- Continuous synthesis of menthol from citronellal and citral over Ni-beta-zeolite-sepiolite composite catalyst
-
One-pot continuous synthesis of menthols both from citronellal and citral was investigated over 5 wt% Ni supported on H-Beta-38-sepiolite composite catalyst at 60–70 °C under 10–29 bar hydrogen pressure. A relatively high menthols yield of 53% and 49% and stereoselectivity to menthol of 71–76% and 72–74% were obtained from citronellal and citral respectively at the contact time 4.2 min, 70 °C and 20 bar. Citral conversion noticeably decreased with time-on-stream under 10 and 15 bar of hydrogen pressure accompanied by accumulation of citronellal, the primary hydrogenation product of citral, practically not affecting selectivity to menthol. A substantial amount of defuctionalization products observed during citral conversion, especially at the beginning of the reaction (ca. 1 h), indicated that all intermediates could contribute to formation of menthanes. Ni/H-Beta-38-sepiolite composite material prepared by extrusion was characterized by TEM, SEM, XPS, XRD, ICP-OES, N2 physisorption and FTIR techniques to perceive the interrelation between the physico-chemical and catalytic properties.
- Er?nen, Kari,M?ki-Arvela, P?ivi,Martinez-Klimov, Mark,Muller, Joseph,Murzin, Dmitry Yu.,Peurla, Markus,Simakova, Irina,Vajglova, Zuzana
-
-
- Remarkable catalytic activity of polymeric membranes containing gel-trapped palladium nanoparticles for hydrogenation reactions
-
Polymeric flat-sheet membranes and hollow fibers were prepared via UV photo-initiated polymerization of acrylic acid at the surface of commercial polyether sulfones (PES) membranes. These polymeric materials permitted to immobilize efficiently palladium nanoparticles (PdNP), which exhibited a mean diameter in the range of 4?6 nm. These materials were synthesized by chemical reduction of Pd(II) precursors in the presence of the corresponding support. We successfully applied the as-prepared catalytic materials in hydrogenation reactions under continuous flow conditions. Flat sheet membranes were more active than hollow fibers due to the flow configuration and defavorable operating conditions. Actually, various functional groups (i.e. C[dbnd]C, C[tbnd]C and NO2) were reduced in flow-through configuration, under mild conditions (between 1.4 and 2.2 bar H2 at 60 °C, using 3.2 mol% of Pd loading), archiving high conversions in short reaction times (12?24 s).
- López-Viveros, Melissa,Favier, Isabelle,Gómez, Montserrat,Lahitte, Jean-Fran?ois,Remigy, Jean-Christophe
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p. 263 - 269
(2020/05/13)
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- Partial and Total Solvent-Free Limonene's Hydrogenation: Metals, Supports, Pressure, and Water Effects
-
Bio-based solvents menthene and menthane were obtained through limonene's partial and total hydrogenation under various catalytic conditions. Heterogeneous catalysts based on different active metals and supports (carbon, alumina, and silica) were systematically tested for solvent-free total and partial hydrogenation of limonene under high and low hydrogen pressure. Influences of these catalysts on the formation of menthene, menthane, and cymene, a dehydrogenated product, were determined. The impact of water addition on the conversion and selectivity of the catalysts was also investigated. Amongst all tested catalysts, Rh/Alumina which was never tested for total and partial hydrogenation of limonene was the most effective as 1-menthene was quantitatively produced at low pressure (0.275 MPa) while menthane was mostly obtained at a higher pressure (2.75 MPa). Water addition on Rh/Alumina favoured menthene production even at high pressure. To propose menthane, menthene, and menthane/menthene mixture as an alternative to fossil-based solvents such as n-hexane for the extraction of natural products, β-carotene, vanillin, and rosmarinic acid solubilizations have been investigated. If a modeling approach using COSMO-RS software predicted a comparable solubilization of these 3 compounds for the 3 solvents, experimental assays revealed that menthene solubilizes β-carotene, vanillin, and rosmarinic acid three to five times better than n-hexane.
- Chemat, Farid,Clarisse, Olivier,Fabiano-Tixier, Anne-Sylvie,Ndongou Moutombi, Fanta J.,Touaibia, Mohamed
-
-
- Convenient synthesis of cobalt nanoparticles for the hydrogenation of quinolines in water
-
Easily accessible cobalt nanoparticles are prepared by hydrolysis of NaBH4 in the presence of inexpensive Co(ii) salts. The resulting material is an efficient catalyst for the hydrogenation of quinoline derivatives in water. The activity and chemoselectivity of this catalyst are comparable to other cobalt-based heterogeneous catalysts.
- Beller, Matthias,Dorcet, Vincent,Fischmeister, Cedric,Hervochon, Julien,Junge, Kathrin
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p. 4820 - 4826
(2020/08/14)
-
- Multistep Engineering of Synergistic Catalysts in a Metal-Organic Framework for Tandem C-O Bond Cleavage
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Cleavage of strong C-O bonds without breaking C-C/C-H bonds is a key step for catalytic conversion of renewable biomass to hydrocarbon feedstocks. Herein we report multistep sequential engineering of orthogonal Lewis acid and palladium nanoparticle (NP) catalysts in a metal-organic framework (MOF) built from (Al-OH)n secondary building units and a mixture of 2,2′-bipyridine-5,5′-dicarboxylate (dcbpy) and 1,4-benzenediacrylate (pdac) ligands (1) for tandem C-O bond cleavage. Ozonolysis of 1 selectively removed pdac ligands to generate Al2(OH)(OH2) sites, which were subsequently triflated with trimethylsilyl triflate to afford strongly Lewis acidic sites for dehydroalkoxylation. Coordination of Pd(MeCN)2Cl2 to dcbpy ligands followed by in situ reduction produced orthogonal Pd NP sites in 1-OTf-PdNP as the hydrogenation catalyst. The selective and precise transformation of 1 into 1-OTf-PdNP was characterized step by step using powder X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, inductively coupled plasma mass spectrometry, infrared spectroscopy, and X-ray absorption spectroscopy. The hierarchical incorporation of orthogonal Lewis acid and Pd NP active sites endowed 1-OTf-PdNP with outstanding catalytic performance in apparent hydrogenolysis of etheric, alcoholic, and esteric C-O bonds to generate saturated alkanes via a tandem dehydroalkoxylation-hydrogenation process under relatively mild conditions. The reactivity of C-O bonds followed the trend of tertiary carbon > secondary carbon > primary carbon. Control experiments demonstrated the heterogeneous nature and recyclability of 1-OTf-PdNP and its superior catalytic activity over the homogeneous counterparts. Sequential engineering of multiple catalytic sites in MOFs thus presents a unique opportunity to address outstanding challenges in sustainable catalysis.
