- Iron(II) Active Species in Iron-Bisphosphine Catalyzed Kumada and Suzuki-Miyaura Cross-Couplings of Phenyl Nucleophiles and Secondary Alkyl Halides
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While previous studies have identified FeMes2(SciOPP) as the active catalyst species in iron-SciOPP catalyzed Kumada cross-coupling of mesitylmagnesium bromide and primary alkyl halides, the active catalyst species in cross-couplings with phenyl nucleophiles, where low valent iron species might be prevalent due to accessible reductive elimination pathways, remains undefined. In the present study, in situ M?ssbauer and magnetic circular dichroism spectroscopic studies combined with inorganic syntheses and reaction studies are employed to evaluate the in situ formed iron species and identify the active catalytic species in iron-SciOPP catalyzed Suzuki-Miyaura and Kumada cross-couplings of phenyl nucleophiles and secondary alkyl halides. While reductive elimination to form Fe(η6-biphenyl)(SciOPP) occurs upon reaction of FeCl2(SciOPP) with phenyl nucleophiles, this iron(0) species is not found to be kinetically competent for catalysis. Importantly, mono- and bis-phenylated iron(II)-SciOPP species that form prior to reductive elimination are identified, where both species are found to be reactive toward electrophile at catalytically relevant rates. The higher selectivity toward the formation of cross-coupled product observed for the monophenylated species combined with the undertransmetalated nature of the in situ iron species in both Kumada and Suzuki-Miyaura reactions indicates that Fe(Ph)X(SciOPP) (X = Br, Cl) is the predominant reactive species in cross-coupling. Overall, these studies demonstrate that low-valent iron is not required for the generation of highly reactive species for effective aryl-alkyl cross-couplings.
- Daifuku, Stephanie L.,Kneebone, Jared L.,Snyder, Benjamin E. R.,Neidig, Michael L.
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- Air-Stable Iron-Based Precatalysts for Suzuki-Miyaura Cross-Coupling Reactions between Alkyl Halides and Aryl Boronic Esters
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The development of an air-stable iron(III)-based precatalyst for the Suzuki-Miyaura cross-coupling reaction of alkyl halides and unactivated aryl boronic esters is reported. Despite benefits to cost and toxicity, the proclivity of iron(II)-based complexes to undergo deactivationviaoxidation or hydrolysis is a limiting factor for their widespread use in cross-coupling reactions compared to palladium-based or nickel-based complexes. The new octahedral iron(III) complex demonstrates long-term stability on the benchtop as assessed by a combination of1H NMR spectroscopy, M?ssbauer spectroscopy, and its sustained catalytic activity after exposure to air. The improved stability of the iron-based catalyst facilitates an improved protocol in which Suzuki-Miyaura cross-coupling reactions of valuable substrates can be assembled without the use of a glovebox and access a diverse scope of products similar to reactions assembled in the glovebox with iron(II)-based catalysts.
- Wong, Alexander S.,Zhang, Bufan,Li, Bo,Neidig, Michael L.,Byers, Jeffery A.
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supporting information
p. 2461 - 2472
(2021/11/01)
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- General C(sp2)-C(sp3) Cross-Electrophile Coupling Reactions Enabled by Overcharge Protection of Homogeneous Electrocatalysts
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Cross-electrophile coupling (XEC) of alkyl and aryl halides promoted by electrochemistry represents an attractive alternative to conventional methods that require stoichiometric quantities of high-energy reductants. Most importantly, electroreduction can readily exceed the reducing potentials of chemical reductants to activate catalysts with improved reactivities and selectivities over conventional systems. This work details the mechanistically-driven development of an electrochemical methodology for XEC that utilizes redox-active shuttles developed by the energy-storage community to protect reactive coupling catalysts from overreduction. The resulting electrocatalytic system is practical, scalable, and broadly applicable to the reductive coupling of a wide range of aryl, heteroaryl, or vinyl bromides with primary or secondary alkyl bromides. The impact of overcharge protection as a strategy for electrosynthetic methodologies is underscored by the dramatic differences in yields from coupling reactions with added redox shuttles (generally >80%) and those without (generally 20%). In addition to excellent yields for a wide range of substrates, reactions protected from overreduction can be performed at high currents and on multigram scales.
