25267-51-0Relevant articles and documents
Temperature Switching of Product Chirality upon Photosensitized Enantiodifferentiating Cis-Trans Isomerization of Cyclooctene
Inoue, Yoshihisa,Yokoyama, Taizo,Yamasaki, Noritsugu,Tai, Akira
, p. 6480 - 6482 (1989)
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Pumice-Supported Pd-Pt Bimetallic Catalysts: Synthesis, Structural Characterization, and Liquid-Phase Hydrogenation of 1,3-Cyclooctadiene
Deganello, Giulio,Duca, Dario,Liotta, Leonarda F.,Martorana, Antonino,Venezia, Anna Maria,et al.
, p. 125 - 134 (1995)
A series of pumice-supported palladium-platinum bimetallic catalysts were prepared and investigated by X-ray scattering (WAXS and SAXS) and XPS technique.An alloy Pd-Pt was formed.The less abundant metal was found to segregate to the surface.The catalysts were tested in the liquid-phase hydrogenation of 1,3-cyclooctadiene to cyclooctene, and compared with similarly prepared pumice-supported palladium and platinum catalysts and other supported Pd-Pt catalysts reported in the literature.The addition of platinum reduces the activity and the selectivity of the palladium catalysts.Differences between the activity of these pumice-supported catalysts and the activity of previously described Pd and Pd-Pt catalysts on other supports, are attributed to the presence, in the latter, of diffusional processes.
Homogeneous Catalytic Photochemical Functionalization of Alkanes by α-Dodecatungstophosphate. Rate Behavior, Energetics, and General Characteristics of the Processes
Renneke, Roman F.,Hill, Craig L.
, p. 5461 - 5470 (1988)
The photochemical functionalization of saturated hydrocarbons catalyzed by the heteropolytungstate α-dodecatungstophospate in acetonitrile solution has been examined in detail.Under anaerobic conditions, the net processes involve oxidation of alkane, RH, and evolution of hydrogen (RH->R+1/2H2) with conversion of light into chemical energy (ΔHo>+30 kcal/mol of RH oxidized in some cases).The processes are catalytic in the polyoxotungstate with or without Pt(0) or other hydrogen evolution catalyst, but Pt(0) greatly accelerates the reoxidation of the photoreduced polyoxotungstate, the slow step, resulting in increased turnover rates.Two oxidative titration procedures adapted for these hydrophobic media, and the sizes and shapes of the electronic absorption chromophores generated as a function of time upon irradiation in the near-UV of α-H3PW12O40 (1) in acetonitrile solutions of representative alkanes, establish that the principal form of the photoreduced catalyst is the one-electron heteropoly blue species α-PW12O40(4-), in contrast to the case for photooxidation of alcohols and other organic substrates by 1.The product distributions have been established for the functionalization of representative branched alkanes and cycloalkanes.The relative yields of the initial alkane-derived oxidation products in these processes, alkene, N-alkylacetamide, alkylalkane dimer, and alkyl methyl ketone, vary with the alkane substrate, the form of the polyoxotungstate, and the reaction conditions.All these organic products are remarkably stable under the reaction conditions.Alcohols are not produced in these polyoxotungstate-based systems.The highest selectivities (ca. 100percent for alkene production) are seen with 1 in the absence of Pt(0).Quantum yields average 0.1 but vary with the form of the polyoxotungstate and the reaction conditions and can be considerably higher.For the exemplary system, substrate = cyclooctane and catalyst = 1, production of α-PW12O40(4-) is a one-photon process that is first order in alkane, inverse order in water for low concentrations of water, and zero order in 1 for high concentrations of 1.A rate law that involves the substrate, solvent, initial products, catalyst, and light intensity in accord with substantial kinetic data is derived.The relative observed rate constants for the production of α-PW12O40(4-) under optically dense conditions by photooxidation of several normal, branched, and cyclic alkanes by 1 are unlike those seen in radical, hydride abstraction, electrophilic, or any type alkane activation process documented for homogeneous liquid-phase reactions.These relative rates, the primary kinetic isotope effects kcyclohexane-h12/kcyclohexane-d12 = 1.38 and kcis-Decalin-h12/Kcis-Decalin-d12 = 1.39, and the product distribution studies are most compatible with electron transfer as the principal alkane activation process in the mechanism.These data also allow analysis...
