.,Jones, William D.
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- Ruthenium nanoparticles ligated by cholesterol-derived NHCs and their application in the hydrogenation of arenes
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Herein we present ruthenium nanoparticles (Ru-NPs) stabilized with two rigid NHC ligands derived from cholesterol. The obtained nanoparticles were fully characterized and applied in the hydrogenation of various aromatic compounds under mild conditions. Interestingly, the more bulky ligand gives a slightly lower ligand coverage and a faster catalyst.
- Rakers, Lena,Martínez-Prieto, Luis M.,López-Vinasco, Angela M.,Philippot, Karine,Van Leeuwen, Piet W. N. M.,Chaudret, Bruno,Glorius, Frank
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- Nickel(0)-catalyzed three-component connection reaction of dimethylzinc, 1,3-dienes, and carbonyl compounds
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Linear 1:1:1 coupling of dimethylzinc, 1,3-dienes, and carbonyl compounds in this order is facilitated by catalytic amounts of [Ni(acac)2] to give (E)-3-hexen-1-ols in good yields under mild conditions [Eq. (a)]. Increasing steric hindrance at the carbonyl group favors formation of the 1:2:1 adduct, and this is the sole product when the carbonyl compound is acetone, acac = acetylacetonate.
- Kimura, Masanari,Matsuo, Shintaro,Shibata, Kazufumi,Tamaru, Yoshinao
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- Water-soluble transition metal complexes of ruthenium(II), osmium(II), rhodium(III) and iridium(III) with chelating N-heterocyclic carbene ligands in hydrogenation and transfer hydrogenation catalysis
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The synthesis of novel Ru(ii), Os(ii), Rh(iii) and Ir(iii) mono-N-heterocyclic carbene (NHC) complexes with a pyridine substituent is reported. The reaction of the imidazolium salts bearing N-alkyl and sulfonated N-alkyl substituents with Ag2O leads to the formation of the corresponding Ag(i) complexes. The metal complexes are available in good yields via transmetallation reactions from the corresponding silver complexes and [ArMCl2]2, where Ar = p-cymene or Cp? and M = Ru, Os, Rh or Ir. While N-alkyl substituted NHC complexes are almost insoluble in water (1.55 mg ml-1), sulfonated N-alkyl substituted NHC complexes display good solubility in water (up to 400 mg mL-1). All complexes were examined as catalysts in the transfer hydrogenation of acetophenone, which is quantitatively and highly selective reduced to 1-phenylethanol and 1-cyclohexylethanol. Additionally, the water-soluble complexes were examined in the complete hydrogenation of acetophenone with hydrogen in an autoclave, showing high conversions compared to literature-known systems.
- Bayón Casta?ón, Esther,Kaposi, Marlene,Reich, Robert M.,Kühn, Fritz E.
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- Aza versus Oxophilicity of SmI2: A Break of a Paradigm
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Ligands that coordinate to SmI2 through oxygen are prevalent in the literature and make up a significant portion of additives employed with the reagent to perform reactions of great synthetic importance. In the present work a series of spectroscopic, calorimetric and kinetic studies demonstrate that nitrogen-based analogues of many common additives have a significantly higher affinity for Sm than the oxygen-based counterparts. In addition, electrochemical experiments show that nitrogen-based ligands significantly enhance the reducing power of SmI2. Overall, this work demonstrates that the use of nitrogen-based ligands provides a useful alternative approach to enhance the reactivity of reductants based on SmII.
- Maity, Sandeepan,Flowers, Robert A.,Hoz, Shmaryahu
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- The use of imidazolium ionic liquids for the formation and stabilization of Ir0 and Rh0 nanoparticles: Efficient catalysts for the hydrogenation of arenes
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Stable transition-metal nanoparticles of the type [M0]n are easily accessible through the reduction of IrI or RhIII compounds dissolved in "dry" 1-n-butyl-3-methylimidazolium hexafluorophosphate ionic liquid by molecular hydrogen. The formation of these [M0]n nanoparticles is straightforward; they are prepared in dry ionic liquid whereas the presence of the water causes the partial decomposition of ionic liquid with the formation of phosphates, HF and transition-metal fluorides. Transmission electron microscopy (TEM) observations and X-ray diffraction analysis (XRD) show the formation of [Ir0]n and [Rh0]n nanoparticles with 2.0-2.5 nm in diameter. The isolated [M0]n nanoparticles can be redispersed in the ionic liquid, in acetone or used in solventless conditions for the liquid-liquid biphasic, homogeneous or heterogeneous hydrogenation of arenes under mild reaction conditions (75 °C and 4 atm). The recovered iridium nanoparticles can be reused several times without any significant loss in catalytic activity. Unprecedented total turnover numbers (TTO) of 3509 in 32 h, for arene hydrogenation by nanoparticles catalysts, have been achieved in the reduction of benzene by the [Ir0]n in solventless conditions. Contrarily, the recovered Rh0 nanoparticles show significant agglomeration into large particles with a loss of catalytic activity. The hydrogenation of arenes containing functional groups, such as anisole, by the [Ir0]n nanoparticles occurs with concomitant hydrogenolysis of the C-O bond, suggesting that these nanoparticles behave as "heterogeneous catalysts" rather than "homogeneous catalysts".
- Fonseca, Gledison S.,Umpierre, Alexandre P.,Fichtner, Paulo F. P.,Teixeira, Sergio R.,Dupont, Jairton
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- Role of NaBH4 stabilizer in the oxazaborolidine-catalyzed asymmetric reduction of ketones with BH3-THF
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When stabilized BH3-THF (BTHF) was added to a mixture of ketone and tetrahydro-1-methyl-3,3-diphenyl-1H,3H-pyrrolo[1,2-c] [1,3,2]oxazaborole (MeCBS-ozaxaborolidine, MeCBS) catalyst 1, low enantioselectivities resulted. Several relative rate experiments showed that a borohydride species in BTHF catalyzed the nonselective borane reduction of ketones, effectively competing with enantioselective MeCBS reduction of ketones, lowering the overall selectivity of the reaction. Improved enantioselectivities in the reaction are obtained by reversing the mode of addition (ketone to BTHF and catalyst), lowering the concentration of NaBH4 stabilizer in the BTHF solution (87- 95% ee) and increasing the concentration or addition rate of BTHF. Decreased reaction temperature and increased catalyst loading only slightly improved the selectivity of the reaction. Upon reaction parameter optimization, simultaneous addition of substrate and BTHF to MeCBS catalyst stabilizer resulted in the highest overall enantioselectivities (96% ee) and diminished the effect of the borohydride. Alternatively, the addition of Lewis acids such as BF3-THF to the reaction mixture effectively destroyed the NaBH4 stabilizer in BTHF solutions, restoring the enantioselectivity to acceptable levels.
- Nettles, Shawn M.,Matos, Karl,Burkhardt, Elizabeth R.,Rouda, Dave R.,Corella, Joseph A.
