- Engineering of Thermostable β-Hydroxyacid Dehydrogenase for the Asymmetric Reduction of Imines
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The β-hydroxyacid dehydrogenase from Thermocrinus albus (Ta-βHAD), which catalyzes the NADP+-dependent oxidation of β-hydroxyacids, was engineered to accept imines as substrates. The catalytic activity of the proton-donor variant K189D was further increased by the introduction of two nonpolar flanking residues (N192 L, N193 L). Engineering the putative alternative proton donor (D258S) and the gate-keeping residue (F250 A) led to a switched substrate specificity as compared to the single and triple variants. The two most active Ta-βHAD variants were applied to biocatalytic asymmetric reductions of imines at elevated temperatures and enabled enhanced product formation at a reaction temperature of 50 °C.
- Stockinger, Peter,Schelle, Luca,Schober, Benedikt,Buchholz, Patrick C. F.,Pleiss, Jürgen,Nestl, Bettina M.
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- CARBALDEHYDE OXIMES AS BUTYRYLCHOLINESTERASE REACTIVATORS
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The present invention relates to compounds for their use in the reactivation of butyrylcholinesterase. Such compounds are useful in the treatment or prevention of the intoxication with at least one organophosphorus nerve agent. The invention also relates
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- Discovery of tetrahydroquinolines and benzomorpholines as novel potent RORγt agonists
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The retinoic acid receptor-related orphan receptor γt (RORγt) is an important nuclear receptor that regulates the differentiation of Th17 cells and production of interleukin 17(IL-17). RORγt agonists increase basal activity of RORγt and could provide a potential approach to cancer immunotherapy. Herein, hit compound 1 was identified as a weak RORγt agonist during in-house library screening. Changes in LHS core of 1 led to the identification of tetrahydroquinoline compound 6 as a partial RORγt agonist (max. act. = 39.3%). Detailed structure-activity relationship on substituent of the LHS core, amide linker and RHS arylsulfonyl moiety was explored and a novel series of tetrahydroquinolines and benzomorpholines was discovered as potent RORγt agonists. Tetrahydroquinoline compound 8g (EC50 = 8.9 ± 0.4 nM, max. act. = 104.5%) and benzomorpholine compound 9g (EC50 = 7.5 ± 0.6 nM, max. act. = 105.8%) were representative compounds with high RORγt agonistic activity in dual FRET assay, and they showed good activity in cell-based Gal4 reporter gene assay and Th17 cell differentiation assay (104.5% activation at 300 nM of 8g; 59.4% activation at 300 nM of 9g). The binding modes of 8g and 9g as well as the two RORγt inverse agonists accidentally discovered were also discussed.
- Xia, Yuehan,Yu, Mingcheng,Zhao, Yunpeng,Xia, Li,Huang, Yafei,Sun, Nannan,Song, Meiqi,Guo, Huimin,Zhang, Yunyi,Zhu, Di,Xie, Qiong,Wang, Yonghui
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- Chemoselective and Tandem Reduction of Arenes Using a Metal–Organic Framework-Supported Single-Site Cobalt Catalyst
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The development of heterogeneous, chemoselective, and tandem catalytic systems using abundant metals is vital for the sustainable synthesis of fine and commodity chemicals. We report a robust and recyclable single-site cobalt-hydride catalyst based on a porous aluminum metal–organic framework (DUT-5 MOF) for chemoselective hydrogenation of arenes. The DUT-5 node-supported cobalt(II) hydride (DUT-5-CoH) is a versatile solid catalyst for chemoselective hydrogenation of a range of nonpolar and polar arenes, including heteroarenes such as pyridines, quinolines, isoquinolines, indoles, and furans to afford cycloalkanes and saturated heterocycles in excellent yields. DUT-5-CoH exhibited excellent functional group tolerance and could be reusable at least five times without decreased activity. The same MOF-Co catalyst was also efficient for tandem hydrogenation–hydrodeoxygenation of aryl carbonyl compounds, including biomass-derived platform molecules such as furfural and hydroxymethylfurfural to cycloalkanes. In the case of hydrogenation of cumene, our spectroscopic, kinetic, and density functional theory (DFT) studies suggest the insertion of a trisubstituted alkene intermediate into the Co–H bond occurring in the turnover limiting step. Our work highlights the potential of MOF-supported single-site base–metal catalysts for sustainable and environment-friendly industrial production of chemicals and biofuels.
- Akhtar, Naved,Begum, Wahida,Chauhan, Manav,Manna, Kuntal,Newar, Rajashree,Rawat, Manhar Singh
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supporting information
(2022/01/19)
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- Homogeneous pressure hydrogenation of quinolines effected by a bench-stable tungsten-based pre-catalyst
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We report on an operationally simple catalytic method for the tungsten-catalyzed hydrogenation of quinolines through the use of the easily handled and self-contained precursor [WCl(η5-Cp)(CO)3]. This half sandwich complex is indefinitely storable on the bench in simple screw-capped bottles or stoppered flasks and can, if required, be prepared on a multi-gram scale while the actual catalytic transformations were performed in the presence of a Lewis acid in order to achieve both decent substrate conversions and product yields. The described method represents a facile and atom-efficient access to a variety of 1,2,3,4-tetrahydroquinolines that circumvents the use of cost-intensive and oxygen-sensitive phosphine ligands as well as auxiliary hydride reagents.
- Heizinger, Christian,Topf, Christoph,Vielhaber, Thomas
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p. 451 - 461
(2021/11/11)
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- Water-involving transfer hydrogenation and dehydrogenation of N-heterocycles over a bifunctional MoNi4 electrode
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A room-temperature electrochemical strategy for hydrogenation (deuteration) and reverse dehydrogenation of N-heterocycles over a bifunctional MoNi4 electrode is developed, which includes the hydrogenation of quinoxaline using H2O as the hydrogen source with 80% Faradaic efficiency and the reverse dehydrogenation of hydrogen-rich 1,2,3,4-tetrahydroquinoxaline with up to 99% yield and selectivity. The in situ generated active hydrogen atom (H*) is plausibly involved in the hydrogenation of quinoxaline, where a consecutive hydrogen radical coupled electron transfer pathway is proposed. Notably, the MoNi4 alloy exhibits efficient quinoxaline hydrogenation at an overpotential of only 50 mV, owing to its superior water dissociation ability to provide H* in alkaline media. In situ Raman tests indicate that the NiII/NiIII redox couple can promote the dehydrogenation process, representing a promising anodic alternative to low-value oxygen evolution. Impressively, electrocatalytic deuteration is easily achieved with up to 99% deuteration ratios using D2O. This method is capable of producing a series of functionalized hydrogenated and deuterated quinoxalines.
