- Merging Halogen-Atom Transfer (XAT) and Copper Catalysis for the Modular Suzuki-Miyaura-Type Cross-Coupling of Alkyl Iodides and Organoborons
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We report here a mechanistically distinct approach to achieve Suzuki-Miyaura-type cross-couplings between alkyl iodides and aryl organoborons. This process requires a copper catalyst but, in contrast with previous approaches based on palladium and nickel
- Zhang, Zhenhua,Górski, Bartosz,Leonori, Daniele
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p. 1986 - 1992
(2022/02/01)
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- Ground-State Electron Transfer as an Initiation Mechanism for Biocatalytic C-C Bond Forming Reactions
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The development of non-natural reaction mechanisms is an attractive strategy for expanding the synthetic capabilities of substrate promiscuous enzymes. Here, we report an "ene"-reductase catalyzed asymmetric hydroalkylation of olefins using α-bromoketones as radical precursors. Radical initiation occurs via ground-state electron transfer from the flavin cofactor located within the enzyme active site, an underrepresented mechanism in flavin biocatalysis. Four rounds of site saturation mutagenesis were used to access a variant of the "ene"-reductase nicotinamide-dependent cyclohexanone reductase (NCR) from Zymomonas mobiles capable of catalyzing a cyclization to furnish β-chiral cyclopentanones with high levels of enantioselectivity. Additionally, wild-type NCR can catalyze intermolecular couplings with precise stereochemical control over the radical termination step. This report highlights the utility for ground-state electron transfers to enable non-natural biocatalytic C-C bond forming reactions.
- Fu, Haigen,Lam, Heather,Emmanuel, Megan A.,Kim, Ji Hye,Sandoval, Braddock A.,Hyster, Todd K.
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p. 9622 - 9629
(2021/07/01)
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- Deciphering Reactivity and Selectivity Patterns in Aliphatic C-H Bond Oxygenation of Cyclopentane and Cyclohexane Derivatives
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A kinetic, product, and computational study on the reactions of the cumyloxyl radical with monosubstituted cyclopentanes and cyclohexanes has been carried out. HAT rates, site-selectivities for C-H bond oxidation, and DFT computations provide quantitative information and theoretical models to explain the observed patterns. Cyclopentanes functionalize predominantly at C-1, and tertiary C-H bond activation barriers decrease on going from methyl- and tert-butylcyclopentane to phenylcyclopentane, in line with the computed C-H BDEs. With cyclohexanes, the relative importance of HAT from C-1 decreases on going from methyl- and phenylcyclohexane to ethyl-, isopropyl-, and tert-butylcyclohexane. Deactivation is also observed at C-2 with site-selectivity that progressively shifts to C-3 and C-4 with increasing substituent steric bulk. The site-selectivities observed in the corresponding oxidations promoted by ethyl(trifluoromethyl)dioxirane support this mechanistic picture. Comparison of these results with those obtained previously for C-H bond azidation and functionalizations promoted by the PINO radical of phenyl and tert-butylcyclohexane, together with new calculations, provides a mechanistic framework for understanding C-H bond functionalization of cycloalkanes. The nature of the HAT reagent, C-H bond strengths, and torsional effects are important determinants of site-selectivity, with the latter effects that play a major role in the reactions of oxygen-centered HAT reagents with monosubstituted cyclohexanes.
- Martin, Teo,Galeotti, Marco,Salamone, Michela,Liu, Fengjiao,Yu, Yanmin,Duan, Meng,Houk,Bietti, Massimo
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supporting information
p. 9925 - 9937
(2021/06/30)
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- Electrochemically Enabled, Nickel-Catalyzed Dehydroxylative Cross-Coupling of Alcohols with Aryl Halides
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As alcohols are ubiquitous throughout chemical science, this functional group represents a highly attractive starting material for forging new C-C bonds. Here, we demonstrate that the combination of anodic preparation of the alkoxy triphenylphosphonium ion and nickel-catalyzed cathodic reductive cross-coupling provides an efficient method to construct C(sp2)-C(sp3) bonds, in which free alcohols and aryl bromides - both readily available chemicals - can be directly used as coupling partners. This nickel-catalyzed paired electrolysis reaction features a broad substrate scope bearing a wide gamut of functionalities, which was illustrated by the late-stage arylation of several structurally complex natural products and pharmaceuticals.
- Li, Zijian,Sun, Wenxuan,Wang, Xianxu,Li, Luyang,Zhang, Yong,Li, Chao
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supporting information
p. 3536 - 3543
(2021/03/08)
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- Photocontrolled Cobalt Catalysis for Selective Hydroboration of α,β-Unsaturated Ketones
-
Selectivity between 1,2 and 1,4 addition of a nucleophile to an α,β-unsaturated carbonyl compound has classically been modified by the addition of stoichiometric additives to the substrate or reagent to increase their “hard” or “soft” character. Here, we demonstrate a conceptually distinct approach that instead relies on controlling the coordination sphere of a catalyst with visible light. In this way, we bias the reaction down two divergent pathways, giving contrasting products in the catalytic hydroboration of α,β-unsaturated ketones. This includes direct access to previously elusive cyclic enolborates, via 1,4-selective hydroboration, providing a straightforward and stereoselective route to rare syn-aldol products in one-pot. DFT calculations and mechanistic experiments confirm two different mechanisms are operative, underpinning this unusual photocontrolled selectivity switch.
