Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 70 , Issue 4
Showing 1-28 articles out of 28 articles from the selected issue
  • Noboru Watanabe, Hisashi Hayashi, Yasuo Udagawa
    1997 Volume 70 Issue 4 Pages 719-726
    Published: 1997
    Released: June 13, 2006
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    By means of inelastic X-ray scattering spectroscopy, the generalized oscillator strength (GOS) of liquid water has been experimentally determined over a range 0.69 ≤ q ≤ 3.59 a.u., where q is the momentum transfer. The Bethe surface was constructed from the GOS, and the loss function, the dielectric response function, and the static structure factor were deduced. It was found that the GOS of liquid water is dominated by individual molecular properties over the q range studied, and that the static structure factor agrees quite well with a calculation including electron-electron correlation effects.
  • Hiroshi Ichikawa, Hirotaka Kagawa
    1997 Volume 70 Issue 4 Pages 727-735
    Published: 1997
    Released: June 13, 2006
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    The total energy of a conjugated unsaturated hydrocarbon can formally be partitioned into the energy of π electrons and the frame energy. This type of partitioning has been used to study the role of π electrons; to know the relationship between the π-electronic structure and its energy, the molecular geometry has been varied. This paper examines the influences of such geometry change on the energy of π electrons from a basic point of view. It was found that there are four types of geometrical influences which disguise the relationship between the π-electronic structure and its energy. Contrary to this, the constrained Hartree–Fock method was shown to disclose the relationship between π-electronic structure and its energy clearly.
    Application of the constrained Hartree–Fock method to D6h and D3h benzenes showed that in a D6h benzene π electrons favor the symmetrically uniform distribution independently of the bond length and the partitioning method, while in a D3h benzene the uniform distribution of π electrons is destroyed. Analysis of gradients of partitioned energies with respect to the bond order at a D3h-distorted benzene indicated that π electrons favor a more uniform delocalization, but this is opposed by one- and two-electron potentials.
  • Masaru Nakagawa, Masahiro Rikukawa, Masayoshi Watanabe, Kohei Sanui, N ...
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 4 Pages 737-744
    Published: 1997
    Released: June 13, 2006
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    Organic photochrome azopyridiniums were systematically prepared by quaternizing azopyridines with either dimethyl sulfate or 1,3-propanesultone. Photochemical, electrochemical, and photoelectrochemical studies on the azopyridiniums as methyl sulfate, hexafluorophosphate, and zwitterionic compounds were carried out in aprotic solvents and in aqueous solutions. The azopyridiniums, which have 3-located quaternized nitrogens to the azo group, exhibited photochemical activity of trans cis isomerization. Quaternization of the pyridine moiety decreased the photochemical conversion between the trans and cis forms. The photochromic properties were influenced by an electronic effect of quaternized nitrogens and an electrostatic interaction of counter anions. In electrochemical studies, new redox-active azopyridiniums were found by using cyclic voltammetry and an electrochemical technique coupled with UV-vis spectroscopy. By the quaternization of azopyridines, the formal reduction potentials were shifted to a positive region up to −0.27 V vs. Fc/Fc+. The reversibility of the electrochemical reactions was strongly dependent on the location of quaternized nitrogen. The trans cis photoisomerization of electroactive azopyridiniums influenced their electrochemical properties. The photochromic molecules exhibited a photoelectric effect, which was a change in the cathodic limiting currents of azopyridiniums, reversibly modulated by ultraviolet light of an external stimulation.
  • Kohjiro Hara, Noriyuki Sonoyama, Tadayoshi Sakata
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 4 Pages 745-754
    Published: 1997
    Released: June 13, 2006
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    Electrocatalytic reduction of CO under high pressure (< 60 atm) using a gas diffusion electrode containing Pt catalyst (Pt-GDE) has been investigated. Acetic acid was formed at a high faradaic efficiency of 32% as a predominant CO reduction product at a constant current density of 200 mA cm−2 under CO 40 atm. Moreover, methane, ethane, ethylene, formaldehyde, acetaldehyde, ethanol, 1-propanol, and allyl alcohol were produced as CO reduction products. The selectivity of the reduction products depends remarkably on electrolysis conditions such as the current density, pressure of CO, and temperature. C2-compounds such as ethylene, ethanol, and acetic acid were preferentially formed at small current densities and/or high CO pressure conditions, whereas methane was predominantly produced at large current densities and/or low CO pressure conditions.
