Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 76 , Issue 6
Showing 1-25 articles out of 25 articles from the selected issue
  • Yukio Hinatsu, Yoshihiro Doi
    Type: Accounts
    Subject area: AI
    2003 Volume 76 Issue 6 Pages 1093-1113
    Published: 2003
    Released: June 15, 2003
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    This account describes the synthesis, crystal structures and magnetic properties of double perovskites A2LnMO6 and 6H-perovskites Ba3LnRu2O9 (A = Sr, Ba; Ln = Y, lanthanides; M = Nb, Ta, Ru). The double perovskites A2LnMO6 have two kinds of cations, Ln and M, in the B site of the perovskite ABO3. These cations adopt the alternative ordered arrangement. Measurements of the magnetic susceptibility, specific heat, and powder neutron diffraction showed that all of the A2LnRuO6 compounds exhibited an antiferromagnetic transition at low temperatures and a complex temperature dependence of the magnetic susceptibility below their transition temperatures. In these compounds, the magnetic interaction between the Ln (4f electrons) and Ru (4d electrons) ions via the Ln–O–Ru pathway contributes greatly to their magnetic cooperative phenomena. The structural and magnetic studies for the 6H-perovskites Ba3LnRu2O9 show that the Ln cations occupy the corner-sharing octahedra (LnO6 octahedron) and the Ru cations occupy the face-sharing octahedra (Ru2O9 dimer). The Ba3LnRu2O9 compounds show a characteristic temperature-dependence of the magnetic susceptibilities, that is, a broad maximum at temperatures above 135 K and a magnetic transition at 5–15 K. These magnetic properties mainly reflect two kinds of the magnetic interactions: the interaction between Ln and Ru ions and that between Ru ions in the Ru2O9 dimer.
  • Yasufumi Ohfune, Tetsuro Shinada
    Type: Accounts
    Subject area: OB
    2003 Volume 76 Issue 6 Pages 1115-1129
    Published: 2003
    Released: June 15, 2003
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    A series of optically active α,α-disubstituted α-amino acids have been synthesized starting with an achiral or a racemic α-hydroxy or α-diazo ketone. In the present synthesis, the key transformation is an asymmetric version of the Strecker synthesis. An α-acyloxy ketone having a chiral amino acid as the acyloxy group afforded cyclic α-amino nitrile in a highly stereoselective manner; in this reaction the amino group and the chirality were diastereoselectively transplanted into the internal ketone group via an imine-enamine equilibrium of the cyclic ketimine intermediate. Oxidation of the amino group followed by removal of the resulting imino group and hydrolysis of the nitrile group afforded α-hydroxymethyl α-amino acid. The use of L-amino acid as the acyloxy group gave R enantiomer, and its S enantiomer was obtained when D-amino acid was employed. Some problematic processes that remained in the Strecker synthesis, i.e., preparation of the starting α-acyloxy ketone and oxidative conversion of α-amino nitrile into α-imino nitrile, are much improved as regards efficiency by the development of a Cu-catalyzed insertion of α-diazo ketone into N-protected α-amino acid, and as regards yields by the use of ozone as the oxidant. With these methods, various types of α,α-disubstituted α-amino acids have been synthesized including cyclic analogs, which can be viewed as a conformational variant of serine. Their incorporations into Leu-enkephalin have revealed that these amino acids play an important role not only to constrain the peptide conformation but also for high affinity bindings to the opioid receptors. Applications to the synthesis of biologically active natural products have been exemplified by the syntheses of the Corey intermediate of lactacystin and of marine natural products, manzacidin A and C.
  • Hideki Ohtsuki, Jalaluddin Ahmed, Takuya Nagata, Tatsuyuki Yamamoto, Y ...