- Beltran, Frédéric,Bergamaschi, Enrico,Funes-Ardoiz, Ignacio,Teskey, Christopher J.
-
supporting information
p. 21176 - 21182
(2020/09/17)
-
- The Silicon-Hydrogen Exchange Reaction: A Catalytic σ-Bond Metathesis Approach to the Enantioselective Synthesis of Enol Silanes
-
The use of chiral enol silanes in fundamental transformations such as Mukaiyama aldol, Michael, and Mannich reactions as well as Saegusa-Ito dehydrogenations has enabled the chemical synthesis of enantiopure natural products and valuable pharmaceuticals. However, accessing these intermediates in high enantiopurity has generally required the use of either stoichiometric chiral precursors or stoichiometric chiral reagents. We now describe a catalytic approach in which strongly acidic and confined imidodiphosphorimidates (IDPi) catalyze highly enantioselective interconversions of ketones and enol silanes. These "silicon-hydrogen exchange reactions"enable access to enantiopure enol silanes via tautomerizing σ-bond metatheses, either in a deprotosilylative desymmetrization of ketones with allyl silanes as the silicon source or in a protodesilylative kinetic resolution of racemic enol silanes with a carboxylic acid as the silyl acceptor.
- Zhou, Hui,Bae, Han Yong,Leutzsch, Markus,Kennemur, Jennifer L.,Bécart, Diane,List, Benjamin
-
supporting information
p. 13695 - 13700
(2020/08/24)
-
- Improved Process for the Palladium-Catalyzed C-O Cross-Coupling of Secondary Alcohols
-
An improved protocol for the Pd-catalyzed C-O cross-coupling of secondary alcohols is described. The use of biaryl phosphine L2 as the ligand was key to achieving efficient cross-coupling of (hetero)aryl chlorides with only a 20percent molar excess of the alcohol. Additionally, we observed an unusual reactivity difference between an electron-rich aryl bromide and the analogous aryl chloride, and deuterium-labeling suggested that currently unidentified pathways for reduction play an important role in explaining this disparity.
- Zhang, Hong,Ruiz-Castillo, Paula,Schuppe, Alexander W.,Buchwald, Stephen L.
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supporting information
p. 5369 - 5374
(2020/07/14)
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- PdBr2-Catalyzed Acetal Formation of Carbonyl Compounds Using Diazophenanthrenequinone: Utility of 9,10-Phenanthrenedioxyacetal
-
We developed a new acetalization method of ketones and aldehydes under non-acidic conditions using diazophenanthrenequinone and PdBr2. The formed acetals that have a phenanthrene skeleton withstand under mild acidic conditions. Removal of acetals was successfully proceeded under strong acidic or oxidation conditions using aqueous ceric ammonium nitrate (CAN) to afford corresponding ketones and aldehydes.
- Kitamura, Mitsuru,Fujimura, Ryo,Nishimura, Tomoaki,Takahashi, Shuhei,Shimooka, Hirokazu,Okauchi, Tatsuo
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supporting information
p. 5319 - 5322
(2020/06/10)
-
- INHIBITORS OF INDOLEAMINE 2,3-DIOXYGENASE AND METHODS OF THEIR USE
-
There are disclosed compounds that modulate or inhibit the enzymatic activity of indoleamine 2,3-dioxygenase (IDO), pharmaceutical compositions containing said compounds and methods of treating proliferative disorders, such as cancer, viral infections and/or inflammatory disorders utilizing the compounds of the disclosure.
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- Zinc substituted Keggin-type polyoxometalate on Dowex: a green heterogeneous catalyst for oxidation of alcohols in water
-
In this work, homogeneous and heterogeneous oxidation of alcohols by H2O2 in the presence of [(n-C4H9)4?N]5[PW11ZnO39].3H2O and [PW11ZnO39]5? supported on Dowex 22 as catalysts have been investigated. Using water as a green solvent, different alcohols were converted into the corresponding aldehydes and ketones in high to excellent yields. Dowex 22 supported polyoxometalate, PW11Zn@Dowex, was also catalyzed highly robust and selective oxidation of unsaturated alcohols. Leaching and recycling experiments on supported catalyst revealed the excellent stability and reusability of this catalytic system.
- Aghayi, Mehdi,Yadollahi, Bahram,Farsani, Mostafa Riahi
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p. 2895 - 2900
(2020/06/17)
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- Catalyst-Free Photodriven Reduction of α-Haloketones with Hantzsch Ester
-
Catalyst-free dehalogenation of α-haloketones under visible light irradiation is studied. The reactions were carried out in common organic solvent. The outcomes of dechlorination are excellent in yields up to 92%, and it is also applicable to bromides, which give even higher yields. The reaction is tolerable to a broad spectrum of substrates, especially to aromatic ketones, including various aryl and hetaryl groups. There are two examples of aliphatic ketones presented in the paper, although their reactivities are not as high as that of the aromatic ketones.
