- Mechanistic study of the rhodium(I)-catalyzed hydroboration reaction
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The objective of this study has been to elucidate the mechanism of the rhodium(I)-catalyzed hydroboration process. Evidence that the reaction proceeds through a multistep pathway analogous to that of transition metal catalyzed olefin hydrogenation is presented. Deuterium labeling experiments reveal reversible elementary steps in the catalytic cycle; the level of reversibility is found to be substrate-dependent. Catalyst contamination through contact with adventitious oxidants has a pronounced effect on the reaction and appears to be the source of reported disparities involving product regioselection and deuterium labeling experiments.
- Evans, David A.,Fu, Gregory C.,Anderson, Benjamin A.
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Read Online
- Phenylthioacetylene as a Source of Stereodefined Trisubstituted Alkenes
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A 1,2-metal-ate rearrangement leads to stereodefined trisubstituted alkenes, as single isomers, in an easy and straightforward one-pot procedure.
- Creton, Isabelle,Marek, Ilane,Brasseur, Denis,Jestin, Jean-Luc,Normant, Jean-F.
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Read Online
- Dinuclear cobalt complex-catalyzed stereodivergent semireduction of alkynes: Switchable selectivities controlled by H2O
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Catalytic semireduction of internal alkynes to alkenes is very important for organic synthesis. Although great success has been achieved in this area, switchable Z/E stereoselectivity based on a single catalyst for the semireduction of internal alkynes is a longstanding challenge due to the multichemo- and stereoselectivity, especially based on less-expensive earth-abundant metals. Herein, we describe a switchable semireduction of alkynes to (Z)- or (E)-alkenes catalyzed by a dinuclear cobalt complex supported by a macrocyclic bis pyridyl diimine (PDI) ligand. It was found that cis-reduction of the alkyne occurs first and the Z-E alkene stereoisomerization process is formally controlled by the amount of H2O, since the concentration of H2O may influence the catalytic activity of the catalyst for isomerization. Therefore, this protocol provides a facile way to switch to either the (Z)- or (E)-olefin isomer in a single transformation by adjusting the amount of water.
- Chen, Ke,Zhu, Hongdan,Li, Yuling,Peng, Qian,Guo, Yinlong,Wang, Xiaoming
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p. 13696 - 13705
(2021/11/16)
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- A simple and efficientin situgenerated copper nanocatalyst for stereoselective semihydrogenation of alkynes
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Development of a simple, effective, and practical method for (Z)-selective semihydrogenation of alkynes has been considered necessary for easy-to-access applications at organic laboratory scales. Herein, (Z)-selective semihydrogenation of alkynes was achieved using a copper nanocatalyst which was generatedin situsimply by adding ammonia borane to an ethanol solution of copper sulfate. Different types of alkynes including aryl-aryl, aryl-alkyl, and aliphatic alkynes were selectively reduced to (Z)-alkenes affording up to 99% isolated yield. The semihydrogenation of terminal alkynes to alkenes and gram-scale applications were also reported. In addition to eliminating catalyst preparation, the proposed approach is simple and practical and serves as a suitable alternative method to the conventional Lindlar catalyst.
- Park, Byoung Yong,Lim, Taeho,Han, Min Su
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supporting information
p. 6891 - 6894
(2021/07/19)
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- SYNTHESIS OF PHEROMONE DERIVATIVES VIA Z-SELECTIVE OLEFIN METATHESIS
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Disclosed herein are methods for synthesizing fatty olefin metathesis products of high Z-isomeric purity from olefin feedstocks of low Z-isomeric purity. The methods include contacting a contacting an olefin metathesis reaction partner, such as acylated alkenol or an alkenal acetal, with an internal olefin in the presence of a Z-selective metathesis catalyst to form the fatty olefin metathesis product. In various embodiments, the fatty olefin metathesis products are insect pheromones. Pheromone compositions and methods of using them are also described.
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Paragraph 0222; 0232
(2021/12/28)
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- Enantiopure 2,9-Dideuterodecane – Preparation and Proof of Enantiopurity
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(R,R)- and (S,S)-(2,9-2H2)-n-Decane were prepared regio- and stereospecifically in 25–26 % yield over five steps from commercially available enantiopure (R)- and (S)-propylene oxide, respectively. The synthetic procedure involved nucleophilic displacement of (R)- and (S)-4-toluenesulfonic acid 1-methyl-4-pentenyl ester with LiAlD4 to furnish the respective (5-2H)-1-hexenes. Subsequent olefin metathesis and reduction of the double bond furnished the title compounds. The optical purity of (R,R)- and (S,S)-(2,9-2H2)-n-decane could not be determined by chromatography or polarimetry. Therefore, (R,R)- and (R,S)-(5-2H)-3-hydroxy-2-hexanone were prepared from their respective hexenes by Wacker oxidation, followed by enantioselective α-hydroxylation. The enantiopurity could then be determined by NMR spectroscopy because the stereospecifically deuterated hydroxyketones showed separated signals for the subterminal carbon atom (C-5) in the 13C NMR spectrum.
- Christoffers, Jens,Eru?ar, Gülsera,Fsadni, Miriam H.,Golding, Bernard T.,Mitschke, Nico,Roberts, Amy R.,Sadeghi, Majid M.,Wilkes, Heinz
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p. 3854 - 3863
(2021/08/24)
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- Cationic Tungsten Imido Alkylidene N-Heterocyclic Carbene Complexes That Contain Bulky Ligands
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Neutral and cationic tungsten imido alkylidene complexes of the general formulas W(NtBu)(CHR1)(OR2)Cl(NHC), W(N-2,6-bis(2,4,6-tri-iPr-C6H4)phenyl)(CHR1)Cl2(NHC), [W(NtBu)(CHR1)(OR2)(NHC)][B(ArF)4] and [W(N-2,6-bis(2,4,6-tri-iPr-C6H4)phenyl)(CHR1)Cl(NHC)][B(ArF)4] (R1= CMe3, CMe2Ph; R2= sterically demanding alkoxide; B(ArF)4= tetrakis(3,5-(CF3)2-C6H3)borate; NHC = N-heterocyclic carbene) were prepared. Two electronically different NHCs, namely 1,3-dimethylimidazol-2-ylidene (IMe) and 1,3-dimethyl-4,5-dichloroimidazol-2-ylidene (IMeCl), as well as a variety of terphenolates and a chiral biphenolate were employed.Z-selective homometathesis (HM) of unfunctionalized olefins was achieved with a selectivity of up to 90% and decent turnover numbers (TON) of up to 480 in the HM of 1-dodecene. Additionally, the reactivity of the cationic tungstentert-butylimido complexes in the reaction with vinyltrimethylsilane and ethylene was investigated, which yielded the corresponding silyl-alkylidene complex and, for the first time, a fully characterized cationic tungsten(IV) NHC ethylene complex.