Catalytic Alkane Transfer Dehydrogenation by PSP-Pincer-Ligated Ruthenium. Deactivation of an Extremely Reactive Fragment by Formation of Allyl Hydride Complexes
Zhou, Xiaoguang,Malakar, Santanu,Zhou, Tian,Murugesan, Sathiyamoorthy,Huang, Carlos,Emge, Thomas J.,Krogh-Jespersen, Karsten,Goldman, Alan S.
, p. 4072 - 4083 (2019)
Iridium complexes bearing PCP-type pincer ligands are the most effective catalysts reported to date for the low-temperature (≤ca. 200 °C) dehydrogenation of alkanes. To investigate the activity of formally isoelectronic ruthenium complexes, we have synthesized the neutral 2,7-di-tert-butyl-4,5-bis(diisopropylphosphino)-9,9-dimethylthioxanthene (iPrxanPSP) pincer ligand and several Ru complexes thereof. The (iPrxanPSP)Ru complexes catalyze alkane transfer dehydrogenation of the benchmark cyclooctane/t-butylethylene (COA/TBE) couple with turnover frequencies up to ca. 1 s-1 at 150 °C and 0.2 s-1 at 120 °C, the highest rates for alkane dehydrogenation ever reported at such temperatures. Dehydrogenation of n-octane, however, is much less effective. A combination of experiment and DFT calculations allow us to explain why (iPrxanPSP)Ru is more effective than (iPrPCP)Ir for dehydrogenation of COA, while the reverse is true for dehydrogenation of n-alkanes. Considering only in-cycle species and simple olefin complexes, the (iPrxanPSP)Ru fragment is calculated to be much more active than (iPrPCP)Ir for dehydrogenation of both COA and n-alkanes. However, the resting state in the (iPrxanPSP)Ru-catalyzed transfer dehydrogenation of n-alkane is a very stable linear-allyl hydride complex, whereas the corresponding cyclooctenyl hydride is much less stable.
Metal dependence in gif-type reactions. The Cu(II)-catalyzed olefination of saturaed hydrocarbons by tert-butyl hydroperoxide
Barton,Beviere,Chavasiri,Doller,Hu
, p. 567 - 570 (1993)
Cycloalkanes are transformed into the corresponding cycloalkanes by treatment with tert-butyl hydroperoxide (TBHP) in pyridine/acetic acid solution in the presence of Cu(OAc)2.H2O. When iron salts are used instead of copper salts, the major reaction product is the corresponding ketone. Differences between the iron-catalyzed and the copper-catalyzed reactions support a metal-dependent reaction pathway.
β',β-Carbanionic Elimination Reaction of a Carboxylic Ester
Aubert, Corinne,Begue, Jean-Pierre,Biellmann, Jean-Francois
, p. 351 - 352 (1984)
The β',β-elimination reaction of the ester (1) gives cis-cyclo-octene in >70 percent yield; the corresponding reactions of the stereoselectively deuterium labelled compounds (1a) and (1b) show that the elimination is syn.
Epoxidation of trans-cyclooctene by methyltrioxorhenium/H2O2: Reaction of trans-epoxide with the monoperoxo complex
Adam, Waldemar,Saha-Moeller, Chantu R.,Weichold, Oliver
, p. 5001 - 5004 (2000)
The epoxidation of trans-cyclooctene (trans-1) with the MTO/H2O2, MTO/UHP, and NaY/MTO/H2O2 oxidants leads to a mixture of trans/cis-olefins 1, trans/cis-epoxides 2, and the cis-diol 3. While the oxygen transfer proceeds stereoselectively, the monoperoxo rhenium complex A, which is generated in situ during the catalytic cycle, is responsible for the facile deoxygenation, isomerization, and hydrolysis of the trans-epoxide. In the case of the homogeneous MTO/H2O2 system, rapid decomposition of the catalytically active rhenium species into HReO4 circumvents the formation of such side products. In contrast, for the heterogeneous oxidants MTO/UHP and NaY/MTO/H2O2, the catalytically active rhenium species are sufficiently stabilized and survive long enough to promote the observed side reactions.