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- Graphene-Modified Ru Nanocatalyst for Low-Temperature Hydrogenation of Carbonyl Groups
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Low-temperature efficient hydrogenation of C=O bonds in various compounds, which is one of the most important processes for producing fuels and chemicals, is of fundamental interest but remains a significant challenge. The primary problem is a lack of heterogeneous catalyst systems that are highly active at ambient or low temperatures. This paper describes an efficient strategy for designing a low-temperature hydrogenation catalyst. Ru nanoparticles supported on reduced graphene oxide (Ru/RGO) show remarkable efficiency for hydrogenation of levulinic acid into γ-valerolactone at temperatures as low as -10 °C. The catalyst is also highly active toward low-temperature hydrogenation of C=O bonds in other carbonyl compounds into C-OH bonds, such as furfural, propionaldehyde, 2-pentanone, hydroxyacetone, acetone, acetophenone, cyclohexanone, and benzophenone. X-ray photoelectron spectroscopy and in situ Fourier transform infrared demonstrate that the electron transfer between Ru0 and RGO leads to the formation of an electron-rich state of Ru0 nanoparticles that are highly effective for activating C=O bonds.
- Tan, Jingjing,Cui, Jinglei,Cui, Xiaojing,Deng, Tiansheng,Li, Xianqing,Zhu, Yulei,Li, Yongwang
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- Selective hydrosilylation of ketones catalyzed by in situ -generated iron NHC complexes
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Aryl alkyl-, heteroaryl alkyl- and dialkyl ketones were readily reduced to their corresponding secondary alcohols in high yields, using the commercially available and inexpensive polymeric silane polymethylhydrosiloxane (PMHS), as reducing agent. The reaction is catalyzed by an in situ-generated iron complex, conveniently generated from iron(II) acetate and the commercially available N-heterocyclic carbene (NHC) precursor IPr·HCl.
- Buitrago, Elina,Zani, Lorenzo,Adolfsson, Hans
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- Influence of support acid-base properties on the platinum-catalyzed enantioselective hydrogenation of activated ketones
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The influence of support acidity and basicity was investigated in the enantioselective hydrogenation of methyl benzoylformate and ketopantolactone on cinchonidine-modified Pt/Al2O3-SiO2 and Pt/Al2O3-Cs2O catalysts. Two series of flame-derived 4.7 wt.% Pt/Al2O3 catalysts in which the acid-base properties of the support were systematically varied by introducing SiO2 (5-80 wt.%) or Cs2O (0.25-10 wt.%) were applied. Addition of SiO2 improved the enantioselectivity with a maximum at 30 wt.%. Enantioselectivity correlated well with the acidity of the catalysts characterized by TPD of NH3 and with the selectivity to hydrogenolysis of methyl cyclohexyl ketone to ethylcyclohexane. On the contrary, doping with Cs was detrimental to the formation of the (R)-alcohols and the drop in enantioselectivity could unambiguously be attributed to the basicity of the support characterized by TPD of CO2. The critical impact of support ionicity on the electronic properties of Pt, and thus on the adsorption and interaction of the reaction components on the metal surface, was further proven by the good correlation between the enantioselectivities of all catalysts and the ratio of CO adsorbed in bridged to linear (B/L) geometry. The practical importance of our findings is demonstrated by the best ee (94 ± 0.5%) achieved so far in the industrially relevant hydrogenation of ketopantolactone to (R)-pantolactone.
- Hoxha, Fatos,Schimmoeller, Bjoern,Cakl, Zdenek,Urakawa, Atsushi,Mallat, Tamas,Pratsinis, Sotiris E.,Baiker, Alfons
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- Selective Hydrogenation of Aromatic Ketone over Pt@Y Zeolite through Restricted Adsorption Conformation of Reactants by Zeolitic Micropores
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With thermodynamically favorable prevailing flat-lying adsorption of aromatic ketone molecules on Pt/Y catalyst via π-electron interaction, the 100 % selective hydrogenation toward aromatic alcohols is hardly achieved because of competitive hydrogenation on benzene rings. Here we developed a general method to prepare encapsulated Pt nanoparticles into Y Zeolite (Pt@Y), which provided a novel method to retard hydrogenation of benzene rings via thermodynamically unfavorable end-on adsorption conformation for almost 100 % selectivity from aromatic ketones to aromatic alcohols even at conversion close to 100 %.
- Chen, Qiang,Kang, Haozhe,Liu, Xuan,Jiang, Kun,Bi, Yunfei,Zhou, Yiming,Wang, Mengyue,Zhang, Meng,Liu, Lei,Xing, Enhui
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- Functionalization of platinum nanoparticles with l -proline: Simultaneous enhancements of catalytic activity and selectivity
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In this work we present the successful application of functionalizing Pt nanoparticles (NPs) with hydrophilic organic ligands as a strategy for enhancing their catalytic activity and selectivity. In the first step, Pt NPs were prepared by a colloidal approach and subsequently functionalized in a separate synthesis step with l-proline (PRO). The functionalized NPs were supported onto Al2O3 and investigated as heterogeneous catalysts for the selective hydrogenation of acetophenone. Whereas significant amounts of side products are formed by supported, unprotected (ligand-free) NPs, the PRO-functionalized Pt NPs are highly chemoselective even at 100% conversion. Experiments under kinetically controlled conditions reveal that this high chemoselectivity is not accompanied by a loss of catalytic activity. In contrast, an enhanced rate toward the desired product was found for PRO-Pt in comparison to the unprotected Pt NPs. This finding demonstrates that the use of ligands in heterogeneous catalysis allows for simultaneous enhancements of activity and selectivity.
- Schrader, Imke,Warneke, Jonas,Backenk?hler, Jana,Kunz, Sebastian
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- Dynamic Kinetic Resolution of Alcohols by Enantioselective Silylation Enabled by Two Orthogonal Transition-Metal Catalysts
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A nonenzymatic dynamic kinetic resolution of acyclic and cyclic benzylic alcohols is reported. The approach merges rapid transition-metal-catalyzed alcohol racemization and enantioselective Cu-H-catalyzed dehydrogenative Si-O coupling of alcohols and hydrosilanes. The catalytic processes are orthogonal, and the racemization catalyst does not promote any background reactions such as the racemization of the silyl ether and its unselective formation. Often-used ruthenium half-sandwich complexes are not suitable but a bifunctional ruthenium pincer complex perfectly fulfills this purpose. By this, enantioselective silylation of racemic alcohol mixtures is achieved in high yields and with good levels of enantioselection.
- Oestreich, Martin,Seliger, Jan
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supporting information
p. 247 - 251
(2020/10/29)
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- Selective C-alkylation Between Alcohols Catalyzed by N-Heterocyclic Carbene Molybdenum
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The first implementation of a molybdenum complex with an easily accessible bis-N-heterocyclic carbene ligand to catalyze β-alkylation of secondary alcohols via borrowing-hydrogen (BH) strategy using alcohols as alkylating agents is reported. Remarkably high activity, excellent selectivity, and broad substrate scope compatibility with advantages of catalyst usage low to 0.5 mol%, a catalytic amount of NaOH as the base, and H2O as the by-product are demonstrated in this green and step-economical protocol. Mechanistic studies indicate a plausible outer-sphere mechanism in which the alcohol dehydrogenation is the rate-determining step.