- Buchmeiser, Michael R.,Frey, Wolfgang,Musso, Janis V.,Schowner, Roman
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p. 3145 - 3157
(2021/09/30)
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- Synthesis and Immobilization of Metal Nanoparticles Using Photoactive Polymer-Decorated Zeolite L Crystals and Their Application in Catalysis
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A facile route to generate Au and Pd nanoparticles (NPs) on zeolite L crystals decorated with photoactive polymer brushes is described. The polymers used in this approach serve a dual role: Upon irradiation with UV light, they release highly reducing ketyl radicals in a Norrish-Type-I reaction. These radicals serve as one electron donors to reduce metal salts to the corresponding metal NPs. At the same time the polymer shell stabilizes the in situ generated metal NPs. It is shown that the zeolite-polymer-NP composites can be used as recyclable catalysts for the oxidation of benzylic alcohols to aldehydes and the stereoselective semihydrogenation of alkynes to Z-alkenes. The polymer shell in these hybrid catalysts protects the NPs from aggregation and also alters their catalytic properties. (Figure presented.).
- Wissing, Maren,Niehues, Maximilian,Ravoo, Bart Jan,Studer, Armido
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supporting information
p. 2245 - 2253
(2020/05/05)
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- Palladium nanoparticles stabilized by novel choline-based ionic liquids in glycerol applied in hydrogenation reactions
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Palladium nanoparticles stabilized by choline-based ionic liquids in glycerol were prepared from Pd(II) precursors by simply heating at 80 °C under argon; in this process, the water present in the ionic liquid was found to be responsible for the reduction of Pd(II) into zero-valent palladium species. Palladium nanoparticles were fully characterized in both liquid phase and solid state. The as-prepared metal nanoparticles exhibited remarkable catalytic activity in hydrogenation processes for a significant variety of functional groups (alkenes, alkynes, nitro derivatives, benzaldehydes, aromatic ketones).
- Garg, Garima,Foltran, Stéphanie,Favier, Isabelle,Pla, Daniel,Medina-González, Yaocihuatl,Gómez, Montserrat
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- Aqueous phase semihydrogenation of alkynes over Ni-Fe bimetallic catalysts
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Bimetallic Ni-Fe catalysts (Ni/Fe, 1?:?1, 1?:?3, and 3?:?1) are synthesized and explored for their catalytic activity in semihydrogenation of internal alkynes using H2 gas in water-ethanol solution. Our findings revealed that over the Ni1Fe3 catalyst a high diastereoselectivity for Z-alkenes with a high conversion for a wide range of internal alkynes can be achieved at moderate reaction temperature (40 °C). Notably, the selectivity for the Z-alkenes is enhanced in the presence of n-butyl amine as an additive. Deuterium labeling experiments evidenced that H2 gas becomes dissociated homolytically over the catalyst surface to hydrogenate alkynes to alkenes. Synthesized catalysts were successfully characterized by HR-TEM, SEM, XPS, EDS, P-XRD and H2-TPD.
- Awasthi, Mahendra K.,Barman, Sudipta Roy,Behrens, Silke,Rai, Rohit K.,Singh, Sanjay K.,Singh, Vipin K.
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p. 4968 - 4980
(2020/08/19)
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- Activation of Low-Valent, Multiply M-M Bonded Group VI Dimers toward Catalytic Olefin Metathesis via Surface Organometallic Chemistry
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Olefin metathesis is a broadly employed reaction with applications that range from fine chemicals to materials and petrochemicals. The design and investigation of olefin metathesis catalysts have been ongoing for over half a century, with advancements made in terms of activity, stability, and selectivity. Immobilization of organometallic complexes onto solid supports such as silica or alumina is a promising strategy for catalyst heterogenization, often resulting in increased activity and stability. Consequently, a broad range of early transition metal catalysts bearing alkyl, oxide/alkoxide, and amide ligands have been grafted onto silica and their reactivities investigated. Herein, we report a series of silica-supported tungsten and molybdenum dimers (X3MMX3, where M = W and Mo; X = neopentyl, tert-butoxide, and dimethyl amide) and their reactivities toward catalytic olefin metathesis. Dynamic nuclear polarization (DNP)-enhanced solid-state nuclear magnetic resonance (SSNMR), diffuse reflectance infrared Fourier transform (DRIFT), UV resonance Raman, and X-ray absorption (XAS) spectroscopies suggest that upon heterogenization the dimers bind to the surface in a monopodal fashion, with the MM triple bond remaining intact. These structural assignments were further corroborated by density functional theory (DFT) calculations. While the homogeneous dimer counterparts are inert, the supported low-valent alkyl W and Mo dimers become active for the disproportionative self-metathesis of propylene to ethylene and butenes and 4-nonene to 4-octene and 5-decene under mild conditions. The lack of activity observed for the free and supported tert-butoxide and dimethyl amide dimers likely suggests that the neopentyl groups are necessary for the formation of a putative alkylidene active species. The difference in reactivity between the free and supported dimers could be explained either by the lowering of the activation barrier of the complex through the electronic effects of the surface or by site isolation of catalytically relevant reactive intermediates.