- Brzezinski, Carter,Chen, Justin S.,Feng, Xuanyu,Lin, Wenbin,Song, Yang,Xu, Ziwan
-
supporting information
p. 4872 - 4882
(2020/04/01)
-
- Rethinking Basic Concepts-Hydrogenation of Alkenes Catalyzed by Bench-Stable Alkyl Mn(I) Complexes
-
An efficient additive-free manganese-catalyzed hydrogenation of alkenes to alkanes with molecular hydrogen is described. This reaction is atom economic, implementing an inexpensive, earth-abundant nonprecious metal catalyst. The most efficient precatalyst is the bench-stable alkyl bisphosphine Mn(I) complex fac-[Mn(dippe)(CO)3(CH2CH2CH3)]. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn-alkyl bond to yield an acyl intermediate which undergoes rapid hydrogenolysis to form the active 16e Mn(I) hydride catalyst [Mn(dippe)(CO)2(H)]. A range of mono- A nd disubstituted alkenes were efficiently converted into alkanes in good to excellent yields. The hydrogenation of 1-alkenes and 1,1-disubstituted alkenes proceeds at 25 °C, while 1,2-disubstituted alkenes require a reaction temperature of 60 °C. In all cases, a catalyst loading of 2 mol % and a hydrogen pressure of 50 bar were applied. A mechanism based on DFT calculations is presented, which is supported by preliminary experimental studies.
- Weber, Stefan,St?ger, Berthold,Veiros, Luis F.,Kirchner, Karl
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p. 9715 - 9720
(2019/10/14)
-
- Regiodivergent hydrosilylation, hydrogenation, [2π + 2π]-cycloaddition and C-H borylation using counterion activated earth-abundant metal catalysis
-
The widespread adoption of earth-abundant metal catalysis lags behind that of the second- and third-row transition metals due to the often challenging practical requirements needed to generate the active low oxidation-state catalysts. Here we report the development of a single endogenous activation protocol across five reaction classes using both iron- and cobalt pre-catalysts. This simple catalytic manifold uses commercially available, bench-stable iron- or cobalt tetrafluoroborate salts to perform regiodivergent alkene and alkyne hydrosilylation, 1,3-diene hydrosilylation, hydrogenation, [2π + 2π]-cycloaddition and C-H borylation. The activation protocol proceeds by fluoride dissociation from the counterion, in situ formation of a hydridic activator and generation of a low oxidation-state catalyst.
- Agahi, Riaz,Challinor, Amy J.,Dunne, Joanne,Docherty, Jamie H.,Carter, Neil B.,Thomas, Stephen P.
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p. 5079 - 5084
(2019/05/24)
-
- Heterogeneously Catalysed Oxidative Dehydrogenation of Menthol in a Fixed-Bed Reactor in the Gas Phase
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For the first time, the oxidative dehydrogenation of (?)-menthol to (?)-menthone and (+)-isomenthone in a marketable quality was carried out in a continuous gas phase reactor as a sustainable process using molecular oxygen as green oxidant and solid catalysts which do not contaminate the product mixture and which are easily to remove. The diastereomeric purity remained largely unchanged. Three types of catalysts were found to be very active and selective in the formation of menthone and isomenthone: AgSr/SiO2, CuO distributed on a basic support and RuMnCe/CeO2, where Ru, Mn and Ce exist in an oxidized state. The best overall yield of menthon/isomenthone obtained with an Ag-based catalyst was 58 % at 64 % selectivity, with a Cu-based catalyst 41 % at 51 % selectivity and with a Ru-based catalyst 68 % at 73 % selectivity. Reaction conditions were widely optimized.
- Kulik, Anna,Neubauer, Katja,Eckelt, Reinhard,Bartling, Stephan,Panten, Johannes,K?ckritz, Angela
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p. 1066 - 1075
(2019/06/24)
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- Recyclable cobalt(0) nanoparticle catalysts for hydrogenations
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The search for new hydrogenation catalysts that replace noble metals is largely driven by sustainability concerns and the distinct mechanistic features of 3d transition metals. Several combinations of cobalt precursors and specific ligands in the presence of reductants or under high-thermal conditions were reported to provide active hydrogenation catalysts. This study reports a new method of preparation of small, monodisperse Co(0) nanoparticles (3-4 nm) from the reduction of commercial CoCl2 in the absence of ligands or surfactants. High catalytic activity was observed in hydrogenations of alkenes, alkynes, imines, and heteroarenes (2-20 bar H2). The magnetic properties enabled catalyst separation and multiple recyclings.
- Büschelberger, Philipp,Reyes-Rodriguez, Efrain,Sch?ttle, Christian,Treptow, Jens,Feldmann, Claus,Jacobi Von Wangelin, Axel,Wolf, Robert
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p. 2648 - 2653
(2018/05/30)
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- Metal vapor synthesis of ultrasmall Pd nanoparticles functionalized with N-heterocyclic carbenes
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The synthesis of N-heterocyclic carbene (NHC)-stabilized palladium nanoparticles (PdNPs) by an entirely new strategy comprising the NHC functionalization of ligand-free PdNPs obtained by metal vapor synthesis is described. Detailed characterization confirms the formation of very small monodisperse PdNPs (2.3 nm) and the presence of the NHC ligand on the Pd surface. The stable NHC-functionalized PdNPs dispersed onto a carbon support showed high activity in the hydrogenation of limonene with enhanced regioselectivity in comparison to bare PdNPs on carbon.