- Liu, Jiahao,Li, Weikang,Li, Yinwu,Liu, Yan,Ke, Zhuofeng
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supporting information
p. 3124 - 3128
(2021/09/20)
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- Highly Active Cooperative Lewis Acid—Ammonium Salt Catalyst for the Enantioselective Hydroboration of Ketones
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Enantiopure secondary alcohols are fundamental high-value synthetic building blocks. One of the most attractive ways to get access to this compound class is the catalytic hydroboration. We describe a new concept for this reaction type that allowed for exceptional catalytic turnover numbers (up to 15 400), which were increased by around 1.5–3 orders of magnitude compared to the most active catalysts previously reported. In our concept an aprotic ammonium halide moiety cooperates with an oxophilic Lewis acid within the same catalyst molecule. Control experiments reveal that both catalytic centers are essential for the observed activity. Kinetic, spectroscopic and computational studies show that the hydride transfer is rate limiting and proceeds via a concerted mechanism, in which hydride at Boron is continuously displaced by iodide, reminiscent to an SN2 reaction. The catalyst, which is accessible in high yields in few steps, was found to be stable during catalysis, readily recyclable and could be reused 10 times still efficiently working.
- Titze, Marvin,Heitk?mper, Juliane,Junge, Thorsten,K?stner, Johannes,Peters, René
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supporting information
p. 5544 - 5553
(2021/02/05)
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- Application of robust ketoreductase from Hansenula polymorpha for the reduction of carbonyl compounds
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Enzyme-catalysed asymmetric reduction of ketones is an attractive tool for the production of chiral building blocks or precursors for the synthesis of bioactive compounds. Expression of robust ketoreductase (KRED) from Hansenula polymorpha was upscaled and applied for the asymmetric reduction of 31 prochiral carbonyl compounds (aliphatic and aromatic ketones, diketones and β-keto esters) to the corresponding optically pure hydroxy compounds. Biotransformations were performed with the purified recombinant KRED together with NADP+ recycling glucose dehydrogenase (GDH, Bacillus megaterium), both overexpressed in Escherichia coli BL21(DE3). Maximum activity of KRED for biotransformation of ethyl-2-methylacetoacetate achieved by the high cell density cultivation was 2499.7 ± 234 U g–1DCW and 8.47 ± 0.40 U·mg–1E, respectively. The KRED from Hansenula polymorpha is a very versatile enzyme with broad substrate specificity and high activity towards carbonyl substrates with various structural features. Among the 36 carbonyl substrates screened in this study, the KRED showed activity with 31, with high enantioselectivity in most cases. With several ketones, the Hansenula polymorpha KRED catalysed preferentially the formation of the (R)-secondary alcohols, which is highly valued.
- Petrovi?ová, Tatiana,Gyuranová, Dominika,Pl?, Michal,Myrtollari, Kamela,Smonou, Ioulia,Rebro?, Martin
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- Co-Catalyzed Synthesis of Primary Amines via Reductive Amination employing Hydrogen under very mild Conditions
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Nanostructured and reusable 3d-metal catalysts that operate with high activity and selectivity in important chemical reactions are highly desirable. Here, a cobalt catalyst was developed for the synthesis of primary amines via reductive amination employing hydrogen as the reducing agent and easy-to-handle ammonia, dissolved in water, as the nitrogen source. The catalyst operates under very mild conditions (1.5 mol% catalyst loading, 50 °C and 10 bar H2 pressure) and outperforms commercially available noble metal catalysts (Pd, Pt, Ru, Rh, Ir). A broad scope and a very good functional group tolerance were observed. The key for the high activity seemed to be the used support: an N-doped amorphous carbon material with small and turbostratically disordered graphitic domains, which is microporous with a bimodal size distribution and with basic NH functionalities in the pores.
- Elfinger, Matthias,Sch?nauer, Timon,Thom?, Sabrina L. J.,St?glich, Robert,Drechsler, Markus,Zobel, Mirijam,Senker, Jürgen,Kempe, Rhett
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p. 2360 - 2366
(2021/05/03)
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- The solvent determines the product in the hydrogenation of aromatic ketones using unligated RhCl3as catalyst precursor
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Alkyl cyclohexanes were synthesized in high selectivity via a combined hydrogenation/hydrodeoxygenation of aromatic ketones using ligand-free RhCl3 as pre-catalyst in trifluoroethanol as solvent. The true catalyst consists of rhodium nanoparticles (Rh NPs), generated in situ during the reaction. A range of conjugated as well as non-conjugated aromatic ketones were directly hydrodeoxygenated to the corresponding saturated cyclohexane derivatives at relatively mild conditions. The solvent was found to be the determining factor to switch the selectivity of the ketone hydrogenation. Cyclohexyl alkyl-alcohols were the products using water as a solvent.
- Bartling, Stephan,Chakrabortty, Soumyadeep,De Vries, Johannes G.,Kamer, Paul C. J.,Lund, Henrik,Müller, Bernd H.,Rockstroh, Nils
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p. 7608 - 7616
(2021/12/13)
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- RhNPs supported onN-functionalized mesoporous silica: effect on catalyst stabilization and catalytic activity
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Amine and nicotinamide groups grafted on ordered mesoporous silica (OMS) were investigated as stabilizers for RhNPs used as catalysts in the hydrogenation of several substrates, including carbonyl and aryl groups. Supported RhNPs on functionalized OMS were prepared by controlled decomposition of an organometallic precursor of rhodium under dihydrogen pressure. The resulting materials were characterized thoroughly by spectroscopic and physical techniques (FTIR, TGA, BET, SEM, TEM, EDX, XPS) to confirm the formation of spherical rhodium nanoparticles with a narrow size distribution supported on the silica surface. The use of nicotinamide functionalized OMS as a support afforded small RhNPs (2.3 ± 0.3 nm), and their size and shape were maintained after the catalyzed acetophenone hydrogenation. In contrast, amine-functionalized OMS formed RhNP aggregates after the catalytic reaction. The supported RhNPs could selectively reduce alkenyl, carbonyl, aryl and heteroaryl groups and were active in the reductive amination of phenol and morpholine, using a low concentration of the precious metal (0.07-0.18 mol%).
- Pulido-Díaz, Israel T.,Serrano-Maldonado, Alejandro,López-Suárez, Carlos César,Méndez-Ocampo, Pedro A.,Portales-Martínez, Benjamín,Gutiérrez-Alejandre, Aída,Salas-Martin, Karla P.,Guerrero-Ríos, Itzel
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p. 3289 - 3298
(2021/03/16)
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- Fe-Catalyzed Anaerobic Mukaiyama-Type Hydration of Alkenes using Nitroarenes
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Hydration of alkenes using first row transition metals (Fe, Co, Mn) under oxygen atmosphere (Mukaiyama-type hydration) is highly practical for alkene functionalization in complex synthesis. Different hydration protocols have been developed, however, control of the stereoselectivity remains a challenge. Herein, highly diastereoselective Fe-catalyzed anaerobic Markovnikov-selective hydration of alkenes using nitroarenes as oxygenation reagents is reported. The nitro moiety is not well explored in radical chemistry and nitroarenes are known to suppress free radical processes. Our findings show the potential of cheap nitroarenes as oxygen donors in radical transformations. Secondary and tertiary alcohols were prepared with excellent Markovnikov-selectivity. The method features large functional group tolerance and is also applicable for late-stage chemical functionalization. The anaerobic protocol outperforms existing hydration methodology in terms of reaction efficiency and selectivity.
