- S-Alkylation of α-Thioether Iron Compounds by + and +
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Treatment of the thiomethyl complexes (R=Me or Ph0 with + or (CO)2(=CH2)>+ results in S-alkylation, affording the sulphonium salts >+ and Fe(η-C5Me
- Guerchais, Veronique,Thepot, Jean-Yves,Lapinte, Claude
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Read Online
- Dichloromethane activation by chlorochromium(II) complexes with TpiPr2: Generation of an electrophilic Cr-methylene species without the action of an external Cl-abstraction reagent
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Five-coordinated chlorochromium(II) complexes with TpiPr2 activate CH2Cl2 to give a metal-carbene species without the action of an external Cl-abstraction reagent, and the resulting methylene fragment is trapped by nucleop
- Sugawara, Ken-Ichiro,Hikichi, Shiro,Akita, Munetaka
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Read Online
- Cooperative NHC/Photoredox Catalyzed Ring-Opening of Aryl Cyclopropanes to 1-Aroyloxylated-3-Acylated Alkanes
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Cyclopropanes are an important class of building blocks in organic synthesis. Herein, a ring-opening/arylcarboxylation/acylation cascade reaction for the 1,3-difunctionalization of aryl cyclopropanes enabled by cooperative NHC and organophotoredox catalysis is reported. The cascade works on monosubstituted cyclopropanes that are in contrast to the heavily investigated donor–acceptor cyclopropanes more challenging to be difunctionalized. The key step is a radical/radical cross coupling of a benzylic radical generated in the photoredox catalysis cycle with a ketyl radical from the NHC catalysis cycle. The transformation features metal-free reaction conditions and tolerates a diverse range of functionalities.
- Daniliuc, Constantin G.,Studer, Armido,Zuo, Zhijun
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supporting information
p. 25252 - 25257
(2021/10/29)
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- Scalable On-Demand Production of Purified Diazomethane Suitable for Sensitive Catalytic Reactions
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We have developed a convenient development-scale reactor (0.44 mol/h) to prepare diazomethane from N-methyl-N-nitroso-p-toluenesulfonamide (MNTS) in ~80% yield. Diazomethane (CH2N2) made with this reactor is extracted into nitrogen gas from the liquid reaction mixture, effectively removing it from reagents and byproducts that may interfere in subsequent reactions. Vertically oriented tubular reactors were used to produce and consume diazomethane in situ. Key features of this reactor include high productivity and correspondingly low reactor volume (reactor volume/liquid flow rate = 6.5 min) and a commercially available gas/liquid separator equipped with a selectively permeating hydrophilic membrane. The design of the reactor keeps the inventory below 53 mg of CH2N2 during normal operation. The reactor was demonstrated by generating CH2N2 that was used in a connected continuous reactor. We evaluated esterification reactions and a continuous Pd-catalyzed cyclopropanation reaction with the reactor and achieved high conversion with 1.5 and 4.1 equiv of MNTS precursor, respectively.
- Sheeran, Jillian W.,Campbell, Kiersten,Breen, Christopher P.,Hummel, Gerald,Huang, Changfeng,Datta, Anamika,Boyer, Serge H.,Hecker, Scott J.,Bio, Matthew M.,Fang, Yuan-Qing,Ford, David D.,Russell, M. Grace
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p. 522 - 528
(2021/02/03)
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- Direct Deamination of Primary Amines via Isodiazene Intermediates
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We report here a reaction that selectively deaminates primary amines and anilines under mild conditions and with remarkable functional group tolerance including a range of pharmaceutical compounds, amino acids, amino sugars, and natural products. An anomeric amide reagent is uniquely capable of facilitating the reaction through the intermediacy of an unprecedented monosubstituted isodiazene intermediate. In addition to dramatically simplifying deamination compared to existing protocols, our approach enables strategic applications of iminium and amine-directed chemistries as traceless methods. Mechanistic and computational studies support the intermedicacy of a primary isodiazene which exhibits an unexpected divergence from previously studied secondary isodiazenes, leading to cage-escaping, free radical species that engage in a chain, hydrogen-atom transfer process involving aliphatic and diazenyl radical intermediates.
- Berger, Kathleen J.,Driscoll, Julia L.,Yuan, Mingbin,Dherange, Balu D.,Gutierrez, Osvaldo,Levin, Mark D.