- Tegeder, Patricia,Marelli, Marcello,Freitag, Matthias,Polito, Laura,Lamping, Sebastian,Psaro, Rinaldo,Glorius, Frank,Ravoo, Bart Jan,Evangelisti, Claudio
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supporting information
p. 12647 - 12651
(2018/09/27)
-
- Structural, electronic and catalytic properties of palladium nanoparticles supported on poly(ionic liquid)
-
The structural, electronic and support effect on palladium nanoparticles (Pd NPs) prepared by sputtering deposition and chemical reduction of a Pd(II) precursor in/on a poly(ionic liquid) (PIL) was investigated in the selective hydrogenation of α,β-unsaturated carbonyl compounds and dienes. Sputtering deposition generates naked NPs with a narrow size distribution (3.2–3.8 nm) that are predominantly composed of Pd(0) (85–100%). Conversely, chemical reduction produces PIL-covered NPs with almost twice the average size (6.6 nm) and only 15% Pd(0). Regard the catalytic performance, support composition (by ionic liquid (IL) addition or not) and NP location are decisive. The best activity and selectivity was obtained with imprinted Pd NPs on a PIL/IL mixture (D-MPIL.NTf2/IL-Pd catalyst). A kinetic investigation was conducted using 2-cyclohexen-1-one (CHN) and D-MPIL.NTf2/IL-Pd catalyst revealing that this reaction follows the Langmuir-Hinshelwood mechanism. Enthalpies obtaining from a Van't Hoff plot show that the adsorption of the CHN substrate on the surface of the PIL-Pd catalyst is an exothermic process (-9 kJ mol?1), whereas H2 adsorption occurs by an endothermic process (12 kJ mol?1). This distinct behavior is consistent with the rate determining step proposed, in which the independent adsorption of reagents is followed by the hydrogenation of a π-allyl intermediate on the catalyst surface.
- Simon, Nathália M.,Abarca, Gabriel,Scholten, Jackson D.,Domingos, Josiel B.,Mecerreyes, David,Dupont, Jairton
-
-
- Revealing Hydrogenation Reaction Pathways on Naked Gold Nanoparticles
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Gold nanoparticles (AuNPs) display distinct characteristics as hydrogenation catalysts, with higher selectivity and lower catalytic activity than group 8-10 metals. The ability of AuNPs to chemisorb/activate simple molecules is limited by the low coordination number of the surface sites. Understanding the distinct pathways involved in the hydrogenation reactions promoted by supported AuNPs is crucial for broadening their potential catalytic applications. In this study, we demonstrate that the mechanism of the hydrogenation reactions catalyzed by AuNPs with "clean" surfaces may proceed via homolytic or heterolytic hydrogen activation depending on the nature of the support. The synthesis of naked AuNPs employing γ-Al2O3 and ionic liquid (IL)-hybrid γ-Al2O3 supports was accomplished by sputtering deposition using ultrapure gold foils. This highly reproducible and straightforward procedure furnishes small (~6.6 nm) and well-distributed metallic gold nanoparticles (Au(0)NPs) that are found to be active catalysts for the partial and selective hydrogenation of substituted conjugated dienes, alkynes, and α,β-unsaturated carbonyl compounds (aldehydes and ketones). Kinetic and deuterium labeling studies indicate that heterolytic hydrogen activation is the primary pathway occurring on the AuNPs imprinted directly on γ-Al2O3. In contrast, AuNPs supported on IL-hybrid γ-Al2O3 materials cause the reaction to proceed via a homolytic hydrogen activation pathway. The IL layer surrounds the AuNPs and acts as a cage, influencing the frequency of the interaction of the catalytically active species and the metal surface and, consequently, the catalytic performance of the AuNPs. The IL layer is shown to improve the product selectivity by the enhancement of the substrate/product discrimination, and to decrease the catalytic activity by shifting the rate-determining step to the H2 and substrate competitive adsorption/activation on the same active sites. A series of kinetic experiments suggest that AuNPs imprinted on an IL-hybrid γ-Al2O3 support are more efficient (lower activation energy, Ea) than group 8-10 metal based catalysts for hydrogenation reactions at moderate to high temperatures (75-150 °C).
- Luza, Leandro,Rambor, Camila P.,Gual, Aitor,Alves Fernandes, Jesum,Eberhardt, Dario,Dupont, Jairton
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p. 2791 - 2799
(2017/05/31)
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- Hybrid catalysts based on platinum and palladium nanoparticles for the hydrogenation of terpenes under slurry conditions
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Catalysts based on platinum and palladium nanoparticles immobilized in mesoporous phenolformaldehyde polymers modified with sulfo groups have been used for the hydrogenation of a number of terpenes, such as (S)-(–)-limonene, α-terpinene, γ-terpinene, and terpinolene. It has been found that Pd-containing catalysts exhibit higher activity in the exhaustive hydrogenation of terpenes, whereas Pt-containing catalysts have high selectivity for p-menthene.
- Karakhanov,Boronoev,Subbotina,Zolotukhina,Maximov,Filippova, T. Yu.
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p. 1114 - 1122
(2017/02/15)
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- Mechanisms into dehydroaromatization of bio-derived limonene to: P -cymene over Pd/HZSM-5 in the presence and absence of H2
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The mechanisms of dehydroaromatization of limonene to p-cymene are intrinsically investigated over Pd/HZSM-5 under different N2/H2 atmospheres using the mathematical tool of Matlab. It is found that the dehydroaromatization reaction network starts with the isomerization step, and is followed by the sequential dehydrogenation in the presence of N2 or H2 at the selected system. The addition of hydrogen in the atmosphere would not change this reaction pathway, but leads to lower selectivity of p-cymene due to the accelerated hydrogenation rates on the double bonds. Besides, the additional hydrogen speeds up the overall reaction by facilitating the isomerization step on limonene while impeding its reverse reaction, as isomerization of limonene is proved to be the determining step of the whole dehydroaromatization reaction. Furthermore, the presence of hydrogen dramatically decreases the apparent and true activity energy of the target dehydroaromatization reaction and reduces the impact of temperatures to such processes compared to that with a N2 gas carrier.
