Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 80 , Issue 8
Showing 1-25 articles out of 25 articles from the selected issue
Vol. 80 Commemorative Accounts
  • N. Jiten Singh, Eun Cheol Lee, Young Cheol Choi, Han Myoung Lee, Kwang ...
    2007 Volume 80 Issue 8 Pages 1437-1450
    Published: August 15, 2007
    Released: August 10, 2007
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    In this account, we highlight the theoretical investigations of various cluster systems comprising of water clusters, π-containing clusters, and metallic clusters. We illustrate how these investigations help us understand and design structures and properties of nanowires, novel functional ionophores/receptors, and nanomaterials. Many of these theoretically predicted systems have been experimentally realized and some of the predicted structures/properties are left for the future which of course could be promising challenges for experimentalists.
    Theoretical investigations of various clusters comprising of water, ions, π-systems, and metals help us design and understand structures and properties of nanowires, nanomaterials, and novel functional ionophores/receptors. Fullsize Image
  • Steven V. Ley, Tom D. Sheppard, Rebecca M. Myers, Mukund S. Chorghade
    2007 Volume 80 Issue 8 Pages 1451-1472
    Published: August 15, 2007
    Released: August 10, 2007
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    Chiral glycolic acid equivalents are used extensively for the enantioselective synthesis of α-hydroxycarbonyl compounds. Their efficacy in enolate reactions and their utility in synthetic applications are discussed, highlighting the relevance of these methods to natural product synthesis.
    Hydroxycarbonyl compounds are valuable intermediates in asymmetric synthesis, particularly in the preparation of complex structures such as terpenes, carbohydrates, and alkaloids. In addition, the use of chiral glycolic acid equivalents has been the approach of choice for α-hydroxycarbonyl-containing natural products such as herbarumin II and rapamycin. Fullsize Image
Accounts
  • Masahide Tominaga, Makoto Fujita
    2007 Volume 80 Issue 8 Pages 1473-1482
    Published: August 15, 2007
    Released: August 10, 2007
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    This article reviews a coordination approach to discrete tubular structures. Families of pyridine-based molecular strands assemble into large tubular molecules through metal-coordination. In particular, cis-protected square-planar metals, [enPdII]2+ (en = ethylenediamine), are very useful building blocks to link these molecules. Pyridine-based oligo(3,5-pyridine) ligands efficiently self-assemble into well-defined tube frameworks having a variety of shapes and sizes upon treatment with [enPd(NO3)2] in the presence of rod-like organic guests as templates. The length of the tube can be strictly controlled according to the numbers of pyridine nuclei involved in the component ligand. These nanotubes collapse when the template molecule is removed. A hexapyridine ligand, in which two tripyridine units are linked by an alkyl spacer, forms a complex with the PdII building block leading to the formation of a stable nanotube with an empty cavity without templates. With the aid of a 3.0 nm template strand molecule, a hexapyridine ligand consisting of two tripyridine units and a biphenyl linker assembles into a 3.5-nm nanotube, in which the four ligands are held together by twelve PdII ions. Facile preparation as well as the stability of the tube, even after the template is removed makes possible the hollow discrete assembly of the tubes. A dodecapyridine ligand possessing four tripyridine podands on a benzenetetracarboxylate scaffold, six PdII ions, and a template molecule generate a mono end-capped tube, which converts into a double open tube upon crystallization. Once formed, there is no route back to the end-capped tube. The structures are not in rapid equilibrium and are kinetically trapped during self-assembly. These tubular structures have been confirmed by NMR, CSI-MS observations, and X-ray crystallographic analysis. Studies on the dynamic behavior of rod-like guests accommodated in the nanotubes are also discussed.
