- Selective hydrogenation of lignin-derived compounds under mild conditions
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A key challenge in the production of lignin-derived chemicals is to reduce the energy intensive processes used in their production. Here, we show that well-defined Rh nanoparticles dispersed in sub-micrometer size carbon hollow spheres, are able to hydrogenate lignin derived products under mild conditions (30 °C, 5 bar H2), in water. The optimum catalyst exhibits excellent selectivity and activity in the conversion of phenol to cyclohexanol and other related substrates including aryl ethers.
- Chen, Lu,Van Muyden, Antoine P.,Cui, Xinjiang,Laurenczy, Gabor,Dyson, Paul J.
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p. 3069 - 3073
(2020/06/17)
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- Cobalt-Nanoparticles Catalyzed Efficient and Selective Hydrogenation of Aromatic Hydrocarbons
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The development of inexpensive and practical catalysts for arene hydrogenations is key for future valorizations of this general feedstock. Here, we report the development of cobalt nanoparticles supported on silica as selective and general catalysts for such reactions. The specific nanoparticles were prepared by assembling cobalt-pyromellitic acid-piperazine coordination polymer on commercial silica and subsequent pyrolysis. Applying the optimal nanocatalyst, industrial bulk, substituted, and functionalized arenes as well as polycyclic aromatic hydrocarbons are selectively hydrogenated to obtain cyclohexane-based compounds under industrially viable and scalable conditions. The applicability of this hydrogenation methodology is presented for the storage of H2 in liquid organic hydrogen carriers.
- Murugesan, Kathiravan,Senthamarai, Thirusangumurugan,Alshammari, Ahmad S.,Altamimi, Rashid M.,Kreyenschulte, Carsten,Pohl, Marga-Martina,Lund, Henrik,Jagadeesh, Rajenahally V.,Beller, Matthias
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p. 8581 - 8591
(2019/09/12)
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- Polysilane-Immobilized Rh-Pt Bimetallic Nanoparticles as Powerful Arene Hydrogenation Catalysts: Synthesis, Reactions under Batch and Flow Conditions and Reaction Mechanism
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Hydrogenation of arenes is an important reaction not only for hydrogen storage and transport but also for the synthesis of functional molecules such as pharmaceuticals and biologically active compounds. Here, we describe the development of heterogeneous Rh-Pt bimetallic nanoparticle catalysts for the hydrogenation of arenes with inexpensive polysilane as support. The catalysts could be used in both batch and continuous-flow systems with high performance under mild conditions and showed wide substrate generality. In the continuous-flow system, the product could be obtained by simply passing the substrate and 1 atm H2 through a column packed with the catalyst. Remarkably, much higher catalytic performance was observed in the flow system than in the batch system, and extremely strong durability under continuous-flow conditions was demonstrated (>50 days continuous run; turnover number >3.4 × 105). Furthermore, details of the reaction mechanisms and the origin of different kinetics in batch and flow were studied, and the obtained knowledge was applied to develop completely selective arene hydrogenation of compounds containing two aromatic rings toward the synthesis of an active pharmaceutical ingredient.
- Miyamura, Hiroyuki,Suzuki, Aya,Yasukawa, Tomohiro,Kobayashi, Shu
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supporting information
p. 11325 - 11334
(2018/09/06)
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- A stable and practical nickel catalyst for the hydrogenolysis of C-O bonds
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The selective hydrogenolysis of C-O bonds constitutes a key step for the valorization of biomass including lignin fragments. Moreover, this defunctionalization process offers the possibility of producing interesting organic building blocks in a straightforward manner from oxygenated compounds. Herein, we demonstrate the reductive hydrogenolysis of a wide variety of ethers including diaryl, aryl-alkyl and aryl-benzyl derivatives catalyzed by a stable heterogeneous NiAlOx catalyst in the presence of a Lewis acid (LA). The special feature of this catalyst system is the formation of substituted cyclohexanols from the corresponding aryl ether.
- Cui, Xinjiang,Yuan, Hangkong,Junge, Kathrin,Topf, Christoph,Beller, Matthias,Shi, Feng
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p. 305 - 310
(2017/01/24)
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- Palladium-Catalyzed Hydrolytic Cleavage of Aromatic C?O Bonds
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Metallic palladium surfaces are highly selective in promoting the reductive hydrolysis of aromatic ethers in aqueous phase at relatively mild temperatures and pressures of H2. At quantitative conversions, the selectivity to hydrolysis products of PhOR ethers was observed to range from 50 % (R=Ph) to greater than 90 % (R=n-C4H9, cyclohexyl, and PhCH2CH2). By analysis of the evolution of products with and without incorporation of H218O, the pathway was concluded to be initiated by palladium metal catalyzed partial hydrogenation of the phenyl group to an enol ether. Water then rapidly adds to the enol ether to form a hemiacetal, which then undergoes elimination to cyclohexanone and phenol/alkanol products. A remarkable feature of the reaction is that the stronger Ph?O bond is cleaved rather than the weaker aliphatic O?R bond.