- Cui, Huimei,Zhang, Jingjing,Luo, Zhicheng,Zhao, Chen
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p. 66695 - 66704
(2016/08/02)
-
- Colloidal and nanosized catalysts in organic synthesis: XV. Gas-phase hydrogenation of alkenes catalyzed by supported nickel nanoparticles
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Gas-phase hydrogenation of alkenes and their derivatives, catalyzed by nickel nanoparticles supported on zeolite or silica gel support occurs at 150–250°С and an atmospheric hydrogen pressure and results in a high conversion. The selectivity of the hydrogenation depends on the amount of hydrogen: at a low diene (triene)–hydrogen ratio, selective hydrogenation of one multiple bond in the substrate is possible.
- Popov, Yu. V.,Mokhov,Nebykov,Latyshova,Panov,Dontsova,Shirkhanyan,Shcherbakova
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p. 2589 - 2593
(2017/03/22)
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- CATALYTIC HYDROGENATION USING COMPLEXES OF BASE METALS WITH TRIDENTATE LIGANDS
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Complexes of cobalt and nickel with tridentate ligand PNHPR are effective for hydrogenation of unsaturated compounds. Cobalt complex [(PNHPCy)Co(CH2SiMe3)]BArF4 (PNHPCy=bis[2-(dicyclohexylphosphino)ethyl]amine, BArF4=B(3,5-(CF3)2C6H3)4)) was prepared and used with hydrogen for hydrogenation of alkenes, aldehydes, ketones, and imines under mild conditions (25-60° C., 1-4 atm H2). Nickel complex [(PNHPCy)Ni(H)]BPh4 was used for hydrogenation of styrene and 1-octene under mild conditions. (PNPCy)Ni(H) was used for hydrogenating alkenes.
- -
-
Paragraph 0035; 0053
(2015/12/07)
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- Being two is better than one - Catalytic reductions with dendrimer encapsulated copper - And copper-cobalt-subnanoparticles
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Copper and copper-cobalt subnanoparticles have been synthesized using 4-carbomethoxypyrrolidone terminated PAMAM-dendrimers as templates. The metal particles were applied in catalytic reduction reactions. While Cu subnanoparticles were only capable of reducing conjugated double bonds, enhancing the Cu particles with Co led to a surprising increase in catalytic activity, reducing also isolated carbon double and triple bonds.
- Ficker, Mario,Petersen, Johannes F.,Gschneidtner, Tina,Rasmussen, Ann-Louise,Purdy, Trevor,Hansen, Jon S.,Hansen, Thomas H.,Husted, S?ren,Moth Poulsen, Kasper,Olsson, Eva,Christensen, J?rn B.
-
supporting information
p. 9957 - 9960
(2015/06/22)
-
- A new approach for bio-jet fuel generation from palm oil and limonene in the absence of hydrogen
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The traditional methodology includes a carbon-chain shortening strategy to produce bio-jet fuel from lipids via a two-stage process with hydrogen. Here, we propose a new solution using a carbon-chain filling strategy to convert C10 terpene and lipids to jet fuel ranged hydrocarbons with aromatic hydrocarbon ingredients in the absence of hydrogen.
- Zhang, Jingjing,Zhao, Chen
-
supporting information
p. 17249 - 17252
(2015/12/08)
-
- Supercritical fluid deposition of Ru nanoparticles onto SiO2 SBA-15 as a sustainable method to prepare selective hydrogenation catalysts
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Ru nanoparticles were successfully deposited onto mesoporous SiO2 SBA-15 using supercritical CO2 (scCO2). The use of scCO2 favoured the metal dispersion and Ru nanoparticles uniformly distributed throughout the support were obtained. Different precursors and methodologies were employed: impregnation with Ru(tmhd)2(COD) in scCO2 at 80°C and 13.5 and 19.3 MPa and further reduction in H2/N2 at 400°C at low pressure, reactive deposition of Ru(tmhd)2(COD) with H2 in scCO2 at 150°C and reactive deposition of RuCl3·xH2O with ethanol in scCO2 at 150 and 200°C. The size of the particles was limited in one dimension by the pore size of the support. The metal loading varied with the methodology and experimental conditions from 0.9 to 7.4% Ru mol. These materials exhibited remarkable catalytic activity. The Ru/SiO2 SBA-15 materials prepared by reactive deposition with H2 in scCO2 were selective catalysts for the hydrogenation reactions of benzene and limonene, allowing the production of partly hydrogenated hydrocarbons that may serve as building blocks for more complex chemicals. scCO2 is shown to be a green solvent that allows the preparation of efficient heterogeneous catalysts to design sustainable processes. Furthermore, in the hydrogenation of limonene, scCO2 was also used as the solvent.
- Morère,Torralvo,Pando,Renuncio,Caba?as
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p. 38880 - 38891
(2015/05/20)
-
- Superacidity in sulfated metal-organic framework-808
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Superacids, defined as acids with a Hammett acidity function H0 ≤ -12, are useful materials, but a need exists for new, designable solid state systems. Here, we report superacidity in a sulfated metal-organic framework (MOF) obtained by treating the microcrystalline form of MOF-808 [MOF-808-P: Zr6O5(OH)3- (BTC)2(HCOO)5(H2O)2, BTC = 1,3,5-benzenetricarboxylate] with aqueous sulfuric acid to generate its sulfated analogue, MOF-808-2.5SO4 [Zr6O5(OH)3(BTC)2- (SO4)2.5(H2O)2.5]. This material has a Hammett acidity function H0 ≤ -14.5 and is thus identified as a superacid, providing the first evidence for superacidity in MOFs. The superacidity is attributed to the presence of zirconiumbound sulfate groups structurally characterized using single-crystal X-ray diffraction analysis.