    Type: Headline
    Subject area: TP
    2003 Volume 76 Issue 6 Pages 1131-1138
    Published: 2003
    Released: June 15, 2003
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    The p-nitrophenolate ion (pNP) was strongly bound to the mono- and dipyridinio derivatives of α-cyclodextrin (α-CD) in an aqueous 0.1 mol dm−3 Na2CO3 solution, and shifted the 1H NMR signals due to the α-CD C5-H’s to different directions, depending on the position of α-D-glucopyranose (anisotropic ring-current effect). In contrast, the iodide ion and p-hydroxybenzoate ion showed no such effect upon complexation. Furthermore, the C5-H’s of a dipyridinio derivative of β-CD was not subject to such an anisotropic ring-current effect of pNP. These results indicate that the molecular rotation of pNP is significantly retarded within the cavities of the pyridinio derivatives of α-CD by electrostatic and van der Waals interactions. Thus, electrostatic interactions are available for controlling the molecular motion or orientation of an ionic guest compound in a CD cavity and for the design of an enzyme-mimic modified CD.
  • Keiichi Sato, Satoshi Furuya, Norimichi Takenaka, Hiroshi Bandow, Yasu ...
    Type: Article
    Subject area: TP
    2003 Volume 76 Issue 6 Pages 1139-1144
    Published: 2003
    Released: June 15, 2003
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    In order to investigate the characteristics of the oxidative reactions of low-valence sulfur compounds with H2O2 in the freezing process, a Na2S2O3 aqueous solution was mixed with a H2O2 aqueous solution, followed by freezing at −15 °C. After the designated time had passed, the concentrations of sulfur compounds were measured. The oxidation of thiosulfates was accelerated due to the freeze-concentration effect. The maximum reaction rate of the freezing reaction (−15 °C) was about 20-times faster than that in an aqueous solution (25 °C). In the aqueous-phase reaction, thiosulfates were transformed to tetrathionates as intermediates, or directly to sulfates, and all sulfur compounds were finally oxidized to sulfates. On the other hand, the tetrathionates and sulfates transformed by the freezing reaction were preserved in ice for a long time. The maximum amounts of the tetrathionates formed by freezing were about twice those in the aqueous-phase reaction. Once tetrathionates were formed by the freezing reaction, most of the formed tetrathionates coexisting with high concentrations of H2O2 were not transformed to sulfate, regardless of whether or not the sample was re-frozen. This observation is probably attributable to the difference in the pH value when tetrathionates are formed.
  • Yo-ichi Ishikawa, Yoshitaka Matsumoto
    Type: Article
    Subject area: TP
    2003 Volume 76 Issue 6 Pages 1145-1153
    Published: 2003
    Released: June 15, 2003
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    The gas-phase reactivity of W (a 7S3 and a 5DJ) with C2H4 and NH3 at room temperature was investigated using a time-resolved laser induced fluorescence (LIF) spectroscopy. Tungsten atoms were produced by a 266-nm multiphoton decomposition (MPD) of W(CO)6. The reactant pressure dependence of the pseudo-first-order depletion rates of W (a 7S3) could allow an estimation of the pseudo-second-order depletion rate constant of W (a 7S3), (4.5 ± 0.5) × 10−10 cm3 molecule−1 s−1 for C2H4 and (0.73 ± 0.10) × 10−10 for NH3 at 6.0-Torr total pressure with an Ar buffer. A simulation of the transient curves based on a modification of the observed apparent decay rate constants, involving nearby a 5DJ states in the presence of C2H4 and NH3, allowed us to separately estimate the contribution of the chemical quenching (W (a 7S3) + R → product(s)) and the physical quenching (W (a 7S3) + R → W (a 5D1) + R) processes. In the case of C2H4, chemical quenching appeared to dominate over the physical quenching, while the physical quenching was the main depletion process in the case of NH3. The large reactivity of the W (a 7S3) state not only for C2H4, but also for NH3, is discussed in terms of the relativistic effects.