- Bhunia, Anup,Bergander, Klaus,Daniliuc, Constantin Gabriel,Studer, Armido
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supporting information
p. 8313 - 8320
(2021/03/08)
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- Hydrogenation Performance of Acetophenone to 1-Phenylethanol on Highly Active Nano Cu/SiO2 Catalyst
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Abstract: In this work, highly active nano Cu/SiO2 catalysts with various copper content were prepared by urea homogeneous precipitation method. The catalysts were characterized by N2 adsorption, XRD, H2-TPR, XPS and TEM. It was found that the nano Cu/SiO2 catalyst displayed excellent catalytic performance for the selective hydrogenation of acetophenone (AP) to 1-phenylethanol (PhE) when copper content was 25?wt%. The Cu/SiO2 catalyst had well dispersed copper species, small particle size, high BET surface area (ca. 540?m2/g) and abundant pore structure. The influence of different reaction conditions on the hydrogenation process were also discussed. AP conversion and the PhE selectivity reached 99.8% and 99.08%, respectively, under the optimal reaction conditions (Temperature: 353?K; Pressure: 2.0?MPa, LHSV: 1.0?h?1 and the molar ratio of H2/AP:15). Besides, the above catalyst maintained a high catalytic performance in the duration of 500?h operation. The synergistic effect between Cu+ and Cu0 improved the activity and stability of Cu/SiO2 catalyst. The research indicated that the catalyst had a wide industrial prospect. Graphic Abstract: The Cu/SiO2 catalyst showed a good performance for AP hydrogenation. The reduced Cu/SiO2 catalyst contains both Cu+ and Cu0 consistent with XPS. Cu+ sties stabilize the methoxy and acyl species and Cu0 facilitates the decomposition of H2. Phenyl in AP and Cu had electrostatic repulsion, which was favorable for desorption of PhE.[Figure not available: see fulltext.].
- Wang, Bing,Jin, Manman,An, Hao,Guo, Zhenmei,Lv, Zhiguo
-
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- Vicinal, Double C-H Functionalization of Alcohols via an Imidate Radical-Polar Crossover Cascade
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A double functionalization of vicinal sp3 C-H bonds has been developed, wherein a β amine and γiodide are incorporated onto an aliphatic alcohol in a single operation. This approach is enabled by an imidate radical chaperone, which selectively affords a transient β alkene that is amino-iodinated in situ. Overall, the radical-polar-crossover cascade entails the following key steps: (i) β C-H iodination via 1,5-hydrogen atom transfer (HAT), (ii) desaturation via I2 complexation, and (iii) vicinal amino-iodination of an in situ generated allyl imidate. The synthetic utility of this double C-H functionalization is illustrated by conversion of aliphatic alcohols to a diverse collection of α,β,γsubstituted products bearing heteroatoms on three adjacent carbons. The radical-polar crossover mechanism is supported by various experimental probes, including isotopic labeling, intermediate validation, and kinetic studies.
- Nagib, David A.,Prusinowski, Allen F.,Twumasi, Raymond K.,Wappes, Ethan A.
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supporting information
(2020/03/16)
-
- Lithium Bromide/HBpin: A Mild and Effective Catalytic System for the Selective Hydroboration of Aldehydes and Ketones
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The catalytic hydroboration of aldehydes and ketones with HBpin was examined using simple and commercially available metal salts (Li, Na, and K). Among the tested salts, LiBr (0.5–1.0 mol%) was found to be an efficient catalyst for the hydroboration of various aldehydes and ketones at room temperature. Further, the chemoselective hydroboration of aldehydes over ketones was also demonstrated.
- An, Duk Keun,Choi, Hyeon Seong,Hwang, Hyonseok,Kim, Hanbi,Lee, Ji Hye,Shin, Hye Lim,Yi, Jaeeun
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p. 1009 - 1018
(2020/10/12)
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- Low-valence anionic α-diimine iron complexes: Synthesis, characterization, and catalytic hydroboration studies
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The synthesis of rare anionic heteroleptic and homoleptic α-diimine iron complexes is described. Heteroleptic BIAN (bis(aryl)iminoacenaphthene) complexes 1-[K([18]c-6)-(thf)0.5] and 2-[K([18]c-6)(thf)2] were synthesized by reduction of the [(BIAN)FeBr2] precursor complex using stoichiometric amounts of potassium graphite in the presence of the corresponding olefin. The electronic structure of these paramagnetic species was investigated by numerous spectroscopic analyses (NMR, EPR, 57Fe M?ssbauer, UV-vis), magnetic measurements (Evans NMR method, SQUID), and theoretical techniques (DFT, CASSCF). Whereas anion 1 is a low-spin complex, anion 2 consists of an intermediate-spin Fe(III) center. Both complexes are efficient precatalysts for the hydroboration of carbonyl compounds under mild reaction conditions. The reaction of bis(anthracene) ferrate(1-) gave the homoleptic BIAN complex 3-[K([18]c-6)(thf)], which is less catalytically active. The electronic structure was elucidated with the same techniques as described for complexes 1-[K([18]c-6)(thf)0.5] and 2-[K([18]c-6)(thf)2] and revealed an Fe(II) species in a quartet ground state.
- Bodensteiner, Michael,Coburger, Peter,Demeshko, Serhiy,Gawron, Martin,Maier, Thomas M.,Meyer, Franc,Wolf, Robert,de Bruin, Bas,van Leest, Nicolaas P.
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p. 16035 - 16052
(2020/11/20)
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- Selective Hydrogenation and Hydrodeoxygenation of Aromatic Ketones to Cyclohexane Derivatives Using a Rh&at;SILP Catalyst
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Rhodium nanoparticles immobilized on an acid-free triphenylphosphonium-based supported ionic liquid phase (Rh&at;SILP(Ph3-P-NTf2)) enabled the selective hydrogenation and hydrodeoxygenation of aromatic ketones. The flexible molecular approach used to assemble the individual catalyst components (SiO2, ionic liquid, nanoparticles) led to outstanding catalytic properties. In particular, intimate contact between the nanoparticles and the phosphonium ionic liquid is required for the deoxygenation reactivity. The Rh&at;SILP(Ph3-P-NTf2) catalyst was active for the hydrodeoxygenation of benzylic ketones under mild conditions, and the product distribution for non-benzylic ketones was controlled with high selectivity between the hydrogenated (alcohol) and hydrodeoxygenated (alkane) products by adjusting the reaction temperature. The versatile Rh&at;SILP(Ph3-P-NTf2) catalyst opens the way to the production of a wide range of high-value cyclohexane derivatives by the hydrogenation and/or hydrodeoxygenation of Friedel–Crafts acylation products and lignin-derived aromatic ketones.