    This account reviews a coordination approach to tubular assemblies via molecular paneling. Families of rectangular planar exo-multidentate organic ligands (molecular panels) can self-assemble into tubular structures possessing very stable, discrete, and well-defined frameworks upon complexation with a PdII building block. Fullsize Image
BCSJ Award Article
  • Takahito Ishikawa, Tomoyuki Morita, Shunsaku Kimura
    2007 Volume 80 Issue 8 Pages 1483-1491
    Published: August 15, 2007
    Released: August 10, 2007
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    Novel helix-peptide wheels, in which three helices were connected by using a template, were prepared, and the dipole–dipole interactions among the helices were studied in relation to the formation of a planar triangle structure containing three helices. The helical segments had a 310-helix structure. 13C spin-lattice relaxation time (T1) measurements showed that the helical segments had restricted mobility. Deuterium exchange rates of amide protons were accelerated in the helix-peptide wheels compared to the respective linear helix peptides, suggesting that there is torsion on the cylindrical shape. Therefore, the predominant structure of the helix-peptide wheels is a planar triangle in solution. Further, the triangle structure was successfully transferred onto a gold substrate.
    Novel helix-peptide wheels, in which three helices were connected by using a template, were prepared, and dipole–dipole interactions among helices were studied in relation to the formation of a planar triangle structure involving three helices. Fullsize Image
 
  • Shinya Katagiri, Yasunori Tsukahara, Yasuchika Hasegawa, Yuji Wada
    2007 Volume 80 Issue 8 Pages 1492-1503
    Published: August 15, 2007
    Released: August 10, 2007
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    Photoluminescence of Terbium(III) complexes was investigated as a function of temperatures in the range of 80–280 K for [Tb(bfa)3(H2O)2] (bfa: 4,4,4-trifluoro-1-phenyl-1,3-butanedionato), [Tb(hfa)3(H2O)3] (hfa: hexafluoroacetylacetonato), [Tb(tfa)3(H2O)2] (tfa: trifluoroacetylacetonato), [Tb(acac)3(H2O)3] (acac: acetylacetonato), and [Tb(hfa)3(tppo)2] (tppo: triphenylphosphine oxide). These complexes were classified into the two groups with different temperature-dependences. The first group consisting of [Tb(bfa)3(H2O)2], [Tb(tfa)3(H2O)2], and [Tb(acac)3(H2O)3] showed a dependence determined by the energy gap between the excited triplet state of the ligand and the emitting level of terbium(III) ion. In contrast, for [Tb(hfa)3(H2O)3] and [Tb(hfa)3(tppo)2] containing hfa as a ligand, not only the energy gap but also the energy barriers of the “Forward energy transfer” from the ligand to terbium(III) ion and “Back energy transfer” from terbium(III) ion to the ligand were taken into account for understanding their dependences. These results are discussed based on the re-orientation of the complexes accompanied by the forward and back energy transfer processes using DFT calculations.
  • Congyi Zhou, Changming Nie
    2007 Volume 80 Issue 8 Pages 1504-1510
    Published: August 15, 2007
    Released: August 10, 2007
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    The novel topological descriptor PE was proposed, using a revised distance matrix involving relative bond length as well as equilibrium electronegativity. Along with PE, the quantitative structure–property relationships were included with path number P3. The analyzed models could be applicable to the condensed-type properties of hydrocarbons. Moreover, the models also were applicable to the Kováts retention indexes under different conditions.
  • Yasuhiko Tanaka, Takamasa Sagara
    2007 Volume 80 Issue 8 Pages 1511-1517
    Published: August 15, 2007
    Released: August 10, 2007
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    Two-dimensional (2D) phase-transition behavior of three different viologens, heptyl viologen and its mono- and dicarboxylated derivatives, is described using the results of voltammetric measurements at an HOPG electrode. The transition was regarded as a typical 2D molecular organization process under oxidation state control. In an acidic medium, the width of the bi-stable potential region of the phase-transition was found to increase by approximately 55 mV with each addition of a carboxylate group. This fact points to a dominant contribution from intermolecular hydrogen bonding to the reductive formation of the 2D condensed phase. The occurrence of an incomplete transition process resulting in the formation of a metastable phase at lower temperatures, higher potential sweep rates, and higher concentrations was observed for dicarboxylated viologen, but not for monocarboxylated one. These results were used to discuss the advantages and disadvantages of multiple intermolecular interaction sites in a molecule in relation to the 2D molecular organization processes.