- Jiang, Juncong,Gándara, Felipe,Zhang, Yue-Biao,Na, Kyungsu,Yaghi, Omar M.,Klemperer, Walter G.
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supporting information
p. 12844 - 12847
(2015/12/26)
-
- NOVEL ALICYCLIC ALCOHOL
-
Provided is an alicyclic alcohol compound which can be used as a raw material for a compound perfume, and which has excellent floral-green-like aromas which are crisp and fresh; also provided are a manufacturing method for the same, and a perfume composit
- -
-
Paragraph 0053-0054
(2013/11/19)
-
- Synthesis, characterization, and reactivity of the first osmium β-diketiminato complexes and application in catalysis
-
The strongly chelating anionic β-diketiminate ligand has been employed to formulate complexes involving almost every metal of the periodic table; however, the heavier metals of the d block remain relatively unexplored. This paper describes the synthesis a
- Schreiber, Dominique F.,O'Connor, Crystal,Grave, Christian,Mueller-Bunz, Helge,Scopelliti, Rosario,Dyson, Paul J.,Phillips, Andrew D.
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p. 7345 - 7356
(2014/04/03)
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- High catalytic performance of palladium nanoparticles supported on multiwalled carbon nanotubes in alkene hydrogenation reactions
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The synthesis of Pd nanoparticles (Pd-NPs) supported on multi-walled carbon nanotubes (MWCNTs) and the cataytic performance of the resulting material (Pd-NPs/MWCNTs) in hydrogenation reactions are presented. Facile preparation approaches based on the decomposition of Pd precursors in the presence of MWCNTs lead to homogeneous dispersions of supported Pd-NPs with an average size of 4 nm and Pd loads of about 12%. The catalytic performance of this material was evaluated in hydrogenation reactions of α,β-unsaturated ketones, alkenes, cyclic di-, tri- and tetraenes, aromatic compounds, terpenes and terpenoids, resulting in very high activity offering short reaction times, high conversion rates, notable selectivity, and acceptable recyclability under mild conditions.
- Cano, Manuela,Benito, Ana M.,Maser, Wolfgang K.,Urriolabeitia, Esteban P.
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p. 1968 - 1972
(2013/10/08)
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- Continuous production of the renewable ρ-cymene from α-pinene
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The aim of this work was to demonstrate the feasibility to produce ρ-cymene, an important commodity chemical, in a continuous, one-pot reaction system from abundant α-pinene, available e.g. as a by-product of pulping industry. The isomerization reactions of α-pinene over bimetallic heterogeneous catalysts, 3 and 5 wt% Pd-Zn (1:1, 1:4, 4:1, 1:0, and 0:1), supported on Al-SBA15 were studied. The principal reaction products were identified as ρ- and m-cymenes, limonene, camphene, and ρ-menthene, respectively. The highest concentration of ρ-cymene reached 77 wt% under the optimized reaction conditions: 300 C and α-pinene feed of 0.03 mL/min. Two main reaction pathways toward ρ- and m-cymenes were described, and a mechanistic kinetic model, based on a plausible reaction network in line with Langmuir-Hinshelwood approach, was developed. The catalyst characterization revealed the reduction in Pd(II) sites, catalyst coking, and decline of surface area over the course of time. The catalyst recovery and reuse was addressed.
- Golets,Ajaikumar,Mohln,Waerna,Rakesh,Mikkola
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p. 305 - 315
(2013/09/24)
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- Application of a versatile nanoparticle stabilizer in phase transfer and catalysis
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Gold and rhodium nanoparticles stabilized by a cationic polymer can be readily modified by anion exchange to afford nanoparticles that may be dispersed in a wide range of organic solvents and ionic liquids. The catalytic activity of the Rh nanoparticle dispersions have been evaluated in the selective hydrogenation of limonene and the nature of the solvent has been shown to play a critical role.
- Biondi, Ilaria,Laporte, Vincent,Dyson, Paul J.
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p. 721 - 726
(2013/01/14)
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- Application of a versatile nanoparticle stabilizer in phase transfer and catalysis
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Gold and rhodium nanoparticles stabilized by a cationic polymer can be readily modified by anion exchange to afford nanoparticles that may be dispersed in a wide range of organic solvents and ionic liquids. The catalytic activity of the Rh nanoparticle dispersions have been evaluated in the selective hydrogenation of limonene and the nature of the solvent has been shown to play a critical role.
- Biondi, Ilaria,Laporte, Vincent,Dyson, Paul J.
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p. 721 - 726
(2014/01/17)
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- METHOD FOR PRODUCING ALICYCLIC ALCOHOL
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Disclosed is a method for producing an alicyclic alcohol represented by general formula (III) which is useful as a starting material for a flavor mixture or the like at low cost in high yield. The alicyclic alcohol represented by general formula (III) is
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Page/Page column 9-10
(2012/05/20)
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- Guanidine catalyzed aerobic reduction: A selective aerobic hydrogenation of olefins using aqueous hydrazine
-
An efficient aerobic reduction of olefins, internal as well as terminal, is developed using guanidine as an organocatalyst. A remarkable chemoselectivity in reduction has been demonstrated in the presence of a variety of functional groups and protective groups and a selective reduction of a terminal olefin in the presence of an internal olefin is revealed.
- Lamani, Manjunath,Guralamata, Ravikumara Siddappa,Prabhu, Kandikere Ramaiah
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supporting information; experimental part
p. 6583 - 6585
(2012/07/14)
-
- Preparation and utilization of perillyl acetate
-
Perillyl acetate is a fragrance compound that was prepared by the reaction of β-pinenoxide with acetic anhydride and using acetic acid as an acid catalyst. Several selected catalysts were tested (homogenous: phosphoric acid, boric acid, acetic acid, and citric acid; heterogeneous: zeolite USY, SSA, and montmorillonite K-10) and the reaction conditions optimized for this reaction. The yield 78.7 % of perillyl acetate was obtained. Mayol (4- isopropylcyclohexylmethanol), a valuable fragrance compound, was further obtained by a two-step synthesis from perillyl acetate. Firstly, perillyl acetate was saponified to perillyl alcohol. The yield of alcohol was 94.4 %. The last step of the entire preparation was the hydrogenation of perillyl alcohol to Mayol. The yield of the desired product of this reaction was 94.6 %. Springer Science+Business Media B.V. 2012.