- Bordet, Alexis,Emondts, Meike,Leitner, Walter,Moos, Gilles
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supporting information
p. 11977 - 11983
(2020/06/02)
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- Multiple Mechanisms Mapped in Aryl Alkyl Ether Cleavage via Aqueous Electrocatalytic Hydrogenation over Skeletal Nickel
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We present here detailed mechanistic studies of electrocatalytic hydrogenation (ECH) in aqueous solution over skeletal nickel cathodes to probe the various paths of reductive catalytic C-O bond cleavage among functionalized aryl ethers relevant to energy science. Heterogeneous catalytic hydrogenolysis of aryl ethers is important both in hydrodeoxygenation of fossil fuels and in upgrading of lignin from biomass. The presence or absence of simple functionalities such as carbonyl, hydroxyl, methyl, or methoxyl groups is known to cause dramatic shifts in reactivity and cleavage selectivity between sp3 C-O and sp2 C-O bonds. Specifically, reported hydrogenolysis studies with Ni and other catalysts have hinted at different cleavage mechanisms for the C-O ether bonds in α-keto and α-hydroxy β-O-4 type aryl ether linkages of lignin. Our new rate, selectivity, and isotopic labeling results from ECH reactions confirm that these aryl ethers undergo C-O cleavage via distinct paths. For the simple 2-phenoxy-1-phenylethane or its alcohol congener, 2-phenoxy-1-phenylethanol, the benzylic site is activated via Ni C-H insertion, followed by beta elimination of the phenoxide leaving group. But in the case of the ketone, 2-phenoxyacetophenone, the polarized carbonyl πsystem apparently binds directly with the electron rich Ni cathode surface without breaking the aromaticity of the neighboring phenyl ring, leading to rapid cleavage. Substituent steric and electronic perturbations across a broad range of β-O-4 type ethers create a hierarchy of cleavage rates that supports these mechanistic ideas while offering guidance to allow rational design of the catalytic method. On the basis of the new insights, the usage of cosolvent acetone is shown to enable control of product selectivity.
- Hegg, Eric L.,Jackson, James E.,Klinger, Grace E.,Saffron, Christopher M.,Zhou, Yuting
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p. 4037 - 4050
(2020/03/10)
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- Mechanistic Study and Development of Catalytic Reactions of Sm(II)
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Samarium diiodide (SmI2) is one of the most widely used single-electron reductants available to organic chemists because it is effective in reducing and coupling a wide range of functional groups. Despite the broad utility and application of SmI2 in synthesis, the reagent is used in stoichiometric amounts and has a high molecular weight, resulting in a large amount of material being used for reactions requiring one or more equivalents of electrons. Although few approaches to develop catalytic reactions have been designed, they are not widely used or require specialized conditions. As a consequence, general solutions to develop catalytic reactions of Sm(II) remain elusive. Herein, we report mechanistic studies on catalytic reactions of Sm(II) employing a terminal magnesium reductant and trimethylsilyl chloride in concert with a noncoordinating proton donor source. Reactions using this approach permitted reductions with as little as 1 mol % Sm. Mechanistic studies provide strong evidence that during the reaction, SmI2 transforms into SmCl2, therefore broadening the scope of accessible reactions. Furthermore, this mechanistic approach enabled catalysis employing HMPA as a ligand, facilitating the development of catalytic Sm(II) 5-exo-trig ketyl olefin cyclization reactions. The initial work described herein will enable further development of both useful and user-friendly catalytic reactions, a long-standing, but elusive goal in Sm(II) chemistry.
- Maity, Sandeepan,Flowers, Robert A.
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supporting information
p. 3207 - 3216
(2019/02/19)
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- Design, synthesis and structure-activity relationship study of aminopyridine derivatives as novel inhibitors of Janus kinase 2
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Janus Kinase 2 (JAK2) is a kind of intracellular non-receptor protein tyrosine kinase and has been certified as an important target for the treatment of myeloproliferative neoplasms and rheumatoid arthritis. However, the low selectivity and potential safety issues restrict the clinical applications of JAK2 inhibitors. Here we found that crizotinib showed good inhibitory activity against JAK2 by enzymatic assays (IC50 = 27 nM). Then we carried out structure-based drug design and synthesized a series of compounds with an aminopyridine scaffold. Finally, compound 12k and 12l were identified as the promising inhibitors of JAK2, which exhibited high inhibitory activity (IC50 = 6 nM and 3 nM, respectively) and selectivity for JAK2 over JAK1 and JAK3, and showed potent antiproliferative activities toward HEL human erythroleukemia cells. Moreover, 12k suppressed symptoms of the collagen-induced arthritis (CIA) model in rats.
- Wang, Wanqi,Diao, Yanyan,Li, Wenjie,Luo, Yating,Yang, Tingyuan,Zhao, Yuyu,Qi, TianTian,Xu, Fangling,Ma, Xiangyu,Ge, Huan,Liang, Yingfan,Zhao, Zhenjiang,Liang, Xin,Wang, Rui,Zhu, Lili,Li, Honglin,Xu, Yufang
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supporting information
p. 1507 - 1513
(2019/04/17)
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- Hydrosilylation of carbonyl and carboxyl groups catalysed by Mn(i) complexes bearing triazole ligands
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Manganese(i) complexes bearing triazole ligands are reported as catalysts for the hydrosilylation of carbonyl and carboxyl compounds. The desired reaction proceeds readily at 80 °C within 3 hours at catalyst loadings as low as 0.25 to 1 mol%. Hence, good to excellent yields of alcohols could be obtained for a wide range of substrates including ketones, esters, and carboxylic acids illustrating the versatility of the metal/ligand combination.
- Martínez-Ferraté, Oriol,Chatterjee, Basujit,Werlé, Christophe,Leitner, Walter
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p. 6370 - 6378
(2019/11/20)
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- Pyridine-Stabilized Rhodium Nanoparticles in Ionic Liquids as Selective Hydrogenation and Transfer Hydrogenation Catalysts
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Rhodium nanoparticles (RhNPs) stabilized with pyridine-based ligands in the ionic liquid [BMIM][BF4] (RhNPs-I to III) were synthesized from the organometallic precursor [Rh(μ-OMe)COD]2 under dihydrogen pressure. The pyridine-stabilized RhNPs showed smaller size compared to the ligand free RhNPs-V and presented higher activity and selectivity in the hydrogenation of acetophenone to 1-phenylethanol. In the case of pyridine-capped RhNPs-I, the system was reused for several runs without loss of activity and selectivity. Nitrobenzene was reduced to aniline with dihydrogen in the presence of RhNPs-I with moderate activity. When the hydrogen source was formic acid-Et3N azeotrope (transfer hydrogenation) the reaction was completed within minutes with high selectivity. Under transfer hydrogenation conditions, it was possible to apply the catalytic system RhNPs-I in multistep processes for the generation of substituted arylic amines through the reductive N-alkylation of nitrobenzene and benzaldehyde; and the synthesis of substituted pyrroles through the nitroarene reduction/Paal-Knorr condensation.