  • Shunlin Liu, Tetsuo Saji
    1997 Volume 70 Issue 4 Pages 755-760
    Published: 1997
    Released: June 13, 2006
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    Patterning dye films were obtained on a transparent polyester plate by ultraviolet (UV) light illumination of an alkaline suspension containing TiO2 particles, methylviologen dichloride (MVCl2), N,N-p-phenylenediamine (PPD), and coupler. The patterning films formed are of high resolution (10 μm). Influences of light intensity (Φ), amount of TiO2 particles, solution acidity, and illumination time on the film formation were studied. Regeneration of MV2+ by oxygen was found to be important for film formation.
  • Iwao Satake, Tadakazu Morita, Tamaki Maeda, Katumitu Hayakawa
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 4 Pages 761-765
    Published: 1997
    Released: June 13, 2006
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    The micellar properties of N,N,N,N′, N′,N′-hexamethyl-1,20-icosanediyldiammonium, or the corresponding di(1-pyridinium)alkanedioates OOC(CH2)nCOO (n = 2—10), were studied by conductivity and pyrene fluorescence measurements. In both systems, the critical micelle concentration (cmc) varied little up to n = 4, but decreased rapidly with a further increase in n. The binding degree (β) of the alkanedioate counter ion was virtually independent of the type of surfactant ion head group and gradually increased from 0.69 at n = 2 to 0.91 at n = 10. The observed n dependences of cmc and β were similar to those of the conventional ionic surfactants with an α,ω-type counter ion, indicating the importance of the hydrophobic interaction between the hydrocarbon part of the counter ion and the micellar core. On the basis of a phase-separation model, the transfer free energy per methylene group of the counter ion from aqueous-to-micellar environments was estimated to be about −1.0 RT. The fluorescence measurements suggest that the surface layer of the micelle becomes progressively loose as n decreases. The micelle aggregation numbers of the bis (trimethylammonium) salts are of the order of 50.
  • Naotoshi Nakashima, Yonekazu Deguchi
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 4 Pages 767-770
    Published: 1997
    Released: June 13, 2006
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    A self-assembled monolayer of 1-dodecanethiol (C12SH) on a gold electrode was prepared by dipping a polished bare electrode into an ethanolic solution of C12SH (1.0 mmol dm−3) for 10 min. The obtained modified electrode blocked the direct electron-transfer reaction of [Fe(CN)6]3− and [Fe(CN)6]4− with the underlying electrode. However, a pH-dependent redox compound, 4,4′-biphenyldiol (1) in solution, was permeable into the monolayer and gave well-defined cyclic voltammograms at both higher and lower pHs. Using this chemical-recognition ability of the modified electrode together with the formal potential shift of 1 according to the Nernst equation, pH–modulated vectorial electron transfer reactions were examined. At pH 3, cyclic voltammograms at the modified electrode in a 1 + [Fe(CN)6]4− aqueous solution revealed that one-way electron flow from [Fe(CN)]4− to the electrode via1 (oxidized form) occurred. On the contrary, at higher pHs (pH 9—11), the vectorial electron flow at the electrode in 1 + [Fe(CN)6]3− solution was reversed. A triggered change (‘switching’) between the anodic and cathodic vectorial electron transfer reactions by changing the pH was also possible at the C12SH-modified electrode in the presence of 1, [Fe(CN)6]4− and [Fe(CN)6]3− in solution. This finding may offer possibilities for the construction of functional molecular devices based on the tuning of rectified electron transfer reactions.
  • Takeshi Kawai
    1997 Volume 70 Issue 4 Pages 771-775
    Published: 1997
    Released: June 13, 2006
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    An order–disorder process in Langmuir–Blodgett (LB) films of dioctadecyldimethylammonium chloride (DODAC) has been studied by FT-IR ATR spectroscopy. This order–disorder process gradually occurred over a wide temperature range, and the transition was shifted to a higher temperature with the number of monolayers. In DODAC LB films immersed in water a similar thermotropic phase behavior was observed, except for the transition temperature. However, this behavior completely differed from that of cast film.