- Han, Shuyan,Huang, Yi,Li, Mengyang,Liu, Cuibo,Zhang, Bin
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p. 1983 - 1991
(2021/09/02)
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- Metallic Barium: A Versatile and Efficient Hydrogenation Catalyst
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Ba metal was activated by evaporation and cocondensation with heptane. This black powder is a highly active hydrogenation catalyst for the reduction of a variety of unactivated (non-conjugated) mono-, di- and tri-substituted alkenes, tetraphenylethylene, benzene, a number of polycyclic aromatic hydrocarbons, aldimines, ketimines and various pyridines. The performance of metallic Ba in hydrogenation catalysis tops that of the hitherto most active molecular group 2 metal catalysts. Depending on the substrate, two different catalytic cycles are proposed. A: a classical metal hydride cycle and B: the Ba metal cycle. The latter is proposed for substrates that are easily reduced by Ba0, that is, conjugated alkenes, alkynes, annulated rings, imines and pyridines. In addition, a mechanism in which Ba0 and BaH2 are both essential is discussed. DFT calculations on benzene hydrogenation with a simple model system (Ba/BaH2) confirm that the presence of metallic Ba has an accelerating effect.
- Stegner, Philipp,F?rber, Christian,Zenneck, Ulrich,Knüpfer, Christian,Eyselein, Jonathan,Wiesinger, Michael,Harder, Sjoerd
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supporting information
p. 4252 - 4258
(2020/12/22)
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- Covalent Organic Frameworks toward Diverse Photocatalytic Aerobic Oxidations
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Photoactive two-dimensional covalent organic frameworks (2D-COFs) have become promising heterogenous photocatalysts in visible-light-driven organic transformations. Herein, a visible-light-driven selective aerobic oxidation of various small organic molecules by using 2D-COFs as the photocatalyst was developed. In this protocol, due to the remarkable photocatalytic capability of hydrazone-based 2D-COF-1 on molecular oxygen activation, a wide range of amides, quinolones, heterocyclic compounds, and sulfoxides were obtained with high efficiency and excellent functional group tolerance under very mild reaction conditions. Furthermore, benefiting from the inherent advantage of heterogenous photocatalysis, prominent sustainability and easy photocatalyst recyclability, a drug molecule (modafinil) and an oxidized mustard gas simulant (2-chloroethyl ethyl sulfoxide) were selectively and easily obtained in scale-up reactions. Mechanistic investigations were conducted using radical quenching experiments and in situ ESR spectroscopy, all corroborating the proposed role of 2D-COF-1 in photocatalytic cycle.
- Liu, Shuyang,Tian, Miao,Bu, Xiubin,Tian, Hua,Yang, Xiaobo
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supporting information
p. 7738 - 7744
(2021/05/07)
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- Nanosized CdS as a Reusable Photocatalyst: The Study of Different Reaction Pathways between Tertiary Amines and Aryl Sulfonyl Chlorides through Visible-Light-Induced N-Dealkylation and C-H Activation Processes
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It has been found that the final products of the reaction of sulfonyl chlorides and tertiary amines in the presence of cadmium sulfide nanoparticles under visible light irradiation are highly dependent on the applied reaction conditions. Interestingly, with the change of a reaction condition, different pathways were conducted (visible-light-induced N-dealkylation or sp3 and sp2 C-H activation) that lead to different products such as secondary amines and various sulfonyl compounds. Remarkably, all of these reactions were performed under visible light irradiation and an air atmosphere without any additive or oxidant in benign solvents or under solvent-free conditions. During this study, the CdS nanoparticles as affordable, heterogeneous, and recyclable photocatalysts were designed, successfully synthesized, and fully characterized and applied for these protocols. During these studies, intermediates resulting from the oxidation of tertiary amines are trapped during the photoinduced electron transfer (PET) process. The reaction was carried out efficiently with a variety of substrates to give the corresponding products at relatively short times in good to excellent yields in parallel with the use of the visible light irradiation as a renewable energy source. Most of these processes are novel or are superior in terms of cost-effectiveness, safety, and simplicity to published reports.
- Firoozi, Somayeh,Hosseini-Sarvari, Mona
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p. 2117 - 2134
(2021/02/05)
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- carba Nicotinamide Adenine Dinucleotide Phosphate: Robust Cofactor for Redox Biocatalysis
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Here we report a new robust nicotinamide dinucleotide phosphate cofactor analog (carba-NADP+) and its acceptance by many enzymes in the class of oxidoreductases. Replacing one ribose oxygen with a methylene group of the natural NADP+ was found to enhance stability dramatically. Decomposition experiments at moderate and high temperatures with the cofactors showed a drastic increase in half-life time at elevated temperatures since it significantly disfavors hydrolysis of the pyridinium-N?glycoside bond. Overall, more than 27 different oxidoreductases were successfully tested, and a thorough analytical characterization and comparison is given. The cofactor carba-NADP+ opens up the field of redox-biocatalysis under harsh conditions.
- D?ring, Manuel,Sieber, Volker,Simon, Robert C.,Tafertshofer, Georg,Zachos, Ioannis
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supporting information
p. 14701 - 14706
(2021/05/13)
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- Discovery and characterization of an acridine radical photoreductant
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Photoinduced electron transfer (PET) is a phenomenon whereby the absorption of light by a chemical species provides an energetic driving force for an electron-transfer reaction1–4. This mechanism is relevant in many areas of chemistry, including the study of natural and artificial photosynthesis, photovoltaics and photosensitive materials. In recent years, research in the area of photoredox catalysis has enabled the use of PET for the catalytic generation of both neutral and charged organic free-radical species. These technologies have enabled previously inaccessible chemical transformations and have been widely used in both academic and industrial settings. Such reactions are often catalysed by visible-light-absorbing organic molecules or transition-metal complexes of ruthenium, iridium, chromium or copper5,6. Although various closed-shell organic molecules have been shown to behave as competent electron-transfer catalysts in photoredox reactions, there are only limited reports of PET reactions involving neutral organic radicals as excited-state donors or acceptors. This is unsurprising because the lifetimes of doublet excited states of neutral organic radicals are typically several orders of magnitude shorter than the singlet lifetimes of known transition-metal photoredox catalysts7–11. Here we document the discovery, characterization and reactivity of a neutral acridine radical with a maximum excited-state oxidation potential of ?3.36 volts versus a saturated calomel electrode, which is similarly reducing to elemental lithium, making this radical one of the most potent chemical reductants reported12. Spectroscopic, computational and chemical studies indicate that the formation of a twisted intramolecular charge-transfer species enables the population of higher-energy doublet excited states, leading to the observed potent photoreducing behaviour. We demonstrate that this catalytically generated PET catalyst facilitates several chemical reactions that typically require alkali metal reductants and can be used in other organic transformations that require dissolving metal reductants.