- Celik, Gokhan,Chapovetsky, Alon,Delferro, Massimiliano,Dogan, Fulya,Ferrandon, Magali S.,Kaphan, David M.,Khetrapal, Navneet,Kim, Hacksung,Kropf, A. Jeremy,Langeslay, Ryan R.,Perras, Frédéric A.,Pruski, Marek,Sattelberger, Alfred P.,Sharma, Prachi,Wegener, Evan C.,Wen, Jianguo,White, Jacob
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supporting information
p. 1035 - 1045
(2020/05/04)
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- Silica-supported Z-selective Ru olefin metathesis catalysts
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Recently reported thiolate-coordinated ruthenium alkylidene complexes show promise in Z-selective and stereoretentive olefin metathesis reactions. Herein we describe the immobilization of three Ru complexes containing a bulky aryl thiolate on mesostructured silica via surface organometallic chemistry. The applied methodology gives isolated catalytic sites homogeneously distributed on the silica surface. The catalytic results with two model substrates show comparable Z-selectivities to those of the homogeneous counterparts.
- Renom-Carrasco, Marc,Mania, Philipp,Sayah, Reine,Veyre, Laurent,Occhipinti, Giovanni,Jensen, Vidar R.,Thieuleux, Chloé
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- Molybdenum Benzylidyne Complexes for Olefin Metathesis Reactions
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The molybdenum benzylidynes [ArCMo(OC(CF3)2CH3)3(1,2-dimethoxyethane)], where Ar = Ph (2a), p-(OCH3)C6H4 (2b), p-(CF3)C6H4 (2c), p-(NO2)C6H4 (2d), or 4-(NO2)-3-(CF3)C6H3 (2e), and [p-(NO2)C6H4CMo(OC(CF3)2CH3)3] (2f) catalyze the ring-closing metathesis (RCM) reaction of diallyl N-tosylamide (3) to produce 1-tosyl-2,5-dihydro-1H-pyrrole (4) and ethylene. The scope of RCM catalytic activity of 2e, cross-metathesis of 1-hexene, and ring-opening metathesis polymerization of cyclooctene were explored. The X-ray crystal structure of 2e was determined. Variable-temperature 1H NMR spectra revealed the formation of intermediates during the reaction of 3 with 2f and the reforming of 2f after completion of the reaction. The use of 13C-labeled Mo benzylidyne did not show transfer of the carbon atom next to Mo to any of the products.
- Acosta, Carlos M.,Bukhryakov, Konstantin V.,Chuprun, Sergey,Mathivathanan, Logesh
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supporting information
p. 3453 - 3457
(2020/11/02)
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- Gram-Scale, Cheap, and Eco-Friendly Iron-Catalyzed Cross-Coupling between Alkyl Grignard Reagents and Alkenyl or Aryl Halides
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A new robust methodology for gram-scale iron-catalyzed cross-coupling between alkyl Grignard reagents and alkenyl or aryl halides is developed. This method does not require toxic additives such as NMP or expensive ligands. Its efficiency relies on the use of simple alkoxide magnesium salts as additives. On the basis of these results, a new procedure for one-pot synthesis of substituted benzamides from chloroesters is also proposed.
- Cahiez, Gérard,Lefèvre, Guillaume,Moyeux, Alban,Guerret, Olivier,Gayon, Eric,Guillonneau, Lo?c,Lefèvre, Nicolas,Gu, Qinzhuo,Zhou, Edouard
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supporting information
p. 2679 - 2683
(2019/04/30)
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- Normal Alpha Olefin Synthesis Using Dehydroformylation or Dehydroxymethylation
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The present invention discloses processes for producing normal alpha olefins, such as 1-hexene, 1-octene, 1-decene, and 1-dodecene in a multistep synthesis scheme from another normal alpha olefin. Also disclosed are reactions for converting aldehydes, primary alcohols, and terminal vicinal diols into normal alpha olefins.
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Paragraph 0139; 0140; 0141
(2019/09/06)
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- Supported Ru olefin metathesis catalysts: Via a thiolate tether
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Thiolate-coordinated ruthenium alkylidene complexes can give high Z-selectivity and stereoretentivity in olefin metathesis. To investigate their applicability as heterogeneous catalysts, we have successfully developed a methodology to easily immobilize prototype ruthenium alkylidenes onto hybrid mesostructured silica via a thiolate tether. In contrast, the preparation of the corresponding molecular complexes appeared very challenging in solution. These prototype supported complexes contain small thiolates but still, they are slightly more Z-selective than their molecular analogues. These results open the door to more active and selective heterogeneous catalysts by supporting more advanced thiolate Ru-complexes.
- Renom-Carrasco, Marc,Mania, Philipp,Sayah, Reine,Veyre, Laurent,Occhipinti, Giovanni,Gajan, David,Lesage, Anne,Jensen, Vidar R.,Thieuleux, Chloé
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supporting information
p. 2886 - 2890
(2019/03/07)
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- Vanadium-Catalyzed Cross Metathesis: Limitations and Implications for Future Catalyst Design
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Self-metathesis of terminal olefins using vanadium(V) alkylidenes is presented. Under various reaction conditions, incomplete conversion is observed due to decomposition of the metallocyclobutane intermediate via β-hydride elimination. The activity was observed to decline when a more electron withdrawing, less sterically bulky ligand was used, in contrast to trends observed in ring-opening metathesis polymerization with vanadium catalysts. These results provide insight into the current limitations of olefin metathesis with vanadium catalysts, as well as guidance for catalyst development.
- Farrell, Wesley S.
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supporting information
p. 3481 - 3485
(2019/11/13)
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- Mixed AuPd Nanoparticles as Highly Active Catalysts for Alkyne Z-Semihydrogenation
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A method for the preparation of mixed AuPd nanoparticles that are used as catalysts for selective alkyne Z-semihydrogenation is described. It is shown that the corresponding monometallic Pd nanoparticles display a lower activity, documenting the cooperative effect exerted by the two metals. These mixed AuPd nanoalloys are readily prepared by irradiation of the corresponding precursor salts in the presence of photoactive polymers or commercially available photoinitiators as reducing and stabilizing agents. Alkyne semihydrogenation using these catalyst systems with H2 proceeds in high yield (up to 97 % yield of isolated product) and excellent Z-selectivity (up to 99 %). Hydrogenations work on larger scale and the hybrid catalyst can be recovered and reused by simple centrifugation.