  • Shunji Kiyoda, Haruo Akashi, Akio Ichimura, Takashi Shibahara
    Type: Article
    Subject area: AI
    2003 Volume 76 Issue 6 Pages 1155-1163
    Published: 2003
    Released: June 15, 2003
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    An oxo- and chloro-bridged dinuclear molybdenum(III) ethylenediamine complex, [Mo2(μ-O)(μ-Cl)(en)4]3+, was synthesized by the reaction of [MoCl3(thf)3] with ethylenediamine in DMF. μ-Oxo-μ-alkoxo-bridged dimolybdenum(III) ethylenediamine complexes [Mo2(μ-O)(μ-OMe)(en)4]3+, [Mo2(μ-O)(μ-OEt)(en)4]3+, and [Mo2(μ-O)(μ-OPr)(en)4]3+ were obtained by reactions of the mononuclear complex with ethylenediamine in methanol, ethanol, and propanol, respectively, where each solution contained LiBr. Bridged dimeric structures of these complexes were determined by X-ray crystallography. In an acidic aqueous solution, these oxo-bridged complexes underwent protonation on the bridging oxygen atoms and changes to the corresponding hydroxo-bridged complexes. Cyclic voltammetric measurements (pH 1.0–10.0) of complexes [Mo2(μ-O)(μ-Cl)(en)4]3+, [Mo2(μ-O)(μ-OMe)(en)4]3+, and [Mo2(μ-O)(μ-OEt)(en)4]3+ clearly showed that, accompanied by the oxidation of the complex, the coordinated amine is deprotonated, and the complex becomes a corresponding amido-coordinated complex.
  • Julietta V. Rau, Valerio Rossi Albertini, Norbert S. Chilingarov, Marc ...
    Type: Article
    Subject area: AI
    2003 Volume 76 Issue 6 Pages 1165-1169
    Published: 2003
    Released: June 15, 2003
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    The thermal decomposition of transition metal trifluorides MF3 (M = Mn, Fe, Co) was studied by collecting sequences of very-high-energy (89 keV) synchrotron radiation diffraction patterns. The real-time evolution of the crystal lattices was followed as a function of temperature and it was observed that the transition from MF3 to MF2 is generally accompanied by the formation of intermediate short-living phases –M2F5. One of them –Co2F5– is a phase which had never been observed before.
  • Md. Nazrul Islam, Takeo Kaneko, Kensei Kobayashi
    Type: Article
    Subject area: AI
    2003 Volume 76 Issue 6 Pages 1171-1178
    Published: 2003
    Released: June 15, 2003
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    A novel supercritical water flow-reactor was constructed in order to simulate submarine hydrothermal systems. The temperature of fluid inside the reaction tube could be monitored with thermocouples, which was proved to be different from the temperature outside the reaction tube. Oligomers of glycine up to tetraglycine were formed when a 100 mM glycine solution was heated at 200–350 °C for 2 minutes. None of glycine peptides were produced at 400 °C. It was suggested, however, that the formation of glycine condensates at higher temperature, including supercritical conditions of water. The stability of some amino acids under hydrothermal conditions was examined. ω-Amino acids and glutamic acid, which can form intramolecular condensates, showed higher stability than other α-amino acids at higher temperature, including supercritical conditions.
  • Li-Juan Zhang, Xiao-Li Zhao, Peng Cheng, Ji-Qing Xu, Xu Tang, Xiao-Bin ...
    Type: Article
    Subject area: AI
    2003 Volume 76 Issue 6 Pages 1179-1184
    Published: 2003
    Released: June 15, 2003
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    A two-dimensional (2D) cobalt coordination polymer [{Co3(tp)2(OH)2(phen)2}n] (1), bridged by the terephthalate (tp) ligand, was synthesized under hydrothermal conditions, and its structure was determined by single-crystal X-ray diffraction. Complex 1 crystallized in the triclinic space group P1- with a = 8.2620(11) Å, b = 10.4409(12) Å, c = 11.0840(10) Å, α = 111.332(8)°, β = 91.394(10)°, γ = 91.638(10)°, Z = 2, V = 889.65(18) Å3. A structure refinement showed that complex 1 is the first example of a two-dimensional (2D) framework with both carboxylate bridges and μ-hydroxo bridges, in which cobalt atoms adopt square-pyramidal and square-planar geometries. Complex 1 exhibited a interesting magnetic behavior: the shape of the μeff curve indicates a ferrimagnetic-like behavior between 300–41.0 K, immediately followed by a strong decay of the magnetic moment. Moreover, complex 1 was characterized by IR spectroscopy, inductively coupled plasma (ICP), elemental and thermogravimetric (TGA) analyses.