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supporting information
p. 17366 - 17373
(2021/11/04)
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- Zn-Mediated Hydrodeoxygenation of Tertiary Alkyl Oxalates
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Herein we describe a general, mild, and scalable method for hydrodeoxygenation of readily accessible tertiary alkyl oxalates by Zn/silane under Ni-catalyzed conditions. The reduction method is suitable for an array of structural motifs derived from tertiary alcohols that bear diverse functional groups, including the synthesis of a key intermediate en route to estrone.
- Ye, Yang,Ma, Guobin,Yao, Ken,Gong, Hegui
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supporting information
p. 1625 - 1628
(2021/01/18)
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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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p. 2461 - 2472
(2021/11/01)
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- Silylium-Ion-Promoted Ring-Opening Hydrosilylation and Disilylation of Unactivated Cyclopropanes
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A silylium-ion-promoted ring-opening hydrosilylation of unactivated cyclopropanes is reported. The reaction is facilitated by the γ-silicon effect, and the regioselectivity is influenced by various stabilizing effects on the carbenium-ion intermediates, including the β-silicon effect. The experimental observations are in accord with the computed reaction mechanism. The work also showcases the ability of silylium ions to isomerize cyclopropyl to allyl groups, and the resulting α-olefins engage in a silylium-ion-mediated disilylation with hexamethyldisilane.
- Bonetti, Vittorio,Klare, Hendrik F. T.,Oestreich, Martin,Roy, Avijit,Wang, Guoqiang,Wu, Qian
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supporting information
(2020/02/04)
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- The Cyclopropane Ring as a Reporter of Radical Leaving-Group Reactivity for Ni-Catalyzed C(sp3)-O Arylation
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The ability to understand and predict reactivity is essential for the development of new reactions. In the context of Ni-catalyzed C(sp3)-O functionalization, we have developed a unique strategy employing activated cyclopropanols to aid the design and optimization of a redox-active leaving group for C(sp3)-O arylation. In this chemistry, the cyclopropane ring acts as a reporter of leaving-group reactivity, since the ring-opened product is obtained under polar (2e) conditions, and the ring-closed product is obtained under radical (1e) conditions. Mechanistic studies demonstrate that the optimal leaving group is redox-active and are consistent with a Ni(I)/Ni(III) catalytic cycle. The optimized reaction conditions are also used to synthesize a number of arylcyclopropanes, which are valuable pharmaceutical motifs.
- Mills, L. Reginald,Monteith, John J.,Dos Passos Gomes, Gabriel,Aspuru-Guzik, Alán,Rousseaux, Sophie A. L.
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p. 13246 - 13254
(2020/09/01)
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- Formation of Cyclopropanes via Activation of (γ-Methoxy)alkyl Gold(I) Complexes with Lewis Acids
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Treatment of the gold 3-methoxy-3-phenylpropyl complex (P)AuCH2CH2CH(OMe)Ph [P = P(t-Bu)2o-biphenyl] with AlCl3 at -78 °C led to the immediate (≤5 min) formation of a 4:1 mixture of phenylcyclopropane and (1-methoxypropyl)benzene in 86 ± 5% combined yield. Lewis acid activation of the stereochemically pure isotopomer erythro-(P)AuCH2CHDCH(OMe)Ph led to the formation of cis-2-deuterio-1-phenylcyclopropane in 84 ± 5% yield as a single stereoisomer, which established that cyclopropanation occurred with inversion of the γ-stereocenter. Similarly, ionization of the stereochemically pure cyclohexyl gold complex cis-(P)AuCHCH2CH(OMe)CH2CH2CH2 at -78 °C formed bicyclo[3.1.0]hexane in 82% ± 5% yield, which validated a low energy pathway for cyclopropanation involving inversion of the α-stereocenter. Taken together, these observations are consistent with a mechanism for cyclopropane formation involving backside displacement of both the Cγleaving group and the Cα (L)Au+ fragment via a W-shaped transition state.
- Kim, Nana,Widenhoefer, Ross A.
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p. 3160 - 3167
(2020/09/12)
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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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- Lewis Base-Promoted Ring-Opening 1,3-Dioxygenation of Unactivated Cyclopropanes Using a Hypervalent Iodine Reagent
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A facile and effective system has been developed for the regio- and chemoselective ring-opening/electrophilic functionalization of cyclopropanes through C?C bond activation by [bis(trifluoroacetoxy)iodo]benzene with the aid of the Lewis basic promoter p-toluenesulfonamide. The p-toluenesulfonamide-promoted system works well for a wide range of cyclopropanes, resulting in the formation of 1,3-diol products in good yields and regioselectivity.