- ?tekrová, Martina,Paterová-Dudková, Iva,Vysko?ilová-Leitmannová, Eli?ka,?erveny, Libor
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p. 2075 - 2084
(2013/02/22)
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- Radical chain reduction of alkylboron compounds with catechols
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The conversion of alkylboranes to the corresponding alkanes is classically per-formed via protonolysis of alkylboranes. This simple reaction requires the use of severe reaction conditions, that is, treatment with a carboxylic acid at high temperature (>150 °C). We report here a mild radical procedure for the transformation of organoboranes to alkanes. 4-tert-Butylcatechol, a well-established radical inhibitor and antioxidant, is acting as a source of hydrogen atoms. An efficient chain reaction is observed due to the exceptional reactivity of phenoxyl radicals toward alkylboranes. The reaction has been applied to a wide range of organoboron derivatives such as B- alkylcatecholboranes, trialkylboranes, pinacolboronates, and alkylboronic acids. Furthermore, the so far elusive rate constants for the hydrogen transfer between secondary alkyl radical and catechol derivatives have been experimentally determined. Interestingly, they are less than 1 order of magnitude slower than that of tin hydride at 80 °C, making catechols particularly attractive for a wide range of transformations involving C-C bond formation.
- Villa, Giorgio,Povie, Guillaume,Renaud, Philippe
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supporting information; experimental part
p. 5913 - 5920
(2011/06/16)
-
- An efficient microwave technique for exo- to endo-double bond migration in natural products
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A few sesquiterpene lactones and monoterpenes when subjected to microwave irradiation on solid surface undergo facile carbon-carbon double bond migration from from exo- to endo-position.
- Kaur, Damandeep,Setia,Chahal,Chhabra
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experimental part
p. 611 - 614
(2011/06/21)
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- A convenient methodology for the chemoselective reduction of a wide variety of functionalized alkenes
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An efficient method to effect chemoselective reduction of alkenes (including trisubstituted olefins) possessing various sensitive and/or reducible groups such as acetals, allylic alcohols, benzyl ethers, epoxides, esters, halides, nitriles, and sulfones is reported. The reduction is facile at 0 °C in aqueous N,N-dimethylacetamide containing sodium borohydride in the presence of 15 mol % ruthenium(III) chloride. Regioselective reduction of dienes is also feasible if the double bonds are sufficiently different in their structural environment.
- Babler, James H.,White, Nicholas A.
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experimental part
p. 439 - 441
(2010/03/04)
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- Thermal isomerization of (+)-cis- and (-)-trans-pinane leading to (-)-β-citronellene and (+)-isocitronellene
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Catalyzed and uncatalyzed rearrangement reactions of terpenoids play a major role in laboratory and industrial-scale synthesis of fine chemicals. Herein, we present our results on the thermally induced isomerization of pinane (1). Investigation of the thermal behavior of (+)-cis- (la) and (-)-trans-pinane (1b) in a flow-type reactor reveals significant differences in both reactivity and selectivity concerning the formation of (-)-β-citronellene (2) and (+)-isocitronellene (3) as main products. Possible explanations for these results are discussed on the basis of reaction mechanism and groundstate geometries for 1a and 1b. To identify side reactions caused from ene cyclizations of 2 and 3, additional pyrolysis experiments were conducted that enabled the identification of almost all compounds in the network of C 10H18-hydrocarbon products formed from 1.
- Stolle, Achim,Ondruschka, Bernd,Bonrath, Werner,Netscher, Thomas,Findeisen, Matthias,Hoffmann, Markus M.
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experimental part
p. 6805 - 6814
(2009/08/07)
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- Lipase-catalyzed resolution of p-menthan-3-ols monoterpenes: Preparation of the enantiomer-enriched forms of menthol, isopulegol, trans- and cis-piperitol, and cis-isopiperitenol
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A study on the enzymic resolution of the most common p-menthan-3-ol monoterpene isomers is described. Enantioenriched alcohols 1, 5, 10, 11 and 12 are obtained by means of the lipase-mediated kinetic acetylation of the corresponding racemic materials. The stereochemical aspects of the enzymic process have been investigated. We found that the structural features of the starting p-menthan-3-ol as well as the kind of lipase used, impacted strongly on the enantioselectivity of the resolution. The potentialities of this approach for preparative purposes are discussed.
- Serra, Stefano,Brenna, Elisabetta,Fuganti, Claudio,Maggioni, Francesco
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p. 3313 - 3319
(2007/10/03)
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- Photo-assisted hydrogen transfer from alcohol to limonene catalyzed by [Rh6(CO)16]
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Partial hydrogenation of the exo-olefinic bond in limonene to carvomenthene proceeds smoothly by photocatalytic hydrogen transfer from 2-propanol using [Rh6(CO)16] as a catalyst under UV-irradiation in the presence of acetone. Hydrogen gas evolves after the formation of carvomenthene has been completed. 1-Hydroxy-1-methylethyl radical formed in the reaction of photochemically excited acetone with 2-propanol serves both as an activator for the catalyst and as a hydrogen source.