- MacKenzie, Ian A.,Wang, Leifeng,Onuska, Nicholas P. R.,Williams, Olivia F.,Begam, Khadiza,Moran, Andrew M.,Dunietz, Barry D.,Nicewicz, David A.
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- On the Virtue of Indium in Reduction Reactions. A Comparison of Reductions Mediated by Indium and Zinc: Is Indium Metal an Effective Catalyst for Zinc Induced Reductions?
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Indium(0)-mediated reductions have been reported for the transformation of several functional groups (imines, oximes, nitro groups, isoxazolidines, and conjugated alkenes, among others), prompted by the opportunity of performing the reactions in aqueous media and green conditions. We describe here the comparison of several reactions using indium or the less expensive zinc, carried out in order to evaluate the effective advantages brought about indium metal. We found some reactions for which use of In is mandatory and others where Zn worked equally well or even better. The reduction of hydroxylamines to the corresponding amines was the only reduction for which use of In provided much better results than Zn and was also possible to apply an efficient catalytic version with use of 2–5 mol-% In in the presence of stoichiometric Zn. Applicability of this catalytic reduction to “one-pot” model processes is also demonstrated.
- Matassini, Camilla,Bonanni, Marco,Marradi, Marco,Cicchi, Stefano,Goti, Andrea
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supporting information
p. 1106 - 1113
(2019/12/24)
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- Easy Access to 2,4-Disubstituted Cyclopentenones by a Gold(III)-Catalyzed A3-Coupling/Cyclization Cascade
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An efficient and convenient synthesis of 2,4-disubstituted cyclopentenones has been achieved through a Au(III)-catalyzed isomerization-A3-coupling/cyclization cascade. A possible mechanism involving an initial Au(III)-catalyzed isomerization, A3-type coupling, and cyclization via an enol intermediate is postulated.
- Hu, Xiwen,Li, Jian,Liu, Li,Xu, Yue,Zhu, Shangrong
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supporting information
p. 9478 - 9483
(2020/12/21)
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- Ir-Catalyzed Reversible Acceptorless Dehydrogenation/Hydrogenation of N-Substituted and Unsubstituted Heterocycles Enabled by a Polymer-Cross-Linking Bisphosphine
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The polystyrene-cross-linking bisphosphine ligand PS-DPPBz was effective for the Ir-catalyzed reversible acceptorless dehydrogenation/hydrogenation of N-heterocycles. Notably, this protocol is applicable to the dehydrogenation of N-substituted indoline derivatives with various N-substituents with different electronic and steric natures. A reaction pathway involving oxidative addition of an N-adjacent C(sp3)-H bond to a bisphosphine-coordinated Ir(I) center is proposed for the dehydrogenation of N-substituted substrates.
- Zhang, Deliang,Iwai, Tomohiro,Sawamura, Masaya
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supporting information
p. 5240 - 5245
(2020/07/03)
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- NHC-Palladium(II) Mononuclear and Binuclear Complexes Containing Phenylene-Bridged Bis(thione) Ligands: Synthesis, Characterization, and Catalytic Activities
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A series of mono- and binuclear Pd(II) complexes with N-heterocyclic carbene (NHC) and phenylene-bridged bis(thione) (SCS) ligands were prepared and characterized by 1H and 13C NMR spectroscopy, IR, and mass spectrometry. The molecular structures of 1b, 2a, and 3b have been determined by the single-crystal X-ray diffraction method. The catalytic activities of the synthesized palladium complexes in the regioselective reduction of quinolines to the corresponding 1,2,3,4-tetrahydroquinolines were thoroughly investigated with ammonia-borane under mild reaction conditions. It is observed that the activities of the binuclear Pd(NHC) complexes were higher than those of the corresponding mononuclear complexes under the same conditions.
- Jia, Wei-Guo,Gao, Li-Li,Wang, Zhi-Bao,Wang, Jing-Jing,Sheng, En-Hong,Han, Ying-Feng
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p. 1790 - 1798
(2020/05/14)
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- Binuclear nitrogen-containing heterocyclic carbene palladium coordination compound as well as preparation method and application thereof
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The invention discloses a binuclear nitrogen-containing heterocyclic carbene palladium coordination compound as well as a preparation method and application thereof. The structure of the binuclear nitrogen-containing heterocyclic carbene palladium coordination compound is as shown in a formula I which is described in the specification, and R1 and R2 are respectively and independently one of H andC1-C6 alkyl. The binuclear nitrogen-containing heterocyclic carbene palladium coordination compound has excellent catalytic performance, and the preparation method has the characteristics of mild conditions, simple operation and low equipment requirements, so that the complex can be used as a catalyst to be applied to hydrogen production by ammonia borane decomposition and reduction of a quinolinecompound into a 1, 2, 3, 4-tetrahydroquinoline compound.
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Paragraph 0070-0072
(2020/07/07)
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- Hydrogenation/dehydrogenation of N-heterocycles catalyzed by ruthenium complexes based on multimodal proton-responsive CNN(H) pincer ligands
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Ru complexes based on lutidine-derived pincer CNN(H) ligands having secondary amine side donors are efficient precatalysts in the hydrogenation and dehydrogenation of N-heterocycles. Reaction of a Ru-CNN(H) complex with an excess of base produces the formation of a Ru(0) derivative, which is observed under catalytic conditions.
- álvarez, Eleuterio,Hernández-Juárez, Martín,López-Serrano, Joaquín,Paneque, Margarita,Rendón, Nuria,Sánchez, Práxedes,Santos, Laura L.,Suárez, Andrés
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supporting information
p. 9583 - 9587
(2020/07/30)
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- Reversible aerobic oxidative dehydrogenation/hydrogenation of N-heterocycles over AlN supported redox cobalt catalysts
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N-heterocycles with quinoline and tetrahydroquinoline structures are highly important in pharmaceutical and chemical industries, and their highly efficient mutual transformations are vital but still challenging. In the present work, AlN supported redox cobalt catalysts (Co3O4/AlN and Co/AlN) were prepared, which could achieve the reversible aerobic oxidative dehydrogenation/hydrogenation of N-heterocycles with good performances. The catalytic performances were stem from the strong interaction between Co species with AlN support, which were confirmed by the characterizations of Raman, XPS, UV–vis DRS, and H2-TPR etc. Both of the catalysts showed good stabilities and reusabilities for the titled reactions. Besides, the gram-scale experiments achieved with good yields to corresponding products, revealing the present protocol possesses great potential applications in industry. The strategy of using redox Co-based catalyst not only provides a potential catalyst for the reversible hydrogenation/oxidative dehydrogenation reactions but also replenishes methods for constructing of other redox catalyst, especially with AlN as a carrier.
