- Volatile components of the liverworts Archilejeunea olivacea, Cheilolejeunea imbricata and Leptolejeunea elliptica
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Three liverworts, Archilejeunea olivacea. Cheilolejeunea imbricata and Leptolejeunea elliptica, belonging to the Lejeuneaceae, have been investigated chemically. Olivacene, a new naturally occurring sesquiterpene hydrocarbon, β-monocyclonerolidol and (-)-spathulenol have been isolated from A. olivacea. The strong milky-like fragrance of C. imbricata is due to a mixture of (R)-dodec-2-en-1, 5-olide and (R)-tetradec-2-en-1,5-olide. Leptolejeunea elliptica produces an intensely fragrant odour which is due to a mixture of 1-ethyl-4-methoxy-, 1-ethyl-4-hydroxy- and 1-ethyl-4- acetoxybenene. There are no chemical affinities between the present three Lejeuneaceae species.
- Toyota, Masao,Koyama, Hiroki,Asakawa, Yoshinori
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- Preparation of Magnetic Tubular Nanoreactors for Highly Efficient Catalysis
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We report an efficient and controllable route to prepare magnetic tubular nanoreactors composed of a mesoporous SiO2 shell with iron-noble metal nanoparticles inside. The key of this method is to design and fabricate Fe nanoparticles encapsulated in a mesoporous SiO2 shell. Making use of a galvanic replacement reaction between Fe and noble metal ions, all of the noble metal nanoparticles are loaded inside the mesoporous SiO2 shell, and thus nanoreactors are formed. Taking Pd as an example, the prepared Pd?Fe@meso-SiO2 tubular nanoreactor exhibits a high catalytic activity and excellent reusability for styrene hydrogenation under mild conditions. This study provides a facile route to fabricate magnetic nanoreactors with enhanced catalytic properties.
- Yang, Shuliang,Peng, Li,Cao, Changyan,Wei, Fang,Liu, Jian,Zhu, Ya-Nan,Liu, Chang,Wang, Xiaoshi,Song, Weiguo
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- Dehydrocoupling of dimethylamine-borane catalysed by rhenium complexes and its application in olefin transfer-hydrogenations
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Re(I) complexes are applied as catalysts for the dehydrocoupling of Me 2NH·BH3 and the transfer-hydrogenation of olefins. The Royal Society of Chemistry.
- Jiang, Yanfeng,Berke, Heinz
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- Synthesis of Ruthenium Complexes with a Nonspectator Si,O,P-Chelate Ligand: Interconversion between a Hydrido(η2-silane) Complex and a Silyl Complex Leading to Catalytic Alkene Hydrogenation
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A ruthenium complex bearing a new phosphine(η2-silane) chelate ligand connected by a xanthene backbone, Ru{κ4(Si,H,O,P)-tBu2xantSiP(H)}(H)Cl(PPh3) (2), was synthesized by a ligand substitution reaction of Ru(H)Cl(PPh3)3 with 2,7-di-tert-butyl-4-dimethylsilyl-5-diphenylphosphino-9,9-dimethylxanthene (1, tBu2xantSiP(H)). Dehydrogenation reaction of 2 with styrene, a hydrogen acceptor, gave a 16-electron phosphine(silyl) complex Ru{κ3(Si,O,P)-tBu2xantSiP}Cl(PPh3) (3) together with ethylbenzene. Complex 2 was reproduced quantitatively by exposure of 3 to H2 (1 atm) at room temperature. Thus, hydrido(η2-silane) complex 2 and silyl complex 3 are interconvertible through alkene hydrogenation (from 2 to 3) and dihydrogen addition to the Ru-Si bond (from 3 to 2) in which tBu2xantSiP functions as a nonspectator ligand by reversibly releasing and accommodating a hydrogen atom. Complex 2 was also found to catalyze hydrogenation of alkenes via this interconversion. (Chemical Presented).
- Komuro, Takashi,Arai, Takafumi,Kikuchi, Kei,Tobita, Hiromi
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- Nanoscale magnetic stirring bars for heterogeneous catalysis in microscopic systems
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Nanometer-sized magnetic stirring bars containing Pd nanoparticles (denoted as Fe3O4-NC-PZS-Pd) for heterogeneous catalysis in microscopic system were prepared through a facile two-step process. In the hydrogenation of styrene, Fe3O4-NC-PZS-Pd showed an activity similar to that of the commercial Pd/C catalyst, but much better stability. In microscopic catalytic systems, Fe3O4-NC-PZS-Pd can effectively stir the reaction solution within microdrops to accelerate mass transfer, and displays far better catalytic activity than the commercial Pd/C for the hydrogenation of methylene blue in an array of microdroplets. These results suggested that the Fe3O4-NC-PZS-Pd could be used as nanoscale stirring bars in nanoreactors.
- Yang, Shuliang,Cao, Changyan,Sun, Yongbin,Huang, Peipei,Wei, Fangfang,Song, Weiguo
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- Iridium(I)/N-Heterocyclic Carbene Hybrid Materials: Surface Stabilization of Low-Valent Iridium Species for High Catalytic Hydrogenation Performance
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An IrI(NHC)-based hybrid material was prepared using a methodology which allowed the precise positioning and isolation of the Ir centers along the pore channels of a silica framework. The full characterization of the material by solid-state NMR spectroscopy showed that the supported Ir sites were stabilized by the silica surface, as low-coordinated single-site complexes. The material is extremely efficient for the hydrogenation of functional alkenes. The catalytic performance (TOF and TON) is one to two orders of magnitude higher than those of their molecular Ir analogues, and could be related to the prevention of the bimolecular deactivation of Ir complexes observed under homogeneous conditions. Lending support: Homogeneous positioning of IrI complexes within the pore-channels of a silica framework stabilizes a low-valent IrI species and leads to drastically improved catalyst efficiency. Catalyst decomposition by formation of iridium-hydride clusters is prevented by the attachment to the support. Mes=2,4,6-trimethylphenyl.
- Romanenko, Iuliia,Gajan, David,Sayah, Reine,Crozet, Delphine,Jeanneau, Erwan,Lucas, Christine,Leroux, Lénaic,Veyre, Laurent,Lesage, Anne,Emsley, Lyndon,Lac?te, Emmanuel,Thieuleux, Chloé
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- Pd Nanoparticles Confined in the Porous Graphene-like Carbon Nanosheets for Olefin Hydrogenation
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As a novel type of defective graphene, porous graphene has been considered an excellent support material for metal clusters, as the interaction between defective carbon atoms surrounded with the metal nanoparticles (NPs) is very different from that on the ordinary supported catalyst. In this work, we reported a facile three-step method to confine the Pd NPs and grow the graphene-like carbon nanosheets (GLCs) in the same interlayer space of the layered silicate, generating embedded Pd NPs in the pores of porous GLCs in situ. The Pd@GLC nanocomposite exhibited not only high activity and stability than the common commercial Pd/C catalyst for the hydrogenation of olefins but also superior ability of resisting high temperature, which benefitted from the two-dimensional structure of layered GLCs, the confinement of Pd, and the increased edge and defect of the unsaturated carbon atoms in GLCs.
- Chen, Zhe,Wang, Weixue,Zhang, Yifei,Liang, Yu,Cui, Zhimin,Wang, Xiangke
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- Selective hydrogenation of substituted styrene to alkylbenzene catalyzed by Al2O3 nanoparticles
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A straightforward and suitable protocol is described for the conversion of substituted styrene to alkylbenzenes in the presence of Al2O3 nanoparticles (nano-Al2O3) as heterogeneous solid catalysts using N2H4·H2O as a hydrogen source under mild reaction conditions. A complete conversion of styrene is obtained using nano-Al2O3 as a heterogeneous catalyst. Besides, this catalyst system is also successfully applied to promote the broad range of styrene substituted derivatives to their respective alkylbenzene compounds in moderate to higher conversions. The reaction is discovered to be heterogeneous in nature and nano-Al2O3 can be reused for three runs with no diminish in its performance. Besides, the analyses of the fresh and three times reused nano-Al2O3 solid by various analytical techniques. Transmission electron microscope indicates that the structural features, surface morphology, and particle size endure unchanged throughout the reaction. Some of the significant features of this procedure are mild reaction conditions, price effectiveness of the catalyst (Pd or Pt free catalyst), high conversion, functional group endurance, absence of noble metals/additives, and reusability of the catalyst. The scope of the reaction procedure can be extended to various linear and cyclic alkenes. Graphical abstract: [Figure not available: see fulltext.]
