- Titania-photocatalyzed transfer hydrogenation reactions with methanol as a hydrogen source: Enhanced catalytic performance by Pd-Pt alloy at ambient temperature
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Hydrogenation reactions are of great importance in scientific research and in industry productions. Herein, we designed a novel system to realize photocatalytic transfer hydrogenation by using solar light as the energy input and methanol as the hydrogen source. In this reaction, titania loaded with Pd-Pt bimetallic alloy nanocrystals as a cocatalyst exhibited photocatalytic performance that was remarkably superior to that exhibited by titania with Pd or Pt alone as the cocatalyst. This work has shed light on the rational design of multifunctional catalysts through selecting appropriate bimetallic alloys as efficient cocatalysts. Light up, as if you have a catalyst: Photocatalytic transfer hydrogenation is efficiently realized on Pd-Pt/TiO2 under mild reaction conditions with the use of light irradiation as the energy input and methanol as the hydrogen source at ambient temperature. The Pd-Pt alloy cocatalyst exhibits enhanced catalytic performance relative to that of the monometallic Pd or Pt component. Copyright
- Zhao, Yubao,Pan, Feng,Li, Hui,Xu, Guo Qin,Chen, Wei
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Read Online
- SELECTIVE, HOMOGENEOUS HYDROGENATION OF CYCLOHEPTATRIENE TO CYCLOHEPTENE CATALYZED BY (η4-CYCLOOCTA-1,5-DIENE)(η6-CYCLOHEPTA-1,3,5-TRIENE)RUTHENIUM(0)
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In the presence of small amounts of 4-COD)(η6-C8H10)> (1), cycloheptatriene is hydrogenated to cycloheptene, under one atmosphere of hydrogen at room temperature in homogeneous phase.The formation of a small amount of cyclooctene and the existence of an induction period, which do not occur when 4-COD)(η6-C7H8)> (2) is used as the catalyst, suggest that 2 is the real catalyst.The selectivity of this hydrogenation is 100percent in n-hexane as solvent, 99.5percent in THF, and low in ethanol.Conversion is quantitative in THF and ethanol, but not more than 65percent in n-hexane.In the presence of 1 or 2, cycloheptene is rapidly hydrogenated to cycloheptane in THF and ethanol, but not in n-hexane.A mechanism for these catalytic hydrogenations is proposed, and discussed on the basis of the dominant role of the solvents.Increase of temperature and/or pressure of hydrogen increases the rate of hydrogenation.
- Airoldi, M.,Deganello, G.,Dia, G.,Gennaro, G.
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Read Online
- Rational Design of an Iron-Based Catalyst for Suzuki–Miyaura Cross-Couplings Involving Heteroaromatic Boronic Esters and Tertiary Alkyl Electrophiles
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Suzuki–Miyaura cross-coupling reactions between a variety of alkyl halides and unactivated aryl boronic esters using a rationally designed iron-based catalyst supported by β-diketiminate ligands are described. High catalyst activity resulted in a broad substrate scope that included tertiary alkyl halides and heteroaromatic boronic esters. Mechanistic experiments revealed that the iron-based catalyst benefited from the propensity for β-diketiminate ligands to support low-coordinate and highly reducing iron amide intermediates, which are very efficient for effecting the transmetalation step required for the Suzuki–Miyaura cross-coupling reaction.
- Byers, Jeffery A.,Crockett, Michael P.,Li, Bo,Wong, Alexander S.
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supporting information
p. 5392 - 5397
(2020/03/04)
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- Iron-Catalyzed Suzuki-Miyaura Cross-Coupling Reactions between Alkyl Halides and Unactivated Arylboronic Esters
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An iron-catalyzed cross-coupling reaction between alkyl halides and arylboronic esters was developed that does not involve activation of the boronic ester with alkyllithium reagents nor requires magnesium additives. A combination of experimental and theoretical investigations revealed that lithium amide bases coupled with iron complexes containing deprotonated cyanobis(oxazoline) ligands were best to obtain high yields (up to 89%) in catalytic cross-coupling reactions. Mechanistic investigations implicate carbon-centered radical intermediates and highlight the critical importance of avoiding conditions that lead to iron aggregates. The new iron-catalyzed Suzuki-Miyaura reaction was applied toward the shortest reported synthesis of the pharmaceutical Cinacalcet.
- Crockett, Michael P.,Tyrol, Chet C.,Wong, Alexander S.,Li, Bo,Byers, Jeffery A.
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supporting information
p. 5233 - 5237
(2018/09/12)
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- Triazolylidene Iridium Complexes for Highly Efficient and Versatile Transfer Hydrogenation of C=O, C=N, and C=C Bonds and for Acceptorless Alcohol Oxidation
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A set of iridium(I) and iridium(III) complexes is reported with triazolylidene ligands that contain pendant benzoxazole, thiazole, and methyl ether groups as potentially chelating donor sites. The bonding mode of these groups was identified by NMR spectroscopy and X-ray structure analysis. The complexes were evaluated as catalyst precursors in transfer hydrogenation and in acceptorless alcohol oxidation. High-valent iridium(III) complexes were identified as the most active precursors for the oxidative alcohol dehydrogenation, while a low-valent iridium(I) complex with a methyl ether functionality was most active in reductive transfer hydrogenation. This catalyst precursor is highly versatile and efficiently hydrogenates ketones, aldehydes, imines, allylic alcohols, and most notably also unpolarized olefins, a notoriously difficult substrate for transfer hydrogenation. Turnover frequencies up to 260 h-1 were recorded for olefin hydrogenation, whereas hydrogen transfer to ketones and aldehydes reached maximum turnover frequencies greater than 2000 h-1. Mechanistic investigations using a combination of isotope labeling experiments, kinetic isotope effect measurements, and Hammett parameter correlations indicate that the turnover-limiting step is hydride transfer from the metal to the substrate in transfer hydrogenation, while in alcohol dehydrogenation, the limiting step is substrate coordination to the metal center.