- Hamby, Taylor B.,Sevov, Christo S.,Truesdell, Blaise L.
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p. 5884 - 5893
(2020/04/10)
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- 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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- Cobalt-Catalyzed Hydrogenations via Olefin Cobaltate and Hydride Intermediates
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Redox noninnocent ligands are a promising tool to moderate electron transfer processes within base-metal catalysts. This report introduces bis(imino)acenaphthene (BIAN) cobaltate complexes as hydrogenation catalysts. Sterically hindered trisubstituted alkenes, imines, and quinolines underwent clean hydrogenation under mild conditions (2-10 bar, 20-80 °C) by use of the stable catalyst precursor [(DippBIAN)CoBr2] and the cocatalyst LiEt3BH. Mechanistic studies support a homogeneous catalysis pathway involving alkene and hydrido cobaltates as active catalyst species. Furthermore, considerable reaction acceleration by alkali cations and Lewis acids was observed. The dinuclear hydridocobaltate anion with bridging hydride ligands was isolated and fully characterized.
- Sandl, Sebastian,Maier, Thomas M.,Van Leest, Nicolaas P.,Kr?ncke, Susanne,Chakraborty, Uttam,Demeshko, Serhiy,Koszinowski, Konrad,De Bruin, Bas,Meyer, Franc,Bodensteiner, Michael,Herrmann, Carmen,Wolf, Robert,Von Jacobi Wangelin, Axel
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p. 7596 - 7606
(2019/08/20)
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- Amine-Borane Dehydrogenation and Transfer Hydrogenation Catalyzed by α-Diimine Cobaltates
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Anionic α-diimine cobalt complexes, such as [K(thf)1.5{(DippBIAN)Co(η4-cod)}] (1; Dipp=2,6-diisopropylphenyl, cod=1,5-cyclooctadiene), catalyze the dehydrogenation of several amine-boranes. Based on the excellent catalytic properties, an especially effective transfer hydrogenation protocol for challenging olefins, imines, and N-heteroarenes was developed. NH3BH3 was used as a dihydrogen surrogate, which transferred up to two equivalents of H2 per NH3BH3. Detailed spectroscopic and mechanistic studies are presented, which document the rate determination by acidic protons in the amine-borane.
- Maier, Thomas M.,Sandl, Sebastian,Shenderovich, Ilya G.,Jacobi von Wangelin, Axel,Weigand, Jan J.,Wolf, Robert
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supporting information
p. 238 - 245
(2019/01/04)
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- Cross-Coupling Reactions of Alkyl Halides with Aryl Grignard Reagents Using a Tetrachloroferrate with an Innocent Countercation
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Bis(triphenylphosphoranylidene)ammonium tetrachloroferrate, (PPN)[FeCl4] (1), was evaluated as a catalyst for cross-coupling reactions. 1 exhibits high stability toward air and moisture and is an effective catalyst for the reaction of secondary alkyl halides with aryl Grignard reagents. The PPN cation is considered as an innocent counterpart to the iron center. We have developed an easy-to-handle iron catalyst for “ligand-free” cross-coupling reactions. (Figure presented.).
- Hashimoto, Toru,Maruyama, Tsubasa,Yamaguchi, Takamichi,Matsubara, Yutaka,Yamaguchi, Yoshitaka
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supporting information
p. 4232 - 4236
(2019/08/16)
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- Olefin-Stabilized Cobalt Nanoparticles for C=C, C=O, and C=N Hydrogenations
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The development of cobalt catalysts that combine easy accessibility and high selectivity constitutes a promising approach to the replacement of noble-metal catalysts in hydrogenation reactions. This report introduces a user-friendly protocol that avoids complex ligands, hazardous reductants, special reaction conditions, and the formation of highly unstable pre-catalysts. Reduction of CoBr2 with LiEt3BH in the presence of alkenes led to the formation of hydrogenation catalysts that effected clean conversions of alkenes, carbonyls, imines, and heteroarenes at mild conditions (3 mol % cat., 2–10 bar H2, 20–80 °C). Poisoning studies and nanoparticle characterization by TEM, EDX, and DLS supported the notion of a heterotopic catalysis mechanism.