- Kaleeswari, Kalairajan,Tamil Selvi, Arunachalam
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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.
- Antil, Neha,Kumar, Ajay,Akhtar, Naved,Begum, Wahida,Chauhan, Manav,Newar, Rajashree,Rawat, Manhar Singh,Manna, Kuntal
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supporting information
p. 1031 - 1040
(2022/01/19)
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- Ligand-enabled and magnesium-activated hydrogenation with earth-abundant cobalt catalysts
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Replacing expensive noble metals like Pt, Pd, Ir, Ru, and Rh with inexpensive earth-abundant metals like cobalt (Co) is attracting wider research interest in catalysis. Cobalt catalysts are now undergoing a renaissance in hydrogenation reactions. Herein, we describe a hydrogenation method for polycyclic aromatic hydrocarbons (PAHs) and olefins with a magnesium-activated earth-abundant Co catalyst. When diketimine was used as a ligand, simple and inexpensive metal salts of CoBr2in combination with magnesium showed high catalytic activity in the site-selective hydrogenation of challenging PAHs under mild conditions. Co-catalyzed hydrogenation enabled the reduction of two side aromatics of PAHs. A wide range of PAHs can be hydrogenated in a site-selective manner, which provides a cost-effective, clean, and selective strategy to prepare partially reduced polycyclic hydrocarbon motifs that are otherwise difficult to prepare by common methods. The use of well-defined diketimine-ligated Co complexes as precatalysts for selective hydrogenation of PAHs and olefins is also demonstrated.
- Han, Bo,Jiao, Hongmei,Ma, Haojie,Wang, Jijiang,Zhang, Miaomiao,Zhang, Yuqi
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p. 39934 - 39939
(2021/12/31)
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- CoPd Nanoalloys with Metal–Organic Framework as Template for Both N-Doped Carbon and Cobalt Precursor: Efficient and Robust Catalysts for Hydrogenation Reactions
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In this work, a series of metal–organic framework (MOF)-derived CoPd nanoalloys have been prepared. The nanocatalysts exhibited excellent activities in the hydrogenation of nitroarenes and alkenes in green solvent (ethanol/water) under mild conditions (H2 balloon, room temperature). Using ZIF-67 as template for both carbon matrix and cobalt precursor coating with a mesoporous SiO2 layer, the catalyst CoPd/NC@SiO2 was smoothly constructed. Catalytic results revealed a synergistic effect between Co and Pd components in the hydrogenation process due to the enhanced electron density. The mesoporous SiO2 shell effectively prevented the sintering of hollow carbon and metal NPs at high temperature, furnishing the well-dispersed nanoalloy catalysts and better catalytic performance. Moreover, the catalyst was durable and showed negligible activity decay in recycling and scale-up experiments, providing a mild and highly efficient way to access amines and arenes.
- Zhu, Jie,Xu, Deng,Ding, Lu-jia,Wang, Peng-cheng
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p. 2707 - 2716
(2021/01/21)
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- Boosting homogeneous chemoselective hydrogenation of olefins mediated by a bis(silylenyl)terphenyl-nickel(0) pre-catalyst
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The isolable chelating bis(N-heterocyclic silylenyl)-substituted terphenyl ligand [SiII(Terp)SiII] as well as its bis(phosphine) analogue [PIII(Terp)PIII] have been synthesised and fully characterised. Their reaction with Ni(cod)2(cod = cycloocta-1,5-diene) affords the corresponding 16 VE nickel(0) complexes with an intramolecularη2-arene coordination of Ni, [E(Terp)E]Ni(η2-arene) (E = PIII, SiII; arene = phenylene spacer). Due to a strong cooperativity of the Si and Ni sites in H2activation and H atom transfer, [SiII(Terp)SiII]Ni(η2-arene) mediates very effectively and chemoselectively the homogeneously catalysed hydrogenation of olefins bearing functional groups at 1 bar H2pressure and room temperature; in contrast, the bis(phosphine) analogous complex shows only poor activity. Catalytic and stoichiometric experiments revealed the important role of the η2-coordination of the Ni(0) site by the intramolecular phenylene with respect to the hydrogenation activity of [SiII(Terp)SiII]Ni(η2-arene). The mechanism has been established by kinetic measurements, including kinetic isotope effect (KIE) and Hammet-plot correlation. With this system, the currently highest performance of a homogeneous nickel-based hydrogenation catalyst of olefins (TON = 9800, TOF = 6800 h?1) could be realised.
- Lücke, Marcel-Philip,Yao, Shenglai,Driess, Matthias
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p. 2909 - 2915
(2021/03/14)
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- Catalytic Hydrogenation of Alkenes and Alkynes by a Cobalt Pincer Complex: Evidence of Roles for Both Co(I) and Co(II)
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The Co(I) complex, [Co(N2)(CyPNP)] (CyPNP = anion of 2,5-bis-(dicyclohexylphosphinomethyl)pyrrole), is active toward the catalytic hydrogenation of terminal alkenes and the semi-hydrogenation of internal alkynes under 2 bar of H2 (g) at room temperature. The products of alkyne semi-hydrogenation are a mixture of E- and Z-alkenes. By contrast, use of the related cobalt(I) precatalyst, [Co(PMe3)(CyPNP)], results in formation of exclusively Z-alkenes. A semi-stable Co(II) species, [CoH(CyPNP)], can also be generated by treatment of degassed solutions of [Co(N2)(CyPNP)] with H2. The CoII-hydride displays activity toward both alkene hydrogenation and isomerization, but its instability hampers implementation as a catalyst. Several species relevant to potential catalytic intermediates have been isolated and detected in solution. These compounds include alkene and alkyne adducts of Co(I) as well as a Co(III) dihydride species. Catalytic results with the compounds examined are most consistent with a process involving shuttling between Co(I) and Co(III) states. However, generation of small quantities of Co(II) during catalytic turnover appears to be responsible for the isomerization observed for alkyne semi-hydrogenation. The interplay of cobalt oxidation states within the same catalyst system is discussed in the context of mechanistic scenarios for catalytic hydrogenation.
- Alawisi, Hussah,Arman, Hadi D.,Tonzetich, Zachary J.
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p. 1062 - 1070
(2021/04/09)
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- Chemoselective Hydrogenation of Olefins Using a Nanostructured Nickel Catalyst
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The selective hydrogenation of functionalized olefins is of great importance in the chemical and pharmaceutical industry. Here, we report on a nanostructured nickel catalyst that enables the selective hydrogenation of purely aliphatic and functionalized olefins under mild conditions. The earth-abundant metal catalyst allows the selective hydrogenation of sterically protected olefins and further tolerates functional groups such as carbonyls, esters, ethers and nitriles. The characterization of our catalyst revealed the formation of surface oxidized metallic nickel nanoparticles stabilized by a N-doped carbon layer on the active carbon support.