- Yanagawa, Akihisa,Hatae, Tomomi,Yada, Satoru,Sugimori, Akira,Takagi, Yuzuru
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p. 899 - 900
(2007/10/03)
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- Preparation, characterisation and performance of encapsulated copper-ruthenium bimetallic catalysts derived from molecular cluster carbonyl precursors
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The advantages of producing high-performance, bimetallic nanoparticle catalysts from their precursor metalcluster carbonylates anchored inside the mesoporous channels of silica (MCM41) are described. In situ X-ray absorption and FT-IR spectroscopies as well as ex situ high-resolution scanning transmission electron microscopy were used to chart the progressive conversion, by gentle thermolysis, of the parent carbonylates to the denuded, bimetallic nanoparticle catalysts. Separate copper and ruthenium K-edge X-ray absorption spectra yield a detailed structural picture of the active, approximately 15 A diameter catalyst: it is a rosette-shaped entity in which twelve exposed Ru atoms are connected to a square base composed of relatively concealed Cu atoms. These in turn are anchored by four oxygen bridges to four Si atoms of the mesopore lining. The bimetallic catalysts exhibit no tendency to sinter, aggregate or fragment into their component metals during use. The nanoparticles perform well in the catalytic hydrogenation of hex-1-ene-a detailed kinetic study at 373 K and 20 bar H2 is presented here (maximum TOF in [(mol(substr)) (mol(cluster))-1 h-1] 51200, average TOF 22 400)-and also in the hydrogenations at 65 bar H2 and 373 K of diphenylacetylene, phenylacetylene, stilbene, cis-cyclooctene and D-limonene, the average TOFs being 17, 610, 70, 150 and 360, respectively.
- Shephard, Douglas S.,Maschmeyer, Thomas,Sankar, Gopinathan,Thomas, John Meurig,Ozkaya, Dogan,Johnson, Brian F. G.,Raja, Robert,Oldroyd, Richard D.,Bell, Robert G.
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p. 1214 - 1224
(2007/10/03)
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- Reducing characteristics of borohydride exchange resin-CuSO4 in methanol
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Reducing characteristics of borohydride exchange resin (BER)-CuSO 4 (cat.) were studied in methanol at room temperature. Carbon-carbon double bonds conjugated with benzene or carbonyl group were more rapidly reduced than was the case with isolated double bonds. Carbonyl groups were readily reduced, whereas esters and amides were inert, and nitriles were slowly reduced. High chemoselectivity was also observed in halide reductions: p-bromochlorobenzene and p-bromoiodobenzene were reduced quantitatively to chlorobenzene and bromobenzene, respectively. Aliphatic epoxides were inert to this reagent; however, styrene oxide derivatives were readily reduced to the corresponding deoxygenated products. Aliphatic azides were reduced slowly during 6 h, whereas phenyl azide was transformed to aniline in 1 h. Nitrocyclohexane was reduced at room temperature, but nitrobenzene, nitrosobenzene, azobenzene, and azoxybenzene required an elevated temperature (65 °C) for rapid reductions (1 h). Similarly, N,N-dimethylanihne N-oxide was reduced at room temperature, whereas pyridine N-oxide required refluxing. Finally, among the sulfur compounds tested, only diphenyl disulfide was reduced readily, and sulfide, aliphatic disulfide, sulfoxide, sulfone, and tosylate were inert to this reducing system.
- Sim, Tae Bo,Yoon, Nung Min
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p. 1101 - 1107
(2007/10/03)
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- An excellent nickel boride catalyst for the selective hydrogenation of olefins
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Nickel boride prepared on borohydride exchange resin (BER) in methanol is an excellent catalyst for the selective hydrogenation of olefins. Thus, monosubstituted olefins and norbornene were hydrogenated quantitatively at 0°C in 1 hour in the presence of disubstituted olefins and trisubstituted α,β-unsaturated acid derivatives, the disubstituted olefins in turn were hydrogenated at 65°C in 1 hour without affecting trisubstituted olefins, benzene, and heteroaromatic compounds.
- Choi, Jaesung,Yoon, Nung Min
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p. 597 - 599
(2007/10/03)
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- Regioselective Hydrogenation Using Platinum-Support Zeolite Modified by CVD-Method
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A platinum-support zeolite coupled with a silica layer was prepared by Chemical Vapor Deposition (CVD) of tetraethoxysilane, and was investigated in order to determine the catalytic characterization in an analysis of the surface.With this catalyst system,
- Kuno, Hideyiki,Shibagaki, Makoto,Takahashi, Kyoto,Honda, Ichiro,Matsushita, Hajime
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p. 2508 - 2512
(2007/10/02)
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- Magnesium activation of dichlorodi-η5-cyclopentadienyltitanium in the catalytic hydrogenation of olefins and acetylenes
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Magnesium activation of dichlorodi-η5-cyclopentadienyltitanium (Cp2TiCl2) in tetrahydrofuran (THF) under a dihydrogen atmosphere has been shown to produce a stable solution which effectively hydrogenates various types of olefins and acetylenes
- Scott, Frederick,Raubenheimer, Helgard G.,Pretorius, Gerard,Hamese, Augustine M.
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p. C17 - C20
(2007/10/02)
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- Use of high pressure in the reduction of organic chlorides with tri-n-butyltin hydride
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The use of the high pressure technique enables reduction of organic halides by tri-n-butyltin hydride to be carried out in the absence of a catalyst or free radical initiator.It leads to a better conservation of the structure of the starting material during the reduction.In the case of some unsaturated halides, a new chemoselectivity has been observed in favour of the addition of the hydride on the carbon-carbon double bond.
- Rahm, A.,Amardeil, R.,Degueil-Castaing, M.
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- Studies on the Decomposition of Alkyl Hydroperoxides by Different Catalysts
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The catalytic decomposition of cumene, 1-methylcyclohexyl and cyclohexyl hydroperoxides was studied in cyclohexane, cis- and trans-1,4-dimethylcyclohexane and cis-pinane as the solvents.The stearates and the acetylacetonates of manganese, cobalt and chromium, the acetylacetonates of molybdenum and vanadium, n-butyl orthoborate and n-butyl metaborate were used as the catalysts.The chromium-, vanadium-, molybdenum- and boron-containing catalysts brought about some Hock-type decomposition of cumene hydroperoxide and thus proved to be acidic.Of these more of less acidic catalysts only molybdenyl acetylacetonate effected a partially stereospecific hydroxylation of the tertiary C-H-bonds in cis- and trans-1,4-dimethylcyclohexane.The well-known selectivity of chromium catalysts for the ketone formation during the decomposition of secondary hydroperoxides is caused by the catalytic oxidation of secondary alcohols by hydroperoxides in the presence of chromium compounds.In the presence of all the catalysts used the free-radical pathways of the hydroperoxide decomposition predominated, and the attack of the intermediate radicals on the starting hydroperoxide was more important than the attack on the solvent molecules.