- He, Zhen-Hong,Sun, Yong-Chang,Wang, Kuan,Wang, Zhong-Yu,Guo, Pan-Pan,Jiang, Chong-Shan,Yao, Man-Qing,Li, Zhu-Hui,Liu, Zhao-Tie
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- A General Catalyst Based on Cobalt Core–Shell Nanoparticles for the Hydrogenation of N-Heteroarenes Including Pyridines
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Herein, we report the synthesis of specific silica-supported Co/Co3O4 core–shell based nanoparticles prepared by template synthesis of cobalt-pyromellitic acid on silica and subsequent pyrolysis. The optimal catalyst material allows for general and selective hydrogenation of pyridines, quinolines, and other heteroarenes including acridine, phenanthroline, naphthyridine, quinoxaline, imidazo[1,2-a]pyridine, and indole under comparably mild reaction conditions. In addition, recycling of these Co nanoparticles and their ability for dehydrogenation catalysis are showcased.
- Beller, Matthias,Chandrashekhar, Vishwas G.,Jagadeesh, Rajenahally V.,Kreyenschulte, Carsten,Murugesan, Kathiravan
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supporting information
p. 17408 - 17412
(2020/08/21)
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- A proton-responsive annulated mesoionic carbene (MIC) scaffold on IR complex for proton/hydride shuttle: An experimental and computational investigation on reductive amination of aldehyde
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A Cp*Ir(III) complex (1) bearing a proton-responsive hydroxy unit on an annulated imidazo[1,2-a][1,8]naphthyridine based mesoionic carbene scaffold was synthesized by two different synthetic routes. The molecular structure of 1 revealed an anionic lactam form of the ligand. The acid?base equilibrium between the lactam-lactim tautomers on the ligand scaffold was examined by 1H NMR and UV?vis spectra. The pKa of the appendage ?OH group in the lactim form of 1 was estimated to assess the proton transfer property of the catalyst. The catalytic efficacy of 1 for reductive amination of aldehyde was evaluated by utilizing three different hydrogen sources: molecular H2iPrOH/KOtBu combination, and HCOOH/Et3N (5:2) azeotropic mixture. The HCOOH/Et3N (5:2) azeotropic mixture rotocol was found to be the best amon the three different h dro enation methods. Catalyst 1 hydrogenates imines chemoselectively over carbonyls under the reaction conditions. A range of aldehydes was reductively aminated to the corresponding secondary amines using the HCOOH/Et3N (5:2) azeotropic mixture. Further, catalyst 1 showed high efficiency for the reduction of a wide variety of N-heterocyclic imine derivatives. The lactam-lactim tautomerization of the ligand system is proposed for direct hydrogenation, whereas only the lactam form operates in the strongly basic medium (iPrOH/KOtBu). Under HCOOH/Et3N (5:2) conditions, the lactam scaffold is not protonated; rather, an outer-sphere hydride transfer from formate to the Ir is proposed, which is supported by 1H NMR and DFT calculations. Finally, ligand-promoted hydride transfer from metal-hydride to the protonated imine affords the corresponding amine. A close agreement between the experimentally estimated and computed thermodynamic/kinetic parameters gives credence to the metal-ligand cooperative mechanism for the imine hydrogenation reaction using the HCOOH/Et3N (5:2) azeotropic mixture.
- Bera, Jitendra K.,Daw, Prosenjit,Din Reshi, Noor U.,Ehmann, Kira R.,H?lscher, Markus,Leitner, Walter,Pandey, Pragati
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p. 3849 - 3863
(2020/11/23)
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- Stereoselective Biotransformations of Cyclic Imines in Recombinant Cells of Synechocystis sp. PCC 6803
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Light-driven biotransformations in recombinant cyanobacteria allow to employ photosynthetic water-splitting for cofactor-regeneration and thus, to save the use of organic electron donors. The genes of three recombinant imine reductases (IREDs) were expressed in the cyanobacterium Synechocystis sp. PCC 6803 and eight cyclic imine substrates were screened in whole-cell biotransformations. While initial reactions showed low to moderate rates, optimization of the reaction conditions in combination with promoter engineering allowed to alleviate toxicity effects and achieve full conversion of prochiral imines with initial rates of up to 6.3 mM h?1. The high specific activity of up to 22 U gCDW ?1 demonstrates that recombinant cyanobacteria can provide large amounts of NADPH during whole cell reactions. The excellent optical purity of the products with up to >99 %ee underlines the usefulness of cyanobacteria for the stereoselective synthesis of amines.
- Büchsenschütz, Hanna C.,Vidimce-Risteski, Viktorija,Eggbauer, Bettina,Schmidt, Sandy,Winkler, Christoph K.,Schrittwieser, Joerg H.,Kroutil, Wolfgang,Kourist, Robert
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p. 726 - 730
(2019/12/27)
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- Catalyst-free cyclization of anthranils and cyclic amines: One-step synthesis of rutaecarpine
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An efficient synthesis of a variety of quinazolinone derivatives via a direct cyclization reaction between commercially available anthranils and cyclic amines is described. The developed transformation proceeds with the merits of high step- and atom-efficiency, a broad substrate scope, and good to excellent yields, without additional catalysts, and offers a practical way for the preparation of rutaecarpine and its derivatives with structural diversity.
- Li, Jian,Wang, Zheng-Bing,Xu, Yue,Lu, Xue-Chen,Zhu, Shang-Rong,Liu, Li
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supporting information
p. 12072 - 12075
(2019/10/14)
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- Light-Driven Intramolecular C?N Cross-Coupling via a Long-Lived Photoactive Photoisomer Complex
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Reported herein is a visible-light-driven intramolecular C?N cross-coupling reaction under mild reaction conditions (metal- and photocatalyst-free, at room temperature) via a long-lived photoactive photoisomer complex. This strategy was used to rapidly prepare the N-substituted polycyclic quinazolinone derivatives with a broad substrate scope (>50 examples) and further exploited to synthesize the natural products tryptanthrin, rutaecarpine, and their analogues. The success of gram-scale synthesis and solar-driven transformation, as well as promising tumor-suppressing biological activity, proves the potential of this strategy for practical applications. Mechanistic investigations, including control experiments, DFT calculations, UV-vis spectroscopy, EPR, and X-ray single-crystal structure of the key intermediate, provides insight into the mechanism.