- Gieuw, Matthew H.,Ke, Zhihai,Yeung, Ying-Yeung
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supporting information
p. 3782 - 3786
(2018/03/13)
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- Ni-Catalyzed Electrochemical Decarboxylative C-C Couplings in Batch and Continuous Flow
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An electrochemically driven, nickel-catalyzed reductive coupling of N-hydroxyphthalimide esters with aryl halides is reported. The reaction proceeds under mild conditions in a divided electrochemical cell and employs a tertiary amine as the reductant. This decarboxylative C(sp3)-C(sp2) bond-forming transformation exhibits excellent substrate generality and functional group compatibility. An operationally simple continuous-flow version of this transformation using a commercial electrochemical flow reactor represents a robust and scalable synthesis of value added coupling process.
- Li, Hui,Breen, Christopher P.,Seo, Hyowon,Jamison, Timothy F.,Fang, Yuan-Qing,Bio, Matthew M.
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supporting information
p. 1338 - 1341
(2018/03/09)
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- Aminofluorination of Cyclopropanes: A Multifold Approach through a Common, Catalytically Generated Intermediate
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We have discovered a highly regioselective aminofluorination of cyclopropanes. Remarkably, four unique sets of conditions-two photochemical, two purely chemical-generated the same aminofluorinated adducts in good to excellent yields. The multiple, diverse ways in which the reaction could be initiated provided valuable clues that led to the proposal of a "unifying" chain propagation mechanism beyond initiation, tied by a common intermediate. In all, the proposed mechanism herein is substantiated by product distribution studies, kinetic analyses, LFERs, Rehm-Weller estimations of ΔGET, competition experiments, KIEs, fluorescence data, and DFT calculations. From a more physical standpoint, transient-absorption experiments have allowed direct spectroscopic observation of radical ion intermediates (previously only postulated or probed indirectly in photochemical fluorination systems) and, consequently, have provided kinetic support for chain propagation. Lastly, calculations suggest that solvent may play an important role in the cyclopropane ring-opening step.
- Pitts, Cody Ross,Ling, Bill,Snyder, Joshua A.,Bragg, Arthur E.,Lectka, Thomas
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supporting information
p. 6598 - 6609
(2016/06/09)
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- Laboratory-Scale Membrane Reactor for the Generation of Anhydrous Diazomethane
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A configurationally simple and robust semibatch apparatus for the in situ on-demand generation of anhydrous solutions of diazomethane (CH2N2) avoiding distillation methods is presented. Diazomethane is produced by base-mediated decomposition of commercially available Diazald within a semipermeable Teflon AF-2400 tubing and subsequently selectively separated from the tubing into a solvent- and substrate-filled flask (tube-in-flask reactor). Reactions with CH2N2 can therefore be performed directly in the flask without dangerous and labor-intensive purification operations or exposure of the operator to CH2N2. The reactor has been employed for the methylation of carboxylic acids, the synthesis of α-chloro ketones and pyrazoles, and palladium-catalyzed cyclopropanation reactions on laboratory scale. The implementation of in-line FTIR technology allowed monitoring of the CH2N2 generation and its consumption. In addition, larger scales (1.8 g diazomethane per hour) could be obtained via parallelization (numbering up) by simply wrapping several membrane tubings into the flask.
- Dallinger, Doris,Pinho, Vagner D.,Gutmann, Bernhard,Kappe, C. Oliver
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p. 5814 - 5823
(2016/07/26)
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- Reductive Cyclopropanations Catalyzed by Dinuclear Nickel Complexes
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Dinuclear Ni complexes supported by naphthyridine-diimine (NDI) ligands catalyze the reductive cyclopropanation of alkenes with CH2Cl2 as the methylene source. The use of mild terminal reductants (Zn or Et2Zn) confers significant functional-group tolerance, and the catalyst accommodates structurally and electronically diverse alkenes. Mononickel catalysts bearing related N chelates afford comparatively low cyclopropane yields (≤20 %). These results constitute an entry into catalytic carbene transformations from oxidized methylene precursors.
- Zhou, You-Yun,Uyeda, Christopher
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supporting information
p. 3171 - 3175
(2016/03/12)
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- A Novel Cathode Material for Cathodic Dehalogenation of 1,1-Dibromo Cyclopropane Derivatives
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Leaded bronze turned out to be an excellent cathode material for the dehalogenation reaction of cyclopropanes without affecting the strained molecular entity. With this particular alloy, beneficial properties of lead cathodes are conserved, whereas the corrosion of cathode is efficiently suppressed. The solvent in the electrolyte determines whether a complete debromination reaction is achieved or if the process can be selectively stopped at the monobromo cyclopropane intermediate. The electroorganic conversion tolerates a variety of functional groups and can be conducted at rather complex substrates like cyclosporine A. This approach allows the sustainable preparation of cyclopropane derivatives.