- Mazloomi, Zahra,Pretorius, René,Pàmies, Oscar,Albrecht, Martin,Diéguez, Montserrat
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p. 11282 - 11298
(2017/09/25)
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- Bisphosphine compd., and Bisphosphine compound and a transition metal catalyst, and method of manufacturing the same (by machine translation)
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PROBLEM TO BE SOLVED: To provide a bisphosphine compound with a new bidentate phosphine ligand having a highly bulky substituent group on a phosphorus atom, which enables highly efficient and highly selective progress in various organic synthesis reactions, especially, cross coupling reaction, and a transition metal catalyst using the bisphosphine compound as a ligand, and a method for manufacturing them.SOLUTION: There are provided a bisphosphine compound represented by general formula (A) or general formula (B) and a transition metal catalyst using the bisphosphine compound as a ligand, and a method for manufacturing them.
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Paragraph 0554; 0560; 0561
(2016/11/17)
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- Reduced graphene oxide supported nickel-palladium alloy nanoparticles as a superior catalyst for the hydrogenation of alkenes and alkynes under ambient conditions
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Addressed herein is the superior catalytic performance of reduced graphene oxide supported Ni30Pd70 alloy nanoparticles (rGO-Ni30Pd70) for the direct hydrogenation of alkenes and alkynes to alkanes, which surpasses the commercial Pd/C catalyst both in activity and stability. A variety of cyclic or aromatic alkenes and alkynes (a total of 17 examples) were rapidly reduced to the corresponding alkanes with high yields (>99%) via the presented direct hydrogenation protocol under ambient conditions. Compared to the commercially available Pd/C (10 wt%) catalyst, the rGO-Ni30Pd70 catalyst provided higher yields in shorter reaction times under the optimized conditions. Moreover, the rGO-Ni30Pd70 catalysts were more stable and durable than the commercial Pd/C catalysts by preserving their initial activity after five consecutive runs in the hydrogenation reactions.
- ?etinkaya, Yasin,Metin, ?nder,Balci, Metin
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p. 28538 - 28542
(2016/04/08)
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- Highly nucleophilic dipropanolamine chelated boron reagents for aryl-transmetallation to iron complexes
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New aryl- and heteroarylboronate esters chelated by dipropanolamine are synthesised directly from boronic acids. The corresponding anionic borates are readily accessible by deprotonation and demonstrate an increase in hydrocarbyl nucleophilicity in comparison to other common borates. The new borates proved competent for magnesium or zinc additive-free, direct boron-to-iron hydrocarbyl transmetallations with well-defined iron(ii) (pre)catalysts. The application of the new borate reagents in representative Csp2-Csp3 cross-coupling led to almost exclusive homocoupling unless coupling is performed in the presence of a zinc additive.
- Dunsford, Jay J.,Clark, Ewan R.,Ingleson, Michael J.
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supporting information
p. 20577 - 20583
(2015/12/04)
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- Carbon-carbon bond formation reactivity of a four-coordinate NHC-supported iron(II) phenyl compound
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The preparation and characterization of a NHC-coordinated (NHC = N-heterocyclic carbene) ferrous phenyl complex [(IPr2Me2)2FePh2] (1; IPr2Me2 = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) as well as its C-C bond formation reactivity have been studied. The four-coordinate iron(II) phenyl complex was prepared from the reaction of ferrous chloride with PhMgBr and IPr2Me2. It reacts with nonactivated primary and secondary alkyl bromides and chlorides to furnish cross-coupling products and the iron(II) monophenyl species (IPr2Me2)2FePhX (X = Br (2), Cl). When it is treated with cyclooctatetraene (cot) or [Cp2Fe][BArF4] in the presence of PMe3, it undergoes coordination or one-electron oxidation induced reductive elimination of biphenyl to form the corresponding iron(0) or iron(I) species [(IPr2Me2)2Fe(?·4-cot)] (3) or [(IPr2Me2)2Fe(PMe3)2][BArF4] (4). All of these iron-containing products have been fully characterized by various spectroscopic methods. Complex 1 and (IPr2Me2)2FeCl2 catalyze the reaction of n-C8H17Br with (p-tolyl)MgBr to afford the cross-coupling product in moderate yields (49% and 47%), whereas the reactions employing 4 and 1/PMe3 as catalysts give the cross-coupling product in very low yields. The results reflect the complexity of the reaction mechanism of iron-catalyzed coupling reactions.
- Liu, Yuesheng,Xiao, Jie,Wang, Lei,Song, You,Deng, Liang
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p. 599 - 605
(2015/03/05)
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- The potential of methylsiloxanes as solvents for synthetic chemistry applications
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The potential use of volatile methylsiloxanes (VMSs) as solvents for chemicals synthesis has been explored. Assessment of the environmental impact of these VMS solvents is made and found to be significantly lower than those of the non-polar organic solvents that they have the potential to replace. The polarities of the VMSs, as expressed by empirical polarity measurements, and miscibilities with other liquids are found to be similar to those of alkane solvents. Finally, some uses of VMSs as solvents for both organic and inorganic transformations are described. The VMSs provide environmentally more sustainable (greener) alternatives to the nonpolar solvents that they have the potential to replace.
