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1.
A Rhodium Nanoparticle–Lewis Acidic Ionic Liquid Catalyst for the Chemoselective Reduction of Heteroarenes 下载免费PDF全文
Alena Karakulina Aswin Gopakumar Dr. İsmail Akçok Bastien L. Roulier Dr. Thomas LaGrange Dr. Sergey A. Katsyuba Dr. Shoubhik Das Prof. Dr. Paul J. Dyson 《Angewandte Chemie (International ed. in English)》2016,55(1):292-296
We describe a catalytic system composed of rhodium nanoparticles immobilized in a Lewis acidic ionic liquid. The combined system catalyzes the hydrogenation of quinolines, pyridines, benzofurans, and furan to access the corresponding heterocycles, important molecules present in fine chemicals, agrochemicals, and pharmaceuticals. The catalyst is highly selective, acting only on the heteroaromatic ring, and not interfering with other reducible functional groups. 相似文献
2.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(12):3264-3268
Herein, a general and efficient method for the homogeneous cobalt‐catalyzed hydrogenation of N‐heterocycles, under mild reaction conditions, is reported. Key to success is the use of the tetradentate ligand tris(2‐(diphenylphosphino)phenyl)phosphine). This non‐noble metal catalyst system allows the selective hydrogenation of heteroarenes in the presence of a broad range of other sensitive reducible groups. 相似文献
3.
A short and efficient synthesis of ent-corsifuran A by a highly asymmetric hydrogenation of a benzofuran precursor is reported. In addition, the electronic influence of the substituents on the asymmetric hydrogenation of benzofurans is provided. Whereas the hydrogenation of electron-deficient benzofurans was achieved under very mild conditions, the presence of electron-donating groups in the benzofuran required harsher reaction conditions for achieving full conversion to the 2,3-dihydrobenzofuran. 相似文献
4.
The Selective Cross‐Coupling of Secondary Alkyl Zinc Reagents to Five‐Membered‐Ring Heterocycles Using Pd‐PEPPSI‐IHeptCl 下载免费PDF全文
Dr. Bruce Atwater Dr. Nalin Chandrasoma Dr. David Mitchell Dr. Michael J. Rodriguez Matthew Pompeo Dr. Robert D. J. Froese Prof. Michael G. Organ 《Angewandte Chemie (International ed. in English)》2015,54(33):9502-9506
The ability to cross‐couple secondary alkyl centers is fraught with a number of problems, including difficult reductive elimination, which often leads to β‐hydride elimination. Whereas catalysts have been reported that provide decent selectivity for the expected (non‐rearranged) cross‐coupled product with aryl or heteroaryl oxidative‐addition partners, none have shown reliable selectivity with five‐membered‐ring heterocycles. In this report, a new, rationally designed catalyst, Pd‐PEPPSI‐IHeptCl, is demonstrated to be effective in selective cross‐coupling reactions with secondary alkyl reagents across an impressive variety of furans, thiophenes, and benzo‐fused derivatives (e.g., indoles, benzofurans), in most instances producing clean products with minimal, if any, migratory insertion for the first time. 相似文献
5.
Claudio Bianchini Pierluigi Barbaro Michela Macchi Andrea Meli Francesco Vizza 《Helvetica chimica acta》2001,84(10):2895-2923
As part of our modelling studies of the hydrodenitrogenation of N‐heterocycles contained in raw oil materials, we investigated the selective hydrogenation of quinoline to 1,2,3,4‐tetrahydroquinoline by rhodium catalysts modified with the tripodal polyphosphane ligand MeC(CH2PPh2)3. Experiments in standard autoclaves and in high‐pressure sapphire NMR tubes, kinetic and isotope labelling studies, and independent reactions with isolated compounds have contributed to the elucidation of the catalytic mechanism as well as identification of the electronic requisites of the metal catalyst for selective and efficient hydrogenation. 相似文献
6.