- Sandl, Sebastian,Schwarzhuber, Felix,P?llath, Simon,Zweck, Josef,Jacobi von Wangelin, Axel
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supporting information
p. 3403 - 3407
(2018/02/13)
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- A Manganese Nanosheet: New Cluster Topology and Catalysis
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While the coordination chemistry of monometallic complexes and the surface characteristics of larger metal particles are well understood, preparations of molecular metallic nanoclusters remain a great challenge. Discrete planar metal clusters constitute nanoscale snapshots of cluster growth but are especially rare owing to the strong preference for three-dimensional structures and rapid aggregation or decomposition. A simple ligand-exchange procedure has led to the formation of a novel heteroleptic Mn6 nanocluster that crystallized in an unprecedented flat-chair topology and exhibited unique magnetic and catalytic properties. Magnetic susceptibility studies documented strong electronic communication between the manganese ions. Reductive activation of the molecular Mn6 cluster enabled catalytic hydrogenations of alkenes, alkynes, and imines.
- Chakraborty, Uttam,Reyes-Rodriguez, Efrain,Demeshko, Serhiy,Meyer, Franc,Jacobi von Wangelin, Axel
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supporting information
p. 4970 - 4975
(2018/03/28)
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- Recyclable cobalt(0) nanoparticle catalysts for hydrogenations
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The search for new hydrogenation catalysts that replace noble metals is largely driven by sustainability concerns and the distinct mechanistic features of 3d transition metals. Several combinations of cobalt precursors and specific ligands in the presence of reductants or under high-thermal conditions were reported to provide active hydrogenation catalysts. This study reports a new method of preparation of small, monodisperse Co(0) nanoparticles (3-4 nm) from the reduction of commercial CoCl2 in the absence of ligands or surfactants. High catalytic activity was observed in hydrogenations of alkenes, alkynes, imines, and heteroarenes (2-20 bar H2). The magnetic properties enabled catalyst separation and multiple recyclings.
- Büschelberger, Philipp,Reyes-Rodriguez, Efrain,Sch?ttle, Christian,Treptow, Jens,Feldmann, Claus,Jacobi Von Wangelin, Axel,Wolf, Robert
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p. 2648 - 2653
(2018/05/30)
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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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- Teaching an old carbocation new tricks: Intermolecular C-H insertion reactions of vinyl cations
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Vinyl carbocations have been the subject of extensive experimental and theoretical studies over the past five decades. Despite this long history in chemistry, the utility of vinyl cations in chemical synthesis has been limited, with most reactivity studies focusing on solvolysis reactions or intramolecular processes. Here we report synthetic and mechanistic studies of vinyl cations generated through silylium-weakly coordinating anion catalysis. We find that these reactive intermediates undergo mild intermolecular carbon-carbon bond-forming reactions, including carbon-hydrogen (C-H) insertion into unactivated sp3 C-H bonds and reductive Friedel-Crafts reactions with arenes. Moreover, we conducted computational studies of these alkane C-H functionalization reactions and discovered that they proceed through nonclassical, ambimodal transition structures. This reaction manifold provides a framework for the catalytic functionalization of hydrocarbons using simple ketone derivatives.
- Popov, Stasik,Shao, Brian,Bagdasarian, Alex L.,Benton, Tyler R.,Zou, Luyi,Yang, Zhongyue,Houk,Nelson, Hosea M.
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p. 381 - 387
(2018/08/07)
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- Alkene Hydrogenations by Soluble Iron Nanocluster Catalysts
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The replacement of noble metal technologies and the realization of new reactivities with earth-abundant metals is at the heart of sustainable synthesis. Alkene hydrogenations have so far been most effectively performed by noble metal catalysts. This study reports an iron-catalyzed hydrogenation protocol for tri- and tetra-substituted alkenes of unprecedented activity and scope under mild conditions (1–4 bar H2, 20 °C). Instructive snapshots at the interface of homogeneous and heterogeneous iron catalysis were recorded by the isolation of novel Fe nanocluster architectures that act as catalyst reservoirs and soluble seeds of particle growth.