- Klarner, Mara,Bieger, Sandra,Drechsler, Markus,Kempe, Rhett
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supporting information
p. 2157 - 2161
(2021/05/21)
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- Room temperature iron catalyzed transfer hydrogenation usingn-butanol and poly(methylhydrosiloxane)
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Reduction of carbon-carbon double bonds is reported using a three-coordinate iron(ii) β-diketiminate pre-catalyst. The reaction is believed to proceedviaa formal transfer hydrogenation using poly(methylhydrosiloxane), PMHS, as the hydride donor and a bio-alcohol as the proton source. The reaction proceeds well usingn-butanol and ethanol, withn-butanol being used for substrate scoping studies. Allyl arene substrates, styrenes and aliphatic substrates all undergo reduction at room temperature. Unfortunately, clean transfer of a deuterium atom usingd-alcohol does not take place, indicating a complex catalytic mechanism. However, changing the deuterium source tod-aniline gives close to complete regioselectivity for mono-deuteration of the terminal position of the double bond. Finally, we demonstrate that efficient dehydrocoupling of alcohol and PMHS can be undertaken using the same pre-catalyst, giving high yields of H2within 30 minutes at room temperature.
- Coles, Nathan T.,Linford-Wood, Thomas G.,Webster, Ruth L.
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supporting information
p. 2703 - 2709
(2021/04/21)
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- Copper(II)-Doped ZIF-8 as a Reusable and Size Selective Heterogeneous Catalyst for the Hydrogenation of Alkenes using Hydrazine Hydrate
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In recent years, synthesis of mixed-metal organic frameworks has received considerable attention due to their superior performance than with mono-metallic metal organic frameworks (MOFs). In the present manuscript, Cu2+ ions are doped within the framework of ZIF-8 (ZIF: Zeolitic Imidazolate Frameworks) to obtain Cu@ZIF-8 and is characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), UV-Visible diffuse reflectance spectra (DRS), scanning electron microscope (SEM) and transmission electron microcope (TEM) studies. The reaction conditions are optimized with styrene as a model substrate using Cu@ZIF-8 as a solid catalyst. Heterogeneity of the reaction is confirmed by leaching test and the solid is reusable for three recycles with no diminishing activity. Further, the structural integrity of Cu@ZIF-8 is also retained after hydrogenation of styrene as evidenced by powder X-ray diffraction. The size selective catalysis of Cu@ZIF-8 is demonstrated by comparing the activity of Cu2+ ions adsorbed over ZIF-8 solid (Cu/ZIF-8) in the hydrogenation of 1-hexene, 1-octene, cyclohexene, cyclooctene and t-stilbene. The catalytic results indicate that Cu/ZIF-8 shows superior activity than Cu@ZIF-8 for all these olefins due to the lack of diffusion to access the active sites (Cu2+). In contrast, Cu@ZIF-8 exhibits higher activity for those olefins with lower molecular dimensions (1-hexene, 1-octene) than the pores of ZIF-8 indicating the facile diffusion of these substrates inside the pores ZIF-8 while poor activity is observed with t-stilbene due to its larger molecular dimension than the pore apertures of ZIF-8. These catalytic data clearly establish the size selective hydrogenation of Cu@ZIF-8 due to the effective confinement provided by ZIF-8 framework and the presence of the active sites within the framework. Furthermore, this is the first report showing the size selective hydrogenation of olefins promoted by Cu@ZIF-8 (mixed-metal MOFs) compared to other noble metal nanoparticles (NPs) embedded over MOFs as catalysts.
- Nagarjun, Nagarathinam,Arthy, Kannan,Dhakshinamoorthy, Amarajothi
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p. 2108 - 2119
(2021/06/01)
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- Photo-Initiated Cobalt-Catalyzed Radical Olefin Hydrogenation
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Outer-sphere radical hydrogenation of olefins proceeds via stepwise hydrogen atom transfer (HAT) from transition metal hydride species to the substrate. Typical catalysts exhibit M?H bonds that are either too weak to efficiently activate H2 or too strong to reduce unactivated olefins. This contribution evaluates an alternative approach, that starts from a square-planar cobalt(II) hydride complex. Photoactivation results in Co?H bond homolysis. The three-coordinate cobalt(I) photoproduct binds H2 to give a dihydrogen complex, which is a strong hydrogen atom donor, enabling the stepwise hydrogenation of both styrenes and unactivated aliphatic olefins with H2 via HAT.
- Sang, Sier,Unruh, Tobias,Demeshko, Serhiy,Domenianni, Luis I.,van Leest, Nicolaas P.,Marquetand, Philipp,Schneck, Felix,Würtele, Christian,de Zwart, Felix J.,de Bruin, Bas,González, Leticia,V?hringer, Peter,Schneider, Sven
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p. 16978 - 16989
(2021/08/09)
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- Ambient Hydrogenation and Deuteration of Alkenes Using a Nanostructured Ni-Core–Shell Catalyst
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A general protocol for the selective hydrogenation and deuteration of a variety of alkenes is presented. Key to success for these reactions is the use of a specific nickel-graphitic shell-based core–shell-structured catalyst, which is conveniently prepared by impregnation and subsequent calcination of nickel nitrate on carbon at 450 °C under argon. Applying this nanostructured catalyst, both terminal and internal alkenes, which are of industrial and commercial importance, were selectively hydrogenated and deuterated at ambient conditions (room temperature, using 1 bar hydrogen or 1 bar deuterium), giving access to the corresponding alkanes and deuterium-labeled alkanes in good to excellent yields. The synthetic utility and practicability of this Ni-based hydrogenation protocol is demonstrated by gram-scale reactions as well as efficient catalyst recycling experiments.
- Beller, Matthias,Feng, Lu,Gao, Jie,Jackstell, Ralf,Jagadeesh, Rajenahally V.,Liu, Yuefeng,Ma, Rui
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supporting information
p. 18591 - 18598
(2021/06/28)
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- Metal-Organic Framework-Confined Single-Site Base-Metal Catalyst for Chemoselective Hydrodeoxygenation of Carbonyls and Alcohols
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Chemoselective deoxygenation of carbonyls and alcohols using hydrogen by heterogeneous base-metal catalysts is crucial for the sustainable production of fine chemicals and biofuels. We report an aluminum metal-organic framework (DUT-5) node support cobalt(II) hydride, which is a highly chemoselective and recyclable heterogeneous catalyst for deoxygenation of a range of aromatic and aliphatic ketones, aldehydes, and primary and secondary alcohols, including biomass-derived substrates under 1 bar H2. The single-site cobalt catalyst (DUT-5-CoH) was easily prepared by postsynthetic metalation of the secondary building units (SBUs) of DUT-5 with CoCl2 followed by the reaction of NaEt3BH. X-ray photoelectron spectroscopy and X-ray absorption near-edge spectroscopy (XANES) indicated the presence of CoII and AlIII centers in DUT-5-CoH and DUT-5-Co after catalysis. The coordination environment of the cobalt center of DUT-5-Co before and after catalysis was established by extended X-ray fine structure spectroscopy (EXAFS) and density functional theory. The kinetic and computational data suggest reversible carbonyl coordination to cobalt preceding the turnover-limiting step, which involves 1,2-insertion of the coordinated carbonyl into the cobalt-hydride bond. The unique coordination environment of the cobalt ion ligated by oxo-nodes within the porous framework and the rate independency on the pressure of H2 allow the deoxygenation reactions chemoselectively under ambient hydrogen pressure.
- Antil, Neha,Kumar, Ajay,Akhtar, Naved,Newar, Rajashree,Begum, Wahida,Manna, Kuntal
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supporting information
p. 9029 - 9039
(2021/06/28)
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- [Mes-B-TMP]+borinium cation initiated cyanosilylation and catalysed hydrosilylation of ketones and aldehydes
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Two aryl amino borinium cations derived from Cl(Mes)B-NR2(NR2= TMP, HMDS) faced divergent outcomes. As the HMDS-substituted one underwent methyl migration from silicon to boron transforming the putative borinium ion to a silylium ion, [Mes-B-TMP]+can initiate cyanosilylation and catalyse hydrosilylation of ketones and aldehydes.