  • Jun-ichi Aihara, Toshimasa Ishida, Hideaki Kanno
    2007 Volume 80 Issue 8 Pages 1518-1521
    Published: August 15, 2007
    Released: August 10, 2007
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    By definition, bond resonance energy (BRE) represents the contribution of a given π-bond to aromaticity. The minimum BRE in a π-system is an excellent measure of kinetic stability. It was found that the BRE for a peripheral π-bond correlated not only to the harmonic oscillator model of aromaticity (HOMA) index for a ring, to which the π-bond belongs, but also to the corresponding bond-order index of aromaticity (BOIA) for local aromaticity. Thus, the BRE for a peripheral π-bond can be used as an energetic indicator of local aromaticity at least for polycyclic aromatic hydrocarbons (PAHs).
  • Iohborlang Mylliem Umlong, Jahar Dey, Snigdha Chanda, Kochi Ismail
    2007 Volume 80 Issue 8 Pages 1522-1526
    Published: August 15, 2007
    Released: August 10, 2007
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    Critical micelle concentration (cmc) values of dioctyl sulfosuccinate (AOT) in aqueous trisodium citrate (NaCit) solution were determined as functions of electrolyte concentration and temperature by using surface tension and EMF methods. Values of surface excess, counter ion binding constant (β), surface area, and standard free energies of micellization and adsorption of AOT were evaluated. Using fluorescence-quenching method, aggregation number and polarity index of AOT were also determined. A sudden increase in the value of β from almost 0.4 to 0.8, associated with a sudden increase in the aggregation number and decrease in the polarity index, was observed with a NaCit concentration of about 0.007 mol kg−1, which is considered to be due to change in the micellar shape of AOT. The present study confirms the special counter ion binding behaviour of AOT as an additional special feature of AOT.
  • Sanyo Hamai
    2007 Volume 80 Issue 8 Pages 1527-1533
    Published: August 15, 2007
    Released: August 10, 2007
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    Molecular interactions of an organic anion, resorufin (Res), with γ-cyclodextrin (γ-CD) and several organic cations were investigated by means of absorption and fluorescence spectroscopy. A 1:1 inclusion complex is formed between γ-CD and Res. In addition, Res forms a 1:1 organic cation–organic anion complex with 1,1′-diheptyl-4,4′-bipyridyl dibromide (DHB) and 1,1′-dimethyl-4,4′-bipyridyl dibromide (DMB), although Res does not form an organic cation–organic anion complex with trimethyloctylammonium bromide (TMOA). The γ-CD–Res inclusion complex forms a ternary inclusion complex with TMOA, DHB, and DMB. The equilibrium constant for the formation of the 1:1:1 γ-CD–Res–TMOA inclusion complex is nearly the same as that of the 1:1:1 γ-CD–Res–DHB inclusion complex. On the other hand, the equilibrium constant for the formation of the 1:1:1 γ-CD–Res–DMB inclusion complex is significantly less than that of 1:1:1 γ-CD–Res–DHB inclusion complex. These findings suggest that the long alkyl-chain in the organic cations examined promotes the formation of a ternary inclusion complex of Res.