- Lu, Zheng,Yang, Yong-Qing
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p. 508 - 515
(2019/01/10)
-
- An investigation into the role of 2,6-lutidine as an additive for the RuCl3-NaIO4 mediated oxidative cleavage of olefins to ketones
-
2,6-Lutidine has been identified as a beneficial additive for the oxidative cleavage of olefins to ketones by NaIO4 in the presence of catalytic RuCl3, improving the yield and shortening the reaction times. In the absence of 2,6-lutidine reactions stalled at the diol intermediate with incomplete conversion to the desired ketones. The reaction protocol described herein also avoids the use of harmful solvents such as CCl4 and DCE and is tolerant of a range of functional groups.
- Watson, David W.,Gill, Matthew,Kemmitt, Paul,Lamont, Scott G.,Popescu, Mihai V.,Simpson, Iain
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supporting information
p. 4479 - 4482
(2018/11/23)
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- Selective C(sp3)?H Aerobic Oxidation Enabled by Decatungstate Photocatalysis in Flow
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A mild and selective C(sp3)?H aerobic oxidation enabled by decatungstate photocatalysis has been developed. The reaction can be significantly improved in a microflow reactor enabling the safe use of oxygen and enhanced irradiation of the reaction mixture. Our method allows for the oxidation of both activated and unactivated C?H bonds (30 examples). The ability to selectively oxidize natural scaffolds, such as (?)-ambroxide, pregnenolone acetate, (+)-sclareolide, and artemisinin, exemplifies the utility of this new method.
- Laudadio, Gabriele,Govaerts, Sebastian,Wang, Ying,Ravelli, Davide,Koolman, Hannes F.,Fagnoni, Maurizio,Djuric, Stevan W.,No?l, Timothy
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supporting information
p. 4078 - 4082
(2018/03/21)
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- Unexpected metal-free transformation of gem-dibromomethylenes to ketones under acetylation conditions
-
Novel conditions for the transformation of gem-dibromomethylenes to ketones are described. gem-Dibromo compounds were treated with acetic anhydride and triethylamine in dichloromethane/water at room temperature under an air atmosphere to give the corresponding ketones in moderate yields. A radical mechanism is proposed based on experimental results.
- Kimura, Rino,Sawayama, Yusuke,Nakazaki, Atsuo,Miyamoto, Kazunori,Uchiyama, Masanobu,Nishikawa, Toshio
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p. 1035 - 1041
(2015/03/31)
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- Building MOF bottles (MIL-101 family as heterogeneous single-site catalysts) around Fe3O4 ships: A highly efficient and magnetically separable catalyst for oxidation of alcohols
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Fe3O4 supported on chromium-based metal-organic framework (MOF), MIL-101(Cr), has emerged as highly efficient and heterogeneous catalyst for selective oxidation of alcohols because of its high specific surface area, tuneable pore size, and unique structure. MIL-101 and its Fe3O4 composite (Fe3O4@MIL-101) was prepared via the impregnation of the Fe3O4 in MIL-101. The surface properties of the functionalized catalyst were analyzed by a series of characterization techniques like FTIR, XRD, N2 adsorption-desorption, and TEM. XRD and adsorption-desorption analysis show that the mesostructure of MIL-101 remains intact after Fe3O4 modifications, while spectral technique show the successful immobilizing of the neat Fe3O4 inside the MIL-101 support. Fe3O4@MIL-101 can be reused several times although they get less active.
- Naghdi, Zahra,Farzaeli, Razieh,Aliyan, Hamid
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p. 1343 - 1350
(2015/12/01)
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- Direct conversion of alcohols to α-chloro aldehydes and α-chloro ketones
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Direct conversion of primary and secondary alcohols into the corresponding α-chloro aldehydes and α-chloro ketones using trichloroisocyanuric acid, serving both as stoichiometric oxidant and α-halogenating reagent, is reported. For primary alcohols, TEMPO has to be added as an oxidation catalyst, and for the transformation of secondary alcohols (TEMPO-free protocol), MeOH as an additive is essential to promote chlorination of the intermediary ketones.
- Jing, Yuanyuan,Daniliuc, Constantin G.,Studer, Armido
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supporting information
p. 4932 - 4935
(2015/04/27)
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- Solar photochemical oxidation of alcohols using catalytic hydroquinone and copper nanoparticles under oxygen: Oxidative cleavage of lignin models
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Alcohols are converted into to their corresponding carbonyl compounds using catalytic amounts of 1,4-hydroquinone with a copper nanoparticle electron transfer mediator with oxygen as the terminal oxidant in acetone as solvent under visible light irradiation. These conditions employing biorenewable hydroquinone as reagent were developed from initial experiments using stoichiometric amounts of 1,4-benzoquinone as oxidant. A range of benzylic and aliphatic primary and secondary alcohols are oxidized, affording the corresponding aldehydes or ketones in moderate to excellent yields. The methodology is also applicable to the oxidative degradation of lignin model compounds that undergo C-C bond cleavage to give simple aromatic compounds.