- Gieshoff, Tim N.,Chakraborty, Uttam,Villa, Matteo,Jacobi von Wangelin, Axel
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supporting information
p. 3585 - 3589
(2017/03/21)
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- Arylation of hydrocarbons enabled by organosilicon reagents and weakly coordinating anions
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Over the past 80 years, phenyl cation intermediates have been implicated in a variety of C-H arylation reactions. Although these examples have inspired several theoretical and mechanistic studies, aryl cation equivalents have received limited attention in organic methodology. Their high-energy, promiscuous reactivity profiles have hampered applications in selective intermolecular processes. We report a reaction design that overcomes these challenges. Specifically, we found that b-silicon-stabilized aryl cation equivalents, generated via silylium-mediated fluoride activation, undergo insertion into sp3 and sp2 C-H bonds. This reaction manifold provides a framework for the catalytic arylation of hydrocarbons, including simple alkanes such as methane. This process uses low loadings of Earth-abundant initiators (1 to 5 mole percent) and occurs under mild conditions (30° to 100°C).
- Shao, Brian,Bagdasarian, Alex L.,Popov, Stasik,Nelson, Hosea M.
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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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- Direct C(sp2)-C(sp3) cross-coupling of diaryl zinc reagents with benzylic, primary, secondary, and tertiary alkyl halides
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The direct C(sp2)-C(sp3) cross-coupling of diaryl zinc reagents with benzylic, primary, secondary, and tertiary alkyl halides proceeded in the absence of coordinating ethereal solvents at ambient temperature without the addition of a catalyst. The C(sp2)-C(sp3) cross-coupling showed excellent functional-group tolerance, and products were isolated in high yields, generally without the requirement for purification by chromatography. This process represents an expedient, operationally simple method for the construction of new C(sp2)-C(sp3) bonds. Zinc and you'll miss it. Direct C(sp2)-C(sp3) cross-coupling of diaryl zinc reagents with alkyl halides proceeded rapidly at ambient temperature without a coordinating ethereal solvent or an added catalyst (see scheme). This versatile, operationally simple approach to C(sp2)-C(sp3) bond formation enables the expedient construction of a diverse array of carbon-based structural motifs.
- Dunsford, Jay J.,Clark, Ewan R.,Ingleson, Michael J.
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supporting information
p. 5688 - 5692
(2015/05/19)
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- Expedient iron-catalyzed coupling of alkyl, benzyl and allyl halides with arylboronic esters
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While attractive, the iron-catalyzed coupling of arylboron reagents with alkyl halides typically requires expensive or synthetically challenging diphosphine ligands. Herein, we show that primary and secondary alkyl bromides and chlorides, as well as benzyl and allyl halides, can be coupled with arylboronic esters, activated with alkyllithium reagents, by using very simple iron-based catalysts. The catalysts used were either adducts of inexpensive and widely available diphosphines or, in a large number of cases, simply [Fe(acac)3] with no added co- ligands. In the former case, preliminary mechanistic studies highlight the likely involvement of iron(I)-phosphine intermediates. More irons in the fire: Primary and secondary alkyl, benzyl and allyl halides were coupled with arylboronic esters by using very simple iron-based catalysts. These were either adducts of inexpensive and widely available diphosphines or, in a large number of cases, simply [Fe(acac)3] with no added co-ligands (see scheme; acac=acetylacetonate). In the former case, preliminary mechanistic studies highlight the likely involvement of low-coordinate iron(I)-phosphine intermediates.
- Bedford, Robin B.,Brenner, Peter B.,Carter, Emma,Carvell, Thomas W.,Cogswell, Paul M.,Gallagher, Timothy,Harvey, Jeremy N.,Murphy, Damien M.,Neeve, Emily C.,Nunn, Joshua,Pye, Dominic R.