  • Yuji Miyazato, Masaaki Ohba, Hiroshi Sakiyama, Hisashi Okawa
    2007 Volume 80 Issue 8 Pages 1534-1541
    Published: August 15, 2007
    Released: August 10, 2007
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    A series of tetrairon(III) complexes of di-μ-oxo-bis[di-μ-phenolatodiiron(III)] core, [{Fe2(L)(L′)}2(μ-O)2](PF6)2 (111), where L2− is the phenol-based macrocyclic compartmental ligand and (L′) is acetate, monochloroacetate, dichloroacetate, trifluoroacetate, pentafluoropropionate, benzoate, p-nitrobenzoate, pentafluorobenzoate, diethyl phosphate, diphenyl phosphate, or diethyldithiophosphate for 111, respectively, were synthesized. X-ray crystallographic studies for 4, 7, and 9 indicated that two {Fe2(L)(L′)} units were connected by two oxo bridges to afford a tetranuclear di-μ-oxo-bis[di-μ-phenolatodiiron(III)] core. Cyclic voltammograms of 111 in acetonitrile showed a quasi-reversible or irreversible reduction wave between −332 and −620 mV (vs. Ag/Ag+), which were attributed to a two-electron process involving the Fe4III,III,III,III/Fe4II,II,III,III. The Fe4III,III,III,III/Fe4II,II,III,III potential shifted positive with a decrease in the electron-donating ability of the end-cap ligand, and a good linear correlation was found between the potentials and the pKa values of HL′. The Fe4II,II,III,III species were generated in acetonitrile by electrochemical reduction and showed broad intervalence transition bands in the range of 900–1500 nm.
  • Abbas Afkhami, Lida Khalafi
    2007 Volume 80 Issue 8 Pages 1542-1548
    Published: August 15, 2007
    Released: August 10, 2007
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    A simple procedure for the kinetic spectrophotometric determination of the formation constant of 1:1 (XL) complexes (or adducts) using rank annihilation factor analysis (RAFA) is proposed. The method was based on the effect of the concentration of L (or X) on the reaction of X (or L) with a reagent (Z). The rate constants for the reactions of X (or L) and XL with Z were also determined. In order to perform RAFA, concentration profiles were calculated by optimizing the value of formation constant. The rank of the original data matrix was reduced by one by annihilating the information of X (or L). The best estimation of rate constant of complex XL reduced the rank of the system to zero (noise level). The performance of the method was evaluated using synthetic data as well as experimental data, and good results were obtained. The spectrophotometric data for the study of the effect of β-cyclodextrin (β-CD) on the oxidation reaction of some catechol derivatives with iodate at pH 3.60 was used as an example. The difference in the rate of the oxidation reaction of catechol derivatives with iodate at pH 3.60 in the presence of different concentrations of β-CD was monitored.
  • Ahmet Bilgin, Beytullah Ertem, Yasar Gök
    2007 Volume 80 Issue 8 Pages 1549-1555
    Published: August 15, 2007
    Released: August 10, 2007
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    A new quinoxaline-substituted vicinal dioxime ligand containing bis(12-diazacrown-4) units (H2L) was synthesized by the reaction of cyanogen di-N-oxide with compound 4. Mononuclear NiII and CuII complexes with a metal:ligand ratio of 1:2 for H2L and a trinuclear CuII complex were also synthesized. The mononuclear CuII species coordinated to two CuII ions through the deprotonated oximate oxygens to yield a trinuclear structure cis-bridged by the oximate groups, with 1,10-phenanthroline as an end-cap ligand. The mononuclear CoIII complex of H2L was isolated with pyridine and chlorine as axial ligands. In addition, a CoIII complex containing the BF2+ bridge macrocycle was synthesized using a precursor hydrogen-bridged CoIII complex via a template effect. The extraction abilities of 1, 3, and 11 were also evaluated in 1,2-dichloroethane by using several alkali (Li+, Na+, K+, and Cs+) and transition-metal picrates, such as Ag+, Pb2+, Cd2+, Cu2+, and Zn2+. Structures of the ligands and metal complexes were solved by elemental analyses, 1H and 13C NMR, FT-IR, UV–vis, and mass spectra.
  • Kenji Funatsu, Naomi Yasuda, Akio Ichimura, Ryoko Santo, Yoichi Sasaki ...