- Ab Rani, Mohd Azri,Borduas, Nadine,Colquhoun, Victoria,Hanley, Robert,Johnson, Henry,Larger, Solene,Lickiss, Paul D.,Llopis-Mestre, Veronica,Luu, Selina,Mogstad, Martin,Oczipka, Philipp,Sherwood, James R.,Welton, Tom,Xing, Jun-Yi
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p. 1282 - 1296
(2014/03/21)
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- Cyclooctane metathesis catalyzed by silica-supported tungsten pentamethyl [(ΞSiO)W(Me)5]: Distribution of macrocyclic alkanes
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Metathesis of cyclic alkanes catalyzed by the new surface complex [(ΞSiO)W(Me)5] affords a wide distribution of cyclic and macrocyclic alkanes. The major products with the formula CnH2n are the result of either a ring contraction or ring expans
- Riache, Nassima,Callens, Emmanuel,Samantaray, Manoja K.,Kharbatia, Najeh M.,Atiqullah, Muhammad,Basset, Jean-Marie
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supporting information
p. 15089 - 15094
(2015/02/19)
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- High catalytic performance of palladium nanoparticles supported on multiwalled carbon nanotubes in alkene hydrogenation reactions
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The synthesis of Pd nanoparticles (Pd-NPs) supported on multi-walled carbon nanotubes (MWCNTs) and the cataytic performance of the resulting material (Pd-NPs/MWCNTs) in hydrogenation reactions are presented. Facile preparation approaches based on the decomposition of Pd precursors in the presence of MWCNTs lead to homogeneous dispersions of supported Pd-NPs with an average size of 4 nm and Pd loads of about 12%. The catalytic performance of this material was evaluated in hydrogenation reactions of α,β-unsaturated ketones, alkenes, cyclic di-, tri- and tetraenes, aromatic compounds, terpenes and terpenoids, resulting in very high activity offering short reaction times, high conversion rates, notable selectivity, and acceptable recyclability under mild conditions.
- Cano, Manuela,Benito, Ana M.,Maser, Wolfgang K.,Urriolabeitia, Esteban P.
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p. 1968 - 1972
(2013/10/08)
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- Synthesis, reactivity, and catalytic application of a nickel pincer hydride complex
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The nickel(II) hydride complex [(MeN2N)Ni-H] (2) was synthesized by the reaction of [(MeN2N)Ni-OMe] (6) with Ph2SiH2 and was characterized by NMR and IR spectroscopy as well as X-ray crystallography. 2 was unstable in solution, and it decomposed via two reaction pathways. The first pathway was intramolecular N-H reductive elimination to give MeN2NH and nickel particles. The second pathway was intermolecular, with H2, nickel particles, and a five-coordinate Ni(II) complex [(MeN2N)2Ni] (8) as the products. 2 reacted with acetone and ethylene, forming [( MeN2N)Ni-OiPr] (9) and [(MeN 2N)Ni-Et] (10), respectively. 2 also reacted with alkyl halides, yielding nickel halide complexes and alkanes. The reduction of alkyl halides was rendered catalytically, using [(MeN2N)Ni-Cl] (1) as catalyst, NaOiPr or NaOMe as base, and Ph2SiH2 or Me(EtO)2SiH as the hydride source. The catalysis appears to operate via a radical mechanism.
- Breitenfeld, Jan,Scopelliti, Rosario,Hu, Xile
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experimental part
p. 2128 - 2136
(2012/06/01)
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- Replacing conventional carbon nucleophiles with electrophiles: Nickel-catalyzed reductive alkylation of aryl bromides and chlorides
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A general method is presented for the synthesis of alkylated arenes by the chemoselective combination of two electrophilic carbons. Under the optimized conditions, a variety of aryl and vinyl bromides are reductively coupled with alkyl bromides in high yields. Under similar conditions, activated aryl chlorides can also be coupled with bromoalkanes. The protocols are highly functional-group tolerant (-OH, -NHTs, -OAc, -OTs, -OTf, -COMe, -NHBoc, -NHCbz, -CN, -SO2Me), and the reactions are assembled on the benchtop with no special precautions to exclude air or moisture. The reaction displays different chemoselectivity than conventional cross-coupling reactions, such as the Suzuki-Miyaura, Stille, and Hiyama-Denmark reactions. Substrates bearing both an electrophilic and nucleophilic carbon result in selective coupling at the electrophilic carbon (R-X) and no reaction at the nucleophilic carbon (R-[M]) for organoboron (-Bpin), organotin (-SnMe3), and organosilicon (-SiMe2OH) containing organic halides (X-R-[M]). A Hammett study showed a linear correlation of σ and σ(-) parameters with the relative rate of reaction of substituted aryl bromides with bromoalkanes. The small ρ values for these correlations (1.2-1.7) indicate that oxidative addition of the bromoarene is not the turnover-frequency determining step. The rate of reaction has a positive dependence on the concentration of alkyl bromide and catalyst, no dependence upon the amount of zinc (reducing agent), and an inverse dependence upon aryl halide concentration. These results and studies with an organic reductant (TDAE) argue against the intermediacy of organozinc reagents.
- Everson, Daniel A.,Jones, Brittany A.,Weix, Daniel J.
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supporting information; experimental part
p. 6146 - 6159
(2012/05/07)
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- An efficient hydrogenation of various alkenes using scrap automobile catalyst
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An efficient, easy, cheap, convenient, and safe procedure for the reduction of various alkenes to the corresponding alkanes is developed by using scrap automobile catalyst as an efficient hydrogenation catalyst. This procedure not only gives high yields, but also allows recycling of automobile wastes as a catalyst in organic reactions and is representative of green chemistry.