Ordered Porous Nitrogen‐Doped Carbon Matrix with Atomically Dispersed Cobalt Sites as an Efficient Catalyst for Dehydrogenation and Transfer Hydrogenation of N‐Heterocycles 下载免费PDF全文
Dr. Yunhu Han Dr. Ziyun Wang Ruirui Xu Dr. Wei Zhang Dr. Wenxing Chen Dr. Lirong Zheng Jian Zhang Dr. Jun Luo Konglin Wu Dr. Youqi Zhu Dr. Chen Chen Dr. Qing Peng Dr. Qiang Liu Prof. Dr. P. Hu Prof. Dr. Dingsheng Wang Prof. Dr. Yadong Li 《Angewandte Chemie (International ed. in English)》2018,57(35):11262-11266
Single‐atom catalysts (SACs) have been explored widely as potential substitutes for homogeneous catalysts. Isolated cobalt single‐atom sites were stabilized on an ordered porous nitrogen‐doped carbon matrix (ISAS‐Co/OPNC). ISAS‐Co/OPNC is a highly efficient catalyst for acceptorless dehydrogenation of N‐heterocycles to release H2. ISAS‐Co/OPNC also exhibits excellent catalytic activity for the reverse transfer hydrogenation (or hydrogenation) of N‐heterocycles to store H2, using formic acid or external hydrogen as a hydrogen source. The catalytic performance of ISAS‐Co/OPNC in both reactions surpasses previously reported homogeneous and heterogeneous precious‐metal catalysts. The reaction mechanisms are systematically investigated using first‐principles calculations and it is suggested that the Eley–Rideal mechanism is dominant. 相似文献
7.
A novel magnetically separable mesoporous silica‐supported palladium catalyst was designed and prepared for the selective hydrogenation of naphthalene to tetralin, which is an important transformation from a practical viewpoint. In the catalyst, Pd nano grains were dispersed uniformly and protected within the mesoporous silica shells being coated on the Fe3O4 core, so that the durability of the catalyst could be significantly improved. 相似文献
8.
9.
Synthesis of Methyl Glycolate by Hydrogenation of Dimethyl Oxalate over Cu-Ag/SiO2 Catalyst 总被引:2,自引:0,他引:2 下载免费PDF全文
Baowei Wang Qian Xu Hua Song Genhui Xu 《天然气化学杂志》2007,16(1):78-80
Methyl glycolate is a good solvent and can be used as feedstock for the synthesis of some important organic chemicals. Catalytic hydrogenation of dimethyl oxalate (DMO) over copper-silver catalyst supported on silica was studied. The Cu-Ag/SiO2 catalyst supported on silica sol was prepared by homogeneous deposition-precipitation of the mixture of aqueous cuprammonia complex and silica sol. The proper active temperature of Cu-Ag/SiO2 catalyst for hydrogenation of DMO was 523—623 K. The most preferable reaction conditions for methyl glycolate (MG) were optimized: temperature at 468—478 K, 40—60 mesh catalyst diameter, H2/DMO ratio 40, and 1.0 h-1 of LHSV. 相似文献
10.
Chemoselective hydrogenation of substituted nitroaromatics using novel water-soluble iron complex catalysts 总被引:2,自引:0,他引:2
Deshpande RM Mahajan AN Diwakar MM Ozarde PS Chaudhari RV 《The Journal of organic chemistry》2004,69(14):4835-4838
Chemoselective hydrogenation of substituted nitroaromatic compounds by water-soluble iron complex catalysts with molecular hydrogen has been reported for the first time. This biphasic catalyst presents an opportunity for a solvent-free hydrogenation. This catalyst system provides a low-cost, efficient alternative to the selective but environmentally unacceptable stoichiometric reductions as well as the supported noble metal catalysts used for hydrogenation. An efficient recycling strategy has resulted in a cumulative turnover number above 6000. 相似文献
11.
12.
Sandee AJ Reek JN Kamer PC van Leeuwen PW 《Journal of the American Chemical Society》2001,123(35):8468-8476
A homogeneous hydroformylation catalyst, designed to produce selectively linear aldehydes, was covalently tethered to a polysilicate support. The immobilized transition-metal complex [Rh(A)CO]+(1+)), in which A is N-(3-trimethoxysilane-n-propyl)-4,5-bis(diphenylphosphino)phenoxazine, was prepared both via the sol-gel process and by covalent anchoring to silica. 1+ was characterized by means of (31)P and (29)Si MAS NMR, FT-IR, and X-ray photoelectron spectroscopy. Polysilicate immobilized Rh(A) performed as a selective hydroformylation catalyst showing an overall selectivity for the linear aldehyde of 94.6% (linear to branched aldehyde ratio of 65). In addition 1-nonanol, obtained via the hydrogenation of the corresponding aldehyde, was formed as an unexpected secondary product (3.6% at 20% conversion). Under standard hydroformylation conditions, 1+ and HRh(A)(CO)(2)(1) coexist on the support. This dual catalyst system performed as a hydroformylation/hydrogenation sequence catalyst (Z), giving selectively 1-nonanol from 1-octene; ultimately, 98% of 1-octene was converted to mainly 1-nonanal and 97% of the nonanal was hydrogenated to 1-nonanol. The addition of 1-propanol completely changes Z in a hydroformylation catalyst (X), which produces 1-nonanal with an overall selectivity of 93%, and completely suppresses the reduction reaction. If the atmosphere is changed from CO/H(2) to H(2) the catalyst system is switched to the hydrogenation mode (Y), which shows a clean and complete hydrogenation of 1-octene and 1-nonanal within 24 h. The immobilized catalyst can be recycled and the system can be switched reversibly between the three "catalyst modes" X, Y, and Z, completely retaining the catalyst performance in each mode. 相似文献
13.