  • Joe Otsuki, Dong-Mei Li, Katsuhiko Sato, Asako Nakagome, Toshio Takido ...
    Type: Article
    Subject area: AI
    2003 Volume 76 Issue 6 Pages 1185-1189
    Published: 2003
    Released: June 15, 2003
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    A tetranuclear Ru complex linked by 4,4″-azobis(2,2′-bipyridine) (azobpy), [Ru{(azobpy)Ru(bpy)2}3][PF6]8 (bpy = 2,2′-bipyridine) has been prepared and fully characterized. Cyclic and differential pulse voltammetries show that two kinds of oxidation occur, the one at the less positive potential being assigned to the oxidation of the three peripheral Ru ions, while the other to that of the central Ru ion. On a cathodic scan, a pair of three-electron (one electron on each azobpy) reductions of azobpy ligands appear at less negative potentials than terminal bpy ligands. A low-energy metal-to-ligand charge transfer (MLCT) absorption band involving the π*-orbitals of azobpy ligands is observed in addition to the usual MLCT band involving terminal bpy ligands. These results indicate the presence of a low-lying π* level of azobpy. A selective reduction of azobpy ligands renders the non-luminescent complex into a moderately luminescent species. This light switch is reversible, implying the utility of this branched structure in energy delivering molecular systems.
  • Yoshitaro Miyashita, Hirokazu Yoshida, Tomohiro Sato, Yasunori Yamada, ...
    Type: Article
    Subject area: AI
    2003 Volume 76 Issue 6 Pages 1191-1197
    Published: 2003
    Released: June 15, 2003
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    The UV-vis spectroelectrochemical properties of S-bridged tricobalt(III) complexes [CoIII{CoIII(aet or L-cys)3}2]3+ or 3− and dicobalt(III) complexes [CoIII{CoIII(aet or L-cys)3}(dien)]3+ or 0 (aet = 2-aminoethanethiolate, L-cys = L-cysteinate, dien = diethylenetriamine) were investigated using a thin-layer quartz cell with a platinum mesh working electrode. The absorption spectroelectrochemical measurements for the tricobalt(III) complexes indicated that a two-electron reduction proceeds through pseudo two-steps, CoIIICoIIICoIII → CoIIICoIICoIII → CoIIICoIICoII for the aet complex, while through pseudo one-step for the L-cys complex. The CD spectroelectrochemical measurements demonstrated that the optically active isomer (ΔΔ form) of the aet tricobalt(III) complex loses chirality during the one-electron reduction, whereas the ΔLLLΔLLL isomer of the L-cys tricobalt(III) complex is reduced with an inversion of configuration, to form the ΛLLLΛLLL isomer. The ΛLLLΛLLL isomer is reduced with a retention of configuration. The aet and L-cys dicobalt(III) complexes were converted to the corresponding tricobalt(III) complexes by electrochemical reduction, accompanied by the release of the Co(II) ion and dien ligand. It was also elucidated that this conversion occurred with a retention of configuration.
  • Tetuya Ohashi, Yoshitaro Miyashita, Yasunori Yamada, Kiyoshi Fujisawa, ...
