Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 69 , Issue 4
Showing 1-40 articles out of 40 articles from the selected issue
  • Masanobu Hidai, Youichi Ishii
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 819-831
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    The hydrazido complexes trans-[MX(NNH2)(dppe)2]+ (3) and cis,mer-[MX2(NNH2)(PMe2Ph)3] (4) (M = Mo, W; X = halogen; dppe = 1,2-bis(diphenylphosphino)ethane), which are readily derived from dinitrogen complexes trans-[M(N2)2(dppe)2] (1) and cis-[M(N2)2(PMe2Ph)4] (2) by protonation with acid, undergo condensation with aldehydes or ketones (RR′C=O) to give a series of diazoalkane complexes, trans-[MX(NNCRR′)(dppe)2]+ and cis,mer-[MX2(NNCRR′)(PMe2Ph)3]. The diazoalkane ligand in those complexes has a singly-bent structure with the N–N–C bond angle of ca. 120° and the essentially linear N–N–M bond, and may be regarded as a four-electron-donating ligand. Owing to the conjugate structure including the metal center M≡N–N=CRR′, the diazoalkane complexes exhibit various reactivities including nucleophilic addition, deprotonation, conjugate addition, and reductive dimerization. Condensation of hydrazido complexes 3 and 4 with dialdehydes or their equivalents leads to complexes with nitrogen heterocyclic ligands incorporating the terminal nitrogen atom by way of the cyclization of intermediary diazoalkane complexes. By this method are prepared complexes containing phthalimidine, 1,3-dihydro-2H-pyrrol-2-one, 1,5-dihydro-2H-pyrrol-2-one, and pyrrole moieties. Interestingly, the (1-pyrrolyl)imido complexes with dppe ligands (26; M = Mo, W) undergo unusual electrophilic substitution reactions at the β-position of the pyrrole ring. Various types of organonitrogen compounds such as acetone azine, pyrazoles, phthalimidines, pyrroles, and N-aminopyrrole are liberateded from the above complexes in good yields. As a typical reaction, pyrrole and N-aminopyrrole are formed by the LiAlH4 reduction of complexes 26. In this reduction, tetrahydrido complexes [MH4(dppe)2] (M = Mo, W) are obtained as the metal products, which can be converted back to the starting dinitrogen complexes 1. Thus, a synthetic cycle for the formation of pyrrole and N-aminopyrrole from dinitrogen has been accomplished by using dinitrogen complexes 1.
  • Ken’ichi Takeuchi, Yasushi Ohga
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 833-851
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    The 1-adamantyl cation reacts with carbon monoxide and adamantane in the presence of a superacid to give 3-hydroxy-4-homoadamantyl 1-adamantanecarboxylate in good yields. This finding has permitted the development of a synthetic route by using ring-expansion of bridgehead aldehydes with benzoic trifluoromethanesulfonic anhydride to give various bicyclic and tricyclic 1,2-diols having different ring flexibility. The diols are transformed to bridgehead compounds having an oxo or a methylene substituent on the vicinal position, which can be used as substrates showing different degrees of π-conjugation between these substituents and the bridgehead cationic center in the transition state of solvolysis. The solvolysis rate ratio of 2-methylene vs. parent bridgehead compounds markedly increases with the ring-flexibility, indicating that the allylic conjugation can be enhanced by increasing ring flexibility. However, the rate ratios for 2-oxo (or α-carbonyl) vs. parent bridgehead compounds are essentially constant, irrespective of the ring flexibility, suggesting the unimportance of π conjugative stabilization of α-carbonyl carbocations. On the contrary, 3-oxo (or β-carbonyl) bridgehead compounds solvolyze markedly faster than expected and support the proposal of pC(1)+σC(2)C(3) ↔ n(CO) hyperconjugative interaction. The comparison of the solvolysis rates of (Z)- and (E)-2-ethylidene bridgehead compounds having a rigid structure provides a new method to evaluate the importance of F-strain effects in solvolysis.
