- Heterogeneous epoxidation of menadione with hydrogen peroxide over the zeolite imidazolate framework ZIF-8
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The zeolite imidazolate framework ZIF-8 exhibits superior catalytic performance in the epoxidation of the electron-deficient CC bond in menadione using aqueous hydrogen peroxide as the oxidant. The catalysis has a truly heterogeneous nature and the framework structure remains intact. This is the first example of oxidation catalysis with ZIF-8.
- Evtushok, Vasilii Yu.,Ivanchikova, Irina D.,Kholdeeva, Oxana A.,Kolokolov, Danil I.,Stepanov, Alexander G.,Zalomaeva, Olga V.
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supporting information
p. 12546 - 12549
(2020/10/05)
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- Nucleophilic versus Electrophilic Activation of Hydrogen Peroxide over Zr-Based Metal-Organic Frameworks
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Zr-based metal-organic frameworks (Zr-MOF) UiO-66 and UiO-67 catalyze thioether oxidation in nonprotic solvents with unprecedentedly high selectivity toward corresponding sulfones (96-99% at ca. 50% sulfide conversion with only 1 equiv of H2O2). The reaction mechanism has been investigated using test substrates, kinetic, adsorption, isotopic (18O) labeling, and spectroscopic tools. The following facts point out a nucleophilic character of the peroxo species responsible for the superior formation of sulfones: (1) nucleophilic parameter XNu = 0.92 in the oxidation of thianthrene 5-oxide and its decrease upon addition of acid; (2) sulfone to sulfoxide ratio of 24 in the competitive oxidation of methyl phenyl sulfoxide and p-Br-methyl phenyl sulfide; (3) significantly lower initial rates of methyl phenyl sulfide oxidation relative to methyl phenyl sulfoxide (kS/kSO = 0.05); and (4) positive slope ρ = +0.42 of the Hammett plot for competitive oxidation of p-substituted aryl methyl sulfoxides. Nucleophilic activation of H2O2 on Zr-MOF is also manifested by their capability of catalyzing epoxidation of electron-deficient C═C bonds in α,β-unsaturated ketones accompanied by oxidation of acetonitrile solvent. Kinetic modeling on methyl phenyl sulfoxide oxidation coupled with adsorption studies supports a mechanism that involves the interaction of H2O2 with Zr sites with the formation of a nucleophilic oxidizing species and release of water followed by oxygen atom transfer from the nucleophilic oxidant to sulfoxide that competes with water for Zr sites. The nucleophilic peroxo species coexists with an electrophilic one, ZrOOH, capable of oxygen atom transfer to nucleophilic sulfides. The predominance of nucleophilic activation of H2O2 over electrophilic one is, most likely, ensured by the presence of weak basic sites in Zr-MOFs identified by FTIR spectroscopy of adsorbed CDCl3 and quantified by adsorption of isobutyric acid.
- Chesalov, Yuriy A.,Evtushok, Vasiliy Yu.,Glazneva, Tatyana S.,Ivanchikova, Irina D.,Kholdeeva, Oxana A.,Larionov, Kirill P.,Skobelev, Igor Y.,Zalomaeva, Olga V.
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- Hydrogenation of Phenol to Cyclohexanone over Bifunctional Pd/C-Heteropoly Acid Catalyst in the Liquid Phase
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Abstract: Cyclohexanone is an important intermediate in the manufacture of polyamides in chemical industry, but direct selective hydrogenation of phenol to cyclohexanone under mild conditions is a challenge. Hydrogenation of phenol to cyclohexanone has been investigated in the presence of the composite catalytic system of Pd/C-heteropoly acid. 100% conversion of phenol and 93.6% selectivity of cyclohexanone were achieved within 3?h under 80?°C and 1.0?MPa hydrogen pressure. It has been found that a synergetic effect of Pd/C and heteropoly acid enhanced the catalytic performance of the composite catalytic system which suppressed the hydrogenation of cyclohexanone to cyclohexanol. Graphic Abstract: [Figure not available: see fulltext.].
- Liu, Shiwei,Han, Jing,Wu, Qiong,Bian, Bing,Li, Lu,Yu, Shitao,Song, Jie,Zhang, Cong,Ragauskas, Arthur J.
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p. 2383 - 2389
(2019/06/19)
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- High-Cluster (Cu9) Cage Silsesquioxanes: Synthesis, Structure, and Catalytic Activity
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Unusual high-cluster (Cu9) cage phenylsilsesquioxanes were obtained via complexation of in situ CuII,Na-silsesquioxane species formed with phenanthroline and neocuproine. In the first case, phenanthroline, acting as "a silent ligand" (not participating in the composition of the final product), favors the formation of an unprecedented cagelike phenylsilsesquioxane of Cu9Na6 nuclearity, 1. In the second case, neocuproine ligands withdraws two Cu ions from the metallasilsesquioxane matrix, producing two cationic fragments Cu+(neocuproine)2. The remaining metallasilsesquioxane is rearranged into an anionic cage of Cu9Na4 nuclearity, finalizing the formation of a specific ionic complex, 2. The impressive molecular architecture of both types of complexes, e.g., the presence of different (cyclic/acyclic) types of silsesquioxane ligands, was established by single-crystal X-ray diffraction studies. Compound 1 was revealed to be highly active in the oxidative amidation of benzylic alcohol and the catalyst loading could be reduced down to 100 ppm of Cu. Catalytic studies of compound 1 demonstrated its high activity in hydroperoxidation of alkanes with H2O2 and oxidation of alcohols to ketones with tert-BuOOH.