    2007 Volume 80 Issue 8 Pages 1556-1562
    Published: August 15, 2007
    Released: August 10, 2007
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    5-(3-Pyridyl)porphyrinatoruthenium(II) tetramers, [{Ru(3-PyT3porph)(CO)}4] (1), [{Ru(3-PytB3porph)(CO)}4] (2), [{Ru(3-PyHex3porph)(CO)}4] (3), and [{Ru(3-PytB3porph)(py)}4] (4) were prepared. The structures of the isolated tetramers were determined to be rhombic shaped with two chemically nonequivalent porphyrinatoruthenium(II) subunits by 1H NMR, IR, and ESI-MS measurements. The tetramers were stable in benzene at 70 °C. However, the tetramers reacted with a large excess of pyridine to give two geometrical isomers of porphyrinatoruthenium(II) in dichloromethane at room temperature as observed by 1H NMR spectrometry. UV–vis spectra of the tetramers showed splitting or broadening of the Soret band due to excitonic interactions. Stepwise oxidations of the porphyrin rings or the ruthenium ions in the cyclic tetramer skeleton were observed in cyclic voltammograms.
  • Kensaku Takanashi, Atsunobu Fujii, Reina Nakajima, Hiroshi Chiba, Masa ...
    2007 Volume 80 Issue 8 Pages 1563-1572
    Published: August 15, 2007
    Released: August 10, 2007
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    Fine-controlled metal–organic hybridization is strongly desired for advanced nano-materials. Dendrimers are highly branched organic macromolecules with successive layers or “generations” of branch units surrounding a central core. Metal–organic hybrid versions have also been produced by trapping metal ions or metal clusters within the voids of dendrimers. Here, we report a technique to form a dendritic organic structure, which includes various metals, with fine control over the number and location of the metal salts through a radial stepwise complexation. FeCl3, GaCl3, VCl3, and SnCl2 were decorated on a phenylazomethine dendrimer with 4th generations at the first, second, third, and forth layers, respectively. These stepwise complexation and heterometal assembling were also supported by TEM observation, 57Fe Mössbauer spectroscopy, XPS measurement, and NMR spectroscopy.
  • Jahan-Bakhsh Raoof, Abolfazl Kiani, Reza Ojani, Mohammad A. Khalilzade ...
    2007 Volume 80 Issue 8 Pages 1573-1576
    Published: August 15, 2007
    Released: August 10, 2007
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    Efficient carbon–carbon bond-forming reaction at the 5- and 6-positions of catechol skeleton was achieved through anodic oxidation of catechol, 3-methylcatechol, and 4-methylcatechol in the presence of 1,3-indandione as a nucleophile. The electrochemical synthesis was carried out in aqueous solution, which is a green solvent, using cyclic voltammetry and controlled-current coulometry techniques. The results indicate that the electrogenerated benzoquinone from the electrooxidation of the corresponding catechol participates in a Michael addition reaction with 1,3-indandione. The mechanism of anodic oxidation was deduced from voltammetric and spectroscopic data. The galavanostatic electrochemical synthesis of compounds 2a, 2b, and 2c was successfully performed in an undivided cell in good yield. The products were characterized by 1H NMR, 13C NMR, DEPT, FT-IR, and mass spectrometry.
  • Takashi Kato, Isao Takahashi, Hideyuki Kumita, Tomohiro Ozawa, Yasuhir ...
    2007 Volume 80 Issue 8 Pages 1577-1579
    Published: August 15, 2007
    Released: August 10, 2007
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    Redox reactions between horse heart cytochrome c and optically active Ru complexes were kinetically studied. The kinetic parameters for the oxidation of ferrocytochrome c with RuIII complexes indicated an apparent enantioselectivity, which clearly shows that exact molecular recognition is achieved through non-polar interactions rather than electrostatic ones.
  • Kozo Toyota, Keiko Horikawa, Rader S. Jensen, Kouhei Omori, Subaru Kaw ...