  • Chihiro Wakai, Masaru Nakahara
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 853-860
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    2H NMR spin-lattice relaxation times have been measured to obtain the rotational correlation times τ2R for benzene C6D6 (50 mol m−3) in various organic solvents, such as benzene (C6H6), hexane, decane, carbon tetrachloride, chloroform, dichloromethane, methanol, ethanol, 1-propanol, 1-butanol, and acetonitrile over the widest possible range of temperature. Plots of the determined values of τ2R against solvent viscosity η divided by temperature T are linear in the apolar and polar aprotic solvents, as predicted by the Stokes–Einstein–Debye (SED) law. However, the plots of τ2R vs. η/T in the alcohols are concave upward, the slope in the high temperature region being ca. 2 times as large as that in the low temperature region. The nonlinearity and the decrease in the slope reflect the influence of the hydrogen-bonded solvent structure. For the benzene rotation in solutions, fairly good positive linear correlations are found between the slopes and the negative dissolution enthalpies at infinite dilution at room temperature. These results indicate an important role played by attractive solute–solvent interactions in controlling the molecular rotation in solution.
  • Mikiya Yamada, Hiromi Tobita, Shinji Inomata, Hiroshi Ogino
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 861-867
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    The reactions of [CpS12Fe2(CO)4] and [CpS22Fe2(CO)4] with elemental sulfur afforded a tetrairon cluster containing two end-on type S2 ligands [CpS14Fe4S6] (1) and a diiron complex containing an end-on type S2 and a side-on type S2 ligands [CpS22Fe2S4] (2), respectively, where CpS1 and CpS2 stand for mono- and bis(trimethylsilyl)cyclopentadienyl ligands, respectively. From these results and the previously reported results which were obtained for the reactions of [Cp2Fe2(CO)4] and [Cp*2Fe2(CO)4] with elemental sulfur, it is suggested that [Cp′2Fe2S4] is an intermediate to give tetrairon sulfur clusters, where Cp* and Cp′ denote pentamethylcyclopentadienyl and substituted cyclopentadienyl ligands, respectively. X-Ray crystal structure analysis was carried out for the compounds 1 and 2. Crystallographic data are as follows: 1: Monoclinic, P21/c, a = 17.302(6), b = 18.646(3), c = 15.310(4) Å, β = 120.71(2)°, V = 4246(2) Å3, Z = 4, and R = 0.061 for 5850 reflections with |Fo| > 3σ(Fo); 2: Triclinic, space group , a = 12.602(2), b = 12.891(2), c = 11.401(1) Å, α = 114.52(1), β = 95.45(1), γ = 88.39(1)°, V = 1677.5(4) Å3, Z = 2, and R = 0.046 for 7343 reflections with |Fo| < 3σ(Fo).
  • Kikuo Miyokawa, Shigeko Ozaki, Takayuki Yano
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 869-873
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    The gas-phase photobromination of fluoroethane was investigated in the temperature range 80—150 °C in both the presence and absence of chloroethane as an external competitor. The rate constant for α-hydrogen abstraction in CH3CH2F was redetermined relative to that in CH3CH2Cl, and the abstraction of β-hydrogen was measured in the internal competition. The relative rates were combined with the known rate parameters for the bromination of C2H6 to obtain the absolute rate constants (cm3 mol−1 s−1): k(α) = (6.50 ± 3.58) × 1012 exp [−(10360 ± 370)/RT] and k(β) = (3.42 ± 1.95) × 1012 exp [−(12950 ± 390)/RT].
    Using a justifiable approximation concerning the magnitude of the activation-energy difference for the reverse reactions between any two competitors with similar complexity the following thermochemical quantities (kcal mol−1) have been derived: ΔH°f(CH3CHF) = −16.8 ± 2, ΔH°f(CH2CH2F) = −14.2 ± 2, D°(CH3CHF–H) = 98.2 ± 2, D°(CH2FCH2–H) = 100.8 ± 2, and D°(CH2CH2–F) = 45.6 ± 2. The influence of halogen substitution on the rate parameters of hydrogen abstraction from monohaloethanes is discussed.