  • Jan Hrušák, Detlef Schröder, Helmut Schwarz, Suehir ...
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 4 Pages 777-787
    Published: 1997
    Released: June 13, 2006
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    The neutral and the lowest cationic (singlet and triplet) potential-energy surfaces of [Si, P, H2] have been explored by means of ab initio MO calculations at the G2 level of theory as well as the hybrid DFT (B3LYP/6-311G**) method. Contrary to the neutral and triplet surfaces, where the H2SiP+/0 isomers represent the global minima, for the singlet cation a doubly bridged P(H)2Si+ structure has been identified as the most stable isomer, with the non-bridged H2SiP+ species being significantly less stable (ΔE = 31.7 kcal mol−1 at G2). As far as the comparison of the two quantum-chemical methods (i.e. G2 and B3LYP) is concerned, the calculated relative energies ΔE are quite close to each other, with deviations smaller than 4 kcal mol−1. However, while the non-bridged SiPH2+ (1A′) represents a minimum at the G2 level, it could not be located using the hybrid DFT method. The computationally predicted singlet and triplet [Si, P, H2]+ potential-energy surfaces provide insight into the course of the ion/molecule reactions of Si+• with phosphine and P+ with silane, respectively, which were examined experimentally. Thus, the reaction of the doublet species Si+• with phosphine allows access to the non-classical, bridged P(H)2Si+ structure, while in the reaction of the P+ triplet cation with silane, no evidence for Si–P bond formation is obtained.
  • Debasis Das, Ashutosh Ghosh, Nirmalendu Ray Chaudhuri
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 4 Pages 789-797
    Published: 1997
    Released: June 13, 2006
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    [NiL3]C4O4 [L = 1,2-ethanediamine (en) and 1,2-N,N′-dimethylethanediamine (N,N′-dmen)], [NiL3]C4O4·nH2O [for L = 1,2-N-methylethanediamine (meen) and 2-methyl-1,2-propanediamine (ibn); n = 1, and for L = 1,2-propanediamine (pn); n = 2], and [NiL2C4O4]·2H2O [L = 1,2-N-ethylethanediamine (eten), 1,2-N-propylethanediamine (pren), 1,2-N,N-dimethylethanediamine (N,N-dmen) and 1,2-N,N′-diethylethanediamine (N,N′-deten)] have been synthesized by the addition of the respective diamines to finely powdered nickel(II)squarate dihydrate, NiC4O4·2H2O. All of the tris-species, except for [Ni(N,N′-dmen)3]C4O4 were also prepared by adding diamines to NiC4O4·2H2O dissolved in aqueous ammonia (25%). When the latter method was followed, the bis-species [NiL2C4O4] [L = eten, pren, 1,2-N-isopropylethanediamine (ipren), N,N-dmen, N,N′-dmen, and N,N′-deten] were also obtained. [NiL2C4O4] (L = en, meen, N,N′-dmen, pn, and ibn) were also prepared from their corresponding tris(diamine) species upon heating in the solid state. [Ni(ibn)3]C4O4·nH2O after dehydration underwent an irreversible endothermic (145—160 °C; ΔH = 6.5 kJ mol−1) phase transition without showing any visual color change. [Ni(ipren)2C4O4] exhibited a reversible phase transition (78—107 °C; ΔH = 1.4 kJ mol−1 for heating and 105—72°C; ΔH = −1.3 kJ mol−1 for cooling). The phase transitions are considered to have been due to conformational changes of the diamine chelate rings. All of the tris as well as bis(diamine) complexes possess an octahedral geometry, except for [Ni(ibn)2]C4O4, which is square-planar. The bis-species [NiL2C4O4] (L = eten, pren, N,N-dmen, and N,N′-deten) exists in two isomeric forms.
  • Akira Ohki, Masato Tsurugasaki, Yasunori Kondo, Kensuke Naka, Shigeru ...