    2007 Volume 80 Issue 8 Pages 1580-1586
    Published: August 15, 2007
    Released: August 10, 2007
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    Sterically protected 1,2-diaryl-3,4-diphosphinidenecyclobutenes were prepared from 3-aryl-2-bromo-1-(2,4,6-tri-t-butylphenyl)-3-(trimethylsiloxy)-1-phosphapropene using t-butyllithium and 1,2-dibromoethane, and the properties of the products, such as 1,2-di(2,2′-bithienyl-5-yl)-3,4-diphosphinidenecyclobutene, were studied. This method is an excellent method for preparing these compounds.
  • Lawrence M. Pratt, Diep Huong Tran Phan, Phuong Thao Thi Tran, Ngan Va ...
    2007 Volume 80 Issue 8 Pages 1587-1596
    Published: August 15, 2007
    Released: August 10, 2007
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    A systematic investigation was performed to determine which levels of theory are required to obtain accurate geometries and dimerization energies for lithium carbenoids. Dimerization free energies of six lithium carbenoids were calculated in the gas phase at the B3LYP and MP2 levels with several different basis sets and at the CCSD(T) level with the aug-cc-pvdz basis set. It was found that the calculated thermal corrections to the dimerization free energy, obtained from frequency calculation, were relatively independent of the basis set for basis sets larger than 6-31+G(d) and that smaller basis sets often generated qualitatively correct results. The dimerization free energies were usually overestimated by small basis sets compared to those using polarization and diffuse functions, whereas only modest gains were obtained by using basis sets larger than 6-31+G(d). The B3LYP DFT method generated geometries consistent with the MP2 and CCSD methods for halomethyllithium carbenoids, but not always for 1-halovinyllithium carbenoids. The B3LYP calculations also severely underestimated the dimerization free energies for the halovinyllithium carbenoids, compared to the MP2, and coupled cluster methods.
  • Kazuhisa Tanabe, Ayako Fujie, Naoki Ohmori, Yoshikazu Hiraga, Satoshi ...
    2007 Volume 80 Issue 8 Pages 1597-1604
    Published: August 15, 2007
    Released: August 10, 2007
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    For the purpose of synthesizing daphnezomine C, model systems were examined to see if the ring-closing metathesis (RCM) reaction could be applied to prepare an 11-membered ring system bearing a tri-substituted alkene. As a result, it was found that the connectivity pattern of the tethers bearing the reacting alkene moieties was crucial. Thus, whereas a system involving a single 1,3- or 1,4-disubstituted cyclohexane derivative did not give RCM products, a flexible system without any rings between the two terminal alkenes gave the cyclic product with a yield of up to 65% using the second generation Grubbs catalyst.
  • Wanny Basuki, Makoto Hiromura, Hiromu Sakurai
    2007 Volume 80 Issue 8 Pages 1605-1610
    Published: August 15, 2007
    Released: August 10, 2007
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    A [meso-tetrakis(4-sulfonatophenyl)porphyrinato]oxovanadium(IV) (VO(tpps)), has been found to have an antidiabetic activity and thus to be effective for treating diabetic animal models. High hypoglycemic effects have been observed not only in streptozotocin (STZ)-induced type 1 diabetic mice but also type 2 diabetic KKAy mice by oral administration of the complex. However, the molecular mechanism for the activities has not yet been examined. The aim of this study was to investigate the molecular mechanism of VO(tpps) in 3T3-L1 adipocytes with respect to insulin signaling pathway. Addition of VO(tpps) was found to phosphorylate the insulin receptor β (IRβ) subunit, insulin receptor substrate 1 (IRS1) and protein kinase B (PKB)/Akt in 3T3-L1 adipocytes, in which all phosphorylations were time dependent. The VO(tpps)-induced Akt phosphorylation was suppressed by a PI3K inhibitor, wortmannin. VO(tpps) also stimulated GLUT4 protein translocation to the plasma membrane. Based on these results, we conclude that VO(tpps) exhibits both insulinomimetic and antidiabetic activities via tyrosine phosphorylations of IRβ and IRS1, which activate the downstream Akt phosphorylation through PI3K, and this signaling cascade finally causes GLUT4 translocation from the cytosol to the plasma membrane.