- Serrano-Maldonado, Alejandro,Martin, Erika,Guerrero-Ríos, Itzel
-
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- Cucurbit[5]uril-mediated electrochemical hydrogenation of α,β-unsaturated ketones
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The potential of cucurbit[5]uril to be used as inverse phase transfer catalyst in electrocatalytic hydrogenation of α,β-unsaturated ketones is illustrated. The interaction behavior among isophorone and cucurbit[5]uril was also investigated using cyclic voltammetry and UV/vis absorption spectroscopy. The results concerning to both techniques revealed an enhancement in the intensity of the absorption peak and also in the current cathodic peak of isophorone in presence of cucurbit[5]uril. This achievement is related to the increase of the isophorone solubility in the medium being an indicative of a host-guest complex formation. The electrochemical hydrogenation of isophorone using cucurbit[5]uril was more efficient than others well-stablish methodologies. Regarding to (R)-(+)-pulegone and (S)-(+)-carvone, the use of cucurbit[5]uril leads to an increase of 17% and 9%, on average, respectively, in the yields when compared to the control reaction. The efficiency of selective C=O bond hydrogenation of 1-acetyl-1-cyclohexene was evaluated. The presence of cucurbit[5]uril increased by 12% the hydrogenations yields of 1-acetyl-1-cyclohexene when compared to the control reaction. In this sense, these results open up an opportunity to carry out electrocatalytic reactions within the cucurbit[5]uril environment.
- Sales, Ayrlane,de Oliveira e Castro, Isabela Andrade,de Menezes, Frederico Duarte,Selva, Thiago Matheus Guimar?es,Vilar, Márcio
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p. 295 - 305
(2019/09/03)
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- Enantioselective Hydrogenation of Ketones using Different Metal Complexes with a Chiral PNP Pincer Ligand
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The synthesis of different metal pincer complexes coordinating to the chiral PNP ligand bis(2-((2R,5R)-2,5-dimethyl-phospholanoethyl))amine is described in detail. The characterized complexes with Mn, Fe, Re and Ru as metal centers showed good activities regarding the reduction of several prochiral ketones. Comparing these catalysts, the non-noble metal complexes produced best selectivities not only for aromatic substrates, but also for different kinds of aliphatic ones leading to enantioselectivities up to 99% ee. Theoretical investigations elucidated the mechanism and rationalized the selectivity. (Figure presented.).
- Garbe, Marcel,Wei, Zhihong,Tannert, Bianca,Spannenberg, Anke,Jiao, Haijun,Bachmann, Stephan,Scalone, Michelangelo,Junge, Kathrin,Beller, Matthias
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supporting information
p. 1913 - 1920
(2019/03/13)
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- Solvent and substituent effects in hydrogenation of aromatic ketones over Ru/polymer catalyst under very mild conditions
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The paper reports on the solvent and the substituent effects in hydrogenation of aromatic ketones (acetophenone and its derivatives) in the presence of Ru catalyst supported on functionalized gel-type methacrylate-styrene resin under very mild conditions
- Duraczyńska,Serwicka,Drelinkiewicz,Socha,Zimowska,Lityńska-Dobrzyńska,Bukowska
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p. 145 - 151
(2019/04/13)
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- Iridium-catalyzed efficient reduction of ketones in water with formic acid as a hydride donor at low catalyst loading
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A highly efficient and chemoselective transfer hydrogenation of ketones in water has been successfully achieved with our newly developed catalyst. Simple ketones, as well as α- or β-functionalized ketones, are readily reduced. Formic acid is used as a traceless hydride source. At very low catalyst loading (S/C = 10:000 in most cases; S/C = 50:000 or 100:000 in some cases), the iridium catalyst is impressively efficient at reducing ketones in good to excellent yields. The TOF value can be as high as up to 26:000 mol mol-1 h-1. A variety of functional groups are well tolerated, for example, heteroaryl, aryloxy, alkyloxy, halogen, cyano, nitro, ester, especially acidic methylene, phenol and carboxylic acid groups.
- Liu, Ji-Tian,Yang, Shiyi,Tang, Weiping,Yang, Zhanhui,Xu, Jiaxi
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supporting information
p. 2118 - 2124
(2018/05/24)
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- Aminotriazole Mn(I) Complexes as Effective Catalysts for Transfer Hydrogenation of Ketones
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A catalytic system based on complexes comprising abundant and cheap manganese together with readily available aminotriazole ligands is reported. The new Mn(I) complexes are catalytically competent in transfer hydrogenation of ketones with 2-propanol as hydrogen source. The reaction proceeds under mild conditions at 80 °C for 20 h with 3 % of catalyst loading using either KOtBu or NaOH as base. Good to excellent yields were obtained for a wide substrate scope with broad functional group tolerance. The obtained results by varying the substitution pattern of the ligand are consistent with an out-sphere mechanism for the H-transfer.
- Martínez-Ferraté, Oriol,Werlé, Christophe,Franciò, Giancarlo,Leitner, Walter
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p. 4514 - 4518
(2018/10/20)
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- Selective hydrogenation of aromatic compounds using modified iridium nanoparticles
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Till now, Ionic liquid-stabilized metal nanoparticles were investigated as catalytic materials, mostly in the hydrogenation of simple substrates like olefins or arenes. The adjustable hydrogenation products of aromatic compounds, including quinoline and relevant compounds, aromatic nitro compounds, aromatic ketones as well as aromatic aldehydes, are always of special interest, since they provide more choices for additional derivatization. Iridium nanoparticles (Ir NPs) were synthesized by the H2 reduction in imidazolium ionic liquid. TEM indicated that the Ir NPs is worm-like shape with the diameter around 12.2?nm and IR confirmed the modification of phosphine-functionalized ionic liquids (PFILs) to the Ir NPs. With the variation of the modifier, solvent and reaction temperature, substrate like quinoline and relevant compounds, aromatic nitro compounds, aromatic ketones as well as aromatic aldehydes could be hydrogenated by Ir NPs with interesting adjustable catalytic activity and chemoselectivity. Ir NPs modified by PFILs are simple and efficient catalysts in challenging chemoselective hydrogenation of quinoline and relevant compounds, aromatic nitro compounds, aromatic ketones as well as aromatic aldehydes. The activity and chemoselectivity of the Ir NPs could be obviously impacted or adjusted by altering the modifier, solvent and reaction temperature.