V. G. Dorokhov N. V. Bykova M. V. Kuznetsov L. A. Bykov V. V. Barelko 《Russian Journal of Applied Chemistry》2016,89(11):1769-1776
Experimental results on the influence exerted by pyridine additives on the selectivity of the process in which the styrene fraction is purified to remove the microscopic admixture of phenylacetylene at low (up to 30°C) temperatures by selective hydrogenation with catalysts on an aluminoborosilicate or silica matrix with filler-metals in the form of platinum or palladium are presented. It was shown that pyridine-modified catalysts in these systems are effective in the selective hydrogenation of phenylacetylene for purification of raw styrene. The modification of a platinum catalyst on the aluminoborosilicate support results in that a deep degree of purification (>95%) is achieved even at low (up to 50°C) temperatures. Use of catalysts composed of 0.160 wt % Pt and silica woven-glass fabric, modified with pyridine additives, leads to a substantially lower loss of styrene (from 0.48 to 0.31% in some cases) in the temperature range of 30–50°C. It was demonstrated that addition of substances containing a unshared electron pair can noticeably affect the selectivity of the process in which the styrene fraction is purified from its impurity content even in the order of 0.01%. Depending from the substrate composition and active filler-metal, the temperature, together with changing the support properties, exerts varied influence on modified metallic catalysts, which is manifested in change in the activation energy and, as a consequence, in that of the hydrogenation mechanism. 相似文献
14.
Catalytic Enantioselective Synthesis of α‐Chiral Azaheteroaryl Ethylamines by Asymmetric Protonation 下载免费PDF全文
Dr. Chao Xu Calum W. Muir Dr. Andrew G. Leach Dr. Alan R. Kennedy Dr. Allan J. B. Watson 《Angewandte Chemie (International ed. in English)》2018,57(35):11374-11377
The direct enantioselective synthesis of chiral azaheteroaryl ethylamines from vinyl‐substituted N‐heterocycles and anilines is reported. A chiral phosphoric acid (CPA) catalyst promotes dearomatizing aza‐Michael addition to give a prochiral exocyclic aryl enamine, which undergoes asymmetric protonation upon rearomatization. The reaction accommodates a broad range of N‐heterocycles, nucleophiles, and substituents on the prochiral centre, generating the products in high enantioselectivity. DFT studies support a facile nucleophilic addition based on catalyst‐induced LUMO lowering, with site‐selective, rate‐limiting, intramolecular asymmetric proton transfer from the ion‐paired prochiral intermediate. 相似文献
15.
Simentsova I. I. Minyukova T. P. Khassin A. A. Dokuchits E. V. Plyasova L. M. Tselyutina M. I. Yurieva T. M. 《Kinetics and Catalysis》2010,51(1):135-138
The dissolution of nickel metal in nitric acid in the presence of the dichromate anion as the oxidizer is reported. The formation
of Ni(II) and Cr(III) nitrates takes place in two steps with the intermediate formation of nitrous acid. A new method to synthesize
the nickel-chromium oxide catalyst from nickel and chromium nitrate solutions is suggested, in which the solutions are obtained
by an environmentally friendly technology from nickel metal, chromium(VI) oxide, and nitric acid. The catalyst is highly active
and selective in benzene hydrogenation and in CO preferential hydrogenation in the presence of CO2. 相似文献
16.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(44):13910-13914
Described herein is the enantioselective construction of oxygen‐containing [5‐6‐5] tricyclic heterocycles by an organocatalyzed asymmetric [4+2] cycloaddition of vinylidene ortho ‐quinone methides and benzofurans. According to this methodology, a series of oxygen‐containing [5‐6‐5] tricyclic heterocycles with various functional groups were synthesized in excellent enantio‐ and diastereoselectivities (>99 % ee , >20:1 d.r.). Furthermore, the deuterium‐labeling experiments and high‐resolution mass spectroscopy demonstrated that a vinylidene ortho ‐quinone methide intermediate was involved and possibly resulted from a prototropic rearrangement of 2‐ethynylphenol. Remarkably, a catalyst loading as low as 0.1 mol %, and a gram‐scale synthesis were achieved for this transformation. 相似文献
17.