    Type: Article
    Subject area: AI
    2003 Volume 76 Issue 6 Pages 1199-1205
    Published: 2003
    Released: June 15, 2003
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    The reactions of Re(V) precursors [ReOX3(PPh3)2] (X = Cl, Br) with 8-amino-2-methylquinoline (H2amq) gave [ReOX2(Hamq)(PPh3)] (X = Cl, 1; Br, 2) as major products and [ReOX2(Hamq)(OPPh3)] (X = Cl, 3; Br, 4) as minor products. 3 and 4 were also obtained from the reaction of 1 and 2 with an excess of free OPPh3 ligand. The crystal structures of 1, 3, and 4 were determined by X-ray analyses. These complex molecules have a distorted octahedral geometry. The Re=O bond in 1 occupies the trans position to the amido N atom of the partially deprotonated H2amq ligand. Its distance (1.724(4) Å) is long due to the trans influence of the amido N atom. The Re=O bonds in 3 and 4 occupy the trans position to the O atom of the OPPh3 ligand, indicating a geometrical conversion during the ligand substitution reaction. Some intramolecular and/or intermolecular stacking interactions are also observed in the crystalline state. All complexes were characterized in the solid state by IR, far-IR, diffuse reflectance, and 31P{1H} CP-MAS NMR spectra. From UV-vis absorption and 31P{1H} NMR spectra, it was indicated that the PPh3 and OPPh3 ligands in 14 are released in solution.
  • Shinya Hayami, Ryo Kawajiri, Gergely Juhász, Takayoshi Kawahara ...
    Type: Article
    Subject area: AI
    2003 Volume 76 Issue 6 Pages 1207-1213
    Published: 2003
    Released: June 15, 2003
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    The thermal spin transitions of iron(II) spin-crossover compounds [Fe(PM-iPA)2(NCS)2] (1) and [Fe(PM-iPA)2(NCSe)2] (2) (PM-iPA = N-(2′-pyridylmethyl)-isopropylamine) have occurred at T1/2 = 267 K and 376 K without thermal hysteresis. No light-induced excited spin state trapping (LIESST) effect was observed for compounds 1 and 2 even at 5 K. The iron(II) spin-crossover compounds [Fe(PM-L)2(NCX)2] (PM-A = N-(2′-pyridylmethyl)-aniline, PM-BiA = N-(2′-pyridylmethyl)-4-aminobiphenyl, PM-TeA = N-(2′-pyridylmethyl)-4-aminoterphenyl, PM-PEA = N-(2′-pyridylmethyl)-4-(phenylethynyl)aniline, and PM-AzA = N-(2′-pyridylmethyl)-4-(phenylazo)aniline; X = S and Se) with ligands having π-systems have exhibited the LIESST effect, and the critical LIESST temperature, Tc(LIESST), has been observed. The compounds 1 and 2 are crystallized at Pnna and C2/c at 298 K, respectively, and the space groups of the compounds remained unchanged until 100 K, although the compounds show the spin transition. The molecular packing structure and thermodynamic parameters of the spin transitions calculated from the magnetic susceptibility curves suggest that compounds 1 and 2 have no strong intermolecular interactions between the complexes, while the compounds with π-system ligands form π–π intra- and intermolecular interactions between the ligands. Our conclusion is that the intermolecular interactions play an important role in trapping a light-induced metastatble state.