- Gütz, Christoph,Selt, Maximilian,B?nziger, Markus,Bucher, Christoph,R?melt, Christina,Hecken, Nadine,Gallou, Fabrice,Galv?o, Tomás R.,Waldvogel, Siegfried R.
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supporting information
p. 13878 - 13882
(2015/09/28)
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- Sultones and Sultines via a Julia-Kocienski Reaction of Epoxides
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The development of the homologous Julia-Kocienski reaction has led to the discovery of two new reaction modes of epoxides with sulfones. These pathways allow rapid and direct access to a range of γ-sultones and γ-sultines.
- Smith, Geoffrey M. T.,Burton, Paul M.,Bray, Christopher D.
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supporting information
p. 15236 - 15240
(2016/01/25)
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- CYCLOPROPANATION
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A method of preparing a cyclopropane ring-bearing compound of the formula (I) in which R1 and R2 are independently selected from C1-C10 alky], optionally substituted, or R1 and R2 together with the bonds linking them to the cyclopropane ring, form a monocyclic or bicyciic ring system, which may comprise at least one hetero-atom, comprising the reaction of a compound of formula (II) in which R1 and R2 have the significances hereinabove defined, with a compound of formula (III) in which X is selected a nucieofuge selected from halides and pseudohalides and Y is an electro flige selected from boranes and borates, in the presence of a metal catalyst complex selected from those that a useful for catalytic cyclopropanation and those useful for catalyzing Heck coupling. The method prov ides a particularly easy and non-hazardous method of cyclopropanation.
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Page/Page column 4; 5; 7
(2015/05/26)
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- Cyclopropanation of styrenes and stilbenes using lithiomethyl trimethylammonium triflate as methylene donor
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Lithiomethyl trimethylammonium triflate, prepared from tetramethylammonium triflate, cyclopropanates several styrenes and stilbenes with electron-donating and selected electron-withdrawing substituents efficiently. Kinetic data support a stepwise nucleophilic addition-ring closure mechanism for this methylenation. This journal is the Partner Organisations 2014.
- Sarria Toro, Juan M.,Den Hartog, Tim,Chen, Peter
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supporting information
p. 10608 - 10610
(2014/10/15)
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- A palladium-catalyzed methylenation of olefins using halomethylboronate reagents
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Methylenation of electron-rich olefins is a highly challenging reaction, for which we have developed a new methodology exploiting Pd-catalysis and halomethylboronate reagents, the latter replacing diazomethane and zinc carbenoids as methylene donors. Optimization of the reaction for norbornene and extension to several other olefins are reported, with reasonable-to-excellent yields of cyclopropanes in combination with β-H elimination products. Several mechanisms are plausible for this methylenation reaction.
- Hartog, Tim Den,Toro, Juan Manuel Sarria,Chen, Peter
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supporting information
p. 1100 - 1103
(2014/03/21)
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- Synthesis of a square-planar rhodium alkylidene N-heterocyclic carbene complex and its reactivity toward alkenes
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The first rhodium alkylidene square-planar complex stabilized by an N-heterocyclic carbene ligand, RhCl(=CHPh)(IPr)PPh3 (2; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-carbene), has been prepared by reaction of RhCl(IPr)(PPh3)2 (1) with phenyldiazomethane and its dynamic behavior in solution studied. Treatment of 2 with alkenes results in the formation of the η2-olefin complexes RhCl(η2- CH2=CHR)(IPr)PPh3 (3, R = H; 4, R = Ph; 5, R = OEt) and new olefins arising from the coupling of the alkylidene with the alkenes, likely via a metallacyclobutane intermediate.
- Palacios, Laura,Miao, Xiaowei,Di Giuseppe, Andrea,Pascal, Simon,Cunchillos, Carmen,Castarlenas, Ricardo,Perez-Torrente, Jesus J.,Lahoz, Fernando J.,Dixneuf, Pierre H.,Oro, Luis A.