- Wissing, Maren,Niehues, Maximilian,Ravoo, Bart Jan,Studer, Armido
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supporting information
p. 3403 - 3409
(2018/07/25)
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- Stable Zero-Valent Nickel Nanoparticles in Glycerol: Synthesis and Applications in Selective Hydrogenations
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Small (mean diameter, ca. 1.2 nm) and well-dispersed zero-valent nickel nanoparticles (NiNPs) stabilized by cinchona-based alkaloids and TPPTS (tris(3-sulfophenyl)phosphine trisodium salt), were synthesized from the organometallic precursor [Ni(cod)2] in neat glycerol under hydrogen pressure. NiNPs were fully characterized ((HR)-TEM, EDX, XPS, XRD, IR, magnetization), both at solid state and directly from the corresponding colloidal solutions in glycerol due to its negligible vapour pressure. NiNPs dispersed in glycerol were applied in hydrogenation reactions, in particular in semihydrogenation of alkynes to give (Z)-alkenes under satisfactory conditions (3 bar H2, 1 mol% Ni, 100 °C), showing remarkable activity and selectivity. The catalytic phase was recycled at least ten times without loss of activity, affording in each case metal-free organic products. Other functional groups such as nitro, nitrile and formyl groups were efficiently hydrogenated to the corresponding anilines, benzylamines and benzylalcohols respectively (77–95% yields). (Figure presented.).
- Reina, Antonio,Favier, Isabelle,Pradel, Christian,Gómez, Montserrat
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supporting information
p. 3544 - 3552
(2018/08/01)
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- SYNTHESIS AND CHARACTERIZATION OF METATHESIS CATALYSTS
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This invention relates generally to olefin metathesis catalysts, to the preparation of such compounds, compositions comprising such compounds, methods of using such compounds, and the use of such compounds in the metathesis of olefins and in the synthesis of related olefin metathesis catalysts. The invention has utility in the fields of catalysis, organic synthesis, polymer chemistry, and in industrial applications such as oil and gas, fine chemicals, and pharmaceuticals.
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Paragraph 000156; 000157
(2018/03/25)
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- Normal Alpha Olefin Synthesis Using Metathesis and Dehydroformylation
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The present invention discloses processes for producing normal alpha olefins, such as 1-hexene, 1-octene, and 1-decene, in a multistep synthesis scheme. Generally, a first normal alpha olefin is subjected to an olefin metathesis step to form a linear internal olefin, which is then subjected to an isomerization-hydroformylation step to form a linear aldehyde, which is then subjected to a dehydroformylation step to form a second normal alpha olefin.
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Paragraph 0099; 0100; 0101
(2018/05/24)
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- SOMC-designed silica supported tungsten Oxo imidazolin-2-iminato methyl precatalyst for olefin metathesis reactions
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Synthesis, structure, and olefin metathesis activity of a surface complex [(Si-O-)W(=O)(CH3)2- ImDippN] (4) (ImDipp = 1,3-bis(2,6-diisopropylphenyl)- imidazolin-2-iminato) supported on silica by a surface organometallic chemistry (SOMC) approach are reported. The reaction of N-silylated 2-iminoimidazoline with tungsten- (VI) oxytetrachloride generated the tungsten oxo imidazolin-2- iminato chloride complex [ImDippNW(O)Cl3] (2). This was grafted on partially dehydroxylated silica pretreated at 700 °C (SiO2-700) to afford a well-defined monopodal surface complex [(Si-O-)W(=O)Cl2-ImDippN] (3). 3 underwent alkylation by ZnMe2 to produce [(Si-O-)W(=O)(CH3)2-ImDippN] (4). The alkylated surface complex was thoroughly characterized by solid-state NMR, elemental microanalysis, Raman, FT-IR spectroscopies, and XAS analysis. 4 proved to be an active precatalyst for self-metathesis of terminal olefins such as propylene and 1-hexene.
- Qureshi, Ziyauddin S.,Hamieh, Ali,Barman, Samir,Maity, Niladri,Samantaray, Manoja K.,Ould-Chikh, Samy,Abou-Hamad, Edy,Falivene, Laura,D'Elia, Valerio,Rothenberger, Alexander,Llorens, Isabelle,Hazemann, Jean-Louis,Basset, Jean-Marie
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supporting information
p. 861 - 871
(2017/01/24)
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- N-Heterocyclic Carbene Complexes Of Metal Imido Alkylidenes And Metal OXO Alkylidenes, And The Use Of Same
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The invention relates to an N-heterocyclic carbene complex of general formulas I to IV (I) (II) (III) (IV), according to which A1 stands for NR2 or PR2, A2 stands for CR2 R2′, NR2, PR2, 0 or S, A3 stands for N or P, and C stands for a carbene carbon atom, ring B is an unsubstituted or a mono or poly-substituted 5 to 7-membered ring, substituents R2 and R2′ stand, inter alia, for a linear or branched C1-Cw-alkyl group and, if N and N each stand for NR2 or PR2, are the same or different, M in formulas I, II, III or IV stands for Cr, Mo or W, X 1 or X2 in formulas I to IV are the same or different and represent, inter alia, C1-C1s carboxylates and C1-C1s-alkoxides, Y is inter alia oxygen or sulphur, Z is inter alia a linear or branched C1-Cw-alkylenoxy group, and R 1 and R1′ in formulas I to IV are, inter alia, an aliphatic or aromatic group. These compounds are particularly suitable for use as catalysts for olefin metathesis reactions and have the advantage, compared to known Schrock carbene complexes, of displaying clearly increased tolerance to functional groups such as, in particular, aldehydes, secondary amines, nitriles, carboxylic acids and alcohols.