- Zengin, Mustafa,Genc, Hayriye,Demirci, Tuna,Arslan, Mustafa,Kucukislamoglu, Mustafa
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experimental part
p. 2333 - 2335
(2011/05/16)
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- CATALYST FOR CROSS-COUPLING REACTION, AND PROCESS FOR PRODUCTION OF AROMATIC COMPOUND USING THE SAME
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The present invention provides a process for efficiently producing an alkylated aromatic compound in good yield, by a cross-coupling reaction between an alkyl halide and an aromatic magnesium reagent. A process for producing an aromatic compound represented by Formula (1): [in-line-formulae]R—Ar′??(1)[/in-line-formulae]wherein R is a hydrocarbon group, and Ar′ is an aryl group;the process comprising:reacting a compound represented by Formula (2): [in-line-formulae]R—X??(2)[/in-line-formulae]wherein X is a halogen atom, and R is as defined above, with a magnesium reagent represented by Formula (3): [in-line-formulae]Ar′—MgY??(3)[/in-line-formulae]wherein Y is a halogen atom, and Ar′ is as defined above, in the presence of a catalyst for cross-coupling reactions comprising an iron compound and a bisphosphine compound represented by Formula (4): wherein Q is a divalent group derived from an aromatic ring by removing two hydrogen (H) atoms on adjacent carbon atoms; and each Ar is independently an aryl group.
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Page/Page column 22
(2011/07/06)
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- A structure-activity study of Ni-catalyzed alkyl-alkyl kumada coupling. Improved catalysts for coupling of secondary alkyl halides
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A structureactivity study was carried out for Ni catalyzed alkylalkyl Kumada-type cross coupling reactions. A series of new nickel(II) complexes including those with tridentate pincer bis(amino)amide ligands (RN2N) and those with bidentate mixed amino-amide ligands (RNN) were synthesized and structurally characterized. The coordination geometries of these complexes range from square planar, tetrahedral, to square pyramidal. The complexes had been examined as precatalysts for cross coupling of nonactivated alkyl halides, particularly secondary alkyl iodides, with alkyl Grignard reagents. Comparison was made to the results obtained with the previously reported Ni pincer complex [( MeN2N)NiCl]. A transmetalation site in the precatalysts is necessary for the catalysis. The coordination geometries and spin-states of the precatalysts have a small or no influence. The work led to the discovery of several well-defined Ni catalysts that are significantly more active and efficient than the pincer complex [(MeN2N)NiCl] for the coupling of secondary alkyl halides. The best two catalysts are [(HNN)Ni(PPh3)Cl] and [(HNN)Ni(2,4-lutidine)Cl]. The improved activity and efficiency was attributed to the fact that phosphine and lutidine ligands in these complexes can dissociate from the Ni center during catalysis. The activation of alkyl halides was shown to proceed via a radical mechanism.
- Ren, Peng,Vechorkin, Oleg,Von Allmen, Kim,Scopelliti, Rosario,Hu, Xile
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supporting information; experimental part
p. 7084 - 7095
(2011/06/26)
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- Kumadatamaocorriu coupling of alkyl halides catalyzed by an ironbisphosphine complex
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An iron(II) chloride complex possessing a sterically demanding ortho-phenylene-tethered bisphosphine ligand shows a high catalytic activity in the KumadaTamaoCorriu coupling of nonactivated alkyl halides with aryl Grignard reagents. Primary, secondary, and tertiary alkyl halides can participate as an electrophilic coupling partner. A radical clock experiment using (iodomethyl)cyclopropane exclusively gives the corresponding ring-opening coupling product, suggesting intermediacy of alkyl radical species.
- Hatakeyama, Takuji,Fujiwara, Yu-Ichi,Okada, Yoshihiro,Itoh, Takuma,Hashimoto, Toru,Kawamura, Shintaro,Ogata, Kazuki,Takaya, Hikaru,Nakamura, Masaharu
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supporting information; experimental part
p. 1030 - 1032
(2011/12/05)
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- The first iron-catalysed aluminium-variant Negishi coupling: Critical effect of co-existing salts on the dynamic equilibrium of arylaluminium species and their reactivity
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The first example of an iron-catalysed Negishi coupling between arylaluminium reagents and alkyl halides illustrates that the co-existing salts highly influence the dynamic equilibrium of the organoaluminium species, and have a critical effect on the reactivity and selectivity of the coupling reaction.
- Kawamura, Shintaro,Ishizuka, Kentaro,Takaya, Hikaru,Nakamura, Masaharu
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supporting information; experimental part
p. 6054 - 6056
(2010/11/02)
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- Reduction of alkyl halides by triethylsilane based on a cationic iridium bis(phosphinite) pincer catalyst: Scope, selectivity and mechanism
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A highly efficient procedure for the reduction of a broad range of alkyl halides by triethylsilane based on a cationic iridium bis(phosphinite) pincer catalyst has been discovered and developed. This reduction chemistry is chemoselective and has unique selectivities compared with conventional radical-based processes and the aluminum trichloride/ triethylsilane (AlCl 3/Et3SiH) and triphenylmethyl tetrakis[pentafluorophenyl] borate/triethylsilane {[Ph3C] [B(C6F5) 4]/Et3SiH} systems. Reductions use three equivalents of triethylsilane relative to the halide and can be carried out with very low catalyst loadings and in a solvent-free manner, which may provide an environmentally attractive and safe alternative to many currently practiced methods for reduction of alkyl halides. Mechanistic studies reveal a unique catalytic cycle. The cationic iridium hydride 2,6-bis[di-(tert-butyl) phosphinyloxy)phenyl-(hydrido)iridium, (POCOP)IrH+ {POCOP= 2,6-[OP(t-Bu)2]2C6H3} binds and activates the silane. This complex serves as a potent silylating reagent to generate silyl halonium ions, Et3SiXR+, which are reduced by the neutral iridium dihydride to yield alkane product and regenerate the cationic (POCOP)IrH+, thus closing the catalytic cycle. All key intermediates have been identified by in situ NMR monitoring and kinetic studies have been completed. An application of this reduction system to the catalytic hydrodehalogenation of a metal chloride complex is also described.