  • Akira Yamaguchi, Tsunehisa Okuno, Kunio Awaga
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 875-882
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    Organic radical cations, 4,4,5,5-tetramethyl-2-(1-methyl-3 or 4-pyridinio)-3-oxide-4,5-dihydro-1H-1-imidazolyloxyl (or, m- and p-N-methylpyridinium nitronyl nitroxides, abbreviated as m- and p-MPYNN+, respectively), were found to crystallize with magnetic counter anions, MCl42− (M = Mn2+ (S = 5/2) and Co2+ (S = 3/2)), although the MnCl42− salts were rather air-sensitive. X-Ray full-crystal analyses were carried out on the stable CoCl42− salts. The structure of (m-MPYNN+)2CoCl42− crystallizes in the monoclinic P21/c space group, while that of (p-MPYNN+)2CoCl42− belongs to the triclinic space group. Although (m-MPYNN+)2MnCl42− and (p-MPYNN+)2MnCl42− were not stable enough for an X-ray full data collection, they were indicated to be isostructural to the corresponding CoCl42− salts, respectively, by their diffractions of 20 > θ > 25°. Variable-temperature magnetic susceptibility measurements reveal a clear contrast between the (m-MPYNN+)2MCl42− and (p-MPYNN+)2MCl42− salts. The two (m-MPYNN+)2MCl42− salts exhibit a ferromagnetic behavior independently of MCl42−, which is attributable to a m-MPYNN+ dimer. However, the magnetic properties of two (p-MPYNN+)2MCl42− salts are strongly dependent on the MCl42− anion: (p-MPYNN+)2MnCl42− exhibits an antiferromagnetic interaction in opposition to a ferromagnetic one in (p-MPYNN+)CoCl42−. The magnetic difference between them can be qualitatively understood in terms of a charge-transfer interaction between MCl42− and p-MPYNN+, in which the difference in the electronic structure between the Mn2+ and Co2+ ions is reflected.
  • Masakatsu Yonese, Masatoshi Kondo, Isamu Miyata, Sin-ichi Kugimiya, Sh ...
    1996 Volume 69 Issue 4 Pages 883-889
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    The effects of the molar masses of solutes on permeability through poly(vinyl alcohol) PVA gel membranes were studied using polyethylene glycol having a wide range of molar masses and other solutes, such as electrolytes, glucose, and maltose. Furthermore, the effects of the network structure and fixed charges on the permeability were studied using opaque, transparent, and charged PVA gels. The permeability coefficients of solutes through PVA gel membranes (P) depended on the hydrodynamic radius of the solute (d0) and the mesh sizes of the network (ξ). When interactions between the matrix and the solute were negligible, the normalized permeability coefficients (P/D0) were found to be the scaling function of ξ/d0.
  • Kayako Hori, Yoshiko Koma, Minako Kurosaki, Koichi Itoh, Hidehiro Ueku ...
    1996 Volume 69 Issue 4 Pages 891-897
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    Four different solid phases were found for the title compound: square-plate and needle crystals, which are metastable, a solid found in a collapsed plate crystal and the most stable crystalline phase found in a commercially available powder specimen. The phase transition behavior of each solid to the nematic phase was investigated by DSC. The phase relations are proposed in terms of Gibbs energy and temperature diagram. The structure of the plate crystal has been determined at 243 K. The crystal has a distinct smectic-like structure composed of bilayers. The CN groups are closely arranged between antiparallel molecules within a bilayer, resulting in infinite networks with the C–N distances; 3.41—3.64 Å.
  • Tatsuo Ishikawa, Hiroshi Saito, Akemi Yasukawa, Kazuhiko Kandori
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 899-907
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    Calcium hydroxyapatites (CaHAP) substituted with Fe3+ ions of different atomic ratios Fe/(Ca + Fe) = XFe from 0 to 0.23 were synthesized and characterized by various methods. The number of Ca2+ ions in CaHAP substituted by one Fe3+ ion was higher than one, implying that the formation of cation vacancies and the protonation of PO43− ions are caused by Fe(III)-substitution. XFe of the surface layer of the particles determined by XPS was less than the total XFe. IR spectra of Fe(III)-substituted CaHAP contain a band at 3707 cm−1 assigned to the surface Fe–OH groups in addition to the surface P–OH bands at 3688, 3677, and 3658 cm−1. With an increase in XFe, the amount of irreversible adsorption of CO2 decreased whilst those of CH3OH and H2O first decreased and then increased. IR results showed that the surface Fe–OH groups act as stronger irreversible adsorption sites for CO2 and CH3OH compared to the surface P–OH groups.