  • Masakazu Hirotsu, Ryota Endo, Takashi Yoshimura, Takumi Konno
    Type: Article
    Subject area: AI
    2003 Volume 76 Issue 6 Pages 1215-1221
    Published: 2003
    Released: June 15, 2003
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    Treatments of a mixture of CoCl2·6H2O, HL (Hpyt = 2-pyridinethiol, Hpymt = 2-pyrimidinethiol), and triethylamine with [Ni(aet)2] (aet = 2-aminoethanethiolate) in methanol led to the isolation of novel S-bridged CoIIINiIICoIII trinuclear complexes, [Ni{Co(aet)2(pyt)}2]2+ ([1]2+) and [Ni{Co(aet)2(pymt)}2]2+ ([2]2+), in which a NiII ion is coordinated by four aet S atoms from two tris(thiolato)-type [Co(aet)2(pyt or pymt)] units. The NiII ion in both [1]2+ and [2]2+ was replaced by a PdII ion through the reaction with Na2[PdCl4] in water, giving the corresponding CoIIIPdIICoIII trinuclear complexes, [Pd{Co(aet)2(pyt)}2]2+ ([3]2+) and [Pd{Co(aet)2(pymt)}2]2+ ([4]2+). The related CoIIIPdIICoIII trinuclear complexes composed of one [Co(aet)2(pyt or pymt)] and one [Co(aet)2(en)]+ units, [Pd{Co(aet)2(pyt)}{Co(aet)2(en)}]3+ ([5]3+) and [Pd{Co(aet)2(pymt)}{Co(aet)2(en)}]3+ ([6]3+), were also prepared by the reactions of a 1:1 mixture of [Ni{Co(aet)2(pyt or pymt)}2]2+ and [Ni{Co(aet)2(en)}2]4+ with Na2[PdCl4] in water, followed by the column chromatographic separation. The electronic absorption, CD, and NMR spectroscopies indicated that these CoIIIMCoIII trinuclear complexes produce only the racemic (ΔΔ⁄ΛΛ) isomer, in which each [Co(aet)2(pyt or pymt)] unit adopts a mer(S) configuration with two aet N atoms at the apical positions. For [1]2+, [2]2+, [3]2+, and [4]2+, another geometrical isomerism of synanti, which arises from the arrangement of the two terminal pyt or pymt S atoms, was identified.
  • Saumitra Sengupta, Subir Kumar Sadhukhan
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 6 Pages 1223-1226
    Published: 2003
    Released: June 15, 2003
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    Based on an azobenzene derived octupolar scaffold, a trigonally symmetric near-IR dye 4max 995 nm) has been prepared from common starting materials. The dye showed a pH dependent as well as a solvent dependent absorption behavior.
  • Takashi Karatsu, Nobuo Shiochi, Takumi Aono, Nobukazu Miyagawa, Akihid ...
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 6 Pages 1227-1231
    Published: 2003
    Released: June 15, 2003
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    3H-pyrazoles were photolyzed in the presence of 2,4,6-triphenylpyrylium tetrafluoroborate (TPP+) or 9,10-dicyanoanthracene (DCA) as a sensitizer. The obtained products were different depending on the sensitizers employed. The cyclopropene derivatives were produced in the cases of the DCA and TPP+ sensitizations and a solvent adduct was obtained for the TPP+ sensitization reaction. The difference in products is explained by the rates of the back electron transfer from the electron accepted sensitizers to the radical cation intermediates. In the DCA sensitization, the absorption band of the diazoalkene was observed but in the TPP+ sensitization it was not observed. From these results, it is apparent that the back electron transfer rates of the DCA sensitization reactions are faster than those of the TPP+ sensitization reactions.
  • Michael Widhalm, Kurt Mereiter
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 6 Pages 1233-1244
    Published: 2003
    Released: June 15, 2003
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    The behavior of BINAP(O)2 upon treatment with lithium or magnesium amides under various conditions has been studied. With 2,2,6,6-tetramethylpiperidinomagnesium bromide, the ortho positions of opposed phenyl rings were selectively metallated, forming stable intermediates, while the use of lithium amides caused rearrangements with displacement of one diphenylphosphinoyl group and the formation of strained P-heterocycles (2, 5, 6) with unusual architectures. Monophosphine oxides 2 and 3a have been reduced to phosphines 13 and 14 in good yield, while substituted BINAP(O)2 derivatives failed to give the desired diphosphines. The stereochemistry of six phosphine oxides (2, 3a, 5, 8, 9, 11a) and one phosphine (13) has been elucidated by crystal structure determinations.