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supporting information
p. 7935 - 7938
(2014/07/07)
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- Cross-coupling of alkyl halides with aryl or alkyl Grignards catalyzed by dinuclear Ni(ii) complexes containing functionalized tripodal amine-pyrazolyl ligands
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Structurally distinctive dinuclear Ni(ii) complexes with furan or thiophene tethered amine-pyrazolyl tripodal hybrid ligands have been synthesized and crystallographically characterized. All complexes are catalytically active towards cross-coupling of aryl/alkyl Grignard reagents with β-H containing alkyl halides at room temperature in the presence of N,N,N',N'- tetramethylethylenediamine (TMEDA). The catalytic efficacy of the complexes is dependent on the tether substituent at the central amine. Two species, Ni(ii) TMEDA and Mg(ii) TMEDA complexes, have been isolated from the catalytic reaction mixtures under different conditions. Some ligand-stabilized Ni(ii) and Mg(ii) bimetallic species have also been identified in the ESI-MS spectra.
- Xue, Fei,Zhao, Jin,Hor, T. S. Andy
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p. 5150 - 5158
(2013/04/10)
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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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- Cross-coupling of non-activated chloroalkanes with aryl grignard reagents in the presence of iron/N-heterocyclic carbene catalysts
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An efficient and high-yielding cross-coupling reaction of various primary, secondary, and tertiary alkyl chlorides with aryl Grignard reagents was achieved by using catalytic amounts of N-heterocyclic carbene ligands and iron salts. This reaction is a simple and efficient arylation method having applicability to a wide range of industrially abundant chloroalkanes, including polychloroalkanes, which are challenging substrates under conventional cross-coupling conditions.
- Ghorai, Sujit K.,Jin, Masayoshi,Hatakeyama, Takuji,Nakamura, Masaharu
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supporting information; experimental part
p. 1066 - 1069
(2012/04/10)
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- A highly efficient precatalyst for amination of aryl chlorides: Synthesis, structure and application of a robust acenaphthoimidazolylidene palladium complex
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A robust palladium NHC complex was synthesized and exhibits exceptional activity and selectivity as a precatalyst in the amination of aryl chlorides and tolerates a wide range of substrates at low catalyst loadings.
- Tu, Tao,Fang, Weiwei,Jiang, Jian
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supporting information; experimental part
p. 12358 - 12360
(2011/12/15)
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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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- 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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- Iron(II) complexes with functionalized amine-pyrazolyl tripodal ligands in the cross-coupling of aryl Grignard with alkyl halides
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Structurally distinctive Fe(ii) complexes with furan, thiophene and pyridine functionalized amine-pyrazolyl tripodal hybrid ligands have been synthesized and crystallographically characterized. The tether substituent at the central amine plays an active role in determining the coordination mode of the ligand and the metal geometry. All complexes are catalytically active towards cross-coupling of aryl Grignard reagents with primary and secondary alkyl halides with β-hydrogen under ambient conditions. ESI-MS spectra analysis revealed the ligand-stabilised Fe(ii) and Mg(ii) species. The Royal Society of Chemistry 2011.
- Xue, Fei,Zhao, Jin,Hor, T. S. Andy
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experimental part
p. 8935 - 8940
(2011/10/19)
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- Iron-catalyzed Suzuki-Miyaura coupling of alkyl halides
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In the presence of novel iron(II) chloride-diphosphine complexes and magnesium bromide, lithium arylborates react with primary and secondary alkyl halides to give the corresponding coupling products in good to excellent yields. High functional group compa
- Hatakeyama, Takuji,Hashimoto, Toru,Kondo, Yoshiyuki,Fujiwara, Yuichi,Seike, Hirofumi,Takaya, Hikaru,Tamada, Yoshinori,Ono, Teruo,Nakamura, Masaharu
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supporting information; experimental part
p. 10674 - 10676
(2010/11/04)
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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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- Iron-catalyzed cross-coupling of alkyl sulfonates with arylzinc reagents
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Iron-catalyzed cross-coupling reactions of primary and secondary alkyl sulfonates with arylzinc reagents proceed smoothly In the presence of excess TMEDA and a concomitant magnesium salt. The arylzinc reagents are prepared from the corresponding aryllithium or magnesium reagents with ZnI2. The In situ formation of alkyl Iodides and consecutive rapid cross-coupling avoids discrete preparation of the unstable secondary alkyl halides and also achieves high product selectivity.