- Yang, Jian,Brookhart, Maurice
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scheme or table
p. 175 - 187
(2009/10/01)
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- A general method for the rapid reduction of alkenes and alkynes using sodium borohydride, acetic acid, and palladium
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Alkenes and alkynes are rapidly reduced to the corresponding alkanes using sodium borohydride and acetic acid in the presence of a small amount of palladium catalyst. The heterogeneous reaction is conducted in open air at room temperature. Reactions typically afford conversions to the alkane product of 98% or more within 15 min. The best solvent system was determined to be isopropyl alcohol, though reduction also takes place in solvents such as tetrahydrofuran, chloroform and, with some substrates, even in water. The method described is a convenient alternative to hydrogenations that require an external supply of hydrogen gas.
- Tran, Anthony T.,Huynh, Vincent A.,Friz, Emily M.,Whitney, Sara K.,Cordes, David B.
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scheme or table
p. 1817 - 1819
(2009/07/19)
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- Iron-catalyzed negishi coupling toward an effective olefin synthesis
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A selective Iron-catalyzed cross-coupling of alkyl halldes with alkenylzinc reagents Is described. Primary and secondary alkyl chlorides, bromides, and iodides take part In the reaction to give the corresponding olefins In good to excellent yields In a stereospecific manner. High functional group compatibility Is also demonstrated by using combinations of substrates possessing rather reactive substituents.
- Hatakeyama, Takuji,Nakagawa, Naohlsa,Nakamura, Masaharu
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supporting information; experimental part
p. 4496 - 4499
(2009/12/06)
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- Iron-catalysed fluoroaromatic coupling reactions under catalytic modulation with 1,2-bis(diphenylphosphino)benzene
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A catalytic amount of 1,2-bis(diphenylphosphino)benzene (DPPBz) achieves selective cleavage of sp3-carbon-halogen bond in the iron-catalysed cross-coupling between polyfluorinated arylzinc reagents and alkyl halides, which was unachievable with
- Hatakeyama, Takuji,Kondo, Yoshiyuki,Fujiwara, Yu-Ichi,Takaya, Hikaru,Ito, Shingo,Nakamura, Eiichi,Nakamura, Masaharu
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supporting information; experimental part
p. 1216 - 1218
(2009/07/10)
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- Catalytic ring expansion, contraction, and metathesis-polymerization of cycloalkanes
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Tandem dehydrogenation-olefin-metathesis catalyst systems, comprising a pincer-ligated iridium-based alkane dehydrogenation catalyst and a molybdenum-based olefin-metathesis catalyst, are reported to effect the metathesis-cyclooligomerization of cyclooctane and cyclodecane to give cycloalkanes with various carbon numbers, predominantly multiples of the substrate carbon number, and polymers. The Royal Society of Chemistry.
- Ahuja, Ritu,Kundu, Sabuj,Goldman, Alan S.,Brookhart, Maurice,Vicente, Brian C.,Scott, Susannah L.
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p. 253 - 255
(2008/03/13)
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- PROCESS FOR PRODUCTION OF AROMATIC COMPOUNDS
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A problem of the present invention is to provide an economical process with minimized toxicity for producing an aromatic compound having a variety of substituents such as various alkyl groups, and the problem is solved by a process for production of an aromatic compound represented by formula (1) below, which comprises reacting a compound represented by formula (2) below with an aromatic magnesium reagent represented by formula (3a) below in the presence of an iron catalyst and a diamine compound: wherein R is an optionally substituted hydrocarbon group or a C 3 - C 10 saturated or unsaturated ring group; A is an optionally substituted C 4 - C 20 aromatic group or an optionally substituted heteroaromatic group; X is a halogen atom or a sulfonic acid ester; and Y 1 is bromine, iodine, chlorine or a carbanion ligand.
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Page/Page column 33-34
(2010/11/24)
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- Silica-supported dendrimer-palladium complex-catalyzed selective hydrogenation of dienes to monoolefins
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The selective hydrogenation of cyclic and acyclic dienes to monoolefins occurs under very mild conditions, in the presence of silica-supported PAMAM-Pd complexes. The activity and selectivity of this reaction is sensitive to the dendrimer structure. These dendritic complexes display excellent recycle properties, retaining activity for up to eight recycles.
- Zweni, Pumza P.,Alper, Howard
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p. 725 - 731
(2007/10/03)
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- C7+ paraffin isomerisation process and catalyst therefore
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There is provided a process for selective isomerisation of C4+ paraffins using a catalyst comprising mixed aluminium, tungsten and zirconium oxides, and a hydrogenation/dehydrogenation component, such as palladium or other Group VIII metals. The feed may optionally also include shorter paraffins, aromatics or cycloparaffins.
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- Iron-Catalyzed Cross-Coupling of Primary and Secondary Alkyl Halides with Aryl Grignard Reagents
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An iron-catalyzed cross-coupling reaction of a primary or secondary alkyl halide with an aryl Grignard reagent proceeds under mild conditions to give the corresponding coupling product in quantitative yield. Copyright
- Nakamura, Masaharu,Matsuo, Keiko,Ito, Shingo,Nakamura, Eiichi
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p. 3686 - 3687
(2007/10/03)
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- Polyoxometalates as reduction catalysts: Deoxygenation and hydrogenation of carbonyl compounds
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Excellent deoxygenation of ketones and aldehydes is achieved with Keggin-type polyoxometalates in the presence of hydrogen (see Equation (1) for an example). The mixed addenda phosphovanadomolybdate [PV2Mo10O4]5- was found to be the best catalyst. X-ray diffraction and IR studies suggest that the polyoxometalates are structurally stable under the strongly reducing conditions.