Deyrup,Betkouski
, p. 3561 (1972)
Dinuclear iridium and rhodium complexes with bridging arylimidazolide-N3,C2 ligands: Synthetic, structural, reactivity, electrochemical and spectroscopic studies
He, Fan,Ruhlmann, Laurent,Gisselbrecht, Jean-Paul,Choua, Sylvie,Orio, Maylis,Wesolek, Marcel,Danopoulos, Andreas A.,Braunstein, Pierre
, p. 17030 - 17044 (2015)
Deprotonation of 1-arylimidazoles (aryl = mesityl (Mes), 2,6-diisopropylphenyl (Dipp)), with n-butyl lithium afforded the corresponding derivatives (1-aryl-1H-imidazol-2-yl)lithium (1a, Ar = Mes; 1b, Ar = Dipp) in good yield. Reaction of 1a with 0.5 equiv. of [Ir(cod)(μ-Cl)]2 yielded two geometrical isomers of a doubly C2,N3-bridged dinuclear complex [Ir(cod){μ-C3H2N2(Mes)-κC2,κN3}]2 (3), 3H-H, a head-to-head (H-H) isomer of CS symmetry, and 3H-T, the thermodynamically preferred head-to-tail (H-T) isomer of C2 symmetry. The metallated carbon of the 4 electron donor anionic bridging ligands has some carbene character, reminiscent of the situation in N-metallated protic NHC complexes. Displacement of cod ligands from 3H-H and 3H-T afforded the tetracarbonyl complexes [Ir(CO)2{μ-C3H2N2(Mes)-κC2,κN3}]24H-H and 4H-T, respectively. The reaction with PMe3, which gave only one complex, [Ir(CO)(PMe3){μ-C3H2N2(Mes)-κC2,κN3}]2 (5), demonstrates that the isomerization of the central core Ir[μ-C3H2N2(Mes)-κC2,κN3]2Ir from H-H to H-T on going from 4H-H to 5 is readily triggered by phosphine substitution under mild conditions. Oxidative-addition of MeI to 5 afforded the formally metal-metal bonded d7-d7 complex [Ir2(CO)2(PMe3)2(Me)I{μ-C3H2N2(Mes)-κC2,κN3}2] (6). The blue [Ir(C2H4)2{μ-C3H2N2(Mes)-κC2,κN3}]2 (7) and purple [Rh(C2H4)2{μ-C3H2N2(Dipp)-κC2,κN3}]2 (9) tetraethylene complexes were also obtained with only a H-T arrangement of the bridging ligands. Although only modestly efficient in alkane dehydrogenation, complex 7 was found to be a more active pre-catalyst than 3H-T, 4H-T and 5, probably because of the favorable lability of the ethylene ligands. From cyclic voltammetry, exhaustive coulometry and spectroelectrochemistry studies, it was concluded that 3H-T undergoes a metal-based one electron oxidation to generate the mixed-valent Ir(i)/Ir(ii) system. The energy of the intervalence band for the orange dirhodium complex [Rh(cod){μ-C3H2N2(Mes)-κC2,κN3}]2 (8) is shifted toward lower energies in comparison with 3H-T, reflecting the decrease of the energy with the intermetallic distance. It was concluded from the EPR study that the Ir and Rh centres contribute substantially to the experimental magnetic anisotropy and thus to the singly occupied molecular orbital (SOMO) in the mixed-valent Ir(i)/Ir(ii) and Rh(i)/Rh(ii) systems. The molecular structures of 3H-H, 3H-T, 8 and 9 have been determined by X-ray diffraction.