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Paragraph 0181
(2017/03/21)
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- Alkyne Semihydrogenation with a Well-Defined Nonclassical Co-H2 Catalyst: A H2 Spin on Isomerization and E-Selectivity
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The reactivity of a CoI-H2 complex was extended toward the semihydrogenation of internal alkynes. Under ambient temperatures and moderate pressures of H2, a broad scope of alkynes were semihydrogenated using a CoI-N2 precatalyst, resulting in the formation of trans-alkene products. Furthermore, mechanistic studies using 1H, 2H, and para-hydrogen induced polarization (PHIP) transfer NMR spectroscopy revealed cis-hydrogenation of the alkyne occurs first. The Co-mediated alkene isomerization afforded the E-selective products from a broad group of alkynes with good yields and E/Z selectivity.
- Tokmic, Kenan,Fout, Alison R.
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supporting information
p. 13700 - 13705
(2016/10/31)
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- High Trans Kinetic Selectivity in Ruthenium-Based Olefin Cross-Metathesis through Stereoretention
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The first kinetically controlled, highly trans-selective (>98%) olefin cross-metathesis reaction is demonstrated using Ru-based catalysts. Reactions with either trans or cis olefins afford products with highly trans or cis stereochemistry, respectively. This E-selective olefin cross-metathesis is shown to occur between two trans olefins and between a trans olefin and a terminal olefin. Additionally, new stereoretentive catalysts have been synthesized for improved reactivity. (Chemical Equation Presented).
- Johns, Adam M.,Ahmed, Tonia S.,Jackson, Bradford W.,Grubbs, Robert H.,Pederson, Richard L.
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supporting information
p. 772 - 775
(2016/03/01)
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- Molybdenum and Tungsten Alkylidene Complexes That Contain a 2-Pyridyl-Substituted Phenoxide Ligand
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In the interest of preparing molybdenum and tungsten alkylidene complexes for olefin metathesis that are longer-lived at high temperatures (~150 °C or above), we synthesized complexes that contain a phenoxide ligand with a 2-pyridyl in one ortho position and a mesityl (Mes) or 2,4,6-i-Pr3C6H2 (Trip) in the other ortho position ([MesON]- or [TripON]-, respectively). The alkylidene (neophylidene) complexes that were prepared include W(O)(CHCMe2Ph)(Me2Pyr)(RON) (R = Mes or Trip), Mo(NC6F5)(CHCMe2Ph)(RON)Cl, Mo(N-2,6-Me2C6H3)(CHCMe2Ph)(RON)Cl, Mo(N-t-Bu)(CHCMe2Ph)(RON)Cl, and M(N-2,6-i-Pr2C6H3)(CHCMe2Ph)(TripON)(OTf) (M = Mo or W). The reaction between Mo(NAr)(CHCMe2Ph)(TripON)(OTf) and ethylene yielded an ethylene complex, Mo(NAr)(C2H4)(TripON)(OTf)(ether). All neophylidene complexes were essentially unreactive toward terminal olefins at 22 °C and showed modest homocoupling activity (at 80 or 100 °C) and alkane metathesis activity (at 150 and 200 °C). W(O)(CHCMe2Ph)(Me2Pyr)(MesON) also stereoselectively polymerized several substituted norbornadienes at 100 °C.
- Sues, Peter E.,John, Jeremy M.,Bukhryakov, Konstantin V.,Schrock, Richard R.,Müller, Peter
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supporting information
p. 3587 - 3593
(2016/11/06)
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- cis-Semihydrogenation of alkynes with amine borane complexes catalyzed by gold nanoparticles under mild conditions
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Supported gold nanoparticles catalyze the semihydrogenation of alkynes to alkenes with ammonia borane or amine borane complexes in excellent yields and under mild conditions. Internal alkynes provide cis-alkenes, making this protocol an attractive alternative of the classical Lindlar's hydrogenation.
- Vasilikogiannaki, Eleni,Titilas, Ioannis,Vassilikogiannakis, Georgios,Stratakis, Manolis
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supporting information
p. 2384 - 2387
(2015/02/05)
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- Highly Z-selective olefins metathesis
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The present invention relates generally to catalysts and processes for the Z-selective formation of internal olefin(s) from terminal olefin(s) via homo-metathesis reactions.
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Page/Page column 35; 44
(2015/07/22)
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- BMIm-PF6@SiO2 Microcapsules: Particulated ionic liquid as a new material for the heterogenization of catalysts
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A method for the preparation of silica microcapsules containing a high loading of ionic liquids (ILs) is described. The method paves the way to the conversion of ionic liquids into particulated materials, which results in ILs with new properties without changing their molecular structures. The synthesis of these new materials is based on the emulsification of ionic liquids in water, using surfactants or dispersants, and the resulting ionic liquid droplets are then confined in a silica shell formed via interfacial hydrolysis and polycondensation of tetraethoxysilane. This material can be isolated by centrifugation, followed by drying to yield a fine powder of ionic liquid-silica microcapsules, which are water and organic solvents redispersible. These new materials are utilized in the heterogenization of palladium catalyst and then applied in the hydrogenation of alkynes. The catalyst shows chemoselectivity in the hydrogenation of internal alkynes such as 4-octyne. Comparative studies have shown that the same catalyst loses this selectivity when it is applied under homogeneous conditions.
- Weiss, Ester,Dutta, Bishnu,Kirschning, Andreas,Abu-Reziq, Raed
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p. 4781 - 4787
(2014/11/07)
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- A one-pot tandem olefin isomerization/metathesis-coupling (ISOMET) reaction
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A tandem catalytic reaction has been developed as part of a process to discover tungsten-based olefin metathesis catalysts that have a strong preference for terminal olefins over cis or trans internal isomers in olefin metathesis. This tandem isomerization/terminal olefin metathesis reaction (ISOMET) converts Cn trans internal olefins into C2n-2cis olefins and ethylene. This reaction is made possible with Ru-based "alkene zipper" catalysts, which selectively isomerize trans olefins to an equilibrium mixture of trans and terminal olefins, plus tungsten-based metathesis catalysts that react relatively selectively with terminal olefins to give Z homocoupled products. The most effective catalysts are W(NAr)(C3H6)(pyr)-(OHIPT) (Ar = 2,6-diisopropylphenyl; pyr = pyrrolide; OHIPT = O-2,6-(2,4,6-i-Pr3C6H2)2C6H3) and various [CpRu(P - N)(MeCN)]X (X-= [B(3,5-(CF3)2C6H3)4]-, PF6-, B(C6F5)4-) isomerization catalysts.