- Astakhov, Grigorii S.,Bilyachenko, Alexey N.,Korlyukov, Alexander A.,Levitsky, Mikhail M.,Shul'Pina, Lidia S.,Bantreil, Xavier,Lamaty, Frédéric,Vologzhanina, Anna V.,Shubina, Elena S.,Dorovatovskii, Pavel V.,Nesterov, Dmytro S.,Pombeiro, Armando J. L.,Shul'Pin, Georgiy B.
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supporting information
p. 11524 - 11529
(2018/09/13)
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- Amorphous Cr/SiO2 Materials Hydrothermally Treated: Liquid Phase Cyclohexanol Oxidation
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Abstract: Amorphous Cr–SiO2 materials were synthesized by the sol–gel method and hydrothermally treated at temperatures between 150 and 220?°C. These materials were used as catalysts for cyclohexanol oxidation with H2O2 as oxidant and CH3CN as a solvent. They were responsible for the decomposition of H2O2, which triggers, by a free?radical mechanism in the homogeneous phase, the oxidation or degradation of the hydrocarbon chain. Metal leaching causes a drop in catalytic activity when the material is recycled. Studies on the hydrothermal treatment effect on the leaching process have demonstrated that the higher the hydrothermal treatment temperature, the higher the metal/support interaction, leading to a diminution of the leaching process. Under mild reaction conditions, and using TBHP as oxidant, leaching was reduced, and improvements were obtained on the selectivity towards the formation of cyclohexanone. The use of these catalysts in the oxidation of verbenol, an allylic alcohol, showed a significant increase in the substrate conversion and in the selectivity to carbonyl derivative formation. Graphical Abstract: [Figure not available: see fulltext.].
- Miranda, José Feliciano,Cuesta Zapata, Pablo M.,Gonzo, Elio E.,Parentis, Mónica L.,Davies, Lilian E.,Bonini, Norberto A.
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p. 2082 - 2094
(2018/05/28)
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- Robustly supported rhodium nanoclusters: Synthesis and application in selective hydrogenation of lignin derived phenolic compounds
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The stabilization of small rhodium nanoclusters (NCs) in a polymer derived silicon carbonitride (SiCN) matrix has been reported to generate highly robust and active solid catalysts for the selective hydrogenation of phenolic compounds. An aminopyridinato Rh complex was used to modify a preceramic polymer (HTT 1800) followed by its pyrolysis at 1100 °C to afford small Rh NCs nicely dispersed over dense SiCN ceramic. For the synthesis of porous catalysts containing Rh NCs, microphase separation (followed by pyrolysis) of a diblock copolymer of HTT 1800 with hydroxy-polyethylene (PE-OH) was used. Both catalysts exhibit high activity in the hydrogenation of substituted phenols at room temperature and under low hydrogen pressure. The catalysts remained highly active and selective for six consecutive catalytic runs.
- Fehn, Sonja,Zaheer, Muhammad,Denner, Christine E.,Friedrich, Martin,Kempe, Rhett
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p. 9252 - 9256
(2016/11/11)
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- Efficient room-temperature aqueous-phase hydrogenation of phenol to cyclohexanone catalyzed by Pd nanoparticles supported on mesoporous MMT-1 silica with unevenly distributed functionalities
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Efficient and selective aqueous-phase hydrogenation of phenol by a novel Pd catalyst supported on dually and selectively functionalized mesoporous MMT-1 silica nanoparticles has been developed. The catalyst features small (~1.1 nm) Pd nanoparticles surrounded by unevenly distributed nitrogen- or heteroatom-free organic groups in the helical mesopores and the presence of non-hydrogen-bonded isolated silanol groups on the mesopore surface. The catalyst exhibited superior conversion of phenol and high selectivity of cyclohexanone at room temperature under atmospheric pressure of hydrogen and remained highly active after ten catalytic runs. The catalyst was active for the aqueous-phase hydrogenation of a variety of mono- and dihydroxylated aromatic compounds. The green protocol with the designed catalyst would be practical for the hydrogenation of phenol and other derivatives.