A binuclear alkenyl-bridged zirconium complex catalyzes the chemoselective hydrogenation of 1,3-cyclooctadiene to cyclooctene
Raoult, Yveline,Choukroun, Robert,Gervais, Daniele,Erker, Gerhard
, p. C1 - C3 (1990)
The oligomeric hydrido zirconium complex 2Zr(H)(CH2PPh2)>n (1) reacts with (η4-butadiene)zirconocene to yield the (μ-1-η1 : 1,2-η2-butenyl), (μ-phosphinomethylene) doubly bridged binuclear zirconocene complex 2Zr(μ-CH=CHC2H5)(μ-CH2PPh2)ZrCp2> 2.Complex 1 reacts with butadiene to give 2 and Ph2PCH3.At 80 deg C complex 2 catalyzes the chemoselective hydrogenation of 1,3-cyclooctadiene to cyclooctene.Formation of a binuclear μ-alkenyl zirconium(IV)/zirconium(II) intermediate, similar to 2, is proposed to explain the effective protection of the remaining C=C double bond in the catalytic cycle.
Dendrimer-encapsulated Pd nanoparticles as fluorous phase-soluble catalysts [15]
Chechik, Victor,Crooks, Richard M.
, p. 1243 - 1244 (2000)
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Waters
, p. 1569 (1971)
Unusual Stereochemistry in the Thermal Deazetation of a Bicyclic Azo Compound
Samuel, Christopher J.
, p. 131 - 132 (1982)
Thermolysis of the stereospecifically deuteriated azo-compound (1D) led to bicyclo-octane (3) with complete retention and octadiene (4) with partial loss of stereochemistry.
First asymmetric photosensitization in supercritical fluid. Exceptionally high pressure/density dependence of optical yield in photosensitized enantiodifferentiating isomerization of cyclooctene
Saito, Ryota,Kaneda, Masayuki,Wada, Takehiko,Katoh, Akira,Inoue, Yoshihisa
, p. 860 - 861 (2002)
The photosensitized enantiodifferentiating isomerization of (Z)-cyclooctene (1Z) in supercritical carbon dioxide has been performed for the first time. The critical control of the enantiomeric excess (ee) of chiral product, (E)-cyclooctene (1E), and even the switching of the product's chirality were achieved through a small change of pressure particularly in the low-density region near the critical density. Quantitative evaluation of these ee changes was achieved by estimating differential activation volumes between the diastereomeric transition states of the reaction.
Inoue et al.
, p. 423 (1976)
Model Pumices Supported Metal Catalysts: II. Liquid Phase Selective Hydrogenation of 1,3-Cyclooctadiene
Liotta, Leonarda F.,Venezia, Anna Maria,Martorana, Antonino,Deganello, Giulio
, p. 177 - 183 (1997)
The catalyzed, selective hydrogenation, in liquid phase, of 1,3-cyclooctadiene was studied on a series of Pd catalysts supported on natural pumice, model pumices (with variable content of alkali metal ions), silica, and sodium-doped silica. At constant pressure of H2 (1 atm.) the reaction follows a zero-order kinetic for all the Pd catalysts. At low metal dispersion (Dx x, the binding energy shift of Pd 3d level is negative in Pd/pumice and positive in Pd/silica with respect to unsupported Pd metal. The different performances of the Pd/pumice catalysts are explained by the presence of alkali metal ions in the framework of the support. Addition of sodium ions to Pd/silica catalysts produces a negative shift of the binding energy, but the activity is not improved because the number of active sites diminished due to decoration of palladium particles by sodium ions. The Pd catalysts with alkali metal ions in the support are resistant to air oxidation. In Pd catalysts containing alkali metal ions the selectivity to cyclooctene is practically 100% and the constant rates ratio k1/k2 is more than 1000 with a maximum at dispersion 35-40%, whereas the selectivity in Pd catalysts without alkali metal ions decreases continuously at increasing dispersion.
Thermal Dehydrogenation of Cyclooctane by Supported Noble Metal Catalysts
Fujii, Takahiro,Yukawa, Kiyoshi,Saito, Yasukazu
, p. 938 - 941 (1991)
Under boiling and refluxing conditions, cyclooctane has been dehydrogenated to cyclooctene and molecular hydrogen selectively with carbon- and alumina-supported Pd, Rh, and Ru catalysts.The activity order among these metal catalysts was Pd>Rh>Ru.The most
Luibrand,Hoffmann
, p. 3887 (1974)
A Readily Synthesized and Highly Active Epoxide Carbonylation Catalyst Based on a Chromium Porphyrin Framework: Expanding the Range of Available β-Lactones
Schmidt, Joseph A. R.,Mahadevan, Viswanath,Getzler, Yutan D. Y. L.,Coates, Geoffrey W.