- Kogan, Vladimir,Aizenshtat, Zeev,Neumann, Ronny
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p. 3331 - 3334
(2007/10/03)
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- Selective Hydrogenations of Dienes and Olefins by t)6(py)2>
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Hydrocarbon solutions of t)6(py)2> in the presence of H2 (3 atm, 23 deg C) hydrogenate linear 1,3-dienes to 3-enes, 1,3- and 1,5-cyclooctadiene to cyclooctene, 1,3-cyclohexadiene to cyclohexene, cyclopentene to cyclopentane, and norbornene to norbornane, but do not hydrogenate α- and internal olefins to alkanes, or internal conjugated or unconjugated dienes.
- Barry, Jane T.,Chisholm, Malcolm H.
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p. 1599 - 1600
(2007/10/02)
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- Hydrogenation via photochemically generated diimide
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Diimide is a well-known reagent for hydrogenating multiple bonds with very high stereospecificity. However, all of the methods for generating diimide require somewhat rigorous conditions. We show here that 1-thia-3,4-diazolidine-2,5-dione (TDADH) can be used to photochemically produce diimide at room temperature under neutral conditions. The diimide thus produced can hydrogenate multiple bonds in high yields.
- Squillacote,De Felippis,Lai
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p. 4137 - 4140
(2007/10/02)
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- Catalytic procedure for the synthesis of cycloalkanemethanols from cycloalkenes and aqueous methyl formate
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Cycloalkanemethanols are synthesized via hydrocarbonylation (hydroformylation) of the corresponding cycloalkenes in the presence of aqueous methyl formate. Methyl formate is the source of carbon monoxide and hydrogen is generated by the water gas shift reaction. The selectivity is affected by the concomitant hydrogenation process.
- Jenner
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p. 505 - 508
(2007/10/02)
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- CATALYTIC HYDROGENOLYSIS OF CYCLOPROPANES: METAL INSERTION INTO A SATURATED CARBON-CARBON BOND AS THE KEY STEP
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Hydrogenolytic ring cleavage of gem-difluorocyclopropanes occurs exclusively at the carbon-carbon bond opposite to the halogen-bearing center and affords mainly gem-difluoroalkanes.The intermediacy of catalyst/cyclopropane derived adducts (e.g., palladocyclobutanes or 1,3-dipalladiopropanes) is postulated in order to rationalize the formation of monofluorinated and halogen-free by-products and, in addition, to explain specific substituent effects on the reaction rates.
- Bessard, Ives,Schlosser, Manfred
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p. 1231 - 1238
(2007/10/02)
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- The Mechanim of Formation of Grignard Reagents: Trapping of Free Alkyl Radical Intermediates by Reaction with Tetramethylpiperidine-N-oxyl
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In the presence of the free radical scavenger 2,2,6,6-tetramethylpiperidine-N-oxyl (TMPO., 0.50 M), cycloheptyl bromide (RBr, 0.001 M) reacts with magnesium metal in a solution containing tert-amyl alcohol (5.0 M), lithium bromide (0.05 M), and diethyl ether at 20 deg C and forms N-cycloheptoxy-2,2,6,6-tetramethylpiperidine (TMPOR) as the major product (>/=93percent yield, based on RBr).In the absence of TMPO., cycloheptane (RH) is formed in >/=95percent yield.The dependence of the relative yields of TMPOR and RH on the initial concentration of TMPO. suggests that bothproducts share a common precursor-free cycloheptyl radical-and that this radical has a median lifetime of ca. 1E-7 s.Cycloheptyl radicals appear to be intermediates on the major path to the Grignard reagent cycloheptylmagnesium bromide.TMPO. is reduced by Mg(0) to the anion of the corresponding hydroxylamine, TMPO(1-), at a rate that is competitive with that of the reaction between RBr and Mg(0).Although the magnesium salts of TMPO(1-) are insoluble in diethyl ether, solutions containing TMPO(1-), Mg(2+), and Li(1+) remain homogeneous.For systems containing a high concentration of tert-amyl alcohol, a simple mathematical model attributes apparent zero-order kinetic behavior to the dependence of reactive surface area on the extent of reaction between alkyl halide and Mg.
- Root, Karen S.,Hill, Craig L.,Lawrence, Lynette M.,Whitesides, George M.
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p. 5405 - 5412
(2007/10/02)
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- CLEMMENSEN REDUCTIONS USING ULTRASONIC IRRADIATION
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A variety of ketones have been reduced to the corresponding methylene compounds using amalgamated zinc and conducting the reaction in an ultrasonic laboratory cleaner.
- Reeves, Preston W.,Murry, Jerry A.,Willoughby, Duke Wayne,Friedrich, William Joel
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p. 1961 - 1966
(2007/10/02)
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- Reduction of Ethylenic Insaturations by in situ Generated Hydrogen
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Selective hydrogenation of carbon-carbon double bond can be easily performed by simultaneous addition of substrate and Me3SiCl or water to NiCRA.It is shown that it is possible to reduce dienes selectively in olefins and carbon-carbon double bond in the presence of carbonyl, ester or acid groups.
- Fort, Y.,Vanderesse, R.,Caubere, P.
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p. 757 - 760
(2007/10/02)
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- CATALYTIC HYDROGENATION OF OLEFINS IN BIPHASIC WATER-LIQUID SYSTEM
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Cyclic and linear olefins and polyenes with or without functional groups are hydrogenated under very mild reaction conditions.Emphasis is put on the advantages of this method which requires no solvent and a water-soluble non air-sensitive catalyst.