- Lin, Chi-Jui,Huang, Shao-Hsien,Lai, Nien-Chu,Yang, Chia-Min
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p. 4121 - 4129
(2015/11/11)
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- Enantioselective Michael addition of water
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The enantioselective Michael addition using water as both nucleophile and solvent has to date proved beyond the ability of synthetic chemists. Herein, the direct, enantioselective Michael addition of water in water to prepare important β-hydroxy carbonyl compounds using whole cells of Rhodococcus strains is described. Good yields and excellent enantioselectivities were achieved with this method. Deuterium labeling studies demonstrate that a Michael hydratase catalyzes the water addition exclusively with anti-stereochemistry.
- Chen, Bi-Shuang,Resch, Verena,Otten, Linda G.,Hanefeld, Ulf
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supporting information
p. 3020 - 3030
(2015/02/05)
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- Synthesis of 2-nickela(II)oxetanes from nickel(0) and epoxides: Structure, reactivity, and a new mechanism of formation
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2-Nickelaoxetanes have been frequently invoked as reactive intermediates in catalytic reactions of epoxides using nickel, but have never been isolated or experimentally observed in these transformations. Herein, we report the preparation of a series of well-defined nickelaoxetanes formed via the oxidative addition of nickel(0) with epoxides featuring ketones. The stereochemistry of the products is retained, which has not yet been reported for nickelaoxetanes. Theoretical calculations support a bimetallic ring-opening/closing pathway over a concerted oxidative addition. Initial reactivity studies of a nickelaoxetane demonstrated protonolysis, oxidatively induced reductive elimination, deoxygenation, and elimination reactions when treated with the appropriate reagents.
- Desnoyer, Addison N.,Bowes, Eric G.,Patrick, Brian O.,Love, Jennifer A.
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supporting information
p. 12748 - 12751
(2015/10/28)
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- Pt nanoparticle supported on nanocrystalline CeO2: Highly selective catalyst for upgradation of phenolic derivatives present in bio-oil
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Pt nanoparticle supported on nanocrystalline CeO2 was prepared, and it was found that the catalyst can selectively hydrogenate phenolic derivatives present in bio-oil. The catalyst was characterized by XRD, XPS, ICP-AES, EXAFS, SEM and TEM. TEM micrograms confirm the presence of very small Pt nanoparticles supported on nanocrystalline CeO2. The catalyst was found to be very effective in liquid phase hydrogenation of phenol and phenolic compounds present in bio-oil in the presence of molecular H2. The synergy between the surface and very small Pt particles on the nanocrystalline CeO2 plays the most vital role towards the extremely high catalytic activity of the catalyst. The reusability of the catalyst was tested, and it was found that the catalyst does not exhibit any significant change in its catalytic activity even after five reuses. The catalyst showed ~100% conversion with very high selectivity after 3 h in phenol conversions of 100% with >98% cyclohexanol selectivity achieved after 3 h of reaction at 100 °C in aqueous medium.
- Sarkar, Bipul,Pendem, Chandrashekar,Konathala, L. N. Sivakumar,Sasaki, Takehiko,Bal, Rajaram
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p. 18398 - 18404
(2015/02/19)
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- Synthesis and Suzuki-Miyaura cross-coupling of enantioenriched secondary potassium β-trifluoroboratoamides: Catalytic, asymmetric conjugate addition of bisboronic acid and tetrakis(dimethylamino)diboron to α,β- unsaturated carbonyl compounds
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Enantioenriched potassium β-trifluoroboratoamides have been synthesized via an asymmetric, copper-catalyzed 1,4-addition of tetrahydroxydiboron (BBA) and tetrakis(dimethylamino)-diboron to α,β-Unsaturated amides. These dibora reagents provide access to the desired organotri-fluoroborates using effective and atom economical sources of boron. The copper-catalyzed β-boration is extended to α,β- Unsaturated ketones and esters. The desired potassium organotrifluoroborates are synthesized with yields up to 92% and enantiomeric ratios up to 98:2. The enantioenriched potassium btrifluoroboratoamides are successfully cross-coupled with an array of aryl and heteroaryl chlorides in high yield with complete stereochemical fidelity as the transmetalation proceeds through an SE2 mechanism via an open transition state.