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 4 Pages 799-804
    Published: 1997
    Released: June 13, 2006
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    The potentiometric responses of ion-selective electrodes (ISEs) based on various liquid anion-exchangers for poly(styrenesulfonate)s (PSSs) were examined. The liquid anion-exchangers included lipophilic monoammonium, monophosphonium, diphosphonium, and triphosphonium salts. The molecular weights of PSSs, which had narrow molecular-weight distributions (Mw/Mn < 1.2), were varied from 1.8 × 103 (PSS-1.8K) to 3.5 × 104 (PSS-35K). For PSS-1.8K, ISEs based on diphosphonium salts, polymethylenebis(trioctylphosphonium) dibromides 13, exhibited good responses, the response slope and linear response range being −20 to −21 mV/decade and 5.0 × 10−5—5.0 × 10−3equiv dm−3, respectively. As the molecular weight of PSS was increased, the linear response range became smaller, while the response slope was almost constant. Finally, PSS-35K gave almost no response. On the other hand, a wide molecular-weight distribution PSS (Mw/Mn = 3.6) provided a good response, although it had a high average molecular weight (Mw = 1.6 × 104). The selectivity coefficients for PSS over various anions of ISEs, based on diphosphonium and monophosphonium salts, were assessed.
  • Aniruddha V. Sherikar, Pradeep N. Phalke, Purushottom M. Dhadke
    1997 Volume 70 Issue 4 Pages 805-808
    Published: 1997
    Released: June 13, 2006
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    The extraction of platinum(II) from hydrochloric acid solution using bis(2-ethylhexyl) hydrogen phosphate in toluene was studied as a function of several variables, such as hydrochloric acid concentration, reagent concentration, metal ion concentration, temperature, effect of various diluents, and effect of various diverse ions. The proposed method was further applied for the separation of platinum from palladium, gold, and osmium in different ratios and to estimate the amount of platinum present in commercially available samples.
  • Hirochika Naganawa, Shoichi Tachimori
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 4 Pages 809-819
    Published: 1997
    Released: June 13, 2006
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    Complex-formation of nitric acid with tributyl phosphate (TBP) and the hydration of the complexes in dodecane were examined from the acid and water distribution data between the aqueous and organic phases at 298 K. The equilibrium constants were determined by analyzing the acid and water distribution data as functions of the TBP concentration in the organic phase, the aqueous acid activity, and the water activity. Three complexes (TBP·HNO3, (TBP)2·HNO3, and (TBP)3·HNO3) were found in the organic phase when the aqueous nitric acid concentration was not higher than 3 mol dm−3. The hydration numbers for these complexes were also obtained. The TBP·HNO3 was chiefly anhydrous, but partially a monohydrate. In contrast, the (TBP)2·HNO3 was only a monohydrate and (TBP)3·HNO3 was only a tetrahydrate. The TBP–HNO3–H2O stoichiometry, by taking account of these complexes in addition to the TBP hydrates and free nitric acid in the organic phase, applied very well, up to 2 mol dm−3 (54.6 vol%) TBP in dodecane without any activity correction.
  • Takashiro Akitsu, Seiko Komorita, Yoshihiko Kushi, Chunmin Li, Nobuko ...
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 4 Pages 821-827
    Published: 1997
    Released: June 13, 2006
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    Copper(II) complexes [CuL2(i-PrNH2)2·H2O] (1a), [CuL2(i-PrNH2)2] (1b), [CuL2(EtNH2)2·H2O] (2a), [CuL2(EtNH2)2]·CHCl3 (2b), [CuL2(EtNH2)2·H2O]·2CHCl3 (2c), and [CuL2(EtNH2)2·MeOH] (2d) (L = 5,5-diphenylhydantoinate) have been prepared. The crystal structures of 1a, 2c, and 2d were determined by X-ray analysis. Each CuN4O chromophore is a five-coordinated square-based pyramidal geometry. The axial Cu–O distances are Cu(1)–O(1)(water) = 2.362(10) Å, Cu(1)–O(1)(water) = 2.436(9) Å and Cu(1)–O(1)(MeOH) = 2.33(1) Å, for complexes 1a, 2c, and 2d, respectively. Intramolecular hydrogen bonds are formed between the carbonyl oxygens and amino hydrogens (C=O···H–N) as well as the axial ligand (C=O···H–O). The latter hydrogen bonds stabilize the axial ligand for coordination. Moreover, double intermolecular hydrogen bonds link the 5,5-diphenylhydantoinate ligands (C=O···H–N) belonging to be adjacent complex molecules in all three complexes. The electronic spectra of the complexes in the solid state and in chloroform solutions were determined at room temperature, and a considerable change in ligand field bands was observed. The five-coordinated complexes in the chloroform solutions release their axial water ligand and the CuN4O chromophore converts into a distorted tetrahedral CuN4 chromophore.