- Mitchell, Lorna J.,Moody, Christopher J.
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p. 11091 - 11100
(2015/01/08)
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- Site-selective oxidation of unactivated C sp 3-H bonds with hypervalent iodine(III) reagents
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By design: The site-selective oxidation of unactivated secondary C sp 3-H bonds was accomplished with hypervalent iodine(III) reagents and tert-butyl hydroperoxide (see scheme). The preparation and derivatization of the hypervalent iodine(III) reagent are simple, thus allowing the rational design of these reagents to optimize the site selectivity of the oxidation. Copyright
- Moteki, Shin A.,Usui, Asuka,Zhang, Tiexin,Solorio Alvarado, Cesar R.,Maruoka, Keiji
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supporting information
p. 8657 - 8660
(2013/09/12)
-
- Highly efficient Cu(I)-catalyzed oxidation of alcohols to ketones and aldehydes with diaziridinone
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A novel and efficient Cu(I)-catalyzed oxidation of alcohols has been achieved with di-tert-butyldiaziridinone as the oxidant under mild conditions. A wide variety of primary and secondary alcohols with various functional groups can be oxidized to aldehydes and ketones in high yields. The reaction proceeds under neutral conditions making it compatible with acid- or base-sensitive substrates, and it is amenable to gram scale.
- Zhu, Yingguang,Zhao, Baoguo,Shi, Yian
-
supporting information
p. 992 - 995
(2013/04/10)
-
- Nickel-catalyzed reductive coupling of aryl halides with secondary alkyl bromides and allylic acetate
-
A room-temperature Ni-catalyzed reductive method for the coupling of aryl bromides with secondary alkyl bromides has been developed, providing C(sp 2)-C(sp3) products in good to excellent yields. Slight modification of this protocol allows efficient coupling of activated aryl chlorides with cyclohexyl bromide and aryl bromides with allylic acetate.
- Wang, Shulin,Qian, Qun,Gong, Hegui
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supporting information; experimental part
p. 3352 - 3355
(2012/08/08)
-
- Overcoming hERG activity in the discovery of a series of 4-azetidinyl-1-aryl-cyclohexanes as CCR2 antagonists
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A series of 4-azetidinyl-1-aryl-cyclohexanes as potent CCR2 antagonists with high selectivity over activity for the hERG potassium channel is discovered through divergent SARs of CCR2 and hERG.
- Zhang, Xuqing,Hufnagel, Heather,Markotan, Thomas,Lanter, James,Cai, Chaozhong,Hou, Cuifen,Singer, Monica,Opas, Evan,McKenney, Sandra,Crysler, Carl,Johnson, Dana,Sui, Zhihua
-
p. 5577 - 5582
(2011/10/09)
-
- A general method for palladium-catalyzed reactions of primary sulfonamides with aryl nonaflates
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A general method for Pd-catalyzed sulfonamidation of aryl nonafluorobutanesulfonates (aryl nonaflates) is described. A biaryl phosphine ligand, t-BuXPhos, formed the most active catalyst, and K3PO 4 in tert-amyl alcohol was found to be the optimal base-solvent combination for the reaction. The reaction conditions were tolerant of various functional groups such as cyano, nitro, ester, aldehyde, ketone, chloride, carbamate, and phenol. Heterocyclic aryl nonaflates were found to be suitable coupling partners. High yields of the coupled products were obtained from the reactions between inherently disfavored substrates such as electron-rich nonaflates and electron-poor sulfonamides. Kinetic data suggest reductive elimination to be the rate-limiting step for the reaction. The only limitation of this methodology that we have identified is the inability of 2,6-disubstituted aryl nonaflates to efficiently participate in the reaction.
- Shekhar, Shashank,Dunn, Travis B.,Kotecki, Brian J.,Montavon, Donna K.,Cullen, Steven C.
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body text
p. 4552 - 4563
(2011/07/31)
-
- Aryl extensions of thienopyrimidinones as fibroblast growth factor receptor 1 kinase inhibitors
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Optimization of thienopyrimidinone derivatives as FGFR1 kinase inhibitors is being pursued. The present results confirm predictions of computational modeling that an aryl substituent can be introduced at the 2-position in structure 3. The substituent is anticipated to project deeper into the binding site and provide opportunities for enhanced activity and selectivity. The most potent analog reported herein, 13, has a 4-hydroxyphenyl substituent and yields an IC50 of 6 μM for inhibition of phosphorylation by FGFR1 kinase. It was also found that the western anisole-containing substituent in 3 can be replaced by a propionic acid group with no loss in potency and with potentially significant gains in pharmacologically relevant properties.
- Ekkati, Anil R.,Mandiyan, Valsan,Ravindranathan, Krishna P.,Bae, Jae H.,Schlessinger, Joseph,Jorgensen, William L.