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scheme or table
p. 5208 - 5213
(2011/11/13)
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- Direct synthesis of cyclic carbonates from olefins and CO2 catalyzed by a MoO2(acac)2-quaternary ammonium salt system
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A highly efficient synthesis of cyclic carbonates from olefins and CO 2 has been achieved by the use of a molybdenyl acetylacetonate (MoO2(acac)2)-quaternary ammonium salt catalytic system with tert-butyl hydroperoxide as an oxidant through a one-pot multistep process. This simple and cheap method can be applied to various olefins, such as 1-octene, 1-hexene, allyl chloride, cyclohexene and styrene, affording the highest yields in comparison with the data reported previously except for styrene. A plausible mechanism is proposed based on the results.
- Chen, Fawang,Dong, Tao,Xu, Tiegang,Li, Xiaofang,Hu, Changwen
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experimental part
p. 2518 - 2524
(2011/10/31)
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- Palladium-catalyzed cyclopropanation of alkenyl silanes by diazoalkanes: Evidence for a Pd0 mechanism
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Alkenyl silanes are efficiently converted to the corresponding silyl cyclopropanes in the presence of a slight excess of diazomethane (2-4 equiv) and a low loading of Pd(OAc)2 (-3 mol%, which corresponds to a turnover frequency of 40000 h-1. Competition experiments revealed that vinyl silanes can be selectively cyclopropanated in the presence of an aliphatic terminal alkene and styrene. The complex [Pd 20(DVTMS)3] (38, DVTMS = divinyltetramethyldisiloxane) proved to be an exceptionally active catalyst for the cyclopropanation reaction, giving complete conversion at -35 °C in 1 min. Intermolecular and intramolecular competition experiments with DVTMS (36), both with Pd(OAc)2 and 38, provided strong evidence for a Pd 0(alkenyl silane)3 resting state. Detailed density functional calculations on the reaction pathways for the cyclopropanation of trimethylvinylsilane and DVTMS by diazomethane with Pd0 corroborated the experimental observations.
- Berthon-Gelloz, Guillaume,Marchant, Melanie,Straub, Bernd F.,Marko, Istvan E.
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body text
p. 2923 - 2931
(2009/12/01)
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- Cyclopropanation of alkenes with CH2I2/Et3Al by the phase-vanishing method based on fluorous phase screen
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Phase-vanishing (PV) method using perfluorohexanes as a screen phase was applied to cyclopropanation reactions with CH2I2/Et2Zn and CH2I2/Et3Al. When Et3Al was used as a carbenoid generator, the reaction proceeded smoothly and desired cyclopropane derivatives were obtained in high yield. The PV cyclopropanation took 2 or 3 days to complete, however, reduction of reaction time by a factor of 2-3 was also achieved by vigorous stirring after the bottom CH2I2 layer disappeared.
- Matsubara, Hiroshi,Tsukida, Masaaki,Yasuda, Shinji,Ryu, Ilhyong
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scheme or table
p. 951 - 954
(2009/04/04)
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- New copper(I) and silver(I) triazolato-complexes: Synthesis, reactivity and catalytic activity in olefin cyclopropanation
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A new class of azolate ligands, deriving from the equimolar condensation of 3,5-diamino-1,2,4-triazole with salicylaldehyde (H3L1) and o-anisaldehyde (H3L2) was prepared. In their anionic form, these species act as bridging moieties upon coordination to Cu(I) and Ag(I), giving rise to the formation of dinuclear complexes with the ligand in the typical N,N′-exobidentate conformation. The copper derivative [Cu(H2L1)(CH3CN)]2 (1) showed attractive reactivity in the replacement of the labile acetonitrile molecules. In particular, it was possible to isolate a dinuclear copper(I)-carbonyl complex [Cu(H2L1)(CO)]2 (4), by substitution of the nitrile with carbon monoxide. Moreover, the reaction of 1 with ethyl diazoacetate (EDA) in CH2Cl2 afforded a mono-carbene product, as established by 13C NMR data. Finally, the copper derivative 1 proved to be a highly diastereoselective catalyst in olefin cyclopropanation in the presence of ethyl diazoacetate. In the case of internal alkenes a trans:cis ratio of up to 97:3 was reached. The X-ray structure of a dinuclear Ag(I) complex, namely [Ag(H2L1)(PPh3)]2 (3), obtained by reacting the polymeric [Ag(H2L1)]n (2), with triphenylphosphine, is also reported.