  • Tomohide Ichikawa, Kiyoshi Sawada
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 4 Pages 829-835
    Published: 1997
    Released: June 13, 2006
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    The protonation equilibria of two types of aminopolyphosphonates ((CH3)2−p(CH2PO3)pN(CH2)mN(CH2PO3)p(CH3)2−p) in aqueous solution were investigated by means of potentiometry and 31P NMR spectroscopy. The protonation behavior of diaminotetramethylenetetraphosphonate (p = p′ = 2) is significantly altered by a change in the number of methylene chains (m = 2, 3, 6). The protonations of the imino fragments of hdtmp, which is connected with a six methylene chain (m = 6), are essentially independent of each other, whereas edtmp, which is connected with a two methylene chain (m = 2), forms a hydrogen bond between both nitrogen atoms (NH+···N) in the mono protonated species. The ethylenediaminepolyphosphonates (m = 2), having an iminodiphosphonate group (p = 2, p′ = 0—2), show a peculiar 31P NMR behavior in which the signal shows a downfield shift at higher protonated species. However, eddmp (N,N′), having one methylenephosphonate group at each imino fragment (p = p′ = 1), does not show such an anomaly. These results indicate the existence of an intramolecular interaction between both fragments, such as a hydrogen bond of a protonated nitrogen atom with unprotonated phosphonates of another imino fragment, where two methylenephosphonate groups in one imino fragment are required to operate such an interaction.
  • Nobuhiro Takano, Akihito Nakade, Noboru Takeno
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 4 Pages 837-840
    Published: 1997
    Released: June 13, 2006
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    A poly[N-(5-hydroxypentyl)pyrrole] film-coated carbon-fiber electrode incorporating palladium metal microparticles was prepared and the catalytic ability in the electrochemical hydrogenation of organic compounds was investigated. This electrode exhibited a high catalytic ability and a strong physical stability with respect to hydrogen evolution. By using this electrode, the electrocatalytic hydrogenation for organic compounds in an organic solvent–buffer solution led to an efficient formation of hydrogenated products, such as saturated compounds, amino compounds, and hydroxy compounds, in high yields and current efficiencies. Furthermore, a catalytic polymer film electrode was successfully applied to the hydrogenative deprotection of a benzyl group and the dehalogenation of bromobenzene in electroreduction media.
  • Satori Ogoshi, Tomoyoshi Mita
    1997 Volume 70 Issue 4 Pages 841-846
    Published: 1997
    Released: June 13, 2006
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    The properties of gramicidin and its action on membranes were investigated by the use of monolayers, organic solvents and phospholipid vesicles in relation to cation-binding. The behavior of a gramicidin monolayer was strongly dependent on the organic solvent in which it was dissolved, showing the dependence of the solvent history. A gramicidin monolayer prepared from an ethanol solution caused a large conformational change upon the binding of K+, whereas that prepared from a 2,2,2-trifluoroethanol (TFE) solution showed no conformational change upon the binding of K+. In two organic solvents, gramicidin showed a different calorimetric behavior, due to a difference in conformation. Gramicidin in ethanol markedly decreased the phase-transition temperature and transition enthalpy (ΔH) upon the binding of K+, whereas gramicidin in TFE did not change in calorimetric behavior upon the binding of K+. Incorporating gramicidin into lipid bilayers led to a broadening of the transition and a decrease in the ΔH of the lipid, showing that about 20 lipid molecules per gramicidin molecule were immobilized. By binding K+ to the gramicidin channel, the perturbing effect of gramicidin for the lipid bilayers was depressed, implying aggregation among the peptide channels.
  • Minoru Sakurai, Masashi Murata, Yoshio Inoue, Akihiro Hino, Syouichi K ...