  • Kazuya Saito, Isao Ikemoto
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 909-913
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    Lattice-dynamics calculations have been made on crystalline trans-stilbene under an atom–atom potential approximation, using both flexible and rigid molecular models in order to clarify the existence of the molecular motion suggested for explaining the abnormal bond-length of the central C=C bond. The intramolecular twisting of the benzene rings strongly couples with the overall rotation of the molecule in some manner, including the suggested manner. The coupled modes form phonon branches and show little dispersion.
  • Kazuhiko Ohashi, Kei Adachi, Nobuyuki Nishi
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 915-924
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    The “unimolecular” dissociation processes of benzene cluster ions prepared by resonant 2-photon ionization (R2PI) of neutral clusters were investigated by using a time-of-flight mass spectrometer equipped with a reflectron. The dissociation rates were determined for fast-decay processes (kfast) in the acceleration region and slow dissociations (kslow) in the drift region of the spectrometer. The ejection of one neutral molecule was a dominant dissociation channel of small (C6H6)n+ in the drift region; in addition, the ejection of two molecules was observed for n − 2 ≥ 14. These size-specific dissociation channels and the size dependence of the kslow values imply a closing of the first shell of (C6H6)n+ at n = 14. The magnitude of both kfast and kslowwas found to be independent of the excess energy upon R2PI, suggesting rapid cooling of the nascent hot ions by prompt dissociation within the laser focus. For slow dissociation within a well-defined time window, the measured values of kslow were compared with those calculated according to a statistical theory of unimolecular reaction. The comparison deduced the average internal energies of (C6H6)n+ at ca. 1 μs after preparation.
  • Tahei Tahara, Hiro-o Hamaguchi
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 925-931
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    The fluorescence lifetimes of jet-cooled trans-stilbene were measured for twenty eight S1 vibronic levels in the 1300—1700 cm−1 region above the 0–0 transition. All fluorescence decay curves were well fitted to single exponential functions in the 0—3 ns time region. It was found that the fluorescence lifetime decreases monotonically with the increase of the excess vibrational energy. No anomalous lifetime dependence on the vibronic level was observed. The (time-integrated) dispersed fluorescence from the corresponding vibronic levels was also measured. The excitation of all twenty eight levels gave indistinguishable fluorescence spectra exhibiting only broad features, indicating that the IVR rate is much larger than the radiative decay rate regardless of the fundamental, overtone or combination levels. No direct evidence supporting the existence of a mode-selective isomerization channel was obtained.
  • Andrei V. Afonin, Alexander V. Vashchenko, Hideaki Fujiwara
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 933-945
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    The hydrogen bond-like intramolecular specific interactions between the α-hydrogen of the vinyl group and endo-cyclic nitrogen are discovered in the hetaryl vinyl ethers, having the vinyloxyl group neighboring to the endocyclic nitrogen by the 1H and 13C NMR data. It is confirmed by AM1 calculations. The intramolecular specific interaction results to the downfield shift of the α-proton signal by 1 ppm, α-carbon signal by 4—5 ppm, the increase of their one-bond coupling constant by 6—7 Hz, and upfield shift of nitrogen by 17—20 ppm, as it was shown by the regression and dispersion analysis of 1H, 13C, and 15N parameters of wide series of aryl and hetaryl vinyl ethers. The cluster analysis of the spectral data indicates the anomaly of common combination of vinyloxyl group parameters in ethers, possessing the intramolecular specific interaction in comparison with ethers which have no such interaction. The factor analysis of spectral parameters shows that influence of specific interaction on the α-proton and α-carbon chemical shifts as well as their one-bond coupling constant prevails over other structural and electronic effects. In accordance with the AM1 calculation, the hetaryl vinyl ethers possessing the intramolecular specific interaction are more planar that is confirmed by 13C and 17O NMR data.
  • Fumio Shimizu, Kazumasa Yoshikai, Hiroshi Kawano, Yoshinori Nibu, Hiro ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 947-952
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    The Raman active inter- and intramolecular vibrations of the [1H10]- and [2H10]p-xylene crystals were studied under various pressures between 1 atm and 7.5 GPa. The pressure effect of the frequency of the Raman bands due to the intermolecular vibrations indicates that the coupling between the intramolecular torsional vibration of the methyl group and the intermolecular rotational vibrations takes place under about 1 and 2.5 GPa in the [1H10]- and [2H10]p-xylene crystals, respectively. The calculated pressure-induced frequency shift of the intramolecular vibrations explains fairly well the observed frequency shifts and supports the conclusion given in the previous work that the contribution of the first-order differential of the intermolecular potential to the pressure-induced frequency shift is vanishingly small when the potential is well approximated.