- Ardizzoia, G. Attilio,Brenna, Stefano,Castelli, Fulvio,Galli, Simona,Marelli, Chiara,Maspero, Angelo
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p. 1870 - 1876
(2008/09/18)
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- Lanthanum metal-assisted cyclopropanation of alkenes with gem-dihaloalkanes
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It was confirmed that lanthanum metal was an efficient reagent for the reductive dehalogenation of gem-dihaloalkanes. When gem-dihaloalkanes were allowed to react with lanthanum metal in the presence of alkenes, cyclopropanation of the alkenes occurred under mild conditions giving the corresponding cyclopropanes in moderate to good yields.
- Nishiyama, Yutaka,Tanimizu, Hana,Tomita, Tsuyoshi
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p. 6405 - 6407
(2008/02/12)
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- 2-Isoxazolines from arylcyclopropanes: I. Monoarylcyclopropanes in a reaction with nitrosyl chloride activated by sulfur(IV) oxide
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A reaction of monoarylcyclopropanes with nitrosyl chloride activated by sulfur (IV) oxide gave in good yields 5-arylisoxazolines. The reaction is of electrophilic character. A scheme of the reaction was suggested. Pleiades Publishing, Inc. 2006.
- Bondarenko,Gavrilova,Kazantseva,Tikhanushkina,Nifant'ev,Saginova,Zyk
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p. 249 - 255
(2007/10/03)
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- Methods, processes and materials for dispensing and recovering supported fluorous reaction components
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A fluorous delivery or recovery material comprising a fluorous support material having a coating thereon, the coating comprising an amount of a fluorous reaction component that may be dispensed using non-gravimetric methods is disclosed. Also disclosed are methods for dispensing a fluorous reaction component comprising dispensing by non-gravimetric methods a predetermined amount of the fluorous reaction component as a coating on a fluorous support material.
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Page/Page column 6-7
(2008/06/13)
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- Indium-mediated, highly efficient cyclopropanation of olefins using CH 2I2 as methylene transfer reagent
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The indium-mediated, one-pot cyclopropanation of a variety of olefins with methylene iodide proceeds smoothly with excellent yields of products.
- Virender,Jain, Suman L.,Sain, Bir
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- Processing of cyclopropylarenes by toluene dioxygenase: Isolation and absolute configuration of metabolites
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Several arenes possessing a cyclopropyl substituent were subjected to enzymatic oxidation with toluene dioxygenase. The absolute configuration of metabolites was established by chemical means.
- Finn, Kevin J.,Rochon, Lena,Hudlicky, Tomas
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p. 3606 - 3613
(2007/10/03)
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- A Novel Class of Tunable Zinc Reagents (RXZnCH2Y) for Efficient Cyclopropanation of Olefins
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A class of zinc reagents (RXZnCH2Y) generated with an appropriate organozinc is very effective for the cyclopropanation of olefins. The reactivity and selectivity of these reagents can be regulated by tuning the electronic and steric nature of the RX group on Zn. A reasonable level of enantioselectivity was obtained for the cyclopropanation of unfunctionalized olefins when a chiral (iodomethyl)zinc species was used, providing a valuable approach for the asymmetric cyclopropanation of unfunctionalized olefins.
- Lorenz, Jon C.,Long, Jiang,Yang, Zhiqiang,Xue, Song,Xie, Yinong,Shi, Yian
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p. 327 - 334
(2007/10/03)
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- Cyclopropylboronic acid: Synthesis and Suzuki cross-coupling reactions
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An efficient synthesis of cyclopropylboronic acid is reported. This compound undergoes efficient Suzuki-type coupling reactions with a range of aryl and heteroarybromides.
- Wallace, Debra J.,Chen, Cheng-Yi
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p. 6987 - 6990
(2007/10/03)
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- Remarkable aromatic substitution by a 1,5-diradical
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Generation of 2,6-dioxa-3-phenylcyclohexylidene in benzene leads to 2,4-diphenyl-1,3-dioxane, the product of apparent insertion into a CH bond of benzene. However, that product arises from attack of a diradical intermediate on benzene.
- Merkley, Nadine,Reid, Darren L,Warkentin, John
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p. 1927 - 1929
(2007/10/03)
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- Thermolysis of a spiro-fused oxadiazoline: The carbonyl ylide-cyclic carbene-diradical sequence
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Thermolysis of spiro-fused oxadiazoline 1 in benzene led to loss of N2 to form a carbonyl ylide intermediate. Most of the ylide fragmented to acetone and 4-phenyl-1,3-dioxane-2-ylidene, which could be trapped with tert-butyl alcohol. In the absence of the trapping agent, the major pathway followed by the carbene was fragmentation to a diradical, 5-phenyl-2-oxa-1-oxo-1,5-pentanediyl. The latter diradical coupled to α-phenyl-δ-butyrolactone and decarboxylated to afford cyclopropylbenzene. Other products from the reaction were those of apparent insertion of the carbene into a C-H bond of the benzene solvent and into a C-H bond of acetone. Such reactions appear to be without precedent - alternative, non-carbene mechanisms are proposed.