- Larpent, Chantal,Dabard, Renee,Patin, Henri
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p. 2507 - 2510
(2007/10/02)
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- NICKELOCENE/LITHIUM ALUMINIUM HYDRIDE - A "HOMOGENEOUS RANEY NICKEL" FOR CATALYTIC HYDROGENATION
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Nickelocene/lithium aluminium hydride in THF has been found to be an active homogeneous catalyst for catalytic hydrogenation.The reaction behaviour is very similar to Raney nickel.
- Ho, Kin Man,Chan, Man-Chor,Luh, Tien-Yau
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p. 5383 - 5384
(2007/10/02)
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- Silica-Supported Cyclopentadienyl-Rhodium(I),-Cobalt(I), and-Titanium(IV) Complexes
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The silylated cyclopentadiene derivative, (MeO)3Si(CH2)3C5H5, synthesised from commercially-available (MeO)3Si(CH2)3Cl, has been used to prepare the complexes 5-(MeO)3Si(CH2)3C5H4>Rh(CO)2, 5(MeO)3Si(CH2)3C5H4>Rh(COD)(COD= cyclo-octa-1,5-diene), and 5-(MeO)3Si(CH2)3C5H4>2TiCl2.The complexes 5(MeO)3Si(CH2)3C5H4>TiCl3, prepared by reaction of NaC5H4(CH2)3Si(OMe)3 with TiCl4 (1/1 molar ratio) and also by reaction of 5-(MeO)3Si(CH2)3C5H4>Ti(OEt)3 with CH3COCl, proved to be very unstable.Attempts to synthesise the complex 5-(MeO)3Si(CH2)3C5H4>(η5-C5H5)TiCl2, either by reaction of 5-(MeO)3Si(CH2)3C5H4>TiCl3 with NaC5H4 or reaction of (η5-C5H5)TiCl3 with NaC5H4(CH2)3Si(OMe)3, gave none of the expected product and only (η5-C5H5)TiCl2 could be isolated from these reactions.The cyclo-octadiene rhodium complex supported on silica has been shown to be an efficient cyclotrimerization catalyst, and the silica-supported titanium complex SIL-(CH2)3C5H4)TiCl2 is, after reduction with butyllithium, an efficient and selective catalyst for the hydrogenation of alk-1-enes.
- Booth, B. L.,Ofunne, G. C.,Stacey, C.,Tait, P. J. T.
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p. 143 - 156
(2007/10/02)
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- Hydrogenolysis of Small Cycloalkanes, X. - Catalytic Hydrogenation of Bicycloalkanes
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Dependent on n different products are obtained from bicycloalkanes by hydrogenation on Pt and Pd/C catalysts: from n = 5 onward only methylcycloalkanes of the same ring size; with n = 4 additionally 2-7 percent of cycloheptane is formed; with n = 3 ring enlargement increases to 5-20 percent and with n = 2 cyclopentane is the only product.Mainly butane is formed from bicyclobutane and no intermediate could be detected.Explanations are attempted.The expected products are produced on hydrogenation of methyl-substituted derivatives and spiroalkanes.
- Stahl, Karl-Johannes,Hertzsch, Winfried,Musso, Hans
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p. 1474 - 1484
(2007/10/02)
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- Biphasic hydrogenation of olefins, dienes, and α,β-unsaturated carbonyl compounds catalyzed by the dimer of chloro(1,5-hexadiene)rhodium
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Olefins, dienes, and trienes can be hydrogenated in an aqueous-organic two-phase medium using the dimer of chloro(1,5-hexadiene)rhodium as the catalyst.Selective reduction of the double bond of α,β-unsaturated carbonyls occurs in high yields.These reactions occur at room temperatures and atmospheric pressure, and are simple to work up.
- Januszkiewicz, Krzysztof R.,Alper, Howard
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p. 1031 - 1033
(2007/10/02)
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- Selective Reductions. 31. Lithium Triethylborohydride as an Exceptionally Powerful Nucleophile. A New and Remarkably Rapid Methodology for the Hydrogenolysis of Alkyl Halides under Mild Conditions
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Lithium triethylborohydride exhibits enormous nucleophilic power in SN2 displacement reactions with alkyl halides, far more powerful than the other common nucleophiles, such as n-butyl mercaptide (14 times), thiophenoxide (20 times), borohydride (1E4 times), and nitrate (1E7 times).The reaction follows second-order kinetics and exhibits typical characteristics of a nucleophilic substitution of the SN2 type.In addition to being the best nucleophile, it is the most powerful nucleophilic reducing agent available for the reduction of alkyl halides, far more powerful and cleaner than lithium aluminum hydride and lithium borohydride.Even hindered alkyl halides, such as cyclohexyl bromide, neopentyl bromide, and exo-norbornyl bromide, undergo facile reduction to the corresponding alkanes in > 96 percent yield with this reagent.Consequently, the new reagent provides a highly useful and simple means as a probe for studying SN2 displacement reactions and also for the facile dehalogenation of hindered alkyl halides where this is required in synthetic transformations.The corresponding deuterated derivative, lithium triethylborodeuteride, conveniently synthesized from lithium deuteride and triethylborane, is useful for the stereospecific introduction of deuterium in the molecule.
- Krishnamurthy, S.,Brown, Herbert C.
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p. 3085 - 3091
(2007/10/02)
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- Hydrogenolysis of Cyclo-octane and Cyclo-octene on Supported Fischer-Tropsch Catalysts. Cyclic vs. Noncyclic Selectivity
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Hydrogenolysis of cyclo-octane or cyclo-octene over silica-supported ruthenium, nickel, and cobalt catalysts gives rise to n-alkanes and cycloalkanes (C5 - C7); ruthenium strongly favours n-alkanes, cobalt, strongly facilitates cycloalkane formation, and
- Kyba, Evan P.,Chiou, Huh-Sun,Cornell, Mary E.