- Lauterbach, Gerlinde,Pritzkow, W.,Tien, Tieu Dung,Voerckel, V.
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p. 933 - 946
(2007/10/02)
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- Studies on organolanthanide complexes. XVIII. The reduction and isomerization of olefins with tricyclopentadienyllanthanides/sodium hydride
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Reduction of 1-hexene with Cp3Ln/NaH (Cp=cyclopentadienyl, Ln=rare earth metals) in THF at 45 deg C, after hydrolysis, gives hexane.The reducing activity of Cp3Ln depends strongly upon the ionic radius of the trivalent rare earth ion.The activity and selectivity of early rare earths for 1-hexene reduction are higher than those of heavy rare earths.The Cp3Ln/NaH systems can be used to regioselectively reduce dienes which contain a terminal carbon-carbon double bond as well as an internal one with high yield.Selectivity is 100percent.Moreover, the Cp3Ln/NaH systems are able to catalyze the hydrogenation of olefins.When Cp3Ln/NaH is used as catalyst, 1-hexene was isomerized at 45 deg C to cis-2-hexene and to trans-2-hexene in excellent yields.In contrast to reducing activity, the catalytic activity of heavy rare earths in the isomerization reaction is higher than that of the early earths.Hence, Cp3Sm/NaN and Cp3Y/NaH are new reducing agents and catalysts for 1-hexene reduction and isomerization, respectively.
- Qian, Changtao,Ge, Yuanwen,Deng, Daoli,Gu, Yongjie,Zhang, Caihua
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p. 175 - 184
(2007/10/02)
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- Reduction of Organic Compounds with Rare-Earth Intermetallics Containing Absorbed Hydrogen
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The hydrogenation of organic compounds with rare-earth intermetallic hydrides has been investigated.Alkynes,alkenes,aldehydes,ketones,nitriles,imines, and nitro compounds are hydrogenated in excellent yields with LaNi5H6 or LaNi4.5Al0.5H5 at 0-60 deg C.The present hydrogenation method has the following characteristic features. (1) The intermetallic compounds (alloys) are not poisoned by compounds containing an amino group or a halogen atom. (2) The alloys can be used repeatedly without decrease in activity. (3) The reaction conditions are mild, and selective hydrogenations of some organic functional groups can be achieved.The reaction mechanism of this hydrogenation is briefly discussed in terms of stereochemistry and H/D exchange reactions.
- Imamoto, Tsuneo,Mita, Takeshi,Yokoyama, Masataka
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p. 5695 - 5699
(2007/10/02)
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- ORGANOBORANES FOR SYNTHESIS. 1. PROTONOLYSIS OF TRIALKYLBORANES. A CONVENIENT NON-CATALYTIC CONVERSION OF ALKENES INTO SATURATED COMPOUNDS via HYDROBORATION-PROTONOLYSIS
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The protonolysis of trialkylboranes with carboxylic acids proceeds very rapidly for the first group, somewhat slower for the second, but requires elevated temperatures for removal of the third.A close examination of the protonolysis of representative symmetrical, as well as mixed trialkylboranes, reveals that the steric requirements of the alkyl groups attached to boron play an important role in the rate.Secondary alkyl groups protonolyze less readily than primary alkyl groups.More hindered alkyl groups are still more resistant.Since the hydroboration-protonolysis sequence involves relatively mild conditions, this procedure can be applied for hydrogenating olefinic derivatives containing labile groups, such as active sulfur, halogen and nitrogen functionalities.The stereochemistry of protonolysis has been established via deuteroboration of norbornene and deuterolysis of the product.It is evident that protonolysis proceeds with retention of configuration at the migrating carbon.Partially alkylated boranes can be used for hydroboration-protonolysis with improved regioselectivity.Subsequent protonolysis of the resulting mixed trialkylboranes provides the desired alkanes in good yields.Products sensitive to the action of hot acetic acid offer difficulties.For example, when this procedure was applied to the preparation of 1-menthene from d-limonene, the product was racemic.
- Brown, Herbert C.,Murray, Kenneth J.
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p. 5497 - 5504
(2007/10/02)
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- Studies on the Mechanism of Transition-Metal-Assisted Sodium Borohydride and Lithium Aluminium Hydride Reductions
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Studies on the course of transition-metal-assisted NaBH4 and LiAlH4 reductions of (1) nitriles, (2) alkenes, and (3) alkyl halides are described. (1) The kinetics of benzonitrile (PhCN) reduction indicate that at high nitrile:catalyst ratios, the rate of reduction is independent of PhCN concentrations.Furthermore, the rate of PhCN reduction exhibits a first-order dependence on NaBH4 concentration, as measured over a fourfold range of BH4(1-) concentration and several half-lives of PhCN.Moreover, when PhCN was reduced with equimolar mixtures of NaBH4 and NaBD4, a significant primary kinetic isotope effect was observed.Rapid complexation of PhCN to be boride surface apparently activates the nitrile group toward rate-determining hydride addition from dissolved, uncoordinated NaBH4. (2) The selective reduction of alkenes by NaBH4-CoCl2 is attributed to adventitious heterogeneous catalytic hydrogenation. (3) The combination of LiAlH4 with CoCl2 forms a black precipitate of cobalt aluminide (CoAl) which was isolated, analyzed by atomic absorption spectroscopy, and shown to play an essential catalytic role in the reduction of alkyl halides.Labeling experiments demonstrate stereochemical randomization by a heterogeneous process involving solvent as the hydrogen donor and LiAlH4 as a co-reductant.A radical mechanism involving halide atom transfer or oxidative addition to the aluminide is proposed.
- Osby, John O.,Heinzman, Stephen W.,Ganem, Bruce
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