- Molander, Gary A.,Wisniewski, Steven R.,Hosseini-Sarvaria, Mona
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p. 3037 - 3057
(2014/03/21)
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- On the Michael addition of water to α,β-unsaturated ketones using amino acids
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The use of water as a nucleophile for Michael additions is still a challenge in organic chemistry. In this report we describe the use of amino acids as catalysts for the Michael addition of water to α,β- unsaturated ketones. All 20 proteinogenic amino aci
- Resch, Verena,Seidler, Christiane,Chen, Bi-Shuang,Degeling, Ian,Hanefeld, Ulf
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supporting information
p. 7697 - 7704
(2013/12/04)
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- Chiral copper(II)-catalyzed enantioselective boron conjugate additions to α,β-unsaturated carbonyl compounds in water
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Copper pins on the boron: The enantioselective 1,4-addition of diboron to α,β-unsaturated compounds proceeds smoothly in the presence of catalytic amounts of Cu(OH)2 and chiral 2,2′-bipyridine ligand in water. A wide substrate scope of α,β-unsaturated carbonyl compounds, including acyclic, cyclic, and β,β-disubstituted enones, α,β-unsaturated esters, amides, and a nitrile, has been shown. Copyright
- Kobayashi, Shu,Xu, Pengyu,Endo, Toshimitsu,Ueno, Masaharu,Kitanosono, Taku
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supporting information
p. 12763 - 12766
(2013/02/22)
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- Kinetic resolution of 3-hydroxycyclohexanone using different lipases
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A new approach to enantiomerically enriched cyclic β-hydroxy ketones was developed. 3-Hydroxycyclohexanone was successfully resolved using lipase catalyzed transesterification. Among the lipases screened PFL, PCL, and PPL-II gave 57%, 39%, and 25% yield o
- Karmee, Sanjib Kumar,Oosten, Remco Van,Hanefeld, Ulf
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experimental part
p. 1736 - 1739
(2012/02/05)
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- METHOD FOR PRODUCING ALDEHYDES AND KETONES FROM PRIMARY AND SECONDARY ALCOHOLS
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The invention relates to a method for producing aldehydes and ketones from easily accessible primary and secondary alcohols by oxidation with atmospheric oxygen or pure oxygen using a catalyst system which consists of a derivative of a free nitroxyl radical.
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Page/Page column 8
(2011/10/19)
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- MhyADH catalysed Michael addition of water and in situ oxidation
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The Michael addition of water is a major challenge. Here an enzymatic approach is described. Interestingly, the enzyme (MhyADH) does not only catalyse the Michael addition of water but also the in situ oxidation of the product.
- Jin, Jianfeng,Oskam, Philip C.,Karmee, Sanjib K.,Straathof, Adrie J. J.,Hanefeld, Ulf
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experimental part
p. 8588 - 8590
(2011/02/16)
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- Selective partial hydrogenation of hydroxy aromatic derivatives with palladium nanoparticles supported on hydrophilic carbon
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Selective hydrogenation of phenol to cyclohexanol in the aqueous phase was achieved using a new catalytic system based on palladium particles supported on hydrophilic carbon prepared by one-pot hydrothermal carbonisation. The Royal Society of Chemistry.
- Makowski, Philippe,Demir Cakan, Rezan,Antonietti, Markus,Goettmann, Frederic,Titirici, Maria-Magdalena
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p. 999 - 1001
(2008/09/21)
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- TBD-catalyzed direct 5- and 6-enolexo aldolization of ketoaldehydes
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Treatment of unfunctionalized acyclic ketoaldehydes with a catalytic amount of 1,5,7-triazabicyclo[4.4.0]dec-5-ene induces a direct intramolecular 5- and 6-enolexo aldolization, furnishing 2-ketocyclopentanols and 2-ketocyclohexanols in good-to-excellent yields. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Ghobril, Cynthia,Sabot, Cyrille,Mioskowski, Charles,Baati, Rachid
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supporting information; experimental part
p. 4104 - 4108
(2009/05/27)
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- Synthesis and identification of hydroxylated metabolites of the anti-estrogenic agent cyclofenil
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The detection of metabolites of the anti-estrogenic substance cyclofenil, listed on the World Anti-Doping Agency (WADA) Prohibited List since 2004 is described. Target substances are hydroxylated metabolites, bearing an aliphatic hydroxyl group either in the 2-, 3- or 4-position of the aliphatic ring, in addition to the phenolic functions on the aromatic rings. Structural identification used NMR as well as high-resolution mass spectrometry after nano-electrospray ionisation (ESI). Unambiguous detection of all three synthesised cyclofenil metabolites M1-M3 was done using gas chromatography for separation and electron ionisation mass spectrometry for detection of the per-silylated compounds in comparison with a reference urine deriving from an excretion study within the WADA 2007 Educational Programme. Copyright
- Gaertner, Peter,Hofbauer, Karin,Reichel, Christian,Geisendorfer, Thomas,Gmeiner, Guenter
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experimental part
p. 958 - 964
(2009/05/07)
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- Selective reduction of α,β-epoxyketones to β-hydroxyketones using silyllithium reagents
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2,3-Epoxy-1-phenyl-1-propanone was reduced to 3-hydroxy-1-phenyl-1-propanone using dimethylphenyl-, methyldiphenyl- or triphenylsilyllithium in THF at -40 °C. The methyldiphenylsilyllithium reagent was superior, providing the product in 70% yield. The rea
- Reynolds, Samantha C.,Wengryniuk, Sarah E.,Hartel, Aaron M.