- Jing, Dong,Lu, Cong,Chen, Zhuo,Jin, Songyang,Xie, Lijuan,Meng, Ziyi,Su, Zhishan,Zheng, Ke
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supporting information
p. 14666 - 14672
(2019/09/06)
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- Method for conducting catalytic hydrogenation on nitrogen-containing unsaturated heterocyclic compound
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The invention provides a method for conducting catalytic hydrogenation on a nitrogen-containing unsaturated heterocyclic compound, and belongs to the technical field of catalytic hydrogenation. The provided method for conducting catalytic hydrogenation on the nitrogen-containing unsaturated heterocyclic compound comprises the following step: in the presence of hydrogen and a manganese catalyst, with the nitrogen-containing unsaturated heterocyclic compound as a substrate, carrying out a hydrogenation reaction. According to the method for conducting catalytic hydrogenation on the nitrogen-containing unsaturated heterocyclic compound, he adopted manganese catalyst is an NNP-type pincer manganese catalyst, has the advantages of being cheap, easy to obtain and low in toxicity compared with noble metal catalysts, has the advantages of being wide in substrate applicability and high in target product yield compared with an existing cheap metal iron catalyst or cobalt catalyst, and is higher in electron donating ability and smaller in steric hindrance compared with a PNP-type pincer manganese catalyst, and thus shows higher reaction activity in a series of hydrogenation reactions, and thetarget product yield is up to 99%.
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Paragraph 0095; 0106-0109
(2020/01/03)
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- General and Chemoselective Copper Oxide Catalysts for Hydrogenation Reactions
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Copper oxide catalysts have been prepared by pyrolysis of copper acetate on aluminum oxide. The material resulting from pyrolysis at 800 °C allows for catalytic hydrogenations at low temperature of a variety of unsaturated compounds such as quinolines, alkynes, ketones, imines, and polycyclic aromatic hydrocarbons as well as nitroarenes with good activity and selectivity.
- Li, Wu,Cui, Xinjiang,Junge, Kathrin,Surkus, Annette-Enrica,Kreyenschulte, Carsten,Bartling, Stephan,Beller, Matthias
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p. 4302 - 4307
(2019/05/08)
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- Homogeneous Hydrogenation with a Cobalt/Tetraphosphine Catalyst: A Superior Hydride Donor for Polar Double Bonds and N-Heteroarenes
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The development of catalysts based on earth abundant metals in place of noble metals is becoming a central topic of catalysis. We herein report a cobalt/tetraphosphine complex-catalyzed homogeneous hydrogenation of polar unsaturated compounds using an air- and moisture-stable and scalable precatalyst. By activation with potassium hydroxide, this cobalt system shows both high efficiency (up to 24 000 TON and 12 000 h-1 TOF) and excellent chemoselectivities with various aldehydes, ketones, imines, and even N-heteroarenes. The preference for 1,2-reduction over 1,4-reduction makes this method an efficient way to prepare allylic alcohols and amines. Meanwhile, efficient hydrogenation of the challenging N-heteroarenes is also furnished with excellent functional group tolerance. Mechanistic studies and control experiments demonstrated that a CoIH complex functions as a strong hydride donor in the catalytic cycle. Each cobalt intermediate on the catalytic cycle was characterized, and a plausible outer-sphere mechanism was proposed. Noteworthy, external inorganic base plays multiple roles in this reaction and functions in almost every step of the catalytic cycle.
- Duan, Ya-Nan,Du, Xiaoyong,Cui, Zhikai,Zeng, Yiqun,Liu, Yufeng,Yang, Tilong,Wen, Jialin,Zhang, Xumu
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supporting information
p. 20424 - 20433
(2019/12/27)
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- HMPA-catalyzed transfer hydrogenation of 3-carbonyl pyridines and other N-heteroarenes with trichlorosilane
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A method for the HMPA (hexamethylphosphoric triamide)-catalyzed metal-freetransfer hydrogenation of pyridines has been developed. The functional group tolerance of the existing reaction conditions provides easy access to various piperidines with ester or ketone groups at the C-3 site. The suitability of this method for the reduction of other N-heteroarenes has also been demonstrated. Thirty-three examples of different substrates have been reduced to designed products with 45–96% yields.
- Fu, Yun,Sun, Jian
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- Iridium-Catalyzed Hydrogenation and Dehydrogenation of N-Heterocycles in Water under Mild Conditions
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An efficient catalytic method is presented for the hydrogenation of N-heterocycles. The iridium-based catalyst operates under mild conditions in water without any co-catalyst or stoichiometric additives. The catalyst also promotes the reverse reaction of dehydrogenation of N-heterocycles, hence displaying appropriate characteristics for a future hydrogen economy based on liquid organic hydrogen carriers (LOHCs).
- Wang, Shengdong,Huang, Haiyun,Bruneau, Christian,Fischmeister, Cédric
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p. 2350 - 2354
(2019/05/21)
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- Birch-Type Photoreduction of Arenes and Heteroarenes by Sensitized Electron Transfer
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The direct reduction of arenes and heteroarenes by visible-light irradiation remains challenging, as the energy of a single photon is not sufficient for breaking aromatic stabilization. Shown herein is that the energy accumulation of two visible-light photons allows the dearomatization of arenes and heteroarenes. Mechanistic investigations confirm that the combination of energy-transfer and electron-transfer processes generates an arene radical anion, which is subsequently trapped by hydrogen-atom transfer and finally protonated to form the dearomatized product. The photoreduction converts planar aromatic feedstock compounds into molecular skeletons that are of use in organic synthesis.
- Chatterjee, Anamitra,K?nig, Burkhard
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supporting information
p. 14289 - 14294
(2019/08/30)
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- Hoveyda–Grubbs catalysts with an N→Ru coordinate bond in a six-membered ring. Synthesis of stable, industrially scalable, highly efficient ruthenium metathesis catalysts and 2-vinylbenzylamine ligands as their precursors
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A novel and efficient approach to the synthesis of 2-vinylbenzylamines is reported. This involves obtaining 2-vinylbenzylamine ligands from tetrahydroisoquinoline by alkylation and reduction followed by the Hofmann cleavage. The resultant 2-vinylbenzyl-amines allowed us to obtain new Hoveyda–Grubbs catalysts, which were thoroughly characterised by NMR, ESIMS, and X-ray crystallography. The utility of this chemistry is further demonstrated by the tests of the novel catalysts (up to 10?2 mol %) in different metathesis reactions such as cross metathesis (CM), ring-closing metathesis (RCM) and ring-opening cross metathesis (ROCM).