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scheme or table
p. 2228 - 2231
(2011/05/05)
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- Visible-light photoredox catalysis: Dehalogenation of vicinal dibromo-, α-halo-, and α,α-dibromocarbonyl compounds
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vic-Dibromo-, α-halo-, or α,α-dibromocarbonyl compounds can be efficiently dehalogenated using catalytic tris(2,2′-bipyridyl) ruthenium dichloride (Ru(bpy)3Cl2) in combination with 1,5-dimethoxynaphthalene (DMN) and ascorbate as sacrificial electron donor. For this process, a visible light promoted photocatalytic cycle is proposed that involves the reduction of carbon halogen bonds via free radical intermediates.
- Maji, Tapan,Karmakar, Ananta,Reiser, Oliver
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supporting information; experimental part
p. 736 - 739
(2011/03/20)
-
- Nanocrystalline magnesium oxide stabilized palladium(0): An efficient reusable catalyst for room temperature selective aerobic oxidation of alcohols
-
Nanocrystalline magnesium oxide-stabilized palladium(0) [NAP-Mg-Pd(0)], as an efficient catalytic system has been employed for the selective oxidation of alcohols using atmospheric oxygen as a green oxidant at room temperature. Various alcohols could be transformed into their corresponding aldehydes or ketones in good to excellent yields using a set of optimal conditions. NanoActive Magnesium Oxide Plus, [NAP-MgO] with its three-dimensional structure and well-defined shape acts as an excellent support for well dispersed palladium(0) nanoparticles. This catalyst can be recovered and reused for several cycles without any significant loss of catalytic activity.
- Layek, Keya,Maheswaran,Arundhathi,Kantam, M. Lakshmi,Bhargava, Suresh K.
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supporting information; experimental part
p. 606 - 616
(2011/04/25)
-
- 1-Cyclohexyl-4-(4-arylcyclohexyl)piperazines: Mixed σ and Human Δ8-Δ7 Sterol Isomerase Ligands with Antiproliferative and P-Glycoprotein Inhibitory Activity
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Many new chemotherapeutic agents are under preclinical investigation and, despite efforts to more selectively target cancer cells, limitations such as toxicity and inherent resistance are often encountered. Therefore, alternative strategies are needed to treat cancer and overcome such limitations. We describe novel cyclohexylpiperazine derivatives, designed as mixed affinity ligands for sigma (σ) receptors and human Δ8-Δ7 sterol isomerase (HSI) ligands, which also exhibit P-glycoprotein (P-gp) inhibitory activity, with the aim of exploiting the antiproliferative effects mediated by σ and HSI sites while overcoming P-gp-mediated resistance. All of the compounds displayed high affinities for σ receptors and HSI sites, P-gp inhibitory activity, and σ2 receptor agonist antiproliferative activity. Antiproliferative activity was also tested in PC-3 cells to establish σ1 and HSI contribution. Compound cis-11, which displayed the best antiproliferative and P-gp inhibitory activities, was co-administered with 0.1 μM doxorubicin in MDCK-MDR1 cells. Compound cis-11 caused 70 % and 90 % cell death when co-administered at 30 μM and 50 μm, respectively. When administered alone, cis-11 resulted in 50 % cell death, demonstrating its single agent antitumor properties in a tumor cell line overexpressing P-gp.Synergistic mixed activity: A series of cyclohexylpiperazines with mixed σ and HSI affinities and P-gp inhibitory activity were synthesized. Their antiproliferative activity, combined with P-gp inhibitory activity, shows the potential of these compounds to be used as antitumor agents devoid of P-gp-mediated resistance, or in association with classic antitumor agents susceptible to P-gp activity.
- Abate, Carmen,Niso, Mauro,Contino, Marialessandra,Colabufo, Nicola Antonio,Ferorelli, Savina,Perrone, Roberto,Berardi, Francesco
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- An expedient reductive method for conversion of ketoximes to the corresponding carbonyl compounds
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A wide array of readily prepared pivalates of ketoximes can be converted to the corresponding ketones in good yields by treatment with iron powder in THF containing catalytic amounts of both trimethylsilyl chloride and glacial acetic acid at room temperature for 30 min, followed by a brief aqueous workup.
- Majireck, Max M.,Witek, Jason A.,Weinreb, Steven M.
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experimental part
p. 3555 - 3557
(2010/08/07)
-
- PHOTO-ACTIVATABLE THERAPEUTIC AGENTS AND METHODS OF USING
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Novel photo-activatable pro-therapeutic agents and methods for their synthesis and use are described. The photo-activatable pro-therapeutic agents are inactive pro-forms of compounds that can be activated in situ, for example, by providing a pro-therapeutic agent to a subject and photo-activating the pro-therapeutic agent at a selected area of the subject. Also disclosed are methods for administering the photo-activatable pro-therapeutic agents to a subject then activating the pro-therapeutic agents at a selected area of the subject by exposing that area to light.
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Page/Page column 21
(2010/04/28)
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- Photooxygenation of hydrocarbons over efficient and reusable decatungstate heterogenized on hydrophobically-modified mesoporous silica
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Decatungstate W10O324- heterogenized on a novel hydrophobically-organomodified SBA-15 was proven an efficient, green and reusable catalyst for photooxygenation by oxygen of a range of aryl alkanes to the corresponding ketones under mild conditions.