    1997 Volume 70 Issue 4 Pages 847-858
    Published: 1997
    Released: June 13, 2006
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    Molecular-dynamics simulation of aqueous solution of trehalose and maltose were performed to reveal any difference in the hydration ability between them, and to obtain information about how trehalose protects biological materials from water stress. Here, in order to examine the spatial distribution of water molecules around the hydroxy oxygen of sugar, a two-dimensional pair distribution function was introduced in addition to the conventional radial-distribution function. Both sugars were found to be extensively hydrogen bonded to solvent molecules. However, in a solution of maltose, defective hydrogen bonding was found at the exocyclic hydroxymethyl group of the reducing residue. Thus, maltose has a smaller value in hydration number than does trehalose. The translational diffusion of water molecules around trehalose has been found to be slightly more restrained than that around maltose. These findings are consistent with available experimental data concerning the solution properties of both sugars. On the basis of these results, the functional mechanism of tolerance is briefly discussed.
  • Michinori Oki, Takanori Hirose, Kiyoka Maeda, Maki Yanagawa, Yasukazu ...
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 4 Pages 859-868
    Published: 1997
    Released: June 13, 2006
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    Reactions of bromine chloride and iodine chloride with the olefinic bond in 1-(9-fluorenyl)-2-(1-methylethenyl)naphthalene rotamers were carried out to examine the product distributions. In the case of the ap-isomer bromine chloride yielded some bromo-olefins in addition to the addition product, whereas the yield of (8R*,14cS*)-8-bromomethyl-8-methyl-8,14c-dihydrodibenzo[a.l]aceanthrylene from the sp-isomer diminished with respect to the case of the reaction between bromine and the sp-isomer. The results are attributed to the low nucleophilicity and high proton affinity of the chloride ion. Iodine chloride afforded more addition product for the ap-isomer than the case of bromine chloride, whereas the sp-isomer reacted with iodine chloride to give a better yield of a cyclized compound, (8R*,14cS*)-8-iodomethyl-8-methyl-8,14c-dihydrodibenzo[a,l]aceanthrylene, than that of the cyclized compound from bromine chloride. Such results are attributed to the better stabilizing effects of an iodo substituent on a β-carbocation than a bromo one. Populations of ap and sp rotamers of 1-(9-fluorenyl)-2-[(E)-2-halo-1-methylethenyl]naphthalenes at equilibrium were unusual in the sense that the ap-isomer of the sterically more crowded iodo compound was favored relative to the less crowded chloro compound. UV absorption spectra were not conclusive for charge transfer interactions but X-ray crystallography of these compounds revealed that the olefinic carbons in the ethenyl group were attracted to the fluorene ring significantly.
  • Yukie Mori, Koko Maeda
    1997 Volume 70 Issue 4 Pages 869-875
    Published: 1997
    Released: June 13, 2006
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    The spectral and photochemical properties of the title compound 1 and bis(9-anthrylmethyl)amine (2) have been investigated. The fluorescence spectrum of 1 in methylcyclohexane showed an emission from the locally excited state of the anthracene part and a weak broad emission at 410—550 nm from the intramolecular exciplex. The fluorescence quantum yields of 1 and 2 decreased along with an increase in the solvent polarity. Both 1 and 2 underwent intramolecular [4+4] cycloaddition. The quantum yield of the cyclomerization of 1 was 0.24 in acidic methanol, while in MeCN the reaction was completely quenched by an intramolecular electron transfer from the amino group to the excited anthracene moiety. Excitation of the cyclomer from 1 at 285 nm brought about fluorescene from both the locally excited anthracene and the exciplex state, indicating that adiabatic cycloreversion took place on the S1 potential surface. To investigate the conformations, the crystal structures of 1 and 2 were determined and PM3 calculations were performed for 1–H+. The calculations indicate that a conformer in which the two chromophores are located close to each other has a higher energy then other stable conformers.
  • Shigekazu Yamazaki
    1997 Volume 70 Issue 4 Pages 877-883
    Published: 1997
    Released: June 13, 2006
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    The methyltrioxorhenium-catalyzed oxidation of secondary amines and primary amines with hydrogen peroxide has been carried out. The oxidation of secondary amines afforded nitrones in good-to-excellent yield. Benzylamines were selectively oxidized to oximes, while general primary alkylamines possessing the α-C–H bond gave mixtures of oximes, nitroso dimers, and azoxy compounds.