  • Shinji Tanaka, Manabu Sugimoto, Hajime Takashima, Masahiko Hada, Hiros ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 953-959
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    The 129Xe chemical shifts of the complexes XeF2n, XeF2n−1+ and XeOnF6−2n (n = 1—3) are studied theoretically by ab initio finite perturbation method. The first-order higher basis functions (FOBFs) are added to the standard basis set for removing the gauge-dependence. The calculated values of the Xe chemical shifts agree reasonably with the experimental values. Though the electronic configuration of Xe is the closed shell 5s25p6, the electronic mechanism of the Xe chemical shift is shown to be the p-mechanism. Namely, the dominant term in the Xe chemical shift is the paramagnetic term and it is mainly governed by the Xe valence p AO contribution. Actually, as expected, the Xe chemical shifts show the U-shaped dependence on the number of the Xe valence p electrons. The diamagnetic term is small and depends linearly on the number of the ligands.
  • Kenzi Tamaru
    1996 Volume 69 Issue 4 Pages 961-962
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    A new adsorption isotherm is proposed, taking the adsorption-assisted desorption into consideration for the first time. The new adsorption isotherm is in reasonable agreement with the experimental data.
  • Nighat Fahmi, Chitra Saxena, Ranvir V. Singh
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 963-969
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    In this article a brief account of the synthesis, stereochemistry, and biochemical behavior of palladium(II) complexes of benzylidenehydrazinecarboxamide or -carbothioamide is presented. The bimolar addition and substitution products have been characterized by elemental analyses, conductance measurements, molecular-weight determinations, magnetic susceptibilities, and spectral studies viz., IR, 1H NMR, 19F NMR, and UV. The data support the binding of sulfur or oxygen and nitrogen to the palladium in and (X is O or S) types of complexes. The square-planar geometry has been proposed. The representative free ligands () and their respective metal complexes were tested in vitro against a number of microorganisms to assess their antimicrobial properties and in vivo to test their sterilizing potential. The results are indeed positive.
  • Masashi Hojo, Hiroshi Hasegawa, Hitoshi Yoneda
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 971-976
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    The salt effects on the proton-transfer from CF3COOH to an acid-base indicator, ‘Methyl Yellow’ [p-(dimethylamino)-azobenzene], were examined in acetonitrile by means of spectrophotometry. The addition of LiClO4 to the indicator (Ind) and CF3COOF mixture (both 2.0 × 10−4 mol dm−3) caused an increase and a successive decrease in the absorbance (λmax = 514 nm) of IndH+. The promoted increase of the IndH+ concentration with increasing concentration of LiClO4 was explained on a quantitative basis concerning the formation of a triple cation, CF3COO(Li+)2, as well as an ion pair, CF3COOLi+: Ind–CF3COOH + 2 Li+ IndH+ + CF3COO(Li+)2. The successive decrease in the absorbance at 514 nm with a large excess of LiClO4 was attributed to an ion-exchange reaction: IndH+ + Li+ IndLi+ + H+. The addition of NaClO4 to Ind–CF3COOH caused only an increase in the IndH+ concentration, and no deprotonation from IndH+. Alkaline-earth metal ions (M2+ = Mg2+, Ca2+, Sr2+, and Ba2+) promoted protonation by the formation of complex species, CF3COOM2+. Although distinct deprotonation from IndH+ was observed with Mg(ClO4)2, no deprotonation occurred with Ba(ClO4)2. The effects of the chloride ion (Et4NCl) on deprotonation from IndH+ (In + CF3SO3H) were explained by the formation of homoconjugated species (HCl2), and not by the mere formation of HCl. The apparent changes in pH or the Hammett acidity function with the presence of various salts were elucidated by the ‘complex’ formation in acetonitrile.