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p. 6751 - 6753
(2008/02/13)
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- Fragmentation of tertiary cyclopropanol compounds catalyzed by vanadyl acetylacetonate
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Tertiary cyclopropanol compounds react with a catalytic amount of vanadyl acetylacetonate in the presence of oxygen affording β-hydroxyketones and β-diketones. For 3-substituted-bicyclo[4.1.0]alkanols, peroxides are obtained, as are the β-hydroxyketones. Conversely, 2- ethoxycarbonylcyclopropyl silyl ethers produce ethyl γ-oxocarboxylate derivatives given the same reaction conditions.
- Kirihara, Masayuki,Kakuda, Hiroko,Ichinose, Motohiro,Ochiai, Yuta,Takizawa, Shinobu,Mokuya, Asuka,Okubo, Kumiko,Hatano, Akihiko,Shiro, Motoo
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p. 4831 - 4839
(2007/10/03)
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- Mild microwave-assisted hydrolysis of acetals under solvent-free conditions
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Acetals are efficiently hydrolyzed with silica gel-supported pyridinium tosylate moistened with water in solvent-free conditions under microwave irradiation. The method is efficient and mild, with acid-sensitive 3-hydroxyacetals and 3-methoxyacetals being hydrolyzed in minutes in good yields.
- He, Yanhong,Johansson, Martin,Sterner, Olov
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p. 4153 - 4158
(2007/10/03)
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- Recyclable Polyurea-Microencapsulated Pd(0) Nanoparticles: An Efficient Catalyst for Hydrogenolysis of Epoxides
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(Matrix presented) Pd nanoparticles (~2 nm in size) microencapsulated in polyurea is an efficient and recyclable catalyst for reductive ring-opening hydrogenolysis of epoxides, using either HCOOH/Et3N or H2 as a hydrogen donor.
- Ley, Steven V.,Mitchell, Claire,Pears, David,Ramarao, Chandrashekar,Yu, Jin-Quan,Zhou, Wuzong
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p. 4665 - 4668
(2007/10/03)
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- Application of high pressure induced by water-freezing to the Michael reaction of alcohols with α,β-enones
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High pressure (about 200MPa), which was realized by freezing water in a sealed autoclave, has been successfully applied to a high-yield Michael reaction of alcohols and α,β-unsaturated ketones in the presence of a catalytic amount of DMAP and LiClO4. Only a moderate yield was obtained under atmospheric pressure.
- Hayashi, Yujiro,Nishimura, Koichi
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p. 296 - 297
(2007/10/03)
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- Hydroxyl radical reaction rate constant and products of cyclohexanol
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The gas phase reaction of the hydroxyl radical (OH) with cyclohexanol (COL) has been studied. The rate coefficient was determined to be (19.0±4.8)×10-12 cm3 molecule-1 s-1 (at 297±3 K and 1 atmosphere total pressure) using the relative rate technique with pentanal, decane, and tridecane as the reference compounds. Assuming an average OH concentration of 1×106 molecules cm-3, an atmospheric lifetime of 15 h is calculated for cyclohexanol. Products of the OH+COL reaction were determined to more clearly define COL's atmospheric degradation mechanism. The observed products and their formation yields were: cyclohexanone (0.55±0.06), hexanedial (0.32±0.15), 3-hydroxycyclohexanone (0.31±0.14), and 4-hydroxycyclohexanone (0.08±0.04). Consideration of the potential reaction pathways suggests that each of these products is formed via hydrogen abstraction at a different site on the COL ring. The products and their relative amounts are discussed in light of the predicted yields for each reaction channel.
- Bradley,Wyatt,Wells,Henley,Graziano
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p. 108 - 117
(2007/10/03)
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- Trisubstituted pyridine dyes
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2,4,6-Trisubstituted pyridines wherein at least one of the substituents is a para-(N,N-diarylamino)phenyl group, and the other two substituents are alkyl, cycloalkyl or aryl groups are useful as image dyes in acid-mediated imaging media, since the colored
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- Efficient oxidation of alcohols to carbonyl compounds with molecular oxygen catalyzed by N-hydroxyphthalimide combined with a Co species
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Highly efficient catalytic oxidation of alcohols with molecular oxygen by N-hydroxyphthalimide (NHPI) combined with a Co species was developed. The oxidation of 2-octanol in the presence of catalytic amounts of NHPI and Co(OAc)2 under atmospheric dioxygen in AcOEt at 70 °C gave 2-octanone in 93% yield. The oxidation was significantly enhanced by adding a small amount of benzoic acid to proceed smoothly even at room temperature. Primary alcohols were oxidized by NHPI in the absence of any metal catalyst to form the corresponding carboxylic acids in good yields. In the oxidation of terminal vic-diols such as 1,2-butanediol, carbon-carbon bond cleavage was induced to give one carbon less carboxylic acids such as propionic acid, while internal vic-diols were selectively oxidized to 1,2-diketones.