- Dobereiner, Graham E.,Erdogan, Gulin,Larsen, Casey R.,Grotjahn, Douglas B.,Schrock, Richard R.
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p. 3069 - 3076
(2015/02/19)
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- Olefin metathesis catalysts
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The present invention refers to novel ruthenium- and osmium-based catalysts for olefin metathesis reactions, particularly to catalysts having stereoselective properties. Z-selectivity is obtained by utilizing two mono-anionic ligands of very different steric requirement. In olefin metathesis reactions these catalysts selectively provide the Z-isomer of disubstituted olefinic products.
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Page/Page column 26; 27
(2014/05/20)
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- Theory-assisted development of a robust and Z-selective olefin metathesis catalyst
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DFT calculations have predicted a new, highly Z-selective ruthenium-based olefin metathesis catalyst that is considerably more robust than the recently reported (SIMes)(Cl)(RS)RuCH(o-OiPrC6H4) (3a, SIMes = 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene, R = 2,4,6-triphenylbenzene) [J. Am. Chem. Soc., 2013, 135, 3331]. Replacing the chloride of 3a by an isocyanate ligand to give 5a was predicted to increase the stability of the complex considerably, at the same time moderately improving the Z-selectivity. Compound 5a is easily prepared in a two-step synthesis starting from the Hoveyda-Grubbs second-generation catalyst 3. In agreement with the calculations, the isocyanate-substituted 5a appears to be somewhat more Z-selective than the chloride analogue 3a. More importantly, 5a can be used in air, with unpurified and non-degassed substrates and solvents, and in the presence of acids. These are traits that are unprecedented among highly Z-selective olefin metathesis catalysts and also very promising with respect to applications of the new catalyst. This journal is the Partner Organisations 2014.
- Occhipinti, Giovanni,Koudriavtsev, Vitali,Toernroos, Karl W.,Jensen, Vidar R.
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p. 11106 - 11117
(2014/07/21)
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- Selective semihydrogenation of alkynes on shape-controlled palladium nanocrystals
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A systematic study on the selective semihydrogenation of alkynes to alkenes on shape-controlled palladium (Pd) nanocrystals was performed. Pd nanocrystals with a cubic shape and thus exposed {100} facets were synthesized in an aqueous solution through the reduction of Na2PdCl4 with L-ascorbic acid in the presence of bromide ions. The Pd nanocubes were tested as catalysts for the semihydrogenation of various alkynes such as 5-decyne, 2-butyne-1,4-diol, and phenylacetylene. For all substrates, the Pd nanocubes exhibited higher alkene selectivity (>90 %) than a commercial Pd/C catalyst (75-90 %), which was attributed to a large adsorption energy of the carbon-carbon triple bond on the {100} facets of the Pd nanocubes. Our approach based on the shape control of Pd nanocrystals offers a simple and effective route to the development of a highly selective catalyst for alkyne semihydrogenation. Catalysis3: The semihydrogenation of various alkynes by Pd nanocubes was investigated. The nanocubes exhibited high alkene selectivity and complete cis-selectivity, thus surpassing the Lindlar catalyst. The shape control of Pd nanocrystals provides a simple and efficient way for generating highly selective catalysts for the semihydrogenation of alkynes.
- Chung, Jooyoung,Kim, Chanhoi,Jeong, Hansaem,Yu, Taekyung,Binh, Do Huy,Jang, Jyongsik,Lee, Jaichan,Kim, B. Moon,Lim, Byungkwon
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p. 919 - 925
(2013/08/25)
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- A well-defined silica-supported tungsten oxo alkylidene is a highly active alkene metathesis catalyst
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Grafting (ArO)2W(i=O)(i=CHtBu) (ArO = 2,6-mesitylphenoxide) on partially dehydroxylated silica forms mostly [(i - SiO)W(i=O)(i=CHtBu) (OAr)] along with minor amounts of [(i - SiO)W(i=O)(CH2tBu) (OAr)2] (20%), both fully ch
- Conley, Matthew P.,Mougel, Victor,Peryshkov, Dmitry V.,Forrest, William P.,Gajan, David,Lesage, Anne,Emsley, Lyndon,Coperet, Christophe,Schrock, Richard R.
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supporting information
p. 19068 - 19070
(2014/01/17)
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- Stabilization of long-chain intermediates in solution. octyl radicals and cations
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The rearrangements of 1-octyl, 1-decyl and 1-tridecyl intermediates obtained from thermal lead(IV) acetate (LTA) decarboxylation of nonanoic, undecanoic and tetradecanoic acid were investigated experimentally through analysis and distribution of the products. The relationships between 1,5-, 1,6- and possibly existing 1,7-homolytic hydrogen transfer in 1-octyl-radical, as well as successive 1,2-hydride shift in corresponding cation have been computed via Monte-Carlo method. Taking into account that ratios of 1,5-/1,6-homolytic rearrangements in 1-octyl- and 1-tridecyl radical are approximately the same, the simulation shows very low involvement of 1,7-hydrogen rearrangement (1,5-/1,6-/1,7-hydrogen rearrangement = 85:31:1) in 1-octyl radical.
- Teodorovi?, Aleksandar V.,Badjuk, Dalibor M.,Stevanovi?, Nenad,Pavlovi?, Radoslav Z.
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- Simple and highly Z-selective ruthenium-based olefin metathesis catalyst
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A one-step substitution of a single chloride anion of the Grubbs-Hoveyda second-generation catalyst with a 2,4,6-triphenylbenzenethiolate ligand resulted in an active olefin metathesis catalyst with remarkable Z selectivity, reaching 96% in metathesis homocoupling of terminal olefins. High turnover numbers (up to 2000 for homocoupling of 1-octene) were obtained along with sustained appreciable Z selectivity (>85%). Apart from the Z selectivity, many properties of the new catalyst, such as robustness toward oxygen and water as well as a tendency to isomerize substrates and react with internal olefin products, resemble those of the parent catalyst.