, p. 373 - 376 (2004)
(Martix presented) Catalytic carbonylation of epoxides to β-lactones was effected by a highly active and selective bimetallic catalyst comprised of a chromium(III) porphyrin cation and a cobalt tetracarbonyl anion. The complex is readily synthesized from commercially available compounds in high yield. Carbonylation of numerous linear epoxides, as well as bicyclic epoxides derived from 8- and 12-membered hydrocarbons, proceeded with high activity, selectivity, and yield.
Inoue et al.
, p. 1024 (1978)
Thermocatalytic Formation of Molecular Hydrogen and Cyclo-octene from Cyclo-octane by Rhodium Complexes
Fujii, Takahiro,Saito, Yasukazu
, p. 757 - 758 (1990)
Dehydrogenation of cyclo-octane, yielding cyclo-octene and molecular hydrogen, proceeds catalytically with the Wilkinson complex RhClL3 or with its dimeric homologue without photo-irradiation under reflux conditions.
First absolute asymmetric synthesis with circularly polarized synchrotron radiation in the vacuum ultraviolet region: Direct photoderacemization of (E)-cyclooctene
Inoue, Yoshihisa,Tsuneishi, Hiroshi,Hakushi, Tadao,Yagi, Kazutoshi,Awazu, Koichi,Onuki, Hideo
, p. 2627 - 2628 (1996)
A newly developed polarizing undulator installed in a storage ring was employed for the first time as a source of circularly polarized synchrotron radiation in the vacuum ultraviolet to effect enantiodifferentiating direct photoisomerization of (E)-cyclooctene; the photolysis is taken as a terrestrial mimic or proof of extraterrestrial absolute asymmetric synthesis on interstellar grains by the polarized synchrotron radiation from fast electrons orbiting a neutron star, which is thought to be a distant origin of the homochirality in the biosphere.
Yarchak et al.
, p. 5224 (1973)
Synthesis of new ferrocenyl amine sulfide and selenide complexes of group 10 metals and their catalytic activites toward selective hydrogenation, isomerisation, and asymmetric Grignard cross-coupling reactions
Naiini, Ahmad A.,Lai, Chung-Kung,Ward, Donald L.,Brubaker, Carl H.
, p. 73 - 90 (1990)
Two series of previously unknown ferrocenyl amine sulfide and selenide ligands (S,R)-C5H4FeC5H3 and C5H4FeC5H3, where E = S and Se; R = Me, Ph, Bz, 4-tolyl, and 4-ClPh, have been prepared.Lithation of (S)-ferrocene and ferrocene first in the presence of ether and then TMEDA followed by treatment with different diselenides and disulfides resulted in the synthesis of these new ligands.Palladium and platinum dichloride adducts of these compounds have been prepared from a benzene solution of (PhCN)2MCl2 where M = Pd and Pt.The palladium complexes are active catalysts for selective hydrogenation of dienes to monoenes both under homogeneous and heterogeneous conditions.In the case of hydrogenation of 2,3-dimethyl-1,3-butadiene, isomerization has been observed.Nickel complexes of the new sulfide ligands were prepared in situ and used as catalysts for the asymmetric Grignard cross-coupling reactions.The possible structures of Pd and Pt complexes are discussed.The X-ray crystal structure was determined for C5H4FeC5H3; it reveals that the Pd atom is coordinated to the S and N atoms of the same cyclopentadienyl ring.
Allylic C-H deprotonation of olefins with PtII(OH) to form η3-allyl PtII complexes in water and aprotic organic solvents
Khusnutdinova, Julia R.,Zavalij, Peter Y.,Vedernikov, Andrei N.