- Iwahama, Takahiro,Yoshino, Yasushi,Keitoku, Takashi,Sakaguchi, Satoshi,Ishii, Yasutaka
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p. 6502 - 6507
(2007/10/03)
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- Tertiary cyclopropanol systems as synthetic intermediates: Novel ring-cleavage of tertiary cyclopropanol systems using vanadyl acetylacetonate
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Tertiary cyclopropanol systems react with a catalytic amount of vanadyl acetylacetonate under an oxygen atmosphere to afford β-hydroxyketones and β-diketones.
- Kirihara, Masayuki,Ichinose, Motohiro,Takizawa, Shinobu,Momose, Takefumi
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p. 1691 - 1692
(2007/10/03)
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- Oxidation of Diols and Ethers by NaBrO3/NaHSO3 Reagent
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NaBrO3 combined with NaHSO3 was found to be an excellent oxidizing reagent of alcohols, diols, and ethers under mild conditions. A variety of aliphatic and cyclic diols were selectively oxidized with satisfactory yields to the corresponding hydroxy ketones and/or diketones, which are difficult to selectively prepare due to a concomitant formation of cleaved products. For example, 2-hydroxycyclohexanone and 1,2-cyclohexanedione were selectively formed by allowing 1,2-cyclohexanediol to react with NaBrO3/NaHSO3 reagent in a selected solvent. On the other hand, an alkyl ether, such as dioctyl ether, reacted with NaBrO3/NaHSO3, in water at room temperature to give octyl octanoate in 82% yield. The same oxidation at higher temperature (60°C) produced the α-brominated ester, octyl 2-bromooctanoate, which is considered to be formed through an alkenyl alkyl ether as the intermediate. The treatment of 1-ethoxy-l-heptene with NaBrO3/NaHSO3 afforded ethyl 2-bromoheptanoate and 2-bromoheptanoic acid as the major products.
- Sakaguchi, Satoshi,Kikuchi, Daisuke,Ishii, Yasutaka
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p. 2561 - 2566
(2007/10/03)
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- The organoselenium-mediated reduction of α,β-epoxy ketones, α,β-epoxy esters, and their congeners to β-hydroxy carbonyl compounds: Novel methodologies for the synthesis of aldols and their analogues
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Novel methods for the reduction of α,β-epoxy ketones, α,β-epoxy esters (glycidic esters), and their congeners to β-hydroxy carbonyl compounds (aldols) by the use of organoselenium reagents are described. The reagents, a sodium phenylseleno(triethyl)borate complex Na[PhSeB(OEt)3] easily prepared by reduction of (PhSe)2 with NaBH4 in EtOH and benzeneselenol (PhSeH) generated in situ from the borate complex by addition of acetic acid, have been demonstrated to serve as excellent reducing agents for these transformations. The organoselenium-mediated reduction of α,β-epoxy carbonyl compounds regiospecifically occurs at the α-carbon to produce a wide variety of cyclic (intramolecular) aldols as well as acyclic (intermolecular) ones in excellent yields. Quantitative mechanistic studies have revealed that the organoselenium-mediated reduction proceeds via an α-substitution process in contrast to the common electron transfer reducing agents.
- Miyashita, Masaaki,Suzuki, Toshio,Hoshino, Masahide,Yoshikoshi, Akira
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p. 12469 - 12486
(2007/10/03)
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- A Versatile and Highly Selective Hypervalent Iodine (III)/ 2,2,6,6-Tetraniethyl-1-piperidinyloxyl-Mediated Oxidation of Alcohols to Carbonyl Compounds
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Catalytic amounts of 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) are used in combination with [bis(acetoxy)iodo]benzene (BAIB) as a stoichiometric oxidant in the conversion of primary and secondary alcohols to carbonyl compounds. This procedure works efficiently at room temperature in almost all common solvents and neat in some cases. This process exhibits a very high degree of selectivity for the oxidation of primary alcohols to aldehydes, without any noticeable overoxidation to carboxyl compounds, and a high chemoselectivity in the presence of either secondary alcohols or of other oxidizable moieties. This procedure allows an easy, convenient, high-yielding method for the oxidation of alcohols starting from commercially available compounds.
- De Mico, Antonella,Margarita, Roberto,Parlanti, Luca,Vescovi, Andrea,Piancatelli, Giovanni
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p. 6974 - 6977
(2007/10/03)
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- Intramolecular aldol condensations: Rate and equilibrium constants
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Rate and equilibrium constants have been determined for both the aldol addition and the elimination steps in the intramolecular condensation reactions of 2,5-hexanedione, 2,6-heptanedione, 1-phenyl-1,5-hexanedione, and 5-oxohexanal. The overall thermodynamics are similar for cyclization of 2,5-hexanedione and 2,6-heptanedione; conversion of 2,5-hexanedione to the corresponding enone is actually more favorable, but the cyclization of 2,5-hexanedione is 2400 times slower than that of 2,6-heptanedione. As expected on the basis of intermolecular analogs, the addition step is less favorable and slower for 1-phenyl-1,5-hexanedione, and the addition step for 5-oxohexanal is more favorable though similar in rate to that for heptanedione. Detailed analysis of the kinetics and equilibrium for all of these compounds, as well as 2-(2-oxopropyl)benzaldehyde, in terms of Marcus theory, leads to the same intrinsic barriers for the intramolecular reactions as were seen previously for the intermolecular reactions. This means that rate constants for intramolecular aldol reactions should be predictable from the energetics of the reactions and that the effective molarity can be calculated. Methods for estimating thermodynamic quantities for reactants and products of these reactions have been examined.