Himadri Paul Sumit Bhaduri Goutam Kumar Lahiri 《Journal of organometallic chemistry》2004,689(2):309-316
Fumed silica, silica gel, silica-alumina and cross-linked (5.5%) polystyrene have been functionalized with quaternary ammonium groups and the Chini cluster [Pt12(CO)24]2− has been anchored onto these functionalized materials by ion pairing. A catalyst has also been prepared by the adsorption of Na2[Pt12(CO)24] on unfunctionalized fumed silica. The catalytic activities of the resultant materials, and that of commercially purchased 5% platinum on alumina have been studied for the hydrogenation of a variety of unsaturated compounds. The substrates studied are: α-acetamidocinnamic acid, cyclohexanone, acetophenone, methyl pyruvate, ethyl acetoacetate, nitrobenzene and benzonitrile. Compared to the polystyrene supported catalyst, the inorganic oxide supported catalysts have higher surface areas and for most of the substrates have notably higher activities. The functionalized fumed silica-based catalyst gives higher conversions than functionalized silica gel and silica-alumina-based catalysts. In the hydrogenation of acetophenone and ethyl acetoacetate, the functionalized fumed silica-based catalyst show superior activity compared to the commercial platinum catalyst, and the catalyst made by conventional adsorption method. In benzonitrile hydrogenation with all the cluster-derived catalysts a hydrazine derivative is selectively formed, but when the commercial platinum catalyst is used benzyl amine is the main product. 相似文献
18.
Liang Ling Yuan He Xue Zhang Meiming Luo Xiaoming Zeng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(20):6626-6630
We herein report the hydrogenation of substituted aryl‐ and heteroaryl boronate esters for the selective synthesis of cis‐substituted borylated cycloalkanes and saturated heterocycles. A cyclic (alkyl)(amino)carbene‐ligated rhodium complex with two dimethyl groups at the ortho‐alkyl scaffold of the carbene showed high reactivity in promoting the hydrogenation, thereby enabling the hydrogenation of (hetero)arenes with retention of the synthetically valuable boronate group. This process constitutes a clean, atom‐economic, as well as chemo‐ and stereoselective route for the generation of cis‐configured, diversely substituted borylated cycloalkanes and saturated heterocycles that are usually elusive and difficult to prepare. 相似文献
19.
A Simple Iridicycle Catalyst for Efficient Transfer Hydrogenation of N‐Heterocycles in Water 下载免费PDF全文
Dinesh Talwar Dr. Ho Yin Li Emma Durham Prof. Jianliang Xiao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(14):5370-5379
A cyclometalated iridium complex is shown to catalyse the transfer hydrogenation of various nitrogen heterocycles, including but not limited to quinolines, isoquinolines, indoles and pyridinium salts, in an aqueous solution of HCO2H/HCO2Na under mild conditions. The catalyst shows excellent functional‐group compatibility and high turnover number (up to 7500), with catalyst loadings as low as 0.01 mol % being feasible. Mechanistic investigation of the quinoline reduction suggests that the transfer hydrogenation proceeds via both 1,2‐ and 1,4‐addition pathways, with the catalytic turnover being limited by the step of hydride transfer. 相似文献
20.
V. Ya. Danyushevsky P. S. Kuznetsov E. A. Katsman A. S. Kupriyanov V. R. Flid A. S. Berenblyum 《Russian Chemical Bulletin》2017,66(3):463-467
The influence of the support nature on the performance of nickel sulfide catalyst in the decarbonylation of stearic acid to heptadecenes was investigated. The catalyst supported on silica demonstrated higher activity and selectivity in comparison with the catalyst on γ-Al2O3 used as a reference. The reaction schemes over these catalysts are nearly the same; however, the contributions from the side reactions of hydrogenation and oligomerization are reasonably different. Introduction of the products of decarbonylation (CO and water vapor) decreases the stearic acid conversion; and in the case of the catalyst supported on silica, the addition of CO strongly reduces the rate of hydrogenation of heptadecenes. The reasons for the observed differences were discussed. It was suggested that the dispersion of the nickel component as well as the nature of support acidity played a significant role. 相似文献