- Merkley, Nadine,Warkentin, John
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p. 1187 - 1195
(2007/10/03)
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- New family of cyclopropanating reagents: Synthesis, reactivity, and stability studies of iodomethylzinc phenoxides
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A valuable alternative to the traditional Simmons-Smith reagents is offered by the title compounds, as a result of their ease of preparation and high reactivities towards unfunctionalized olefins (see scheme).
- Charette, Andre B.,Francoeur, Sebastien,Martel, Jonathan,Wilb, Nicole
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p. 4539 - 4542
(2007/10/03)
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- Aryl and vinyl cyclopropanes through the in situ generation of B- cyclopropyl-9-BBN and its Suzuki-Miyaura coupling
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Dihydroboration of propargyl bromide with 9-BBN-H followed by treatment of the adduct with aqueous sodium hydroxide affords the hydroxy(cycloropropyl)borate complex (1), which undergoes efficient palladium-catalyzed cross-coupling to produce a variety of aryl and vinyl cyclopropanes (2) in good to excellent yields. (C) Elsevier Science Ltd.
- Soderquist, John A.,Huertas, Ramon,Leon-Colon, Gisela
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p. 4251 - 4255
(2007/10/03)
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- Exploring new reactive species for cyclopropanation
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An organozinc species RXZnCH2I generated by reacting Zn(CH2I)2 with RXH was found to be an efficient reagent for the cyclopropanation of olefins at room temperature. A 50.7% ee was obtained for the cyclopropanation of trans-β-methylstyrene when a chiral alcohol was used.
- Yang, Zhiqiang,Lorenz, Jon C.,Shi, Yian
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p. 8621 - 8624
(2007/10/03)
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- The nickel and palladium catalyzed stereoselective cross coupling of cyclopropyl nucleophiles with aryl halides
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The reaction of 2-phenylcyclopropylzinc chloride with some substituted (het)aryl halides gave the corresponding coupling products with good yields and stereoselectivities under the influence of a catalytic amount of Pd(PPh3)4. Other Ni- and Pd-catalysts were less efficient. Alkyl-substituted cyclopropyl nucleophiles gave lower yields.
- De Lang,Brandsma
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p. 225 - 232
(2007/10/03)
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- Photoinduced reduction of gem-dichlorocyclopropanes with SmI2 and benzenethiol
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Upon irradiation with visible light, gem-dichlorocyclopropanes undergo reductive dechlorination with samarium diiodide and benzenethiol to provide the corresponding cyclopropanes in good yields. The reaction may proceed via the hydrogen abstraction from PhSH by cyclopropyl radicals formed in situ by the reduction with SmI2.
- Ogawa, Akiya,Ohya, Syoji,Hirao, Toshikazu
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p. 275 - 276
(2007/10/03)
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- A simple and efficient hydrodehalogenation of 1,1-dihalocyclopropanes
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1,1-Dibromo- and 1,1-dichlorocyclopropanes are converted into the corresponding monohalocyclopropanes (as mixtures of stereoisomers where appropriate) by reaction with 1.2-1.3 mol. equiv. of ethyl magnesium bromide and a small amount of titanium isopropoxide in ether. In the presence of an excess of ethylmagnesium bromide the product from the dibromide is the non- halogenated cyclopropane. Copyright (C) 1996 Elsevier Science Ltd.
- Dulayymi, Juma'a R. Al,Baird, Mark S.,Bolesov, Ivan G.,Tveresovsky, Viacheslav,Rubin, Michael
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p. 8933 - 8936
(2007/10/03)
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- Convenient preparation of a cyclopropanation reagent: α-Siloxymethyliron complex
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A convenient preparation of α-siloxymethyliron complex (7) was developed from commercially available s-trioxane and/or paraformaldehyde. For synthetic utility, iron methylidene complex (8) was generated in situ from the α-siloxymethyliron complex (7) and cyclopropanes (10) by treatment with alkenes.
- Du, Hong,Yang, Fukang,Mahmun Hossain
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p. 1371 - 1377
(2007/10/03)
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- Conversion of non-activated alkenes into cyclopropanes with lithiated sulfones under nickel catalysis
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Summary -Lithiated alkyl ierf-butyl sulfones convert alkenes into cyclopropane derivatives under nickel catalysis. The new reaction appears to differ from the known cyclopropanation reactions from both the stereochemical and the electronic points of view. Elsevier.