  • Mitsuru Sano, Hiromitsu Sago, Atsuko Tomita
    1996 Volume 69 Issue 4 Pages 977-981
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    The oxidation of [Ru(NH3)5(butyl sulfoxide)]2+ by cis-[Ru(NH3)4(pyridine-4-carboxamide)2]3+ has been studied as a case of an electron transfer reaction accompanied by a structural change. Even in an excess of one of the reaction partners, the reaction shows complex kinetic behavior. Treatment of the experimental data points to a mechanism in which the first step is an up-hill electron transfer between the complexes and in which the second step involves isomerization of the unstable sulfoxide complex produced in the first step.
  • Yoshitaka Yamaguchi, Hiroshi Nakazawa, Tomonori Itoh, Katsuhiko Miyosh ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 983-995
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    Group 6 transition-metal phosphite complexes, fac-[(bpy)(CO)3M{PXY(OMe)}] (M = Cr, Mo, and W; XY = (NEt2)2, 1a; N(Me)CH2CH2O, 2a; (NEt2)(OMe), 3a; OCMe2CMe2O, 4a; (OMe)2, 5a) have been prepared and subjected to the reaction with BF3·OEt2. In these reactions, cationic phosphenium complexes [(bpy)(CO)3M{PXY}]+ are formed by an OMe abstraction as an anion from the phosphorus ligand for 1a, 2a, and 3a (M = Mo, W). The reaction of 3a (M = Cr) yields fac-[(bpy)(CO)3Cr{P(OMe)2F}] (Cr-5c) and [(bpy)(CO)3Cr{P(NEt2)F2}] (Cr-7d). In the reaction of 4a and 5a for all group 6 congeners, an OMe/F substitution reaction takes place to give and fac-[(bpy)(CO)3M{P(OMe)2F}]. These results reveal that the stability of cationic phosphenium complexes increases with (i) going to a heavier congener, (ii) increasing the number of amino substituents on the phosphenium phosphorus, and (iii) adding an ethylene bridge between X and Y when at least one of X and Y is an amino substituent.
  • Kiyoharu Nakatani, Norifumi Terui, Noboru Kitamura
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 997-1001
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    Kinetic analyses of a sulfonation reaction between electrochemically-generated diethyl(4-imino-3-methyl-2,5-cyclohexylidene)ammonium salt (quinone diimine derivative (QDI) and SO32− in water have been performed by a generation-collection mode of twin-microband electrodes. The collection efficiency of QDI (φ), defined as the ratio of the current at a generator to that at a collector, was dependent on the interelectrode distance and the SO32− concentration. The rate constant of the sulfonation reaction was determined by both a two-dimentional digital simulation of the concentration gradient of QDI and kinetic analyses of the observed φ values.
  • Jun-ichi Isizawa, Kazuhisa Sakakibara, Minoru Hirota
    1996 Volume 69 Issue 4 Pages 1003-1015
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    The ΔχB constant, defined as the difference of Bratsch’s electronegativity of a substituent group from that of CH3, was shown to serve as a versatile polar substituent constant in the multiple regression analysis using Ωs as the steric constant. Reactivities, which are usually expressed by the rate constants (k) and/or biological activities, could be expressed well in the form of a correlation equation using the steric (Ωs) and electronic (ΔχB: Bratsch’s group electronegativity) substituent parameters. As both parameters for any substituents can be obtained easily by calculations, the substituent effect on any reaction can be evaluated easily with good reliability. The correlation analyses among the Ωs, ΔχB, and the well-known Taft’s Es steric parameters showed that it must be reasonable to think that the Es parameters for the substituents containing hetero-atoms had an electronic nature to some extent as well as the steric effect.
  • Masa-aki Wakita, Tsuneyasu Adachi, Jun-ichi Ida, Masanori Hashimoto
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 1017-1021
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    Cationic lipid membranes of N-octadecylchitosan consisting of 2-deoxy-2-octadecylamino-D-glucopyranose, 2-amino-2-deoxy-D-glucopyranose, and 2-acetamido-2-deoxy-D-glucopyranose were covalently immobilized to carboxylated porous supports and used for the adsorption of pyrogenic lipopolysaccharide (LPS). When bovine serum albumin (BSA) solution, including 5 mg mL−1 of BSA and 100—148 ng mL−1 of LPS, was passed through a column packed with the porous supports bearing the cationic lipid membranes, LPS was selectively adsorbed and removed to as low as 0.1 ng mL−1 with quantitative recovery of BSA. LPS seemed to be dissociated from molecular complexes with BSA, and adsorbed selectively to the cationic lipid membranes by both an ionic interaction and a hydrophobic one.