- Occhipinti, Giovanni,Hansen, Fredrik R.,T?rnroos, Karl W.,Jensen, Vidar R.
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supporting information
p. 3331 - 3334
(2013/04/23)
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- Copper-catalyzed highly selective semihydrogenation of non-polar carbon-carbon multiple bonds using a silane and an alcohol
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A copper catalyst bearing a suitable Xantphos derivative or NHC ligand was found to be highly efficient for the selective semihydrogenation of non-polar unsaturated compounds using a mixture of a silane and an alcohol as reducing agent. The catalytic system was useful for the selective semihydrogenation of internal alkynes to (Z)-alkenes with suppression of overreduction to the corresponding alkanes. Furthermore, semihydrogenations of terminal alkyne, 1,2-diene, 1,3-diene, 1,3-enyne and 1,3-diyne systems were also achieved selectively. Copyright
- Semba, Kazuhiko,Fujihara, Tetsuaki,Xu, Tinghua,Terao, Jun,Tsuji, Yasushi
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experimental part
p. 1542 - 1550
(2012/08/08)
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- Stereodivergent ruthenium-catalyzed transfer semihydrogenation of diaryl alkynes
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[Ru3(CO)12]-catalyzed transfer semihydrogenation of various functionalized diaryl alkynes with N,N-dimethylformamide (DMF) and water as hydrogen source affords cis- and trans-stilbenes. The stereodivergent approach can be switched by the use of acetic (HOAc) or trifluoroacetic (TFA) acid as additives. The catalytic processes can be applied to the synthesis of analogues of natural products such as cis-combretastatin A-4 and trans-resveratrol. Copyright
- Li, Jie,Hua, Ruimao
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supporting information; experimental part
p. 8462 - 8465
(2011/08/07)
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- HIGHLY Z-SELECTIVE OLEFINS METATHESIS
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The present invention relates generally to catalysts and processes for the Z-selective formation of internal olefin(s) from terminal olefin(s) via homo-metathesis reactions.
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Page/Page column 18-19
(2011/04/19)
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- Room-temperature Z-selective homocoupling of α-olefins by tungsten catalysts
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3,5-Dimethylphenylimido complexes of tungsten can be prepared using procedures analogous to those employed for other tungsten catalysts, as can bispyrrolide species and MonoAryloxide-Pyrrolide (MAP) species. Homocouplings of 1-hexene, 1-octene, and methyl 10-undecenoate are achieved in 45-89% yield and a Z selectivity of >99% with W(Nar″)(C3H6)(pyr) (OHIPT) as a catalyst. Homocoupling of terminal olefins in the presence of (E)-olefins elsewhere in the molecule also was achieved with excellent selectivity.
- Marinescu, Smaranda C.,Schrock, Richard R.,Mueller, Peter,Takase, Michael K.,Hoveyda, Amir H.
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scheme or table
p. 1780 - 1782
(2011/06/22)
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- Z -selective homodimerization of terminal olefins with a ruthenium metathesis catalyst
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The cross-metathesis of terminal olefins using a novel ruthenium catalyst results in excellent selectivity for the Z-olefin homodimer. The reaction was found to tolerate a large number of functional groups, solvents, and temperatures while maintaining excellent Z-selectivity, even at high reaction conversions.
- Keitz, Benjamin K.,Endo, Koji,Herbert, Myles B.,Grubbs, Robert H.
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supporting information; experimental part
p. 9686 - 9688
(2011/08/05)
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- A selective Ru-catalyzed semireduction of alkynes to Z olefins under transfer-hydrogenation conditions
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By using a readily available, air- and moisture-stable dihydrido-Ru complex, a variety of Z olefins are accessible under transfer-hydrogenation conditions with formic acid as the hydrogen source in excellent yields and Z/E selectivities. A discerning transformation: Z-Configured C=C bonds are stereoselectively formed from alkynes in the presence of a Ru catalyst with formic acid as the sole H2 source at room temperature (see scheme). A variety of functional groups are compatible with this novel procedure. Operational simplicity and the lack of overreduction products are characteristics for this unprecedented process.
- Belger, Christian,Neisius, N. Matthias,Plietker, Bernd
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supporting information; experimental part
p. 12214 - 12220
(2011/03/17)
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- Highly chemo- and stereoselective palladium-catalyzed transfer semihydrogenation of internal alkynes affording cis -alkenes
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DMF (N,N-dimethylformamide)/KOH was found to be an efficient hydrogen source in the Pd(OAc)2-catalyzed transfer semihydrogenation of various functionalized internal alkynes to afford cis-alkenes in good to high yields with excellent chemo- and stereoselectivity. This catalytic process was also applied to the synthesis of analogues of combretastatin A-4.
- Li, Jie,Hua, Ruimao,Liu, Tao
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supporting information; experimental part
p. 2966 - 2970
(2010/06/19)
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- Effect of solvent and temperature on the lithium?bromine exchange of vinyl bromides: Reactions of n -butyllithium and t -butyllithium with (E)-5-bromo-5-decene
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The outcome of reactions of (E)-5-bromo-5-decene (1), a representative vinyl bromide, with t-BuLi or n-BuLi at 0 °C and room temperature, respectively, in a variety of solvent systems has been investigated. Vinyl bromide 1 does not react with t-BuLi in pure heptane; however, the presence of even small quantities of an ether in a predominantly heptane medium resulted in virtually complete consumption of 1 at 0 °C, resulting in nearly the same distribution of products, including 60?80% of (Z)-5-decenyllithium, regardless of the solvent composition. Vinyl bromide 1 reacts slowly with n-BuLi at room temperature in a variety of ether and heptane-ether mixtures to afford a mixture of products including significant quantities of recovered starting material. The results of these experiments demonstrate that lithium?bromine exchange between a vinyl bromide and either t-BuLi or n-BuLi at temperatures significantly above ?78 °C is not an efficient method for the generation of a vinyllithium.