  • Ken-ichi Sato, Akira Yoshitomo, Yoshimitsu Takai
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 4 Pages 885-890
    Published: 1997
    Released: June 13, 2006
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    An efficient construction of the β-D-mannosidic, 2-Acetamido-2-deoxy-β-D-mannosidic, 2-deoxy-2-fluoro-β-D-mannosidic, and 2-deoxy-β-D-arabino-hexopyranosidic units from the same intermediate, 2-4-bis(O-trifluoromethylsulfonyl) derivative of β-D-galactoside, was achieved in good yields in a stepwise inversion at C-4 and C-2 by using cesium acetate, n-Bu4NN3, n-Bu4NF, and n-Bu4NBH4. A convenient and practical protection of β-D-mannoside to the straightforward synthesis of antennary oligosaccharides was also achieved by using cesium trifluoroacetate.
  • Hideji Osuga, Hitomi Suzuki, Kazuhiko Tanaka
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 4 Pages 891-897
    Published: 1997
    Released: June 13, 2006
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    Optically active 2-(hydroxymethyl)- and 2-(ethylthiocarbonyl)[1]benzothieno[5′,4′ : 2,3][1]benzothieno [4′,5 : 4,5]thieno[3,2-f]quinolines containing π-excessive thiophene and π-deficient pyridine units were prepared by the use of exo-3-amino-2-hydroxybornane as a chiral auxiliary. This procedure consists of separation of the helical diastereomers prepared by photocyclization of 1,2-diarylethylenes and removal of the chiral auxiliary by a thiolate ion. Large scale preparation of the helicenes can be accomplished by a modified procedure of the photocyclization reaction. Optical purities of both enantiomers of 2-(hydroxymethyl)- and 2-(ethylthiocarbonyl)[1]benzothieno[5′,4′ : 2,3][1]benzothieno[4′,5′ : 4,5]thieno[3,2-f]quinolines were >99.5%. Their absolute configurations were determined by comparison of CD spectra.
  • Makoto Tamaki, Seiji Komiya, Sadatoshi Akabori, Ichiro Muramatsu
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 4 Pages 899-904
    Published: 1997
    Released: June 13, 2006
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    To investigate the contribution of the D-Phe–Pro–Val sequence in the direct formation of gramicidin S (GS) by the dimerization–cyclization of pentapeptide-active esters having no protecting group on the side chain of the Orn residue, the cyclization of four H–X–Pro–Y–Orn–Leu–ONSu’s (X = L- or D-Phe, Y = L- or D-Val, –ONSu = succinimide ester) was examined. Only H–D-Phe–Pro–Val–Orn–Leu–ONSu gave semi-GS (cyclic monomer) and GS (cyclic dimer) in yields of 15 and 38%, respectively. The active ester with a D-Phe–Pro–D-Val sequence produced exclusively [D-Val]–semi-GS in 58% yield. On the other hand, the active esters having Phe–Pro–Val and Phe–Pro–D-Val sequences did not yield any amount of cyclic monomer and cyclic dimer. The change in the configurations of the Phe and Val residues around the Pro residue greatly affected the CD spectra in ethanol and the 1H NMR spectra in DMSO-d6 of the pentapeptide ethyl esters corresponding to four H–X–Pro–Y–Orn–Leu–ONSu’s. A good correlation among the CD spectra, NMR spectra of the pentapeptide ethyl esters, and the main products in the cyclization of the active esters was found.
  • Kazuhiko Sato, Masao Aoki, Masami Ogawa, Tadashi Hashimoto, David Pany ...
    1997 Volume 70 Issue 4 Pages 905-915
    Published: 1997
    Released: June 13, 2006
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    A catalytic system consisting of sodium tungstate dihydrate, (aminomethyl)phosphonic acid, and methyltrioctylammonium hydrogensulfate, effects the epoxidation of olefins using 30% hydrogen peroxide with a substrate-to-catalyst molar ratio of 50—500. The reaction proceeds in high yield without solvents, or, alternatively, with added toluene under entirely halide-free conditions. Lipophilic ammonium hydrogensulfate, which replaces the conventional chloride, and an (α-aminoalkyl)phosphonic acid are crucial for the high reactivity. This method is operationally simple, environmentally benign, and much more economical than the oxidation with m-chloroperbenzoic acid, allowing for a large-scale preparation of epoxides. Various substrates including terminal olefins, 1,1- and 1,2-disubstituted olefins, cyclic olefins, and tri- and tetrasubstituted olefins as well as allylic alcohols, esters, α,β-unsaturated ketones, and ethers can be epoxidized in high yield. The scope and limitations of this new reaction system are discussed.