- Ni, Lingli,Ni, Ji,Lv, Yuan,Yang, Ping,Cao, Yong
-
supporting information; experimental part
p. 2171 - 2173
(2009/09/06)
-
- Aerobic oxidation of alcohols using various types of immobilized palladium catalyst: The synergistic role of functionalized ligands, morphology of support, and solvent in generating and stabilizing nanoparticles
-
Preparation and characterization of a variety of immobilized palladium catalyst, based on either ligand functionalized amorphous or ordered mesoporous silica, is described. The resulting Pd-loaded materials act as efficient catalyst for the oxidation of a variety of alcohols using molecular oxygen and air. Our studies show that in the case of supported palladium catalyst on hybrid amorphous silica, the nature of ligand and the solvent could effectively control the generation of nanoparticles. Furthermore, we have found that nanoparticles with smaller size and higher activity were generated from the anchored palladium precursor when the aerobic oxidation of alcohols was carried out in α,α,α-trifluorotoluene (TFT) instead of toluene. On the other hand, in the case of aerobic oxidation reactions by using supported palladium catalyst on hybrid SBA-15, the combination of organic ligand and ordered mesoporous channels resulted in an interesting synergistic effect that led to enhanced activity, prevention of Pd nanoparticles agglomeration, and finally generation of a durable catalyst.
- Karimi, Babak,Zamani, Asghar,Abedi, Sedigheh,Clark, James H.
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experimental part
p. 109 - 119
(2010/04/22)
-
- Cleavage of 1,3-dithianes via acid-catalyzed hydrolysis of the corresponding 1,3-dithianemonooxides
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The hydrolysis of 1,3-dithianes to their parent carbonyl compounds via their corresponding monosulfoxides was systematically investigated. The oxidation of the 1,3-dithianes was carried out in high yields using tert-butyl hydroperoxide. Acid-catalyzed hydrolysis of the monosulfoxides to the carbonyl compounds was then performed in excellent yields. The cleavage reactions were monitored by gas chromatography and kinetics were investigated on substrates varying in electron density and steric requirements. Neither effect prevented high overall yields in the cleavage reaction. Georg Thieme Verlag Stuttgart.
- Krohn, Karsten,Cludius-Brandt, Stephan
-
experimental part
p. 2369 - 2372
(2009/04/07)
-
- Sequential removal of photolabile protecting groups for carbonyls with controlled wavelength
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(Chemical Equation Presented) A group of robust and easy-to-make photolabile protecting groups (PPGs) for carbonyl compounds has been developed. Sequential removal of different PPGs is achieved via control of irradiation wavelength.
- Wang, Pengfei,Wang, Yun,Hu, Huayou,Spencer, Cierra,Liang, Xing,Pan, Lurong
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p. 6152 - 6157
(2008/12/22)
-
- Expedient synthesis and solvent dependent oxidation behavior of a water-soluble IBX derivative
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IBX derivative 6, synthesized in two steps from 2-aminoterephthalic acid, 8, is soluble in both DMF and water. A variety of alcohols are oxidized using 6 in DMF with ease and selectivity identical to that of parent IBX. However, oxidations carried out in water and other aqueous solvent mixtures using 6 exhibit unique selectivities toward different substrates and provide products different from reactions carried out in DMF. A mechanistic rationale is provided for this solvent dependent behavior of 6.
- Kommreddy, Amitha,Bowsher, Michael S.,Gunna, Meena R.,Botha, Kirankumar,Vinod, Thottumkara K.
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p. 4378 - 4382
(2008/12/21)
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- Palladium-catalyzed aerobic alcohol oxidation supported by a new type of α-diimine ligands
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A series of new ionic sulfonated α-diimine ligands were prepared and employed as supporting ligands for the palladium-catalyzed aerobic alcohol oxidation. The electronic properties, rigidity, and steric hindrance of ligands have remarkable influences upon the catalytic activity of the palladium complexes. The best catalytic result could be achieved using ligand 9 with an electron-withdrawing sulfonyl substituent together with bulky groups (iso-propyl in 2,6-positions). This diimine/palladium-catalyzed system is highly efficient for the oxidation of various benzylic alcohols, and showed moderate yields for the secondary aliphatic alcohols and cyclic alcohols.
- Zhou, Jin,Li, Xiaoyan,Sun, Hongjian
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p. 782 - 790
(2008/12/20)
-
- Intramolecular cyclopropanation of unsaturated terminal epoxides and chlorohydrins
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Lithium 2,2,6,6-tetramethylpiperidide (LTMP)-induced intramolecular cyclopropanation of unsaturated terminal epoxides provides an efficient and completely stereoselective entry to bicyclo[3.1.0]hexan-2-ols and bicyclo[4.1.0]heptan-2-ols. Further elaboration of C-5 and C-6 stannyl-substituted bicyclo[3.1.0]-hexan-2-ols via Sn-Li exchange/electrophile trapping or Stille coupling generates a range of substituted bicyclic cyclopropanes. An alternative straightforward cyclopropanation protocol using a catalytic amount of 2,2,6,6-tetramethylpiperidine (TMP) allows for a convenient (1 g-7.5 kg) synthesis of bicyclo[3.1.0]-hexan-2-ol and other bicyclic adducts. The synthetic utility of this chemistry has been demonstrated in a concise asymmetric synthesis of (+)-β-cuparenone. The related unsaturated chlorohydrins also undergo intramolecular cyclopropanation via in situ epoxide formation.