- Polyanskii, Kirill B.,Alekseeva, Kseniia A.,Raspertov, Pavel V.,Kumandin, Pavel A.,Nikitina, Eugeniya V.,Gurbanov, Atash V.,Zubkov, Fedor I.
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p. 769 - 779
(2019/04/17)
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- Heterogeneous nickel-catalysed reversible, acceptorless dehydrogenation of N-heterocycles for hydrogen storage
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Nickel-based nanocatalysts were used in acceptorless, reversible dehydrogenation and hydrogenation reactions of N-heterocycles. Both processes were realized in the same solvent using a single catalyst, without isolation of products and workup, which makes it attractive for hydrogen storage purposes. This concept has been demonstrated in a continuous hydrogenation/dehydrogenation sequence of quinaldine with negligible loss in activity of the nickel catalyst after three hydrogen storage cycles. The scope of acceptorless dehydrogenation has been explored and control experiments suggest that hydrogen liberation is initiated via amine dehydrogenation and supports the direct alkane dehydrogenation from the partially oxidized N-heterocycles.
- Ryabchuk, Pavel,Agapova, Anastasiya,Kreyenschulte, Carsten,Lund, Henrik,Junge, Henrik,Junge, Kathrin,Beller, Matthias
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supporting information
p. 4969 - 4972
(2019/05/21)
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- Selective hydrogenation of quinolines over a CoCu bimetallic catalyst at low temperature
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Quinoline derivatives are widely exist in the environment, and mainly separated from the coal tar pitch fraction. Hydrogenation of these compounds to 1,2,3,4-tetrahydroquinolines, an important class of natural products and medicinal agents, is a significant transformation of waste to valuable chemicals. In the present work, we developed a cheap and highly efficient Co3Cu1Ox bimetallic catalyst and used it for the hydrogenation of quinolines at a temperature down to 60 °C. The introduction of Cu into Co catalyst changed the physical and chemical features of Co catalyst, which was characterized by Raman spectra, N2-adsorption/desorption isotherms, H2-TPR and H2-TPD tests. The recycling experiments indicated the catalyst was stable and possessed good reusability. Importantly, the gram-scale experiment provided a high yield (92%) to the target product, demonstrating that the catalytic system has a potential practical application.
- He, Zhen-Hong,Li, Na,Wang, Kuan,Wang, Wei-Tao,Liu, Zhao-Tie
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p. 120 - 126
(2019/04/10)
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- Iodine catalyzed reduction of quinolines under mild reaction conditions
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A reduction of quinolines to synthetically versatile tetrahydroquinoline molecules with I2 and HBpin is described. In the presence of iodine (20 mol%) as a catalyst, reduction of quinolines and other N-heteroarenes proceeded readily with hydroboranes as the reducing reagents. The broad functional-group tolerance, good yields and mild reaction conditions imply high practical utility.
- Yang, Chun-Hua,Chen, Xixi,Li, Huimin,Wei, Wenbo,Yang, Zhantao,Chang, Junbiao
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supporting information
p. 8622 - 8625
(2018/08/06)
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- A Practical and Chemoselective Ammonia-Free Birch Reduction
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A novel protocol for a significantly improved, practical, and chemoselective ammonia-free Birch reduction mediated by bench-stable sodium dispersions and recoverable 15-crown-5 ether is reported. A broad range of aromatic and heteroaromatic compounds is reduced with excellent yields.
- Lei, Peng,Ding, Yuxuan,Zhang, Xiaohe,Adijiang, Adila,Li, Hengzhao,Ling, Yun,An, Jie
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supporting information
p. 3439 - 3442
(2018/06/26)
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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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- Novel electronic salt system and method for reducing unsaturated hydrocarbon compound
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The invention discloses an electronic salt system and a method for reducing unsaturated hydrocarbon compounds by using the electronic salt system, belongs to the field of organic synthesis, and solvesthe problems such as complicated operation, harsh conditions, easy generation of complex over-reduction products of methods for reducing the unsaturated hydrocarbon compounds in the prior art. An electron salt may be synthesized by an alkali metal reagent, an ether and an alcohol, the ether can be a crown ether or a cryptand; and the method adopts the electronic salt system, the unsaturated hydrocarbon compounds is reduced by the electronic salt system in an organic solvent. The method for reducing the unsaturated hydrocarbon compounds is used for reducing the unsaturated hydrocarbon compounds.
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Paragraph 0116-0120
(2018/09/08)
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- Aerobic oxidative dehydrogenation of N-heterocycles catalyzed by cobalt porphyrin
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An efficient catalytic procedure has been developed for the aerobic oxidative dehydrogenation of N-heterocycles by cobalt porphyrin in the absence of any additives. The catalytic system could tolerate various 1,2,3,4-tetrahydroquinoline derivatives and some other N-heterocycles. The corresponding N-heteroaromatics could be obtained in 59–86% yields. The mechanism investigation suggested that the aerobic oxidative dehydrogenation might proceed with imine intermediate through radical paths.