  • Shin′ichi Nakatsuji, Yuya Ogawa, Hiroki Akutsu, Jun-ichi Yamada
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 6 Pages 1245-1250
    Published: 2003
    Released: June 15, 2003
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    The preparation and magnetic properties of organic radical anion salts derived from styrylpyrylium derivatives 1a and 2a are described and compared to those of the corresponding photo-dimers. The magnetic properties of the radical anions for TCNQ salt 1b and TCNQF4 salt 1c are rather different, showing antiferromagnetic interactions based on the 1-D Heisenberg model in the former, and ferromagnetic interactions in the latter. This difference is considered to be a result of the fairly large difference in their crystal structures. A considerable change in the magnetic properties was found between the radical anion salts of monomers and the corresponding photo-dimers, in which magnetic susceptibilities are largely diminished.
  • Takanori Mizutani, Yutaka Ukaji, Katsuhiko Inomata
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 6 Pages 1251-1256
    Published: 2003
    Released: June 15, 2003
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    γ-Lactams were synthesized from N-tosylhomoallylamines by a carbonylation reaction catalyzed by palladium and copper salts under the normal pressure of CO and O2 at room temperature. Monocarbonylation proceeded by the use of [PdCl2(CH3CN)2] and CuCl2 to afford 3-methyl-2-pyrrolidones, while the use of PdCl2 and CuCl switched the reaction from monocarbonylation to dicarbonylation to produce alkyl 2-oxopyrrolidine-3-acetate in good yields, respectively.
  • Kazuhiro Kobayashi, Ryoji Nakahashi, Masaaki Mano, Osamu Morikawa, His ...
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 6 Pages 1257-1259
    Published: 2003
    Released: June 15, 2003
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    A magnesium amide-induced sequential conjugate addition/Claisen-type condensation between methyl 2-(methylamino)benzoate and α,β-unsaturated carboxylates has been found to provide convenient access to 4-hydroxy-1,2-dihydroquinoline-3-carboxylate derivatives and 4-oxo-1,2,3,4-tetrahydroquinoline-3-carboxylates.
  • Masato Nanjo, Takashi Oda, Kunio Mochida
    Type: Article
    Subject area: OB
    2003 Volume 76 Issue 6 Pages 1261-1264
    Published: 2003
    Released: June 15, 2003
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    Bis[tris(trimethylsilyl)germyl]zinc, [(Me3Si)3Ge]2Zn, was prepared by the reaction of [tris(trimethylsilyl)germyl]lithium, (Me3Si)3GeLi(thf), with zinc chloride, ZnCl2, and by the reaction of tris(trimethylsilyl)germane, (Me3Si)3GeH, with diethylzinc, Et2Zn. The molecular structure of [(Me3Si)3Ge]2Zn was determined by spectroscopic and X-ray diffraction methods. In [(Me3Si)3Ge]2Zn, the two tris(trimethylsilyl)germyl ligands, (Me3Si)3Ge, are bonded in a linear fashion to the zinc atom and are staggered with respect to each other. The reactions of bis(germyl)zinc with substrates were also examined.
  • Vilas. D. Athawale, Priti. S. Pillay
    Type: Article
    Subject area: AM
    2003 Volume 76 Issue 6 Pages 1265-1271
    Published: 2003
    Released: June 15, 2003
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    In this article we review the synthesis and morphology as well as the physical and mechanical properties of full- and semi-interpenetrating polymer networks (IPNs) obtained from polyester based polyurethane (PU) and poly(butyl methacrylate) (PBMA). The polyurethane was subsequently interpenetrated with butyl methacrylate monomer and ethylene glycol dimethacrylate as a crosslinker by radical polymerization using benzoyl peroxide as an initiator. Both full and semi IPNs (PU/PBMA IPNs) were obtained as soft films when cast in a glass mold. All PU/PBMA IPNs were characterized with respect to the swelling (%), apparent densities, thermal stability, morphology and mechanical properties. The morphology of the IPNs was studied by scanning electron microscopy. The effects of variations of the blend ratios on the above-mentioned properties were examined. Increasing the polyurethane component in the composite system notably increased the mechanical properties of all the IPNs. Full-IPNs exhibited higher apparent densities, mechanical properties and thermal stability than the corresponding semi-IPNs.