- Jiang, He-Yan,Xu, Jie,Sun, Bin
-
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- Effect of the Crystallographic Phase of Ruthenium Nanosponges on Arene and Substituted-Arene Hydrogenation Activity
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Identifying crystal structure sensitivity of a catalyst for a particular reaction is an important issue in heterogeneous catalysis. In this context, the activity of different phases of ruthenium catalysts for benzene hydrogenation has not yet been investigated. The synthesis of hcp and fcc phases of ruthenium nanosponges by chemical reduction method has been described. Reduction of ruthenium chloride using ammonia borane (AB) and tert-butylamine borane (TBAB) as reducing agents gave ruthenium nanosponge in its hcp phase. On the other hand, reduction using sodium borohydride (SB) afforded ruthenium nanosponge in its fcc phase. The as prepared hcp ruthenium nanosponge was found to be catalytically more active compared to the as prepared fcc ruthenium nanosponge for hydrogenation of benzene. The hcp ruthenium nanosponge was found to be thermally stable and recyclable over several cycles. This self-supported hcp ruthenium nanosponge shows excellent catalytic activity towards hydrogenation of various substituted benzenes. Moreover, the ruthenium nanosponge catalyst was found to bring about selective hydrogenation of aromatic cores of phenols and aryl ethers to the respective alicyclic products without hydrogenolysis of the C?O bond.
- Ghosh, Sourav,Jagirdar, Balaji R.
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p. 3086 - 3095
(2018/05/29)
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- CHIRAL METAL COMPLEX COMPOUNDS
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The invention comprises novel chiral metal complex compounds of the formula (I) wherein M, PR2, R3 and R4 are outlined in the description, its stereoisomers, in the form as a neutral complex or a complex cation with a suitable counter ion. The chiral metal complex compounds can be used in asymmetric reactions, particularly in asymmetric reductions of ketones, imines or oximes.
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Page/Page column 18; 19; 22; 24; 26
(2018/11/10)
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- Efficient cleavage of aryl ether C-O linkages by Rh-Ni and Ru-Ni nanoscale catalysts operating in water
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Bimetallic Ru-Ni and Rh-Ni nanocatalysts coated with a phase transfer agent efficiently cleave aryl ether C-O linkages in water in the presence of hydrogen. For dimeric substrates with weaker C-O linkages, i.e. α-O-4 and β-O-4 bonds, low loadings of the precious metal (Rh or Ru) in the nanocatalysts quantitatively afford monomers, whereas for the stronger 4-O-5 linkage higher amounts of the precious metal are required to achieve complete conversion. Under the optimized, relatively mild operating conditions, the C-O bonds in a range of substituted ether compounds are efficiently cleaved, and mechanistic insights into the reaction pathways are provided. This work paves the way to sustainable approaches for the hydrogenolysis of C-O bonds.
- Bulut, Safak,Siankevich, Sviatlana,Van Muyden, Antoine P.,Alexander, Duncan T. L.,Savoglidis, Georgios,Zhang, Jiaguang,Hatzimanikatis, Vassily,Yan, Ning,Dyson, Paul J.
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p. 5530 - 5535
(2018/07/06)
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- Ultrasmall Platinum Stabilized on Triphenylphosphine-Modified Silica for Chemoselective Hydrogenation
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Chemoselective hydrogenation of substrates with more than one functional group that could be hydrogenated is quite challenging and is of fundamental importance. Here, the enhanced chemoselectivity of ultrasmall (1 nm) platinum nanoparticles (NPs) stabili
- Jayakumar, Sanjeevi,Modak, Arindam,Guo, Miao,Li, He,Hu, Xiangping,Yang, Qihua
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supporting information
p. 7791 - 7797
(2017/06/06)
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- NHC-stabilised Rh nanoparticles: Surface study and application in the catalytic hydrogenation of aromatic substrates
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New Rh-NPs stabilised by N-Heterocyclic Carbenes (NHC) were synthesized by decomposition of [Rh(η3-C3H5)3] under H2 atmosphere and fully characterized. Surface studies by FT-IR and NMR spectroscopy employing isotopically labelled ligands were also performed. The Rh0.2 NPs are active catalysts in the reduction of various aromatic substrates. In the reduction of phenol, high selectivities to cyclohexanone or cyclohexanol were obtained depending on the reaction conditions. However, this catalytic system exhibited much lower activity in the hydrogenation of substituted phenols. Pyridine was easily hydrogenated under mild conditions and interestingly, the hydrogenation of 4-methyl and 4-trifluoromethylpyridine resulted slower than that of 2-methylpyridine. The hydrogenation of 1-(pyridin-2-yl)propan-2-one provided the β-enaminone 13a in high yield as a consequence of the partial reduction of the pyridine ring followed by isomerization. Quinoline could be either partially hydrogenated to 1,2,3,4-tetrahydroquinoline or fully reduced to decahydroquinoline by adjusting the reaction conditions.
- Martinez-Espinar, Francisco,Blondeau, Pascal,Nolis, Pau,Chaudret, Bruno,Claver, Carmen,Castillón, Sergio,Godard, Cyril
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p. 113 - 127
(2017/09/08)
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- Chemoselective continuous-flow hydrogenation of aldehydes catalyzed by platinum nanoparticles dispersed in an amphiphilic resin
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A chemoselective continuous-flow hydrogenation of aldehydes catalyzed by a dispersion of platinum nanoparticles in an amphiphilic polymer (ARP-Pt) has been developed. Aromatic and aliphatic aldehydes bearing various reducible functional groups, such as keto, ester, or amide groups, readily underwent flow hydrogenation in aqueous solutions within 22 s in a continuous-flow system containing ARP-Pt to give the corresponding primary benzylic or aliphatic alcohols in ≤99% yield with excellent chemoselectivity. Moreover, the long-term continuous-flow hydrogenation of benzaldehyde for 8 days was realized, and the total turnover number of the catalyst reached 997. The flow hydrogenation system provides an efficient and practical method for the chemoselective hydrogenation of aldehydes bearing reducible functional groups.
- Osako, Takao,Torii, Kaoru,Hirata, Shuichi,Uozumi, Yasuhiro
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p. 7371 - 7377
(2017/11/09)
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- AN ECO-FRIENDLY PROCESS FOR HYDROGENATION OR/AND HYDRODEOXYGENATION OF ORGANIC COMPOUND USING HYDROUS RUTHENIUM OXIDE CATALYST
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The invention discloses aneco-friendly process for hydrogenation (alkenealkene, carbonyl compound and aromatic) and hydrodeoxygenation (methoxy phenols) of organic compound using hydrous ruthenium oxide (HRO) and its supported form as a recyclable heterogeneous catalyst in aqueous medium with good yield of desired compounds (70-100%) under mild reaction conditions. The invention also discloses hydrogenation of organic compound such as alkene, carbonyl compound and substituted aromatic and also for the processes that involve hydrodeoxygenation, for example, lignin derived aromatic (methoxy phenols).
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Page/Page column 15; 22
(2017/08/01)
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- Catalytic Hydrogenation of Arenes in Water Over In Situ Generated Ruthenium Nanoparticles Immobilized on Carbon
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We describe a tandem process to generate active Ru nanoparticles (≈7 nm) immobilised in situ on carbon from an organometallic precursor and formic acid to afford the hydrogenation of a wide range of arenes and heteroarenes in yields up to 72 % with high conversions and selectivities for the desired products. The hydrogenation of several substrates analogous to lignin-derived fragments to the corresponding alicyclic products was also achieved. Our experimental investigations evidenced that the observed enhanced activity for arene hydrogenation was driven by the unique structural advantages of the organometallic precursor to activate formic acid, in which the presence of a nitrogen ligand is crucial to achieve a high catalytic activity. TEM analysis revealed the formation of Ru0 nanoparticles, and Hg0 poisoning experiments support the heterogeneous nature of the active catalyst.