- Chen, Po-Han,Chiu, Ching-Wen,Hsu, Ching-Pei,Liu, Yi-Hung,Tseng, Hsi-Ching
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supporting information
p. 13732 - 13735
(2021/12/27)
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- Substituent effects in dioxovanadium(V) schiff-base complexes: Tuning the outcomes of oxidation reactions
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Dioxovanadium(V) salicylaldehyde semicarbazone complexes with substituents on the ligand that span the range of electron donating (methoxy) to electron withdrawing (nitro) have been synthesized and characterized by NMR, IR, CV and EPR. The reactivity of these complexes toward the oxidation of styrene (as compared to the proteo complex and vanadyl acetylacetonate) has been studied in the presence of two different oxidants (hydrogen peroxide and tert-butyl hydrogen peroxide, TBHP). The complexes have been shown to exhibit different selectivity towards epoxidation versus oxidative cleavage based on the substitution of the ligand and the oxidant chosen. Epoxidation is favored with the methoxy substituted complex in the presence of hydrogen peroxide, while oxidative cleavage is the preferred reaction pathway for the nitro substituted complex with hydrogen peroxide. Conversions for these reaction are comparable to similar catalysts but with improved selectivity.
- McCaffrey, Vanessa P.,Conover, Olivia Q.,Bernard, Michael A.,Yarranton, Jonathan T.,Lessnau, Nicholas R.,Hempfling, Jordan P.
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- Eco-friendly preparation of ultrathin biomass-derived Ni3S2-doped carbon nanosheets for selective hydrogenolysis of lignin model compounds in the absence of hydrogen
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Lignin is an abundant source of aromatics, and the depolymerization of lignin provides significant potential for producing high-value chemicals. Selective hydrogenolysis of the C-O ether bond in lignin is an important strategy for the production of fuels and chemical feedstocks. In our study, catalytic hydrogenolysis of lignin model compounds (β-O-4, α-O-4 and 4-O-5 model compounds) over Ni3S2-CS catalysts was investigated. Hence, an array of 2D carbon nanostructure Ni3S2-CSs-X-Yderived catalysts were produced using different compositions at different temperatures (X= 0 mg, 0.2 mg, 0.4 mg, 0.6 mg, and 0.8 mg; Y = 600 °C, 700 °C, 800 °C, and 900 °C) were prepared and applied for hydrogenolysis of lignin model compounds and depolymerization of alkaline lignin. The highest conversion of lignin model compounds (β-O-4 model compound) was up to 100% and the yield of the obtained corresponding ethylbenzene and phenol could achieve 92% and 86%, respectively, over the optimal Ni3S2-CSs-0.4-700 catalyst in iPrOH at 260 °C without external H2. The 2D carbon nanostructure catalysts performed a good dispersion on the surface of the carbon nanosheets, which facilitated the cleavage of the lignin ether bonds. The physicochemical characterization studies were carried out by means of XRD, SEM, TEM, H2-TPR, NH3-TPD, Raman and XPS analyses. Based on the optimal reaction conditions (260 °C, 4 h, 2.0 MPa N2), various model compounds (β-O-4, α-O-4 and 4-O-5 model compounds) could also be effectively hydrotreated to produce the corresponding aromatic products. Furthermore, the optimal Ni3S2-CSs-0.4-700 catalyst could be carried out in the next five consecutive cycle experiments with a slight decrease in the transformation of lignin model compounds.
- Chen, Changzhou,Jiang, Jianchun,Li, Jing,Liu, Peng,Wu, Dichao,Xia, Haihong,Zhou, Minghao
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p. 3090 - 3103
(2021/05/07)
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- Controlling the Lewis Acidity and Polymerizing Effectively Prevent Frustrated Lewis Pairs from Deactivation in the Hydrogenation of Terminal Alkynes
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Two strategies were reported to prevent the deactivation of Frustrated Lewis pairs (FLPs) in the hydrogenation of terminal alkynes: reducing the Lewis acidity and polymerizing the Lewis acid. A polymeric Lewis acid (P-BPh3) with high stability was designed and synthesized. Excellent conversion (up to 99%) and selectivity can be achieved in the hydrogenation of terminal alkynes catalyzed by P-BPh3. This catalytic system works quite well for different substrates. In addition, the P-BPh3 can be easily recycled.
- Geng, Jiao,Hu, Xingbang,Liu, Qiang,Wu, Youting,Yang, Liu,Yao, Chenfei
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p. 3685 - 3690
(2021/05/31)
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- A regionally selective hydrogenation method for chromium-catalyzed thick cyclic aromatic hydrocarbons and olefins based on magnesium-activated ligands
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The present invention relates to the field of hydrogenation, specifically to a chromium-activated complex cyclic aromatic hydrocarbons and olefins promoted by magnesium-activated ligands regionally selective hydrogenation method, which is based on the in situ reduction strategy of magnesium, with biimides as ligands, CrCl2 as catalyst precursors, to construct an efficient low-costchromium hydrogenation system, under mild conditions, to achieve unilateral cyclic hydrogenation of thick ring aromatic hydrocarbons and high-selective hydrogenation of olefins. The system of the present invention is suitable for a variety of substrates of fused cyclic aromatic hydrocarbons, such as tetraphenyl, benzoanthracene, pentabenzo and alfalfa and the like. This provides a simple and efficient strategy and pathway for the synthesis of partially saturated thick cyclic aromatic hydrocarbon compounds.
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Paragraph 0020
(2022/01/10)
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- Environmentally responsible, safe, and chemoselective catalytic hydrogenation of olefins: ppm level Pd catalysis in recyclable water at room temperature
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Textbook catalytic hydrogenations are typically presented as reactions done in organic solvents and oftentimes under varying pressures of hydrogen using specialized equipment. Catalysts new and old are all used under similar conditions that no longer reflect the times. By definition, such reactions are both environmentally irresponsible and dangerous, especially at industrial scales. We now report on a general method for chemoselective and safe hydrogenation of olefins in water using ppm loadings of palladium from commercially available, inexpensive, and recyclable Pd/C, together with hydrogen gas utilized at 1 atmosphere. A variety of alkenes is amenable to reduction, including terminal, highly substituted internal, and variously conjugated arrays. In most cases, only 500 ppm of heterogeneous Pd/C is sufficient, enabled by micellar catalysis used in recyclable water at room temperature. Comparison with several newly introduced catalysts featuring base metals illustrates the superiority of chemistry in water.
- Gallou, Fabrice,Gao, Eugene S.,Lipshutz, Bruce H.,Takale, Balaram S.,Thakore, Ruchita R.
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supporting information
p. 6055 - 6061
(2020/10/14)
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- Generalized Chemoselective Transfer Hydrogenation/Hydrodeuteration
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A generalized, simple and efficient transfer hydrogenation of unsaturated bonds has been developed using HBPin and various proton reagents as hydrogen sources. The substrates, including alkenes, alkynes, aromatic heterocycles, aldehydes, ketones, imines, azo, nitro, epoxy and nitrile compounds, are all applied to this catalytic system. Various groups, which cannot survive under the Pd/C/H2 combination, are tolerated. The activity of the reactants was studied and the trends are as follows: styrene'diphenylmethanimine'benzaldehyde'azobenzene'nitrobenzene'quinoline'acetophenone'benzonitrile. Substrates bearing two or more different unsaturated bonds were also investigated and transfer hydrogenation occurred with excellent chemoselectivity. Nano-palladium catalyst in situ generated from Pd(OAc)2 and HBPin extremely improved the TH efficiency. Furthermore, chemoselective anti-Markovnikov hydrodeuteration of terminal aromatic olefins was achieved using D2O and HBPin via in situ HD generation and discrimination. (Figure presented.).