- Ito, Shingo,Fujiwara, Yu-Ichi,Nakamura, Eiichi,Nakamura, Masaharu
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supporting information; experimental part
p. 4306 - 4309
(2009/12/26)
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- Vanadium-catalyzed cross-coupling reactions of alkyl halides with aryl grignard reagents
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Vanadium(III) chloride catalyzed cross-coupling reactions of alkyl halides with arylmagnesium bromides. Various arylmagnesium bromides, except for an ortho-substituted arylmagnesium reagent, could be used for the reaction. Among alkyl halides tested, cyclohexyl halides and primary alkyl halides were good substrates. The reactions likely proceed via carbon-centered radical intermediates. 2008 The Chemical Society of Japan.
- Yasuda, Shigeo,Yorimitsu, Hideki,Oshima, Koichiro
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experimental part
p. 287 - 290
(2009/03/12)
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- Iron-catalyzed alkylations of aromatic Grignard reagents
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(Chemical Equation Presented) Any old iron: Two efficient iron-catalyzed cross-coupling reactions between aryl Grignard reagents and alkyl bromides were developed that are suitable for large-scale applications. The first procedure uses iron acetylacetonate and involves a cooperative effect between the two ligands N,N,N′,N′-tetramethylethylenediamine (TMEDA) and hexamethylenetetraamine (HMTA), while the second procedure uses [(FeCl 3)2(tmeda)3] as catalyst. 2007 Wiley-VCH Verlag GmbH & Co. KGaA.
- Cahiez, Gerard,Habiak, Vanessa,Duplais, Christophe,Moyeux, Alban
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p. 4364 - 4366
(2008/03/12)
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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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- Iron-catalyzed chemoselective cross-coupling of primary and secondary alkyl halides with arylzinc reagents
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Functional-group-compatible cross-coupling reaction of alkyl halides with arylzinc reagents takes place under iron catalysis in the presence of TMEDA, producing a variety of aromatic compounds in good to excellent yield. The pronounced effect of a magnesium salt was found to be the key to the promotion of the iron-catalyzed coupling reaction. Georg Thieme Verlag Stuttgart.
- Nakamura, Masaharu,Ito, Shingo,Matsuo, Keiko,Nakamura, Eiichi
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p. 1794 - 1798
(2007/10/03)
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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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- Hydrocarbon activation. Synthesis of β-cycloalkyl (Di)nitriles through photosensitized conjugate radical addition
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Photoinduced hydrogen abstraction from aliphatic cyclic hydrocarbons (C5 to C7, C12, as well as adamantane) by triplet aromatic ketones in the presence of α,β-unsaturated (di)nitriles offers a straightforward entry to the corresponding alkylated (di)nitriles via the alkyl radicals. Yields are moderate to good depending on the olefins structure (substitution in β slows down the addition to mononitriles, but with α,α-dinitriles electronic activation allows efficient alkylation also of β,β-disubstituted substrates). A tandem alkylation - cyclization process has been obtained with (1-methylpent-4-enylidene)malononitrile.
- Cardarelli,Fagnoni,Mella,Albini
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p. 7320 - 7327
(2007/10/03)
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- A new convenient Friedel-Crafts alkylation of aromatic compounds with secondary alcohol methanesulfonates in the presence of scandium(III) trifluoromethanesulfonate or trifluoromethanesulfonic acid as the catalyst
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Scandium(III) triflate and triflic acid were both found to be efficient catalysts for the Friedel-Crafts alkylation of aromatic compounds using methanesulfonates derived from secondary alcohols as alkylating agents.
- Kotsuki, Hiyoshizo,Ohishi, Takeshi,Inoue, Motoshi,Kojima, Tomoyuki
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p. 603 - 606
(2007/10/03)
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- Synthesis of Certain Mesogenic Azomethines Derived from 4-Cycloalkylanilines and from 4-Cycloalkylbenzaldehydes
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General procedures are described for the synthesis of members of five pairs of related homologous series of mesogenic azomethines differing in the mode of linkage of the CH=N group and containing a cycloalkyl group in a terminal position.