- Hodgson, David M.,Ying, Kit Chung,Nuzzo, Irene,Freixas, Gloria,Kulikiewicz, Krystyna K.,Cleator, Ed,Paris, Jean-Marc
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p. 4456 - 4462
(2008/02/02)
-
- Novel photolabile protecting group for carbonyl compounds
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Equation presented A novel type of photo-protecting group for carbonyl compounds is described. The protecting group is readily accessed in one step from commercially available material. Installation of the protecting group upon the carbonyl compounds is achieved in excellent yields. The carbonyl compounds in their protected form are remarkably stable under various conditions and can be released photochemically in high efficiency.
- Pengfei, Wang,Huayou, Hu,Yun, Wang
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p. 1533 - 1535
(2008/02/02)
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- Highly efficient aerobic oxidation of alcohols using a recoverable catalyst: The role of mesoporous channels of SBA-15 in stabilizing palladium nanoparticles
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(Chemical Equation Presented) Scaling down the activity: An efficient recyclable palladium-based catalyst has been developed for the aerobic oxidation of alcohols (see scheme). The combination of a substituted bipyridyl ligand and ordered mesoporous channels (in SBA) causes a synergistic effect that results in enhanced activity, the prevention of agglomeration of the palladium nanoparticles, and the generation of a durable catalyst.
- Karimi, Babak,Abedi, Sedigheh,Clark, James H.,Budarin, Vitaly
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p. 4776 - 4779
(2007/10/03)
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- Mild and efficient deprotection of 1,3-dithianes with N,N′-diiodo-N, N′-1,2-ethanediyl-bis(p-toluenesulphonamide)
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Aliphatic and aromatic 1,3-dithiane are oxidized to the corresponding carbonyl compounds in good yields under mild conditions by N,N′-diiodo-N, N′-1,2-ethanediyl-bis(p-toluenesulphonamide) [NIBTSl and silver nitrate.
- Ghorbani-Vaghei, Ramin,Zolfigol, Mohammad Ali
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p. 327 - 330
(2007/10/03)
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- Quinolinium fluorochromate: An efficient and convenient reagent for oxidative cleavage of thioacetals to their parent carbonyl compounds
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Deprotection of thioacetals to their parent carbonyl compounds in high yields has been carried out using quinolinium fluorochromate under mild conditions. Copyright Taylor & Francis Inc.
- Tajbakhsh, Mahmood,Alimohammadi, Kamal,Ramzanian-Lehmali, Farhad,Barghamadi, Mohamad,Shakeri, Alireza
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p. 2587 - 2591
(2007/10/03)
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- CrO3/Al2O3: Rapid oxidation of alcohols to carbonyl compounds in a solvent- free system
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Primary and secondary alcohols are efficiently oxidized to the corresponding carbonyl compounds using CrO3 supported onto alumina under solvent- free conditions. It has been found that the presence of small amount of t-butanol in the reaction media is essential. Over-oxidation of aldehydes to carboxylic acids and cleavage of carbon-carbon double bond is not observed by this method.
- Kiasat,Kazemi,Nourbakhsh
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p. 1524 - 1526
(2007/10/03)
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- In situ alcohol oxidation-protection reactions
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The one-pot conversion of primary and secondary alcohols into phenylhydrazones and 2,4-dintrophenylhydrazones is reported using chromium trioxide supported on silica gel and phenylhydrazines or 2,4- dintrophenylhydrazines under solvent-free conditions. This oxidation arylhydrazone formation reaction has been applied to a range of aliphatic and benzylic alcohols. Copyright Taylor & Francis, Inc.
- Kiasat,Kazemi,Nourbakhsh
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p. 1555 - 1558
(2007/10/03)
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- Facile and efficient method for deprotection of 1,3-oxathiolanes with N,N′-dibromo-N,N′-1,2-ethanediylbis(p-toluenesulphonamide)
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Aliphatic and aromatic 1,3-oxathiolanes are readily oxidized to aldehydes and ketones in good yields under mild conditions by N,N′-dibromo-N, N′-1,2-ethanediylbis(p-toluenesulphonamide) [BNBTS].
- Ghorbani-Vaghei, Ramin,Khazaei, Ardeshir
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p. 1787 - 1791
(2007/10/03)
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- Caro's acid supported on silica gel, Part VIII: An efficient and selective reagent for conversion of phenylhydrazones and semicarbazones to the corresponding carbonyl compounds
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Deprotection of phenylhydrazones and semicarbazones to their parent aldehydes and ketones in high yields has been carried out using caro's acid supported on silica gel as a selective oxidant under mild conditions.