- Wang, Yong,Cao, Xinyi,Zhao, Leyao,Pi, Chao,Ji, Jingfei,Cui, Xiuling,Wu, Yangjie
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supporting information
p. 4119 - 4129
(2020/08/10)
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- Bioinspired Hollow Nanoreactor: Catalysts that Carry Gaseous Hydrogen for Enhanced Gas-Liquid-Solid Three-Phase Hydrogenation Reactions
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For conventional gas-liquid-solid three-phase heterogeneous hydrogenation reactions, hydrogen must be dissolved into the solvent to be a participating reactant, restricting the reaction rates. In this study, we demonstrate that gaseous hydrogen could be directly involved in gas-liquid-solid hydrogenation reactions through a bioinspired hollow nanoreactor with superaerophilic surface to enhance the reaction rates. We produce Pd@meso-SiO2 hollow nanoreactor, whose external surface is modified with perfluorodecyltriethoxysilane (PFDTS). In aqueous solutions, H2 gas could be spread quickly on the surface and stored in the cavity of hollow spheres, and participated in hydrogenation reactions, thereby enhancing H2 concentration around Pd nanoparticles. In hydrogenation of olefin reactions, such three-phase interface allows rapid and direct transportation of H2 bubbles to the surface of Pd nanoparticles rather than through diffusion of dissolved H2 in liquid phase, leading to an enhanced catalytic rate. This strategy is expected to be useful for designing and developing new catalytic systems of gas-liquid-solid three-phase reaction.
- Li, Zhaohua,Zhu, Zhongpeng,Cao, Changyan,Jiang, Lei,Song, Weiguo
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p. 459 - 462
(2019/12/24)
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- Hydrogenation of Alkenes Catalyzed by a Non-pincer Mn Complex
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Hydrogenation of substituted styrenes and unactivated aliphatic alkenes by molecular hydrogen has been achieved using a Mn catalyst with a non-pincer, picolylphosphine ligand. This is the second reported example of alkene hydrogenation catalyzed by a Mn complex. Mechanistic studies showed that a Mn hydride formed by H2 activation in the presence of a base is the catalytically active species. Based on experimental and DFT studies, H2 splitting is proposed to occur via a metal-ligand cooperative pathway involving deprotonation of the CH2 arm of the ligand, leading to pyridine dearomatization.
- Rahaman, S. M. Wahidur,Pandey, Dilip K.,Rivada-Wheelaghan, Orestes,Dubey, Abhishek,Fayzullin, Robert R.,Khusnutdinova, Julia R.
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p. 5912 - 5918
(2020/10/30)
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- An Electroreductive Approach to Radical Silylation via the Activation of Strong Si-Cl Bond
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The construction of C(sp3)-Si bonds is important in synthetic, medicinal, and materials chemistry. In this context, reactions mediated by silyl radicals have become increasingly attractive but methods for accessing these intermediates remain limited. We present a new strategy for silyl radical generation via electroreduction of readily available chlorosilanes. At highly biased potentials, electrochemistry grants access to silyl radicals through energetically uphill reductive cleavage of strong Si-Cl bonds. This strategy proved to be general in various alkene silylation reactions including disilylation, hydrosilylation, and allylic silylation under simple and transition-metal-free conditions.
- Lu, Lingxiang,Siu, Juno C.,Lai, Yihuan,Lin, Song
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supporting information
p. 21272 - 21278
(2020/12/21)
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- Bottleable NiCl2(dppe) as a catalyst for the Markovnikov-selective hydroboration of styrenes with bis(pinacolato)diboron
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Although transition-metal-catalysed hydroboration reactions of alkenes have been extensively studied, only three examples using Ni complexes have been reported so far. In this study, we have examined hydroboration reactions of alkenes using Ni/phosphine complexes. The commercially available and bottleable complex NiCl2(dppe) (dppe = 1,2-bis(diphenylphosphino)ethane) serves as a catalyst for the highly Markovnikov-selective hydroboration of styrene derivatives that affords the desired Markovnikov products in high yield.
- Hashimoto, Toru,Ishimaru, Toshiya,Shiota, Keisuke,Yamaguchi, Yoshitaka
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supporting information
p. 11701 - 11704
(2020/10/20)
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- Iterative Preparation of Platinum Nanoparticles in an Amphiphilic Polymer Matrix: Regulation of Catalytic Activity in Hydrogenation
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We demonstrate that iteration of the seeded preparation of platinum nanoparticles dispersed in an amphiphilic polystyrene-poly(ethylene glycol) resin (ARP-Pt) regulates their catalytic activity in the hydrogenation of aromatic compounds in water. The catalytic activity of the fifth generation of ARP-Pt [G5] prepared through four iterations of the seeded preparation was far superior to that of the initial ARP-Pt [G1] in the hydrogenation of aromatic compounds in water.
- Hamasaka, Go,Osako, Takao,Srisa, Jakkrit,Torii, Kaoru,Uozumi, Yasuhiro
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supporting information
p. 147 - 152
(2020/01/23)
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- Combined lignin defunctionalisation and synthesis gas formation by acceptorless dehydrogenative decarbonylation
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The valorization of lignin, consisting of various phenylpropanoids building blocks, is hampered by its highly functionalized nature. The absence of the γ-carbinol group in an unnatural C2 β-O-4 motif compared to the native lignin C3 β-O-4 motif provides great opportunities for developing new valorization routes. Thus efficient defunctionalisation approaches that transform the C3 β-O-4 motif into a simplified C2 β-O-4 motif are of interest. Based on a study with a series of model compounds, we established a feasible application of an iridium-catalysed acceptorless dehydrogenative decarbonylation method to efficiently remove the γ-carbinol group in a single step. This defunctionalisation generates valuable synthesis gas, which can be collected as a reaction product. By this direct catalytic transformation, a yield of ~70percent could be achieved for a C3 β-O-4 model compound that was protected from undergoing retro-aldol cleavage by alkoxylation of the benzylic secondary alcohol in the α position. A phenylcoumaran model compound containing a γ-carbinol group as well as a benzylic primary alcohol also proved to be reactive under dehydrogenative decarbonylation conditions, which can further contribute to the reduction of the structural complexity of lignin. Notably, the liberation of synthesis gas was confirmed and the signals for the defunctionalized C2 β-O-4 motif were observed when this dehydrogenative decarbonylation approach was applied on organosolv lignins. This selective defunctionalized lignin in conjunction with the formation of synthesis gas has the potential to enhance the development of profitable and sustainable biorefineries.
- Deuss, Peter. J.,Lahive, Ciaran W.,Zhang, Zhenlei,Zijlstra, Douwe S.
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p. 3791 - 3801
(2020/07/14)
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- Reductive Deamination with Hydrosilanes Catalyzed by B(C6F5)3
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The strong boron Lewis acid tris(pentafluorophenyl)borane B(C6F5)3 is known to catalyze the dehydrogenative coupling of certain amines and hydrosilanes at elevated temperatures. At higher temperature, the dehydrogenation pathway competes with cleavage of the C?N bond and defunctionalization is obtained. This can be turned into a useful methodology for the transition-metal-free reductive deamination of a broad range of amines as well as heterocumulenes such as an isocyanate and an isothiocyanate.
- Fang, Huaquan,Oestreich, Martin
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supporting information
p. 11394 - 11398
(2020/05/25)
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- Method for selective depolymerization of non-noble metal catalytic lignin
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The invention relates to a method for preparing an aromatic compound by catalyzing lignin to select depolymerization. The method comprises the following steps: taking an M(mpo)n complex (M=Fe, Co, n=3; M=Ni, n=2) as a catalyst, taking various beta-O-4 model molecules, organic lignin, lignosulfonate and alkali lignin as raw materials, and realizing high-selectivity catalytic cracking aryl-ether bands in a nitrogen atmosphere of 0.1 MPa at the temperature of 80 to 200 DEG C so as to obtain a phenolic compound. The conversion rate of the beta-O-4 model molecules reaches 100% at most, the productive rate of guaiacol reaches 95% at most, and the yield of styrene reaches 71% at most; when different lignins are used as raw materials for conversion, the yield of aromatic biological oil is 34% to 71%. The method has the characteristics of mild reaction conditions, no consumption of hydrogen source, high activity and selectivity, environment-friendly reaction process and the like.