- Guthrie,Guo
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p. 11472 - 11487
(2007/10/03)
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- Pyridinium-Ionen in Nachbarschaft zu Oxiranringen: nuetzliche Zwischenstufen zur stereospezifischen Synthese von β-Hydroxyketonen
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Keywords: Chirale Reagentien; 3-Desoxyketosen; β-Hydroxycarbonylverbindungen; Kohlenhydrate; N-Vinylpyridiniumderivate
- Al-Abed, Yousef,Naz, Noshena,Khan, Khalid Mohammed,Voelter, Wolfgang
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p. 581 - 582
(2007/10/03)
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- NMR studies of three types of highly coordinated organotin hydrides: Chemo-, regio-, and stereoselective reduction of 2,3-epoxy ketones
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Three types of highly coordinated organotin hydrides, Bu2SnIH-Lewis base (Lewis bases; HMPA or tripiperidinophosphine oxide) (type A), Bu2SnFH-HMPA (type B), and Bu3SnH-Bu4NX (X = F, CN) (type C), were characterized as nucleophilic, chelation, and nonchelation types of reductants, respectively, in the reaction with 2,3-epoxy ketones 1. These reagents, which promoted a reduction of the epoxy ring and syn-selective and anti-selective carbonyl reduction, respectively, were spectroscopically confirmed with 1H, 13C, 19F, and 119Sn NMR and FT-IR. Furthermore, the correlations between their structures and selective reducing abilities were discussed.
- Kawakami, Takayo,Shibata, Ikuya,Baba, Akio
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- Reductive Oxa Ring Opening of 7-Oxabicycloheptan-2-ones. Synthesis of C-α-Galactosides of Carbapentopyranoses
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Photoinduced electron transfer from Et3N to 7-oxabicycloheptan-2-ones can generate the corresponding 3-hydroxycyclohexanone derivatives.The method has been applied to the synthesis of C-α-D-galactopyranosides of carbapentapyranoses.Radical α-D-gaactosidation of (+/-)- (1RS,4RS,5RS,6RS)-6-endo-methoxy-3-methylidene-5-exo-(phenylseleno)-7-oxabicyclohept-2-one ((+/-)/51) followed by seleno-Pummerer rearrangement and reduction with Bu3SnH gave (+)-(1R,2S,3S,4R,6S)-((+)-58) and (+)-(1S,2R,3R,4S,6S)-3-endo-methoxy-5-oxo-6-endo--7-oxabicyclo hept-2-endo-yl acetate ((+)-59), which were separated by column chromatography.Irradiation (254 nm) in the presence of Et3N gave (+)-(1S,2R,3R,6R)- ((+)-60) and (+)-(1R,2S,3S,6S)-2-hydroxy-6-methoxy-4-oxo-3-,(2',3',4',6'-tetra-O-acetyl-α-D-galactopyranosyl)methyl>cyclohexyl acetate (+)-61, respectively.NaBH4 reduction and acetylation provided (+)-(1S,2S,3R,4R,5R)- ((+()-62) and (+)-(1R,2R,3S,4S,5S)-5-methoxy-2-cyclohexa-1,3,4-triyl triaceate ((+)-64).
- Cossy, Janine,Ranaivosata, Jean-Luc,Bellosta, Veronique,Ancerewicz, Jacek,Ferritto, Rafael,Vogel, Pierre
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p. 8351 - 8359
(2007/10/02)
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- Chemo- and Regioselective Reductions of Functionalized Epoxides by Bu3SnH/Bu3SnI-Phosphine Oxide
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A novel reagent, Bu3SnH/Bu3SnI-phosphine oxide, reduced functionalized epoxides to the corresponding alcohols in high chemo- and regioselectivities.
- Kawakami, Takayo,Tanizawa, Daisuke,Shibata, Ikuya,Baba, Akio
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p. 9357 - 9360
(2007/10/02)
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- Efficient desymmetrization of 1,2 and 1,3 diols by dimethyldioxirane
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Dimethyldioxirane was used to monooxide 1,2 and 1,3 sec,sec-diols to the corresponding ketoalcohols, exploiting the inhibiting effect of the formed carbonyl group on the course of the process.