, p. 3392 - 3399 (2011)
Hydroxo olefin platinum(II) complex (dpms)PtII(OH)(olefin) (olefin = cis-cyclooctene) reacts in water, in methanol, and, much faster, in aprotic solvents, DMF, acetone, or CH2Cl2 at 20 °C to produce the corresponding η3-allylic complex. Allylic C-H bond deprotonation in (dpms)PtII(OH)(cis-cyclooctene) is reversible, leading to the selective H/D exchange of the olefin in D2O solutions. Attempted olefin-for-olefin ligand exchange in (dpms)PtII(OH)(C 2H4) with olefin = cycloheptene or cyclopentene aimed at the preparation of other (dpms)PtII(OH)(olefin) complexes in water-organic solvent mixtures leads to corresponding η3-allylic derivatives via the intermediacy of (dpms)PtII(OH)(olefin) species. Consistent with mechanistic tests and results of DFT calculations, the Pt II(OH) group is responsible for deprotonation of the allylic C-H bond of the coordinated olefin.
Diverse Mechanistic Pathways in Single-Site Heterogeneous Catalysis: Alcohol Conversions Mediated by a High-Valent Carbon-Supported Molybdenum-Dioxo Catalyst
Bedzyk, Michael J.,Das, Anusheela,Kratish, Yosi,Li, Jiaqi,Ma, Qing,Marks, Tobin J.
, p. 1247 - 1257 (2022/02/07)
With the increase in the importance of renewable resources, chemical research is shifting focus toward substituting petrochemicals with biomass-derived analogues and platform-molecule transformations such as alcohol processing. To these ends, in-depth mechanistic understanding is key to the rational design of catalytic systems with enhanced activity and selectivity. Here we discuss in detail the structure and reactivity of a single-site active carbon-supported molybdenum-dioxo catalyst (AC/MoO2) and the mechanism(s) by which it mediates alcohol dehydration. A range of tertiary, secondary, and primary alcohols as well as selected bio-based terpineols are investigated as substrates under mild reaction conditions. A combined experimental substituent effect/kinetic/kinetic isotope effect/EXAFS/DFT computational analysis indicates that (1) water assistance is a key element in the transition state; (2) the experimental kinetic isotopic effect and activation enthalpy are 2.5 and 24.4 kcal/mol, respectively, in good agreement with the DFT results; and (3) several computationally identified intermediates including Mo-oxo-hydroxy-alkoxide and cage-structured long-range water-coordinated Mo-dioxo species are supported by EXAFS. This structurally and mechanistically well-characterized single-site system not only effects efficient transformations but also provides insight into rational catalyst design for future biomass processes.
Selective C-O Bond Reduction and Borylation of Aryl Ethers Catalyzed by a Rhodium-Aluminum Heterobimetallic Complex
Hara, Naofumi,Nakao, Yoshiaki,Saito, Teruhiko,Seki, Rin
, p. 6388 - 6394 (2021/05/31)
We report the catalytic reduction of a C-O bond and the borylation by a rhodium complex bearing an X-Type PAlP pincer ligand. We have revealed the reaction mechanism based on the characterization of the reaction intermediate and deuterium-labeling experiments. Notably, this novel catalytic system shows steric-hindrance-dependent chemoselectivity that is distinct from conventional Ni-based catalysts and suggests a new strategy for selective C-O bond activation by heterobimetallic catalysis.
Catalytic Dehydrogenation of Alkanes by PCP-Pincer Iridium Complexes Using Proton and Electron Acceptors
Shada, Arun Dixith Reddy,Miller, Alexander J. M.,Emge, Thomas J.,Goldman, Alan S.
, p. 3009 - 3016 (2021/03/09)
Dehydrogenation to give olefins offers the most broadly applicable route to the chemical transformation of alkanes. Transition-metal-based catalysts can selectively dehydrogenate alkanes using either olefinic sacrificial acceptors or a purge mechanism to remove H2; both of these approaches have significant practical limitations. Here, we report the use of pincer-ligated iridium complexes to achieve alkane dehydrogenation by proton-coupled electron transfer, using pairs of oxidants and bases as proton and electron acceptors. Up to 97% yield was achieved with respect to oxidant and base, and up to 15 catalytic turnovers with respect to iridium, using t-butoxide as base coupled with various oxidants, including oxidants with very low reduction potentials. Mechanistic studies indicate that (pincer)IrH2 complexes react with oxidants and base to give the corresponding cationic (pincer)IrH+ complex, which is subsequently deprotonated by a second equivalent of base; this affords (pincer)Ir which is known to dehydrogenate alkanes and thereby regenerates (pincer)IrH2.