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Paragraph 0037-0052
(2020/09/25)
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- Novel nickel nanoparticles stabilized by imidazolium-amidinate ligands for selective hydrogenation of alkynes
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The main challenge in the hydrogenation of alkynes into (E)- or (Z)-alkenes is to control the selective formation of the alkene, avoiding the over-reduction to the corresponding alkane. In addition, the preparation of recoverable and reusable catalysts is of high interest. In this work, we report novel nickel nanoparticles (Ni NPs) stabilized by three different imidazolium-amidinate ligands (ICy·(Ar)NCN; L1: Ar = p-tol, L2: Ar = p-anisyl and L3: Ar = p-ClC6H4). The as-prepared Ni NPs were fully characterized by (HR)-TEM, XRD, WASX, XPS and VSM. The nanocatalysts are active in the hydrogenation of various substrates. They present a remarkable selectivity in the hydrogenation of alkynes towards (Z)-alkenes, particularly in the hydrogenation of 3-hexyne into (Z)-3-hexene under mild reaction conditions (room temperature, 3% mol Ni and 1 bar H2). The catalytic behaviour of Ni NPs was influenced by the electron donor/acceptor groups (-Me, -OMe, -Cl) in the N-aryl substituents of the amidinate moiety of the ligands. Due to the magnetic character of the Ni NPs, recycling experiments were successfully performed after decantation in the presence of an external magnet, which allowed us to recover and reuse these catalysts at least 3 times preserving both activity and chemoselectivity.
- López-Vinasco, Angela M.,Martínez-Prieto, Luis M.,Asensio, Juan M.,Lecante, Pierre,Chaudret, Bruno,Cámpora, Juan,Van Leeuwen, Piet W. N. M.
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p. 342 - 350
(2020/02/04)
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- Efficient heterogeneous palladium-catalyzed transfer hydrogenolysis of benzylic alcohols by formic acid
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An efficient heterogeneous palladium-catalyzed transfer hydrogenolysis- of primary, secondary, and tertiary benzylic alcohols using formic acid as hydrogen source has been developed. The resulting hydrocarbon products were obtained in excellent yields. Moreover, the system exhibits high chemoselectivity, reacting only with the hydroxy groups in the presence of other functional groups, and excellent re-cyclability.
- Afewerki, Samson,Córdova, Armando,Palo-Nieto, Carlos
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supporting information
p. 2330 - 2336
(2020/08/19)
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- Copper-catalyzed formal transfer hydrogenation/deuteration of aryl alkynes
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A copper-catalyzed reduction of alkynes to alkanes and deuterated alkanes is described under transfer hydrogenation and transfer deuteration conditions. Commercially available alcohols and silanes are used interchangeably with their deuterated analogues as the hydrogen or deuterium sources. Transfer deuteration of terminal and internal aryl alkynes occurs with high levels of deuterium incorporation. Alkyne-containing complex natural product analogues undergo transfer hydrogenation and transfer deuteration selectively, in high yield. Mechanistic experiments support the reaction occurring through a cis-alkene intermediate and demonstrate the possibility for a regioselective alkyne transfer hydrodeuteration reaction.
- Sloane, Samantha E.,Reyes, Albert,Vang, Zoua Pa,Li, Lingzi,Behlow, Kiera T.,Clark, Joseph R.
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supporting information
p. 9139 - 9144
(2020/11/30)
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- Alkene Transfer Hydrogenation with Alkaline-Earth Metal Catalysts
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The alkene transfer hydrogenation (TH) of a variety of alkenes has been achieved with simple AeN′′2 catalysts [Ae=Ca, Sr, Ba; N′′=N(SiMe3)2] using 1,4-cyclohexadiene (1,4-CHD) as a H source. Reaction of 1,4-CHD with AeN′′2 gave benzene, N′′H, and the metal hydride species N′′AeH (or aggregates thereof), which is a catalyst for alkene hydrogenation. BaN′′2 is by far the most active catalyst. Hydrogenation of activated C=C bonds (e.g. styrene) proceeded at room temperature without polymer formation. Unactivated (isolated) C=C bonds (e.g. 1-hexene) needed a higher temperature (120 °C) but proceeded without double-bond isomerization. The ligands fully control the course of the catalytic reaction, which can be: 1) alkene TH, 2) 1,4-CHD dehydrogenation, or 3) alkene polymerization. DFT calculations support formation of a metal hydride species by deprotonation of 1,4-CHD followed by H transfer. Convenient access to larger quantities of BaN′′2, its high activity and selectivity, and the many advantages of TH make this a simple but attractive procedure for alkene hydrogenation.
- Bauer, Heiko,Thum, Katharina,Alonso, Mercedes,Fischer, Christian,Harder, Sjoerd
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supporting information
p. 4248 - 4253
(2019/03/07)
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- Visible-Light-Driven Photocatalytic Hydrogenation of Olefins Using Water as the H Source
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In this work, a highly efficient PCN-KCl (KCl-modified polymeric carbon nitride) nanosheet photocatalyst was synthesized with the assistance of KCl. The as-prepared PCN-KCl catalyst shows a more than 30-fold enhancement in the photocatalytic activity for H2 evolution from water compared to the pristine PCN. More importantly, when PCN-KCl was composited with a second catalyst (Pd nanoparticles), the simultaneous production and utilization of active H species for alkenes hydrogenation was achieved by visible light irradiation under ambient conditions.
- Fan, Xin,Yao, Yanling,Xu, Yangsen,Yu, Lei,Qiu, Chuntian
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p. 2596 - 2599
(2019/05/10)
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- Iridium-Catalyzed Alkene-Selective Transfer Hydrogenation with 1,4-Dioxane as Hydrogen Donor
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The iridium-catalyzed transfer hydrogenation of alkenes using 1,4-dioxane as a hydrogen donor is described. The use of 1,2-bis(dicyclohexylphosphino)ethane (DCyPE), featuring bulky and highly electron-donating properties, led to high catalytic activity. A polystyrene-cross-linking bisphosphine PS-DPPBz produced a reusable heterogeneous catalyst. These homogeneous and heterogeneous protocols achieved chemoselective transfer hydrogenation of alkenes over other potentially reducible functional groups such as carbonyl, nitro, cyano, and imino groups in the same molecule.
- Zhang, Deliang,Iwai, Tomohiro,Sawamura, Masaya
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supporting information
p. 5867 - 5872
(2019/08/26)
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- Combined Photoredox/Enzymatic C?H Benzylic Hydroxylations
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Chemical transformations that install heteroatoms into C?H bonds are of significant interest because they streamline the construction of value-added small molecules. Direct C?H oxyfunctionalization, or the one step conversion of a C?H bond to a C?O bond, could be a highly enabling transformation due to the prevalence of the resulting enantioenriched alcohols in pharmaceuticals and natural products,. Here we report a single-flask photoredox/enzymatic process for direct C?H hydroxylation that proceeds with broad reactivity, chemoselectivity and enantioselectivity. This unified strategy advances general photoredox and enzymatic catalysis synergy and enables chemoenzymatic processes for powerful and selective oxidative transformations.
- Betori, Rick C.,May, Catherine M.,Scheidt, Karl A.