  • Yoshihito Kayaki, Isao Shimizu, Akio Yamamoto
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 4 Pages 917-927
    Published: 1997
    Released: June 13, 2006
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    Cationic solvent-coordinated organopalladium complexes [PdR(solvent)(L)2]+A 2 (R = organic group, L = tertiary phosphine, A = counter anion such as BF4, PF6, and triflate) have been prepared by removal of the halide ligand X in neutral complexes, [PdR(X)(L)2] 1 with an equimolar amount of silver salt. The cationic complexes 2 show much greater rates of CO insertion than the parent neutral complexes 1. Comparison of the reactivities of 2 and of the other cationic complexes [PdMe(Y)(L)2]+ (Y = strongly coordinating ligand such as tertiary phosphine, pyridine, and isocyanide) toward CO insertion indicates that availability of the site for incoming CO is a dominant factor in determining their reactivities. In contrast, insertion of isocyanides into Pd–C bond is not hindered by occupation of the vacant site in the organopalladium complexes. Successive hetero-insertions of isocyanide and CO into Me–Pd bond, i.e., CO insertion into the 1-iminoalkyl–Pd bond and isocyanide insertion into the acetyl–Pd, were realized. Olefins were found not to undergo the insertion into Pd–Me bond in phosphine-coordinated complexes, whereas insertion of methyl acrylate into the Me–Pd bond in a cationic complex having bipyridine ligand was observed.
  • Mizue Fujio, Makoto Ohe, Kazuhide Nakata, Yutaka Tsuji, Masaaki Mishim ...
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 4 Pages 929-936
    Published: 1997
    Released: June 13, 2006
    JOURNALS RESTRICTED ACCESS
    Substituent effects on the solvolysis rates of α-t-butyl-α-neopentylbenzyl and α-t-butyl-α-isopropylbenzyl p-nitrobenzoates in 50% (v/v) aqueous EtOH at 75 °C were correlated with the Yukawa–Tsuno equation to give ρ = −3.37 and r = 0.78, and ρ = −3.09 and r = 0.68, respectively. The reduction in r values from r = 1.00 characteristic of full conjugation is ascribed to deviation from coplanarity of the carbocationic center and the benzylic π-system in the transition state. The torsion angles for twisting out of coplanarity were estimated from the relationship r/rmax = cos2 θ for a series of sterically hindered tertiary dialkylbenzylic solvolyses. The torsion angles assigned for these twisted benzylic systems are in good agreement with theoretically calculated dihedral angles of the corresponding 6-31G*optimized carbenium ions. This identity provides convincing evidence for occurrence of steric inhibition of resonance through loss of coplanarity, and, in turn, provides strong support for our characterization of the r value as a resonance demand parameter reflecting the degree of resonance (π-delocalization) interaction between an aryl group and the reaction site.
  • Katsuhiro Aoyagi, Toshihiko Haga, Hiroo Toi, Yasuhiro Aoyama, Tadashi ...
    1997 Volume 70 Issue 4 Pages 937-943
    Published: 1997
    Released: June 13, 2006
    JOURNALS RESTRICTED ACCESS
    A variety of 3-perfluoroalkyl pyrroles were prepared by reaction of β-perfluoroalkyl α,β-unsaturated carbonyl compounds with p-tolylsulfonylmethyl isocyanide in moderate yields. Tetrakis(perfluoroalkyl)porphyrins were readily obtained by oxidative cyclization of 3-alkyl-2-hydroxymethyl-4-perfluoroalkylpyrroles in acidic media, including water-soluble 3,8,13,18-tetrakis(p-carboxybenzyl)-2,7,12,17-tetrakis(trifluoromethyl)porphyrin. The pKa value for the monoprotonation of its inner nitrogen is less than 1, while that of Copro-I is 7.2. Diprotonation at the inner nitrogen occurs only in concd HCl, while the pKa value of the corresponding non-fluoro porphyrin is 4. The reduction potential of 3,8,13,18-tetrakis(p-methoxycarboxybenzyl)-2,7,12,17-tetrakis(trifluoromethyl)porphyrin was shifted by 580 mV to a less negative value.
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