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p. 1220 - 1222
(2007/10/02)
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- Ionization Energies and Entropies of Cycloalkanes. Kinetics of Free Energy Controlled Charge-Transfer Reactions.
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Enthalpies and entropies of ionization (ΔH0ion and ΔS0ion) of alkylcyclohexanes, as well as cycloheptane, cyclooctane, and trans-Decalin, have been determined by charge-transfer equilibrium measurements.Values of ΔHion, in units of kcal mol-1 (or eV), range from 229.6 (9.96) for cycloheptane to 210.7 (9.14) for trans-Decalin.A major effect of alkyl substitution is observed following substitution at a site α to a tertiary hydrogen atom (as from methylcyclohexane to 1,2-dimethylcyclohexane), or following replacement of a tertiary hydrogen atom (as from methylcyclohexane to 1,1-dimethylcyclohexane).In both cases, ΔH0 ion decreases by ca. 5 kcal mol-1.Entropies of ionization are near zero for alkylcyclohexanes but range up to 5 cal deg-1 mol-1 for nonsubstituted cycloalkanes (cyclooctane).The charge-transfer reactions involving the cycloalkanes are shown to be fast processes; i.e., the sum of the reaction efficiencies (r=k/kcollision) of the forward and reverse processes is near unity.The efficiencies of these processes appear to be determined uniquely by the overall free energy change (or equilibrium constant K).Specifically, the reaction efficiencies are defined, within a factor of 2 by the relation r=K/(1+K), which can be justified by using transition-state theory applied to the decomposition of a collision complex over surfaces lacking energy barriers.These reactions are defined as intrinsically fast processes in that they are slowed only by the overall reaction thermochemistry and not by any properties or reactions of the intermediate complex.
- Sieck, L. Wayne,Mautner, Michael
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p. 3646 - 3650
(2007/10/02)
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- Heterogeneous Catalysis, VI. Direct Reduction of Alcohols to Hydrocarbons
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Secondary and tertiary alcohols are converted cleanly to the parent hydrocarbons in the gas phase with H2 in the presence of a Ni/Al2O3 catalyst at 190 deg C.Primary alcohols are dehydroxymethylated; e.g., 1-hydroxymethyladamantane (4) gives adamantane (1).Alumina alone, in the absence of Ni, results in the formation of homoadamantane (5) from 4. - Keywords: Gas Phase Hydrogenolysis, Homoadamantane Preparation
- Maier, Wilhelm F.,Thies, Irina,Rague Schleyer, Paul von
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p. 392 - 394
(2007/10/02)
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- A HIGHLY ACTIVE SUPPORTED CATALYST FOR OLEFIN HYDROGENATION FROM COLLOIDAL NICKEL BORIDE
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Supported catalysts, which were prepared from colloidal nickel boride by immobilizing on inorganic substances such as Mg(OH)2, exhibited higher activity for olefin hydrogenation than a sol-type catalyst of colloidal nickel boride protected by polyvinylpyrrolidone.
- Nakao, Yukimichi
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p. 997 - 998
(2007/10/02)
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- NEW METALLIC CATALYSTS OBTAINED BY SUPPORTING PLATINUM ON AlPO4-Al2O3 AND AlPO4-SiO2 SYSTEMS
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The synthesis of metallic catalysts obtained by supporting platinum on AlPO4/γ-Al2O3 and AlPO4/SiO2 systems is described.Their performance in the reduction of alkenes at low hydrogen pressure (1-5 bar) is reported.
- Aramendia, M. A.,Borau, V.,Jimenez, C.,Marinas, J. M.
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- Thermochemical Bond Dissociation Energies of Carbon-Magnesium Bonds
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The heats of formation of 29 alkylmagnesium bromides, isobutyl bromide, and neopentyl bromide have been determined, and bond dissociation energies have been derived for the Grignard reagents.For saturated alkyl derivatives the C-Mg bond strength decreases with an increasing number of β-hydrogens in the series methyl, neopentyl, isobutyl, butyl, ethyl, 1-ethylpropyl, 1-methylpropyl, isopropyl, and t-butyl.Bonding in alkyl bromides and alkylmagnesium bromides is discussed.
- Holm, Torkil
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p. 464 - 467
(2007/10/02)
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- HETEROGENEOUS DEOXYGENATION OF KETONES
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Relatively unhindered ketones are converted directly to the corresponding hydrocarbons in the presence of hydrogen at normal pressures and a Ni/Al2O3 catalyst in a simple gas-phase reactor.
- Maier, W. F.,Bergmann, K.,Bleicher, W.,Schleyer, P. v. R.
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p. 4227 - 4230
(2007/10/02)
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- Surface Compounds of Transition Metals, XXIII The Reaction of Cycloolefines with Surface Chromium(II) on Silicagel at Higher Temperature
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By reaction with surface chromium(II) on silicagel at T>150 deg C, cycloolefins can undergo ring contraction, methylation/demethylation, hydrogenation/dehydrogenation, and isomerization.Furthermore, n-alkanes (C1...C4) are formed incorporating support hydrogen.- As in the case of the corresponding acyclic olefins, a common intermediate MC3 (metallacyclobutaneHM-allyl complex) for all these reactions is postulated; the transfer of C1 units is claimed to proceed via a carbene M = CH2 derived from the MC3 precurser. - Keywords: Surface Compounds, Ring Contraction, Methylation/Demethylation, Hydrogenation/Dehydrogenation, Carbene Intermed iates
- Krauss, Hans-Ludwig,Hums, Erich
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p. 848 - 854
(2007/10/02)
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