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supporting information
p. 16490 - 16494
(2019/11/03)
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- Room Temperature Iron-Catalyzed Transfer Hydrogenation and Regioselective Deuteration of Carbon-Carbon Double Bonds
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An iron catalyst has been developed for the transfer hydrogenation of carbon-carbon multiple bonds. Using a well-defined β-diketiminate iron(II) precatalyst, a sacrificial amine and a borane, even simple, unactivated alkenes such as 1-hexene undergo hydrogenation within 1 h at room temperature. Tuning the reagent stoichiometry allows for semi- and complete hydrogenation of terminal alkynes. It is also possible to hydrogenate aminoalkenes and aminoalkynes without poisoning the catalyst through competitive amine ligation. Furthermore, by exploiting the separate protic and hydridic nature of the reagents, it is possible to regioselectively prepare monoisotopically labeled products. DFT calculations define a mechanism for the transfer hydrogenation of propene with nBuNH2 and HBpin that involves the initial formation of an iron(II)-hydride active species, 1,2-insertion of propene, and rate-limiting protonolysis of the resultant alkyl by the amine N-H bond. This mechanism is fully consistent with the selective deuteration studies, although the calculations also highlight alkene hydroboration and amine-borane dehydrocoupling as competitive processes. This was resolved by reassessing the nature of the active transfer hydrogenation agent: experimentally, a gel is observed in catalysis, and calculations suggest this can be formulated as an oligomeric species comprising H-bonded amine-borane adducts. Gel formation serves to reduce the effective concentrations of free HBpin and nBuNH2 and so disfavors both hydroboration and dehydrocoupling while allowing alkene migratory insertion (and hence transfer hydrogenation) to dominate.
- Espinal-Viguri, Maialen,Neale, Samuel E.,Coles, Nathan T.,MacGregor, Stuart A.,Webster, Ruth L.
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supporting information
p. 572 - 582
(2019/01/08)
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- Mechanistic Insight into Synergistic Catalysis of Olefin Hydrogenation by a Hetero-Dinuclear RuII-CoII Complex with Adjacent Reaction Sites
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We have designed and synthesized a hetero-dinuclear RuII-CoII complex with a dinucleating ligand inspired by hetero-dinuclear active sites of metalloenzymes. A synergistic effect between the adjacent RuII and CoII sites has been confirmed in catalytic olefin hydrogenation by the complex, exhibiting a much higher turnover number than those of mononuclear RuII or CoII complexes as the components. A RuII-hydrido species was detected by 1H NMR and electrospray ionization (ESI)-time-of-flight (TOF)-MS measurements as an intermediate to react with olefins, and CoII-bound methanol was suggested to act as a proton source.
- Hong, Dachao,Ohgomori, Yuji,Shimoyama, Yoshihiro,Kotani, Hiroaki,Ishizuka, Tomoya,Kon, Yoshihiro,Kojima, Takahiko
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supporting information
p. 11284 - 11288
(2019/09/03)
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- Monodisperse CuPt alloy nanoparticles assembled on reduced graphene oxide as catalysts in the transfer hydrogenation of various functional organic groups
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We present herein a new nanocatalyst, namely binary CuPt alloy nanoparticles (NPs) supported on reduced graphene oxide (CuPt-rGO), as a highly active heterogeneous catalyst for the transfer hydrogenation (TH) protocol that is demonstrated to be applicable over the reduction of various unsaturated organic compounds (olefins, aldehydes/ketones and nitroarenes) in aqueous solutions at room temperature. CuPt alloy NPs were synthesized by the co-reduction of metal (II) acetylacetonates by borane-tert-butylamine (BTB) complex in hot oleylamine (OAm) solution and then assembled on reduced graphene oxide (rGO) via ultrasonic-assisted liquid phase self-assembly method. The structure of yielded CuPt NPs and CuPt-rGO nanocatalyst were characterized by TEM, XRD and ICP-MS. The activity of Cu7Pt3-rGO nanocatalysts were then tested for the THs that were conducted in a commercially available high-pressure tube using water as sole solvent and ammonia borane as a hydrogen donor at room temperature. The presented catalytic TH protocol was successfully applied over nitroarenes, olefines and aldehydes/ketones, and all the tested compounds were converted to corresponding reduction products with the yields reaching up to 99% under ambient conditions. Moreover, the Cu7Pt3-rGO nanocatalyst was also reusable in the TH by providing 99% yield after five consecutive runs in TH of nitrobenzene as an example.
- Ganjehyan, Khadijeh,Ni?anc?, Bilal,Sevim, Melike,Da?tan, Arif,Metin, ?nder
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- Square Planar Cobalt(II) Hydride versus T-Shaped Cobalt(I): Structural Characterization and Dihydrogen Activation with PNP-Cobalt Pincer Complexes
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The carbazole-based pincer ligand R(CbzPNP)H (R = iPr, tBu) has been used for the synthesis and characterization of various low- and high-spin cobalt complexes. Upon treatment of the high-spin complexes R(CbzPNP)CoCl (2R-CoIICl) with NaHBEt3, the selective formation of cobalt(II) hydride 3iPr-CoIIH and T-shaped cobalt(I) complex 4tBu-CoI was observed, depending on the substituents at the phosphorus atoms. For an unambiguous characterization of the reaction products, a density functional theory (DFT) supported paramagnetic NMR analysis was carried out, which established the electron configuration and the oxidation states of the metal atoms, thus demonstrating the significant impact of ligand substitution on the outcome of the reaction. A distinct one-electron reactivity was found for 4tBu-CoI in the dehalogenation of tBuCl and cleavage of PhSSPh. On the other hand, the CoI species displayed two-electron redox behavior in the oxidative addition of dihydrogen. The resulting dihydride complex 6tBu-CoIII(H)2 was found to display sluggish reactivity toward alkenes, whereas the cobalt(II) hydride 3iPr-CoIIH was successfully employed in the catalytic hydrogenation of unhindered alkenes. The stoichiometric hydrogenolysis of 8iPr-CoIIBn at elevated pressure (10 bar) led to a rapid cleavage of the Co-C bond to yield hydride complex 3iPr-CoIIH. On the other hand, treatment of 2iPr-CoIICl with phenethylmagnesium chloride directly resulted in the formation of 3iPr-CoIIH, indicating facile β-H elimination of the alkene insertion product (reversibly) generated in the catalytic hydrogenation. On the basis of these observations, a mechanistic pathway involving a key σ-bond metathesis step of the CoII-alkyl species is proposed.
- Merz, Lukas S.,Blasius, Clemens K.,Wadepohl, Hubert,Gade, Lutz H.
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p. 6102 - 6113
(2019/05/16)
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- Cu3(BTC)2 metal organic framework as heterogeneous solid catalyst for the reduction of styrenes with silane as reducing agent
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In this work, a well known metal organic framework, Cu3(BTC)2 (BTC: 1,3,5-benzenetricarboxylate) is reported as a heterogeneous solid catalyst for the reduction of styrene and its derivatives with silane as a reducing agent. Under these reaction conditions, a quantitative conversion of styrene is achieved with very high selectivity to ethylbenzene. A control experiment with pyridine as a catalyst poison revealed that Cu2+ located within the framework plays a crucial role in promoting this reduction. Further, hot-filtration test indicated the absence of metal leaching and Cu3(BTC)2 is used four times with no significant decay in its activity. In addition, the four times used Cu3(BTC)2 was compared with the fresh solid by powder X-ray diffraction, FT-IR, UV–Visible diffuse reflectance spectra, scanning electron microscope and electron paramagnetic resonance methods and observing no significant changes in its structural integrity, crystallinity and morphology. This process is extended for other styrene derivatives to their respective reduced products.
- Anbu, Nagaraj,Dhakshinamoorthy, Amarajothi
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- Selective hydrothermal reductions using geomimicry
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Reduction of carbon-carbon π-bonds has been demonstrated using iron powder as the reductant and simple powdered nickel as the catalyst in water as the solvent at 250 °C and the saturated water vapor pressure, 40 bars. Stereochemical, kinetic and electronic probes of the mechanism suggest reaction via a conventional Horiuti-Polyani process for hydrogenation at the nickel metal surface. Selective reduction of carbon-carbon π-bonds is observed in the presence of other functional groups. The reactions use benign and Earth-abundant reagents that are at low depletion risk and take place in water as the only solvent under conditions that are characteristic of many geochemical processes.