- Byron, D. J.,Matharu, A. S.,Rees, M.,Wilson, R. C.
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p. 229 - 238
(2007/10/02)
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- Side Chain Hydroxylation of Aromatic Compounds by Fungi. Part 5. Exploring the Benzylic Hydroxylase of Mortierella isabellina
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The active site topography of the hydroxylase enzyme of Mortierella isabellina ATCC 42613, which carries out the benzylic hydroxylation of toluene, ethylbenzene, and related compounds, has been explored.Operating in a whole cell biotransformation mode, this enzyme shows selectivity in substrate processing based on the nature, position and size of substituent side chains close to the site of hydroxylation.The results of determination of the yield and stereochemistry of hydroxylation of over twenty substrates and potential substrates, together with previously reported data, have been used to propose an active site model for the benzylic hydroxylase enzyme.
- Holland, Herbert L.,Kindermann, Maik,Kumaresan, Sudalaiyandi,Stefanac, Tomislav
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p. 1353 - 1364
(2007/10/02)
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- Synthesis and evaluation of 4-alkylanilines as mammary tumor inhibiting aromatase inhibitors
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The 4-alkylanilines 1-20 were synthesized to elucidate the importance of the glutarimide moiety for the aromatase inhibiting activity of aminoglutethimide [3-(4-aminophenyl)-3-ethylpiperidine-2,6-dione, AG], the only non-steroidal aromatase inhibitor which is commercially available at present. The most interesting compounds were the (4-aminophenyl)cycloalkanes 4-6 (4, c-pentyl; 5, c-hexyl; 6, c-heptyl) and the 1-alkyl-1-(4-aminophenyl)cyclohexanes 1-3 (1, CH3; 2, C2H5; 3, n-C3H7). Derivatives 1-6 are stronger inhibitors of human placental aromatase than AG exhibiting relative potencies from 1.5 to 2.7 (AG≡1). For selectivity of action, the inhibition of desmolase (cholesterol side chain cleavage enzyme) was determined. Compounds 1-3 showed an inhibition comparable to AG, whereas compounds 4-6 exhibited no effect on desmolase. Being more potent and selective aromatase inhibitors in vitro, compounds 4-6, however, were not superior to AG in vivo, when the reduction of plasma estradiol concentration and the tumor inhibiting activity (PMSG-primed SD rats and DMBA-induced mammary carcinoma of the SD rat, postmenopausal model) were concerned.
- Hartmann,Batzl
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p. 537 - 544
(2007/10/02)
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- CH ACIDITY OF SUBSTITUTED CYCLOALKANES. V. THE KINETIC ISOTOPE EFFECT OF HYDROGEN EXCHANGE IN PHENYLCYCLOALKANES
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The kD/kT value for the isotope exchange of hydrogen in phenylcycloalkanes with cyclohexylamine (catalyzed by lithium cyclohexylamide) and with dimethyl sulfoxide decreases from 2.0 - 2.5 (for phenylcyclopentane and phenylcyclooctane) to 1.3 - 1.4 (for phenylcyclopropane).It was concluded that the reaction rate in the listed catalytic systems is controlled by the ionization of the CH acid.The relationships governing the variation of the kD/kT values in the ionization of phenylcycloalkanes are explained by the effect of structural rearrangement in the anionic fragments of the hydrocarbons on the mechanism of the elementary proton transfer event.
- Zharova, N. G.,Shapiro, O. I.
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p. 602 - 609
(2007/10/02)
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- Studies on the Autoxidation of Phenyl Cycloalkanes
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The products of the autoxidation of phenyl cyclopropane (I), phenyl cyclobutane (II), phenyl cyclopentane (III), phenyl cyclohexane (IV), phenyl cycloheptane (V) and phenyl cyclooctane (VI) were analyzed after reduction of the reaction mixtures with LiAlH4.As products of the attack on the α-C-H bonds the corresponding 1-phenyl cycloalkanols and 1-phenyl alkan-1-ols were found.In the case of phenyl cyclopropane some SR2 ring opening probably takes place.The oxidabilities , the chain termination constants kt, the absolute chain propagation constants kp and the relative chain propagation constants (kp)rel were determined for the phenyl cycloalkanes I-VI.As it is to be expected on the basis of the I-strain concept the autoxidation rate of phenyl cyclopentane (III) is considerably higher than that of phenyl cyclobutane (II) and phenyl cyclohexane (IV).