  • Long-Biao Lai, Dong-Hwang Chen, Ting-Chia Huang
    Type: Article
    Subject area: AM
    2003 Volume 76 Issue 6 Pages 1273-1278
    Published: 2003
    Released: June 15, 2003
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    A novel Pd-doped Pt/Ti nanostructured electrode was prepared by the electrophoretic co-deposition of Pt and Pd nanoparticles on a Ti support in a reverse micellar solution of water/Aerosol OT/isooctane, followed by a heat treatment in air at 400 °C. The total catalyst loading (Pt and Pd) was fixed at 0.015 mmol/cm2, referred to the geometric area. The crystal structure, surface morphology, and elemental distribution of the resultant electrode were characterized by XRD, SEM, and SEM-WDS, respectively. The surface composition and electrocatalytic activity of the electrode were investigated by cyclic voltammetry in a solution of 0.5 M H2SO4 and a mixed solution of 0.1 M CH3OH and 1.0 M NaOH, respectively. The composition on the electrode surface could be controlled by adjusting the composition of the electrodeposition solution. Also, with increasing the Pd content on the electrode surface, the electrocatalytic activity of the Pd-doped Pt/Ti nanostructured electrodes for the oxidation of CH3OH first increased, and then decreased after reaching a maximum at a surface composition of 20 atom % Pd. When the Pd content on the electrode surface was larger than 60%, the electrocatalytic activity of the Pd-doped Pt/Ti nanostructured electrode was lower than that of the Pt/Ti electrode because most active sites were occupied by the relatively inactive Pd. This result revealed that the activity enhancement or diminution resulted from the doping of Pd in Pt at an atomic level might be achieved via the interaction between Pt and Pd nanoparticles. In addition, at a surface composition of 20 atom % Pd, the current density at 25 °C was 55 mA/cm2, revealing that the resultant electrode had a rather high current density and specific activity.
  • Ryoka Matsushima, Naoko Nishimura, Kuniaki Goto, Yoshiumi Kohno
    Type: Article
    Subject area: AM
    2003 Volume 76 Issue 6 Pages 1279-1283
    Published: 2003
    Released: June 15, 2003
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    Solid thin films of sugar gels containing ionic dyes, such as flavylium and thionine salts, exhibit extensive and vapor-specific color changes upon exposure to volatile organic compounds, such as methanol, ethanol, acetone, benzene, ether, and pyridine. Some of them show good vapochromic reversibility after repeated exposures, although extensive degradation occurs with pyridine vapor. Vapochromism has been explained in terms of solvation and stabilization of the dye molecules by permeated vapors, resulting in a shift of dye aggregation–deaggregation equilibria.
  • Akira Tsujiko, Kenji Kajiyama, Masatoshi Kanaya, Kei Murakoshi, Yoshih ...
    Type: Article
    Subject area: AM
    2003 Volume 76 Issue 6 Pages 1285-1290
    Published: 2003
    Released: June 15, 2003
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    The ion implantation method is applied to the improvement of the oxygen-evolution activity for metal oxide electrodes. The implantation of metal ions such as Co+, Zn+, and Ru+ into nanocrystalline RuO2 and RuxTi1−xO2 (x = 1/2 and 2/3) film electrodes caused negative shifts of current density (j) vs potential (U) curves for oxygen evolution by about 20–100 mV, indicating the lowering of the overvoltage for oxygen evolution. Detailed experiments have shown that the lowering of the overvoltage is neither due to a change in the chemical composition of the electrode surface nor due to an increase in the effective area of the electrode surface, but rather is due to production of certain crystal defects (such as atomic gaps) that can act as active sites for oxygen evolution. The result is of much interest, suggesting that the control of surface defect structures is a promising approach for the improvement of the oxygen evolution activity.
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