- Zhou, Weiyou,Chen, Dongwei,Sun, Fu'an,Qian, Junfeng,He, Mingyang,Chen, Qun
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supporting information
p. 949 - 953
(2018/02/09)
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- Transfer Hydrogenation of Alkenes Using Ethanol Catalyzed by a NCP Pincer Iridium Complex: Scope and Mechanism
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The first general catalytic approach to effecting transfer hydrogenation (TH) of unactivated alkenes using ethanol as the hydrogen source is described. A new NCP-type pincer iridium complex (BQ-NCOP)IrHCl containing a rigid benzoquinoline backbone has been developed for efficient, mild TH of unactivated C-C multiple bonds with ethanol, forming ethyl acetate as the sole byproduct. A wide variety of alkenes, including multisubstituted alkyl alkenes, aryl alkenes, and heteroatom-substituted alkenes, as well as O- or N-containing heteroarenes and internal alkynes, are suitable substrates. Importantly, the (BQ-NCOP)Ir/EtOH system exhibits high chemoselectivity for alkene hydrogenation in the presence of reactive functional groups, such as ketones and carboxylic acids. Furthermore, the reaction with C2D5OD provides a convenient route to deuterium-labeled compounds. Detailed kinetic and mechanistic studies have revealed that monosubstituted alkenes (e.g., 1-octene, styrene) and multisubstituted alkenes (e.g., cyclooctene (COE)) exhibit fundamental mechanistic difference. The OH group of ethanol displays a normal kinetic isotope effect (KIE) in the reaction of styrene, but a substantial inverse KIE in the case of COE. The catalysis of styrene or 1-octene with relatively strong binding affinity to the Ir(I) center has (BQ-NCOP)IrI(alkene) adduct as an off-cycle catalyst resting state, and the rate law shows a positive order in EtOH, inverse first-order in styrene, and first-order in the catalyst. In contrast, the catalysis of COE has an off-cycle catalyst resting state of (BQ-NCOP)IrIII(H)[O(Et)···HO(Et)···HOEt] that features a six-membered iridacycle consisting of two hydrogen-bonds between one EtO ligand and two EtOH molecules, one of which is coordinated to the Ir(III) center. The rate law shows a negative order in EtOH, zeroth-order in COE, and first-order in the catalyst. The observed inverse KIE corresponds to an inverse equilibrium isotope effect for the pre-equilibrium formation of (BQ-NCOP)IrIII(H)(OEt) from the catalyst resting state via ethanol dissociation. Regardless of the substrate, ethanol dehydrogenation is the slow segment of the catalytic cycle, while alkene hydrogenation occurs readily following the rate-determining step, that is, β-hydride elimination of (BQ-NCOP)Ir(H)(OEt) to form (BQ-NCOP)Ir(H)2 and acetaldehyde. The latter is effectively converted to innocent ethyl acetate under the catalytic conditions, thus avoiding the catalyst poisoning via iridium-mediated decarbonylation of acetaldehyde.
- Wang, Yulei,Huang, Zhidao,Leng, Xuebing,Zhu, Huping,Liu, Guixia,Huang, Zheng
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supporting information
p. 4417 - 4429
(2018/04/05)
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- Highly active and recyclable Pt nanocatalyst for hydrogenation of quinolines and isoquinolines
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Thermoregulated phase-transfer Pt nanocatalyst was shown to be highly active, selective and recyclable in the hydrogenation of quinolines and isoquinolines. The catalyst could be easily separated from the product by simple phase separation and directly reused in the next cycle without evident loss in catalytic activity and selectivity, even after ten recycles. Importantly, for quinoline, the TON of 10,474 is the highest value ever reported among Pt catalysts. More remarkably, for isoquinoline, the TON of 5340 is far ahead of the highest record among transition metal catalysts.
- Xue, Xiuru,Zeng, Min,Wang, Yanhua
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- A robust iron catalyst for the selective hydrogenation of substituted (iso)quinolones
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By applying N-doped carbon modified iron-based catalysts, the controlled hydrogenation of N-heteroarenes, especially (iso)quinolones, is achieved. Crucial for activity is the catalyst preparation by pyrolysis of a carbon-impregnated composite, obtained from iron(ii) acetate and N-aryliminopyridines. As demonstrated by TEM, XRD, XPS and Raman spectroscopy, the synthesized material is composed of Fe(0), Fe3C and FeNx in a N-doped carbon matrix. The decent catalytic activity of this robust and easily recyclable Fe-material allowed for the selective hydrogenation of various (iso)quinoline derivatives, even in the presence of reducible functional groups, such as nitriles, halogens, esters and amides. For a proof-of-concept, this nanostructured catalyst was implemented in the multistep synthesis of natural products and pharmaceutical lead compounds as well as modification of photoluminescent materials. As such this methodology constitutes the first heterogeneous iron-catalyzed hydrogenation of substituted (iso)quinolones with synthetic importance.
- Sahoo, Basudev,Kreyenschulte, Carsten,Agostini, Giovanni,Lund, Henrik,Bachmann, Stephan,Scalone, Michelangelo,Junge, Kathrin,Beller, Matthias
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p. 8134 - 8141
(2018/11/20)
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- Reversible Dehydrogenation and Hydrogenation of N-Heterocycles Catalyzed by Bimetallic Nanoparticles Encapsulated in MIL-100(Fe)
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Pd?Ni bimetallic nanoparticles (BMNPs) encapsulated in MIL-100(Fe) (Pd-Ni@MIL-100(Fe) was fabricated and employed as an efficient catalyst for the reversible dehydrogenation/hydrogenation of N-Heterocycles derivatives in water under mild conditions. Excellent catalytic performance for both reactions endows Pd-Ni@MIL-100(Fe) great potential value in organic chemistry. Alloying Pd with Ni can enhance the catalytic performance due to the bimetallic synergy. Both Lewis acidity and ordered mesoporous structure of MIL-100(Fe) are beneficial to the performance of the catalyst owing to its stabilization of BMNPs, reduction of the electron density of Pd atoms and enhancement of substrates adsorption capacity.
- Zhang, Jia-Wei,Li, Dan-Dan,Lu, Guo-Ping,Deng, Tao,Cai, Chun
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p. 4980 - 4986
(2018/10/15)
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- Regioexhaustive Functionalization of the Carbocyclic Core of Isoquinoline: Concise Synthesis of Oxoaporphine Core and Ellipticine
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A general and versatile strategy has been developed for the functionalization of the carbocyclic core of the isoquinoline. This regioexhaustive approach employs electrophilic halogenation as a toolbox methodology and delivers highly decorated intermediates that can be further elaborated toward medicinally relevant building blocks or natural products.
- Horváth, Dániel Vajk,Domonyi, Frigyes,Palkó, Roberta,Lomoschitz, Andrea,Soós, Tibor
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p. 2181 - 2190
(2018/03/21)
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- Sequence-Based In-silico Discovery, Characterisation, and Biocatalytic Application of a Set of Imine Reductases
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Imine reductases (IREDs) have recently become a primary focus of research in biocatalysis, complementing other classes of amine-forming enzymes such as transaminases and amine dehydrogenases. Following in the footsteps of other research groups, we have established a set of IRED biocatalysts by sequence-based in silico enzyme discovery. In this study, we present basic characterisation data for these novel IREDs and explore their activity and stereoselectivity using a panel of structurally diverse cyclic imines as substrates. Specific activities of >1 U/mg and excellent stereoselectivities (ee>99 %) were observed in many cases, and the enzymes proved surprisingly tolerant towards elevated substrate loadings. Co-expression of the IREDs with an alcohol dehydrogenase for cofactor regeneration led to whole-cell biocatalysts capable of efficiently reducing imines at 100 mM initial concentration with no need for the addition of extracellular nicotinamide cofactor. Preparative biotransformations on gram scale using these ‘designer cells’ afforded chiral amines in good yield and excellent optical purity.