- Dwivedi, Ambikesh Dhar,Rai, Rohit Kumar,Gupta, Kavita,Singh, Sanjay Kumar
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p. 1930 - 1938
(2017/06/13)
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- α-Sulfinyl Benzoates as Precursors to Li and Mg Carbenoids for the Stereoselective Iterative Homologation of Boronic Esters
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The stereoselective reagent-controlled homologation of boronic esters is one of a small number of iteratable synthetic transformations that if automated could form the basis of a veritable molecule-making machine. Recently, α-stannyl triisopropylbenzoates and α-sulfinyl chlorides have emerged as useful building blocks for the iterative homologation of boronic esters. However, α-stannyl benzoates need to be prepared using stoichiometric amounts of the (+)- or (-)-enantiomer of the scarcely available and expensive diamine sparteine; also, these building blocks, together with the byproducts that are generated during homologation, are perceived as being toxic. On the other hand, α-sulfinyl chlorides are difficult to prepare with high levels of enantiopurity and are prone to undergo deleterious acid-base side-reactions under the reaction conditions for homologation, leading to low stereospecificity. Here, we show that the use of a hybrid of these two building blocks, namely, α-sulfinyl triisopropylbenzoates, largely overcomes the above drawbacks. Through either the sulfinylation of α-magnesiated benzoates with either enantiomer of Andersen's readily available menthol-derived sulfinate or the α-alkylation of enantiopure S-chiral α-sulfinyl benzoates, we have prepared a range of highly enantiopure mono- and disubstituted α-sulfinyl benzoates, some bearing sensitive functional groups. Barbier-type reaction conditions have been developed that allow these building blocks to be converted into lithium (t-BuLi) and magnesium (i-PrMgCl·LiCl) carbenoids in the presence of boronic esters, thus allowing efficient and highly stereospecific homologation. The use of magnesium carbenoids allows carbon chains to be grown with the incorporation of sensitive functional groups, such as alkyl/aryl halides, azides, and esters. The use of lithium carbenoids, which are less sensitive to steric hindrance, allows sterically encumbered carbon-carbon bonds to be forged. We have also shown that these building blocks can be used consecutively in three- and four-step iterative homologation processes, without intervening column chromatography, to give contiguously substituted carbon chains with very high levels of enantio- and diastereoselectivity.
- Casoni, Giorgia,Kucukdisli, Murat,Fordham, James M.,Burns, Matthew,Myers, Eddie L.,Aggarwal, Varinder K.
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supporting information
p. 11877 - 11886
(2017/09/07)
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- Iron cyclopentadienone complexes derived from C2-symmetric bis-propargylic alcohols; Preparation and applications to catalysis
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A series of complexes containing the iron-cyclopentadienone structure were prepared by cyclising bis-propargylic alcohols and their derivatives with iron pentacarbonyl. The resulting complexes were characterised and tested in the catalysis of ketone reduction and alcohol oxidation. The complexes are competent catalysts for ketone reduction and alcohol oxidations.
- Hodgkinson, Roy,Del Grosso, Alessandro,Clarkson, Guy,Wills, Martin
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supporting information
p. 3992 - 4005
(2016/03/05)
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- Selective hydrogenation of arenes to cyclohexanes in water catalyzed by chitin-supported ruthenium nanoparticles
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The selective hydrogenation of aromatic compounds to cyclohexanes was found to be promoted by chitin-supported ruthenium nanoparticles (Ru/chitin) under near-neutral, aqueous conditions without the loss of C-O/C-N linkages at benzylic positions.
- Morioka, Yuna,Matsuoka, Aki,Binder, Kellie,Knappett, Benjamin R.,Wheatley, Andrew E.H.,Naka, Hiroshi
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p. 5801 - 5805
(2016/08/06)
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- Long-chain NHC-stabilized RuNPs as versatile catalysts for one-pot oxidation/hydrogenation reactions
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The synthesis and catalytic activity of long-chain NHC-stabilized RuNPs are presented. Full characterization of these novel nanostructures including surface state studies show that the ligand influences the number and the location of Ru active sites which impacts the NP catalytic activity, especially in hydrogenation reactions. The high stability and versatility of these nanosystems make them successful catalysts for both oxidation and hydrogenation reactions that can even be performed successively in a one pot-fashion.
- Martínez-Prieto,Ferry,Rakers,Richter,Lecante,Philippot,Chaudret,Glorius
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supporting information
p. 4768 - 4771
(2016/04/09)
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- Enhancing the Catalytic Properties of Ruthenium Nanoparticle-SILP Catalysts by Dilution with Iron
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The partial replacement of ruthenium by iron ("dilution") provided enhanced catalytic activities and selectivities for bimetallic iron-ruthenium nanoparticles immobilized on a supported ionic liquid phase (FeRuNPs@SILP). An organometallic synthetic approach to the preparation of FeRuNPs@SILP allowed for a controlled and flexible incorporation of Fe into bimetallic FeRu NPs. The hydrogenation of substituted aromatic substrates using bimetallic FeRuNPs@SILP showed high catalytic activities and selectivities for the reduction of a variety of unsaturated moieties without saturation of the aromatic ring. The formation of a bimetallic phase not only leads to an enhanced differentiation of the hydrogenation selectivity, but even reversed the order of functional group hydrogenation in certain cases. In particular, bimetallic FeRuNPs@SILP (Fe:Ru = 25:75) were found to exhibit accelerated reaction rates for C=O hydrogenation within furan-based substrates which were >4 times faster than monometallic RuNPs@SILP. Thus, the controlled incorporation of the non-noble metal into the bimetallic phase provided novel catalytic properties that could not be obtained using either of the monometallic catalysts.
- Luska, Kylie L.,Bordet, Alexis,Tricard, Simon,Sinev, Ilya,Grünert, Wolfgang,Chaudret, Bruno,Leitner, Walter
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p. 3719 - 3726
(2016/07/06)
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- Mechanistic implications of the enantioselective addition of alkylzinc reagents to aldehydes catalyzed by nickel complexes with α-amino amide ligands
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The enantioselective alkylation of aldehydes catalysed by nickel(ii)-complexes derived from α-amino amides was studied by means of density functional theory (DFT) and ONIOM (B3LYP:UFF) calculations. A mechanism was proposed in order to investigate the origin of enantioselectivity. The chirality-determining step for the alkylation was the formation of the intermediate complexes with the involvement of a 5/4/4-fused tricyclic transition state. The predominant products predicted theoretically were of (S)-configuration, in good agreement with experimental observations. The scope of the reaction was examined and high yields and enantioselectivities were observed for the enantioselective addition of Et2Zn and Me2Zn to aromatic and aliphatic aldehydes.
- Escorihuela, Jorge,Burguete, M. Isabel,Ujaque, Gregori,Lledós, Agustí,Luis, Santiago V.
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supporting information
p. 11125 - 11136
(2016/12/07)
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