- Batke, Birgit,Lauterbach, Gerlinde,Pritzkow, Wilhelm,Voerckel, Volkmar,Belyakov, Vladimir A.
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p. 424 - 430
(2007/10/02)
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- CH ACIDITY OF SUBSTITUTED CYCLOALKANES. I. KINETIC ACIDITY OF PHENYLCYCLOALKANES
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The kinetic acidities of phenylcycloalkanes were determined in a solution of lithium cyclohexylamide in cyclohexylamine.The obtained values are compared with the analogous values for cycloalkanes and with the heats of hydrogenation of methylenecycloalkanes.The introduction of the phenyl substituent increases the proton mobility of the hydrogen in the cycloalkanes.A relation was established between the kinetic acidity of the phenylcycloalkanes and the strain in the alkane rings of their carbanions.
- Zharova, N. G.,Shapiro, I. O.,Shatenshtein, A. I.
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p. 211 - 214
(2007/10/02)
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- Regioselectivity in the Catalytic Hydrogenolysis of 7-Fluoro-1-phenylbicycloheptanes
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The palladium-catalyzed hydrogenolysis of 7-chloro-7-fluoro-1-phenyl-, 7-fluoro-1-phenyl-, and 7,7-difluoro-1-phenylbicycloheptane was investigated.The hydrogenolysis of the cyclopropane ring occurs at the C1-C6 bond selectively, accompained by the
- Isogai, Koji,Sakai, Jun-ichi,Kosugi, Katsuhibo
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p. 1349 - 1354
(2007/10/02)
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- Studies on Thermal Conversion of Phenylcyclopentane, -hexane, -heptane, and -octane in the Gas Phase
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The title compounds were pyrolyzed from 700 to 780 deg C in a metallic laboratory tubular reactor in the presence of steam.The reaction products were analyzed by gas chromatography and by a combination of gas chromatography and mass spectrometry.From the phenylcyclanes tested, more than 65 hydrocarbons could be detected in the liquids, besides gaseous reaction products.In most cases unambiguous structures could be derived by using different analytical methods.As typical initial-step products phenylcyclenes, ω-phenyl-1-alkenes and 1-phenyl-1-alkenes are formed by dehydrogenation and isomerization of the title compounds.The detection of phenylalkenes corresponds well with the isomerization of unsubstituted cyclanes to the corresponding α-olefines described in former papers.
- Lam, Ho Son,Zimmermann, G.,Anders, G.,Bach, G.,Rennecke, D.,Zychlinski, W.
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p. 759 - 766
(2007/10/02)
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- Thermolabile Hydrocarbons, XXV. Relationships between Thermal Stability, Strain, and Structure of 1,1'-Diphenyl-1,1'-bicycloalkyls
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The products and activation parameters of the thermolysis reaction of the title hydrocarbons 1a (n = 4-8) and 1b (n = 12) were determined.Strain enthalpies and structural data of the compounds 1a and of the radicals 2a, which are generated on thermolysis, were obtained from force field calculations.For 1a (n = 8) a crystal structure analysis was carried out. - The importance of i-strain action is estimated from the relationship between ΔG% of the thermolysis reaction and the strain enthalpy of 1 from which the ring strain of the corresponding cycloalkane was substracted as a correction factor.In addition, a linear correlation between ΔG% and the change in strain enthalpy (MM2 results) in the course of the dissociation process was found.The large variation in ΔS% can be rationalized by consideration of the change in internal mobility (MM2 results) during the dissociation process.
- Bernloehr, Werner,Beckhaus, Hans-Dieter,Lindner, Hans-Joerg,Ruechardt, Christoph
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p. 3303 - 3319
(2007/10/02)
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