- Velikogne, Stefan,Resch, Verena,Dertnig, Carina,Schrittwieser, Joerg H.,Kroutil, Wolfgang
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p. 3236 - 3246
(2018/08/03)
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- Heterogeneous Cobalt-Catalyzed Direct N-Formylation of Isoquinolines with CO2 and H2
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Isoquinolines (IQs) are an abundant feedstock, and N-formyl-1,2,3,4-tetrahydroisoquinolines (FTHIQs) are valuable fine chemicals and key intermediates. Herein, we report for the first time the Co0/ZnCl2-catalyzed direct N-formylation of IQs by using CO2 with H2 to produce FTHIQs. It was discovered that the Co catalyst and ZnCl2 worked synergistically in catalyzing the N-formylation reactions, and moderate to high yields of the desired products could be obtained, depending on the nature of the substrates. The Co0 catalyst could be reused at least five times without a notable decrease in activity. A possible reaction mechanism is proposed on the basis of control experiments.
- He, Zhenhong,Liu, Hangyu,Liu, Huizhen,Qian, Qingli,Meng, Qinglei,Mei, Qingqing,Han, Buxing
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p. 1947 - 1952
(2017/06/13)
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- B(C6F5)3-Catalyzed Cascade Reduction of Pyridines
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B(C6F5)3 has been found to be an effective catalyst for reduction of pyridines and other electron-deficient N-heteroarenes with hydrosilanes (or hydroboranes) and amines as the reducing reagents. The success of this development hinges upon the realization of a cascade process of dearomative hydrosilylation (or hydroboration) and transfer hydrogenation. The broad functional-group tolerance (e.g. ketone, ester, unactivated olefins, nitro, nitrile, heterocycles, etc.) implies high practical utility.
- Liu, Zhi-Yun,Wen, Zhi-Hui,Wang, Xiao-Chen
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supporting information
p. 5817 - 5820
(2017/05/12)
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- A General and Highly Selective Cobalt-Catalyzed Hydrogenation of N-Heteroarenes under Mild Reaction Conditions
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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.
- Adam, Rosa,Cabrero-Antonino, Jose R.,Spannenberg, Anke,Junge, Kathrin,Jackstell, Ralf,Beller, Matthias
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supporting information
p. 3216 - 3220
(2017/03/17)
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- Gold Particles Supported on Amino-Functionalized Silica Catalyze Transfer Hydrogenation of N-Heterocyclic Compounds
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In this work we demonstrate that exceptionally small gold particles (d=0.6±0.2 nm) supported on amino-functionalized mesoporous silicate SBA-15 are highly active in transfer hydrogenation of structurally diverse unsaturated N-heterocyclic compounds. The heterocyclic ring is reduced selectively. The gold particles aggregate to a diameter of 4–5 nm in the presence of formic acid/triethylamine (hydrogen donor) during the first catalytic run. In subsequent cycles the nanoparticles maintain their size, yielding a very stable catalytic system that was recycled more than five times. In contrast, analogous SBA catalysts featuring larger (~5–35 nm) gold particles are not active. Excess formic acid also leads to the formation of formamide derivatives of the products of hydrogenation, which can be deformylated quantitatively. Fifteen structurally different substrates, including the scaffolds of quinoline, isoquinoline, quinoxaline, acridine, phenanthroline, quinazoline, and phenanthridine are hydrogenated and deformylated to give the amine products in >90% overall yield. Deuterium labeling experiments indicate that 1,2-addition with subsequent disproportionation of the formed intermediate is the preferred reaction path over the 1,4-addition one, suggesting the participation of a gold hydride species. (Figure presented.).
- Vilhanová, Beáta,van Bokhoven, Jeroen A.,Ranocchiari, Marco
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p. 677 - 686
(2017/02/23)
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- Pd/C-Al-water facilitated selective reduction of a broad variety of functional groups
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The chemoselective reduction of a broad variety of functional groups by a Pd/C-Al-H2O system is described. The reduction is based on the reaction of Al with the solvent water that in situ produces hydrogen that is utilized by the supported Pd catalyst toward the hydrogenation of the target functional groups. The hydrogenations are carried out under mild conditions and provided the products in high yields and selectivity. The reduction system appeared to be effective for a broad range of functional groups, including C-C, C-N, C-O and N-O multiple bonds, aromatic rings, hydrogenolysis of C-O, C-N and C-Halogen bonds. The appropriate selection of the reaction conditions allowed the selective preparation of different products from the same substrate. The simplicity, cost, tunability and the environmentally benign character of the catalytic system offer numerous advantages over the currently available methods.
- Sch?fer,Ellstrom,Cho,T?r?k
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p. 1230 - 1234
(2017/03/20)
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- Uncoordinated Amine Groups of Metal-Organic Frameworks to Anchor Single Ru Sites as Chemoselective Catalysts toward the Hydrogenation of Quinoline
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Here we report a precise control of isolated single ruthenium site supported on nitrogen-doped porous carbon (Ru SAs/N-C) through a coordination-assisted strategy. This synthesis is based on the utilization of strong coordination between Ru3+ and the free amine groups (-NH2) at the skeleton of a metal-organic framework, which plays a critical role to access the atomically isolated dispersion of Ru sites. Without the assistance of the amino groups, the Ru precursor is prone to aggregation during the pyrolysis process, resulting in the formation of Ru clusters. The atomic dispersion of Ru on N-doped carbon can be verified by the spherical aberration correction electron microscopy and X-ray absorption fine structure measurements. Most importantly, this single Ru sites with single-mind N coordination can serve as a semihomogeneous catalyst to catalyze effectively chemoselective hydrogenation of functionalized quinolones.
- Wang, Xin,Chen, Wenxing,Zhang, Lei,Yao, Tao,Liu, Wei,Lin, Yue,Ju, Huanxin,Dong, Juncai,Zheng, Lirong,Yan, Wensheng,Zheng, Xusheng,Li, Zhijun,Wang, Xiaoqian,Yang, Jian,He, Dongsheng,Wang, Yu,Deng, Zhaoxiang,Wu, Yuen,Li, Yadong
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supporting information
p. 9419 - 9422
(2017/07/24)
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- Selective hydrogenation of N-heterocyclic compounds using Ru nanocatalysts in ionic liquids
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N-Heterocyclic compounds have been tested in the selective hydrogenation catalysed by small 1-3 nm sized Ru nanoparticles (NPs) embedded in various imidazolium based ionic liquids (ILs). Particularly a diol-functionalised IL shows the best performance in the hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline (1THQ) with up to 99% selectivity.
- Konnerth, Hannelore,Prechtl, Martin H. G.
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supporting information
p. 2762 - 2767
(2017/07/24)
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