- Gai, Yonghua,Julia, Marc,Verpeaux, Jean-Noel
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p. 817 - 829
(2007/10/03)
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- The Stereochemistry of Rearrangements of Aryl and Hetaryl Groups to Primary Carbenic Centers
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The products and stereochemistries of carbenic decompositions of varied 2-aryl-1-diazoalkanes and 1-diazo-2-(2-hetaryl)propanes have been determined.
- Slack, W. E.,Taylor, W.,Moseley, C. G.,Chang, K. T.,Kraska, A.,et al.
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p. 2647 - 2650
(2007/10/02)
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- STEREOSELECTIVE REDUCTION OF gem-DICHLOROCYCLOPROPANES TO cis-MONOCHLOROCYCLOPROPANES BY LITHIUM ALUMINUM HYDRIDE IN THE PRESENCE OF TITANIUM AND ZIRCONIUM COMPLEXES
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A versatile stereoselective method in presented for the synthesis of cis-monochlorocyclopropanes by the reduction of dehalogenated alkyl- and aryl-gem-dichlorocyclopropanes in the presence of catalytic quantities of titanium and zirconium complexes.
- Dzhemilev, U. M.,Gaisin, R. L.,Turchin, A. A.,Tolstikov, G. A.
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p. 1845 - 1848
(2007/10/02)
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- Electrochemical Cyclopropanation of Alkenes Using Dibromomethane and Zinc in CH2Cl2/DMF Mixture
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An efficient electrosynthesis of cyclopropanes from gem-dibromoalkanes and alkenes is achieved in a one-compartment cell fitted with a sacrificial zinc anode.The part played by the anodically generated Zn(II) in the coupling reaction is pointed out, and evidence for the existence of an organozinc species as intermediate is presented.
- Durandetti, Sylvie,Sibille, Soline,Perichon, Jacques
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p. 3255 - 3258
(2007/10/02)
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- Investigation of the stereochemistry of Fe-Cα bond cleavage when phenylcyclopropane is generated by γ-ionization of stereospecifically deuterated C5H5(CO)2 FeCHDCHDCH(OCH3)C6H5 complexes.
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C5H5(CO)2FeCH2CH 2CH(OCH3)C6H5, 4, and stereospecifically deuterium labeled threo-d2-C5H5-(CO) 2FeCHDCHDCH(OCH3)C6H5, 7a,b and erythro-d2-C5H5(CO) 2FeCHDCHDCH(OCH3)C6H5, 8a,b were synthesized. Treatment of compound 4 with trimethylsilyl triflate results in ionization of the γ-methoxy group and formation of phenylcyclopropane in good yields. Ionization of 7a,b gives a 1:1 mixture of cis-2,cis-3-dideuterio- and trans-2,trans-3-dideuterio-r-1-phenylcyclopropane, while ionization of 8a,b gives cis-2,trans-3-dideuterio-r-1-phenylcyclopropane. These results established that the cyclopropane ring is formed by backside attack of electrophilic Cγ on Cα with net inversion of stereochemistry at Cα. These reactions serve as models for the reactions of carbene complexes C5H5(CO)2Fe=CHR+ with alkenes to give cyclopropanes and suggest that in the transfer reactions Fe-Cα is cleaved with inversion.
- Brookhart, Maurice,Liu, Yumin
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p. 939 - 944
(2007/10/02)
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- EFFICIENT METHOD FOR THE SYNTHESIS OF MONOHALOCYCLOPROPANES BY REDUCTION OF GEM-DIHALOCYCLOPROPANES BY REDUCTION OF GEM-DIHALOCYCLOPROPANES WITH i-Bu2AlH IN THE PRESENCE OF Ti AND Zr COMPLEXES
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We have investigated the reductive dehalogenation reaction of alkyl and aryl substituted gem-dihalocyclopropanes with diisobutyl aluminum hydride in the presence of catalytic amounts of titanium and zirconium complexes.As a result we propose a general method for the synthesis of substituted monohalocyclopropanes and cyclopropanes of various structures.We have also studied the stereochemistry of the reduction.
- Dzhemilev, U. M.,Gaisin, R. L.,Turchin, A. A.,Khalikova, N. R.,Baikova, I. P.,Tolstikov, G. A.
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p. 967 - 974
(2007/10/02)
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