- Bovicelli, Paolo
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p. 3031 - 3034
(2007/10/02)
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- Thiol/Diselenide Exchange for the Generation of Benzeneselenolate Ion. Catalytic Reductive Ring-Opening of α,β-Epoxy Ketones
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In the presence of N-acetylcysteine sodium salt, benzeneselenolate ion was generated in situ from diphenyl diselenide via thiol/diselenide and thiol/selenenyl sulfide exchange in aqueous methanol under mild conditions.Benzeneselenolate ion thus formed was efficiently alkylated and arylated to afford alkyl phenyl selenides and aryl phenyl selenides, respectively. α,β-Epoxy ketones were catalytically reduced by benzeneselenolate ion to afford β-hydroxy ketones (aldols) in good yields.The stereospecificity of the reaction was demonstrated in the preparation of optically active β-hydroxy ketones from chiral α,β-epoxy ketones.
- Engman, Lars,Stern, David
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p. 5179 - 5183
(2007/10/02)
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- Efficient Cleavage of Cyclopropyl Bond by Adjacent Ketyl Radical Generated Under PET Conditions
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Photolysis of various conjugated cyclopropyl and epoxy ketones in 20percent triethyl amine (TEA) and ethanol leads to cleavage of cyclopropyl bond.Significant wavelength dependence phenomenon is observed during photolysis for the cleanliness and efficient photo transformation.Steroidal cyclopropyl ketones cleave efficiently at 300nm photolysis, whereas exo-cyclopropyl ketones cleave at 254nm.The regiochemistry of cyclopropyl bond cleavage is governed by the principle of maximum overlap.The nature of chemistry generated by ketyl radical is shown to be a function of methodology of their generation.
- Pandey, Bipin,Rao, Ashok T.,Dalvi, Pramod V.,Kumar, Pradeep
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p. 3843 - 3848
(2007/10/02)
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- Radical anion ring opening reactions via photochemically induced electron transfer
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Ketyl radical anions can induce the opening of adjacent strained ring such as cyclopropane, cyclobutane, epoxide and 7-oxabicyclo[2.2.1]hepane.
- Cossy,Aclinou,Bellosta,Furet,Baranne-Lafont,Sparfel,Souchaud
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p. 1315 - 1316
(2007/10/02)
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- Meerwein-Ponndorf-Verley-Type Reduction of Dicarbonyl Compounds to Hydroxy Carbonyl Compounds and α,β-Unsaturated Carbonyl Compounds to Allylic Alcohols Catalyzed by Zirconocene and Hafnocene Complexes
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Group IVA metallocene complexes such as bis(η5-cyclopentadienyl)zirconium dihydrides, Cp2ZrH2 (1), and hafnium dihydrides, Cp2HfH2 (8), catalyze the chemoselective reduction of polycarbonyl compounds to hydroxy carbonyl compounds.For instance, the reduction of keto aldehydes 3-ketobutanal (2g) and 2-phenyl-2-ketoethanal (2h) proceeded selectively at aldehyde group to provide the corresponding hydroxy ketones 3g and 3h in 91percent and 93percent yields, respectively.Under similar conditions, however, cyclohexanediones were easily aromatized to benzenediols.On the other hand, 1 and 8 also catalyze the selective 1,2-reduction of various types of α,β-unsaturated carbonyl compounds, giving the corresponding allylic alcohols in good to excellent yields.Thus, steroidal dicarbonyl compounds, having an enone framework in their molecules Δ4-androstene-3,17-dione (11a) and Δ4-progestene-3,20-dione (11b) were reduced by 1 to 17-hydroxy-Δ4-androsten-3-one (12a) and 20-hydroxy-Δ4-progest-3-one (12b), which are essential human hormones, in 80percent and 67percent yields, respectively.
- Nakano, Tatsuya,Umano, Shigetoshi,Kino, Yoshio,Ishii, Yasutaka,Ogawa, Masaya
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p. 3752 - 3757
(2007/10/02)
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- ORGANOSELENIUM-MEDIATED REDUCTION OF α,β-EPOXY KETONES TO β-HYDROXY KETONES: A NEW ACCESS TO INTER- AND INTRAMOLECULAR ALDOLS
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The organoselenium-mediated reduction of α,β-epoxy ketones has been demonstrated to be a promising entry to a variety of cyclic and acyclic aldols.
- Miyashita, Masaaki,Suzuki, Toshio,Yoshikoshi, Akira
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p. 4293 - 4296
(2007/10/02)
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- PHOTOLYSIS OF SATURATED BICYCLIC PEROXIDES
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Under direct photolysis (n.2.1)-peroxides (n=3-5) isomerise chiefly to epoxyaldehydes, (n.2.2)-peroxides (n=2-4) mainly undergo dehydrogenation to cycloalkane-1,4-diones, and 2,3-dioxabicyclo(2.2.1)heptane exhibits both types of behaviour; photo-isomerisation of 6,7- into 6,8-dioxabicyclooctane occurs when benzophenone is present as sensitiser.
- Bloodworth, A.J.,Eggelte, Henny J.
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p. 1525 - 1528
(2007/10/02)
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