- Wang, Meng,Shi, Hui,Camaioni, Donald M.,Lercher, Johannes A.
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supporting information
p. 2110 - 2114
(2017/02/15)
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- Chemoselective formation of unsymmetrically substituted ethers from catalytic reductive coupling of aldehydes and ketones with alcohols in aqueous solution
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A well-defined cationic Ru-H complex catalyzes reductive etherification of aldehydes and ketones with alcohols. The catalytic method employs environmentally benign water as the solvent and cheaply available molecular hydrogen as the reducing agent to afford unsymmetrical ethers in a highly chemoselective manner.
- Kalutharage, Nishantha,Yi, Chae S.
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supporting information
p. 1778 - 1781
(2015/04/14)
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- Catalytic reductive etherification of ketones with alcohols at ambient hydrogen pressure: A practical, waste-minimized synthesis of dialkyl ethers
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A heterogeneous platinum catalyst was found to efficiently mediate the reductive etherification of ketones at ambient hydrogen pressure. In this environmentally benign transformation, water is released as the only by-product, and this is trapped with molecular sieves. The preparative utility of the new reaction protocol is demonstrated by the synthesis of ten unsymmetrical ethers from the corresponding ketones and primary or secondary alcohols. Georg Thieme Verlag Stuttgart.
- Goo?en, Lukas J.,Linder, Christophe
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p. 3489 - 3491
(2007/10/03)
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- SYNTHETIC APPLICATION OF MICELLAR CATALYSIS. WILLIAMSON'S SYNTHESIS OF ETHERS
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A simple, rapid and efficient procedure for the preparation of di-alkyl, simple phenyl-alkyl and hindered phenyl-alkyl ethers has been developed.Based on the principle of micellar catalysis the method involves alkylation of the alkoxide or the phenoxide ion with an alkyl chloride at 80 deg C in the presence of cationic micelles.For the preparation of phenyl-alkyl ethers normal micelles were used, while for the di-alkyl ethers reverse micelles were more effective.By increasing the ionic strength of the solution the rate of formation of phenyl-alkyl ethers could be increased.
- Jursic, Branko
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p. 6677 - 6680
(2007/10/02)
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- General Ether Synthesis under Mild Acid-Free Conditions. Trimethylsilyl Iodide Catalyzed Reductive Coupling of Carbonyl Compounds with Trialkylsilanes to Symmetrical Ethers and Reductive Condensation with Alkoxysilanes to Unsymmetrical Ethers
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Facile synthesis of symmetrical ethers is achieved by either trimethylsilyl triflate or trimethylsilyl iodide catalyzed reductive coupling of carbonyl compounds (aldehydes and ketones) with trialkylsilanes.The method was also extended to the trimethylsilyl iodide catalyzed preparation of unsymmetrical ethers by reductive condensation (of carbonyl compounds) with alkoxysilanes.The scope and limitations of the reactions are discussed with emphasis on diastereoselectivity.
- Sassaman, Mark B.,Kotian, Kirtivan D.,Prakash, G. K. Surya,Olah, George A.
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p. 4314 - 4319
(2007/10/02)
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- COPOLYESTERAMIDES CONTAINING POLY(ETHYLENE OXIDE) SOFT SEGMENTS AS NEW AND EFFICIENT PHASE-TRANSFER CATALYSTS
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Copolyesteramides, 1, prepared by melt polycondensation of N,N'-bis(4-methoxycarbonylbenzoyl)hexamethylenediamine, 2, 1,6-hexanediol and poly(ethylene glycol) (PEG 1000), are a new class of polymeric phase-transfer catalysts.Their catalytic activity has been tested in nucleophilic aliphatic substitutions, eliminations, alkylations of activated methylene groups, dichlorocyclopropanation of C=C double bonds, reductions of ketones to alcohols and oxydation of primary alcohols to aldehydes.
- Montanari, Fernando,Penso, Michele,Fortuna, Giorgio della,Re, Alberto
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p. 427 - 432
(2007/10/02)
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