- Bockisch, Christiana,Lorance, Edward D.,Shaver, Garrett,Williams, Lynda B.,Hartnett, Hilairy E.,Shock, Everett L.,Gould, Ian R.
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p. 4159 - 4168
(2019/08/07)
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- Cleavage of lignin C-O bonds over a heterogeneous rhenium catalyst through hydrogen transfer reactions
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Hydrogenolysis is one of the most popular strategies applied in the depolymerization of lignin for the production of aromatic chemicals. Currently, this strategy is mainly conducted under high hydrogen pressure, which can pose safety risks and is not sustainable and economical. Herein, we reported that heterogeneous rhenium oxide supported on active carbon (ReOx/AC) exhibited excellent activity in the selective cleavage of lignin C-O bonds in isopropanol. High yields of monophenols (up to 99.0%) from various lignin model compounds and aromatic liquid oils (>50%) from lignin feedstock were obtained under mild conditions in the absence of H2. The characterization of the catalyst by X-ray absorption fine structure, X-ray photoelectron spectroscopy and H2-temperature-programed reduction suggested that the activity of ReOx/AC could be attributed to the presence of ReIV-VI. The interaction between the surface oxygen groups of the active carbon and rhenium oxide could also play an important role in the cleavage of the C-O bonds. Notably, an ReOx/AC-catalyzed C-O bond cleavage pathway beyond a typical deoxydehydration mechanism was disclosed. More importantly, 2D-HSQC-NMR and GPC characterizations showed that ReOx/AC exhibited high activity not only in β-O-4 cleavage, but also in the deconstruction of more resistant β-5 and β-β linkages in lignin without destroying the aromatic ring. This study paves the way for the development of rhenium-based catalysts for the controlled reductive valorization of realistic lignin materials through a hydrogen transfer pathway.
- Zhang, Bo,Qi, Zaojuan,Li, Xinxin,Ji, Jianwei,Zhang, Leilei,Wang, Hua,Liu, Xiaoyan,Li, Changzhi
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supporting information
p. 5556 - 5564
(2019/10/28)
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- Light-enabled metal-free pinacol coupling by hydrazine
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Efficient carbon-carbon bond formation is of great importance in modern organic synthetic chemistry. The pinacol coupling discovered over a century ago is still one of the most efficient coupling reactions to build the C-C bond in one step. However, traditional pinacol coupling often requires over-stoichiometric amounts of active metals as reductants, causing long-lasting metal waste issues and sustainability concerns. A great scientific challenge is to design a metal-free approach to the pinacol coupling reaction. Herein, we describe a light-driven pinacol coupling protocol without use of any metals, but with N2H4, used as a clean non-metallic hydrogen-atom-transfer (HAT) reductant. In this transformation, only traceless non-toxic N2 and H2 gases were produced as by-products with a relatively broad aromatic ketone scope and good functional group tolerance. A combined experimental and computational investigation of the mechanism suggests that this novel pinacol coupling reaction proceeds via a HAT process between photo-excited ketone and N2H4, instead of the common single-electron-transfer (SET) process for metal reductants.
- Qiu, Zihang,Pham, Hanh D. M.,Li, Jianbin,Li, Chen-Chen,Castillo-Pazos, Durbis J.,Khaliullin, Rustam Z.,Li, Chao-Jun
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p. 10937 - 10943
(2019/12/23)
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- Mild and efficient rhodium-catalyzed deoxygenation of ketones to alkanes
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A new and simple method for the deoxygenation of ketones to alkanes is presented. Most substrates are reduced under mild conditions by triethylsilane in the presence of catalytic amounts of [Rh(μ-Cl)(CO)2]2. This system selectively provides the methylene hydrocarbons in good to excellent yields starting from acetophenones and diaryl ketones. A rapid examination of the reaction pathway suggests that the ketone is first converted into an alcohol, which then undergoes hydrogenolysis to give the alkane.
- Argouarch, Gilles
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supporting information
p. 11041 - 11044
(2019/07/31)
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- New photocatalytic fixed-point deuteration method for carbon-carbon unsaturated bonds
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The invention relates to a new photocatalytic fixed-point deuteration method for carbon-carbon unsaturated bonds. The method is characterized in that an olefin or alkyne compound and a deuterium source undergoes a deuteration reaction under the catalysis of a light source and a photocatalyst to obtain a deuterated product, wherein the deuterium source is deuterated water, deuterated alcohol or deuterated acid, and the reaction temperature is between room temperature and 80 DEG C. The fixed-point deuteration reaction of the olefin or alkyne compound is realized under the photocatalysis action of the photocatalyst with environmentally-friendly and cheap deuterated water or a deuteration reagent as a deuterium source to substitute deuterium gas. Compared with traditional deuteration reactions, the method has a higher selectivity, milder reaction conditions and higher economical suitability, and is suitable for large-scale deuterated chemical substance production.
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Paragraph 0055; 0057; 0058; 0061
(2019/01/21)
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- MICROCAPSULES AND PROCESSES FOR THEIR PREPARATION
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The present invention provides microcapsules encapsulating hydrophilic or hydrophobic active agents in an inorganic shell, processes for their preparation and compositions comprising them.
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Page/Page column 43-45
(2019/06/11)
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- COBALT COMPLEXES, PROCESS FOR PREPARATION AND USE THEREOF
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The present invention discloses a cobalt compound of formula (I), a process for the preparation and use thereof. The present invention further relates to a pharmaceutical composition and a method inhibition of Tau Aggregation in a subject in need thereof using compound of formula (I).
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Page/Page column 17; 18
(2019/01/06)
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- A Co2B Mediated NaBH4 Reduction Protocol Applicable to a Selection of Functional Groups in Organic Synthesis
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A high-yielding and high-rate reduction method that operates with alkenes, alkynes, azides, nitriles, and nitroarenes was developed and optimized. The method makes use of sodium borohydride reduction of CoSO4 under release of hydrogen along with the formation of Co2B as a nanoparticle material. The produced Co2B activates the various functional groups for hydride reduction. The protocol was proven to operate with an assortment of functional groups to provide good to excellent yields. Furthermore, the reduction method was successfully adapted, implemented, and developed for a continuous flow approach using the multi-jet oscillating disk (MJOD) flow reactor platform at atmospheric pressure.
- Lundevall, Frida Johanne,Elumalai, Vijayaragavan,Drageset, Audun,Totland, Christian,Bj?rsvik, Hans-René
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supporting information
p. 3416 - 3425
(2018/07/29)
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- Phosphine-free cobalt pincer complex catalyzed: Z -selective semi-hydrogenation of unbiased alkynes
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Herein, we report a novel, molecularly defined NNN-type cobalt pincer complex catalyzed transfer semi-hydrogenation of unbiased alkynes to Z-selective alkenes. This unified process is highly stereo- and chemo-selective and exhibits a broad scope as well as wide functional group tolerance. Ammonia-borane (AB), a bench-stable substrate with high gravimetric hydrogen capacity, was used as a safe and practical transfer hydrogenating source.
- Landge, Vinod G.,Pitchaimani, Jayaraman,Midya, Siba P.,Subaramanian, Murugan,Madhu, Vedichi,Balaraman, Ekambaram
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p. 428 - 433
(2018/02/07)
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- Substituted Hantzsch Esters as Versatile Radical Reservoirs in Photoredox Reactions
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Substituted Hantzsch esters can act as radical reservoirs in photoredox reactions, steadily releasing a carbon radical and a hydrogen atom radical in the absence of an additional electron acceptor. We propose that radical release by substituted Hantzsch esters occurs via a mechanism involving an internal redox cycle. Cinnamidecinnamides, styrenes, α,β-unsaturated acids, and diarylethenes could be alkylated smoothly with these reagents. (Figure presented.).
- Gu, Fangjun,Huang, Wenhao,Liu, Xu,Chen, Wenxin,Cheng, Xu
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supporting information
p. 925 - 931
(2018/01/04)
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