  • Takashi Okazoe, Kunio Watanabe, Masahiro Itoh, Daisuke Shirakawa, Hiro ...
    2007 Volume 80 Issue 8 Pages 1611-1616
    Published: August 15, 2007
    Released: August 10, 2007
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    A new synthetic procedure for the preparation of perfluorinated ketones from nonfluorinated sec-alcohols was developed. A key step in the synthetic route was a liquid-phase direct fluorination reaction with elemental fluorine. Direct fluorination of a partially fluorinated ester, which was prepared from a nonfluorinated sec-alcohols and a perfluorinated acyl fluoride, followed by thermal elimination, gave a perfluorinated ketone and the starting perfluorinated acyl fluoride, which could be recycled. Application to the synthesis of a precursor polyfluoroketone for fluoropolymer resists for 157 nm microlithography was also established.
  • Akihiro Orita, Junji Okano, Genta Uehara, Lasheng Jiang, Junzo Otera
    2007 Volume 80 Issue 8 Pages 1617-1623
    Published: August 15, 2007
    Released: August 10, 2007
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    It has been shown that solventless reactions are accelerated when the reactants are mixed at molecular level. Accordingly, a solid film obtained by evaporating a solution of reactants mixture underwent facile reaction either upon grinding or upon simply standing. The effectiveness of these methods is evident from comparison with conventional solventless and solution reactions. It was concluded consequently that, once the molecular-level contacts are formed between reactants, the reaction occurs more efficiently under solventless conditions than in solution. Due to this pre-mixing method, efficient synthesis of [2]rotaxanes and rate acceleration of the Wittig reaction were achieved.
  • Yusuke Ide, Makoto Ogawa
    2007 Volume 80 Issue 8 Pages 1624-1629
    Published: August 15, 2007
    Released: August 10, 2007
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    An efficient method to immobilize silane-coupling reagents on the interlayer space of a layered silicate, magadiite (Na2Si14O29·nH2O), is reported. The silylation was conducted by concentrating a mixture containing the pre-synthesized dodecyltrimethylammonium-exchanged magadiite and a stoichiometric amount (molar ratio of silane-coupling reagent/Si14O29 unit of magadiite = 2.0) of (3-mercaptopropyl)trimethoxysilane. The resulting silylated derivative possessed basal spacing and had a composition comparable to those of the silylated derivative, prepared by using a previous silylation method, which involves dodecyltrimethylammonium-exchanged form with a much larger amount (molar ratio of silane-coupling reagent/Si14O29 unit of magadiite = 57) of the silane-coupling reagent. When the present method was employed, the surface coverage with (3-mercaptopropyl)silyl groups on the layer surface directly correlated to the amount of the silane-coupling reagent.
  • Makoto Saito, Masahiro Itoh, Jun Iwamoto, Ken-ichi Machida
    2007 Volume 80 Issue 8 Pages 1630-1634
    Published: August 15, 2007
    Released: August 10, 2007
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    Ammonia synthesis was performed using a hydrogen-permeable membrane reactor with a Ru/(MgO–CeO2) catalyst (Mg:Ce = 50:50 in molar ratio; Ru loading = 5 wt %). The catalytic activity with permeated hydrogen (atomic hydrogen) was 1.6 times higher than those of with non-permeated hydrogen (molecular hydrogen). Temperature-programmed reaction experiments, which were conducted by flowing hydrogen onto the catalysts, revealed that the ceria component of the MgO–CeO2 support became much more reductive by hybridization with magnesia. The partially reduced ceria promoted the dissociative adsorption of molecular nitrogen by donating the electrons of Ce3+ ions to Ru metal particles. Furthermore, hydrogen poisoning of the Ru metal catalysts was suppressed by supplying atomic hydrogen through a Ag–Pd hydrogen-permeable membrane under well-controlled conditions to accelerate the catalytic reaction.
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