- Tajbakhsh, Mahmood,Lakouraj, Moslem-Mansor,Gholami, Mohammad-Hosein,Ramzanian-Lehmali, Farhad
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p. 1731 - 1736
(2007/10/03)
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- Nitrous oxide oxidation catalyzed by ruthenium porphyrin complex
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Dinitrogen oxide was employed as a clean oxidant for various oxidations in the presence of a catalytic amount of dioxoruthenium tetramesitylporphyrin complex (Ru(tmp)(O)2). A variety of olefins, secondary alcohols, and benzyl alcohols were smoothly oxidized to the corresponding epoxides, ketones, and aldehydes in high yields. In the oxidation of 9,10-dihydroanthracene derivatives, the competitive reactions affording anthraquinones and anthracenes could be regulated by the reaction conditions. At a high temperature (200°C), anthraquinones were selectively produced, while the anthracenes were selectively produced by the addition of sulfuric acid.
- Tanaka, Hirotaka,Hashimoto, Kentaro,Suzuki, Kyosuke,Kitaichi, Yasunori,Sato, Mitsuo,Ikeno, Taketo,Yamada, Tohru
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p. 1905 - 1914
(2007/10/03)
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- Chromium trioxide supported onto copper sulfate as an efficient oxidizing agent for oxidation of alcohols under solvent free conditions
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Alcohols are rapidly oxidized to carbonyl compounds using CrO3 supported onto CuSO4 under solvent free conditions. Over-oxidation of aldehydes to carboxylic acids and damage to carbon-carbon double bond is not observed by this method.
- Kiasat, Ali Reza,Kazemi, Foad,Nourbakhsh, Kazem
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p. 457 - 461
(2007/10/03)
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- 2,6-Dicarboxypyridinium chlorochromate. An efficient and selective reagent for the mild deprotection of acetals, thioacetals, and 1,1-diacetates to carbonyl compounds
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2,6-Dicarboxypyridinium chlorochromate (2,6-DCPCC) was found to be an efficient reagent for the conversion of acetals, thioacetals, and 1,1-diacetates to their corresponding carbonyl compounds under neutral and anhydrous conditions in good to excellent yields. Selective deprotection of acetals or 1,1-diacetates in the presence of thioacetals at room temperature is also observed with this reagent. Springer-Verlag 2004.
- Hosseinzadeh, Rahman,Tajbakhsh, Mahmood,Shakoori, Alireza,Niaki, Mohammad Yazdani
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p. 1243 - 1249
(2007/10/03)
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- Caro's acid supported on silica gel. Part VI. A mild reagent for regeneration of carbonyl compounds from acetals, ketals, and 1,1-diacetates
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Efficient conversion of acetals, ketals, and diacetates to carbonyl compounds is described using Caro's acid supported on silica gel. The deacetalization reactions are carried out in acetonitrile at room temperature. Reaction of diacetates is performed in refluxing dichloromethane, and their parent carbonyl compounds are obtained in good-to-excellent yields.
- Lakouraj,Tajbakhsh,Khojasteh,Gholami
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p. 2645 - 2651
(2007/10/03)
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- Application of aryloximes as solid-phase ketone linkers.
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In both solution and the solid phase, a variety of ketone oxime anions have been treated with 4-substituted-2-fluorobenzonitriles to give the corresponding nucleophilic aromatic substitution aryloxime adducts. Under aqueous acidic conditions, these adducts underwent cyclization to give the corresponding ketones. Suzuki and amide coupling reactions were also successfully performed on two resin-bound oximes followed by subsequent cyclorelease to give ketone product in good yields and purities. [reaction--see text]
- Lepore, Salvatore D,Wiley, Michael R
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- 1-Benzenesulfinyl piperidine (BSP)/triflic anhydride: An effective combination for the hydrolysis of dithioacetals
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The combination of 1-benzenesulfinyl piperidine and triflic anhydride, in conjunction with an aqueous workup, hydrolyses a broad range of dithioacetals to the corresponding carbonyl compounds under very mild, non-oxidative conditions.
- Crich, David,Picione, John
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p. 1257 - 1258
(2007/10/03)
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- N-tert-Butylbenzenesulfenamide-catalyzed oxidation of alcohols to the corresponding carbonyl compounds with N-chlorosuccinimide
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N-tert-Butylbenzenesulfenamide (1)-catalyzed oxidation of various primary and secondary alcohols to the corresponding aldehydes and ketones was efficiently carried out by using N-chlorosuccinimide (NCS) in the coexistence of potassium carbonate and molecular sieves 4? at easy-to-control temperatures ranging from 0°C to room temperature. The present catalytic oxidation was performed without giving any damage to the functional groups in alcohols, and was particularly effective in the oxidation of alcohols that formed labile aldehydes because of its mild reaction conditions. Further, selective oxidation of primary hydroxy groups took place in 1-catalyzed oxidation of several diols. Mechanistic investigation suggested that the chlorination of the sulfenamide 1 by NCS led to the formation of a key species, N-tert-butylbenzenesulfinimidoyl chloride (2), which in turn oxidized alcohols in the presence of potassium carbonate to afford carbonyl products by accompanying regeneration of the catalyst 1.
- Matsuo, Jun-Ichi,Iida, Daisuke,Yamanaka, Hiroyuki,Mukaiyama, Teruaki
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p. 6739 - 6750
(2007/10/03)
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