- Bailey, William F.,Luderer, Mark R.,Uccello, Daniel P.,Bartelson, Ashley L.
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experimental part
p. 2661 - 2666
(2010/08/19)
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- Highly Z-selective metathesis homocoupling of terminal olefins
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(Chemical Equation Presented) Mo and W MonoAryloxide-Pyrrolide (MAP) olefin metathesis catalysts can couple terminal olefins to give as high as >98% Z-products in moderate to high yields with as little as 0.2% catalyst. Results are reported for 1-hexene, 1-octene, allylbenzene, allyltrimethylsilane, methyl-10-undecenoate, methyl-9-decenoate, allylB(pinacolate), allylOBenzyl, allylNHTosyl, and allylNHPh. It is proposed that high Z-selectivity is achieved because a large aryloxide only allows metallacyclobutanes to form that contain adjacent cis substituents and because isomerization of Z-product to E-product can be slow in that same steric environment.
- Jiang, Annie J.,Zhao, Yu,Schrock, Richard R.,Hoveyda, Amir H.
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supporting information; experimental part
p. 16630 - 16631
(2010/02/16)
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- Effect of the nature of carbene fragments in the tungsten complexes PhMe2E-CH=W(NAr)(OR')2 and Me3E-CH=W(NAr)(OR') 2 (E = C, Si) on their catalytic properties in olefin metathesis reactions
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Catalytic properties of the silicon-containing carbene complexes of tungsten Me3Si-CH=W(NAr)(OR')2(1) and PhMe 2Si-CH=W(NAr)(OR')2 (2) and their hydrocarbon analogs Me3C-CH=W(NAr)(OR')2 (3) and PhMe2C-CH=W(NAr) (OR')2 (4) (Ar = 2,6-Pri 2C6H 3, R' = CMe2CF3) were studied in homometathesis of hex-1-ene, metathesis polycondensation of deca-1,9-diene, and ring opening metathesis polymerization of cyclooctene. The nature of the carbene fragment in the tungsten catalysts substantially affects their catalytic activity. Silicon-containing catalysts 1 and 2 were found to be 3-5 times less active than their hydrocarbon analogs 3 and 4. Metathesis polymerization of cyclooctene in the bulk with initiators 1-4 completed within a few minutes to form a block. Stereoregularity of the formed polyoctenamers depends to a considerable extent on the nature of the carbene fragments in the starting initiators. Initiators 1-2 lead to polyoctenamers mainly containing the cis-units, whereas the use of complexes 3 and 4 affords polyoctenamers mainly containing the trans-units. The structures of novel compound 2 and known complexes 1, 3, and 4 were determined by X-ray diffraction analysis.
- Bochkarev,Begantsova,Platonova,Basova,Grigor'eva,Stolyarova,Malysheva,Fukin,Baranov,Kurskii,Bochkarev,Abakumov
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experimental part
p. 1874 - 1879
(2009/12/02)
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- New method for cycloalumination of disubstituted acetylenes with 1,2-dichloroethane
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A new procedure has been developed for the synthesis of 2,3-dialkyl(phenyl)aluminacyclopent-2-enes by Cp2TiCl 2-catalyzed cycloalumination of disubstituted acetylenes with EtAlCl2 in the presence of ethylene generated in situ from 1,2-dichloroethane and activated magnesium.
- Ramazanov,Ibragimov,Dzhemilev
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scheme or table
p. 781 - 784
(2009/06/28)
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- Iron-catalyzed alkenylation of Grignard reagents by enol phosphates
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Stereoselective preparation of trisubstituted olefins can be easily performed from an Z/E-mixture of enol phosphates by reacting only the E-isomer with a Grignard reagent in the presence of Fe(acac)3. This procedure combines a kinetic differentiation and a stereoselective reaction. The coupling is very chemoselective in the presence of an alkyl chloride, an ester, a ketone or a nitrile. Georg Thieme Verlag Stuttgart.
- Cahiez, Gerard,Gager, Olivier,Habiak, Vanessa
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experimental part
p. 2636 - 2644
(2009/04/07)
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- Highly selective hydrogenation of multiple carbon-carbon bonds promoted by nickel(0) nanoparticles
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A new method for the highly stereoselective cis semihydrogenation of internal alkynes, semihydrogenation of terminal alkynes, reduction of dienes to alkenes, and reduction of alkynes and alkenes to alkanes is described based on in situ generated both Ni(0) nanoparticles and molecular hydrogen.
- Alonso, Francisco,Osante, I?aki,Yus, Miguel
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- Highly stereoselective semihydrogenation of alkynes promoted by nickel(0) nanoparticles
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A new method for the highly stereoselective cis-semihydrogenation of internal alkynes is described based on in situ generated Ni(0) nanoparticles and molecular hydrogen. This reduction system also allows the semihydrogenation of terminal alkynes.
- Alonso, Francisco,Osante, Inaki,Yus, Miguel
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p. 305 - 308
(2007/10/03)
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- One-carbon homologation of N-sulfonylaziridines to allylic amines using dimethylsulfonium methylide
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(Chemical Equation Presented) Regio- and stereodefined allylic N-sulfonylamines are synthesized in high yields and under experimentally straightforward conditions by reaction of N-sulfonylaziridines with excess dimethylsulfonium methylide.
- Hodgson, David M.,Fleming, Matthew J.,Stanway, Steven J.
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p. 3295 - 3298
(2007/10/03)
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- Cross-coupling of (Z)-1,2-bis(ethylseleno)ethene with the Grignard reagents
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The nickel-catalyzed cross-coupling of (Z)-1,2-bis(ethylseleno)ethene with the alkyl magnesium bromides proceeds with substitution of both ethylseleno groups to afford symmetrical alkenes, (Z)-RCH=CHR, in high yield with complete retention of configuratio
- Martynov, Alexander V.,Potapov, Vladimir A.,Amosova, Svetlana V.,Makhaeva, Nataliya A.,Beletskaya, Irina P.,Hevesi, Laszlo
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p. 101 - 103
(2007/10/03)
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