  • Manabu Uchida, Makoto Kume, Masahiro Irie
    1996 Volume 69 Issue 4 Pages 1023-1027
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    New photochromic benzochromene derivatives condensed with a benzothiophene ring were synthesized. The condensation positions of the thiophene ring influenced the photochromism. 7a-Methyl-7aH-benzo[f][1]benzothieno[2,3-b]chromene (1) underwent a two-photon two-step photochromism, while 7a-methyl-7aH-benzo[f][1]benzothieno[3,2-b]chromene (2) showed an ordinary chromene-type photochromic reaction. The yellow color of 1 disappeared upon irradiation with 405 nm light, and a thermally stable oxabicyclo[3.1.0]hexene isomer was reversibly produced. On the other hand, compound 2 turned orange upon irradiation with 366 nm light, and the orange color quickly returned to the original pale yellow in the dark. Upon irradiation with both 366 and >420 nm light compound 2 isomerized to an oxabicyclo[3.1.0]hexene form.
  • Jitsuo Kiji, Tamon Okano, Yukiko Higashimae, Yasuyuki Fukui
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 1029-1031
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    Palladium-catalyzed, atmospheric pressure carbonylation of allylic halides under alcohol-potassium carbonate (liquid–solid) two-phase conditions affords β,γ-unsaturated esters without formation of the α,β-isomers. Phosphine-free palladium compounds such as Pd(OAc)2 (1) and Na2[PdCl4] (2) are a convenient catalyst for this reaction. Presence of triphenylphosphine retards the carbonylation. A mixture of Pd(OAc)2-PPh3 or [PdCl2(PPh3)2] (3) catalyzes the carbonylation under pressure.
  • Tokunaru Horie, Takeshi Kitou, Yasuhiko Kawamura, Kazuyo Yamashita
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 1033-1041
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    The Friedel–Crafts acetylation with boron trifluoride was studied and it was found that 1-(2,4-dihydroxy-3,5,6-trimethoxyphenyl)ethanone was conveniently synthesized from 2,3,5,6-tetramethoxyphenyl acetate in a mixture of acetic anhydride and acetic acid. 1-[2-Hydroxy-3,5,6-trimethoxy-4-(methoxymethoxy)phenyl]ethanone was cyclized to 7-hydroxy-5,6,8-trimethoxyflavone by using the Baker–Venkataraman transformation. The 7-benzyl ether of the flavone was oxidized with dimethyldioxirane and then treated with a small amount of p-toluenesulfonic acid to give 7-benzyloxy-3-hydroxy-5,6,8-trimethoxyflavone, which was converted into the methyl ether and tosylate. The 5-methoxy group in the methyl ether or tosylate was selectively cleaved with anhydrous aluminum bromide in acetonitrile under mild conditions to give the corresponding 5-hydroxyflavones and the latter compound with a 3-tosyloxy group was smoothly converted into the 3,5-dihydroxyflavone by hydrolysis with potassium carbonate in methanol. The hydrogenolysis of the 7-benzyloxy-3,5-dihydroxyflavone and its 3-methyl ether afforded quantitatively 3,5,7-trihydroxy-6,8-dimethoxyflavone and its 3-methyl ether. The process was suitable as a general method for synthesizing 3,5,7-trihydroxy-6,8-dimethoxyflavones and their 3-methyl ethers and the six flavones were synthesized for the clarification of their 1H and 13C NMR, MS, and UV spectral properties.
  • Kazuaki Shimada, Akihiro Otaki, Masaki Yanakawa, Shosuke Mabuchi, Naoy ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 1043-1054
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    Aldehydes and ketones were converted into 2-methylsulfinyl-5,6-dihydro-4H-1,3,4-thiadiazines via the formation and base-induced ring-closure of N-alkylidene-N′-bis(alkylthio)methylenehydrazines followed by mCPBA oxidation. The subsequent Pummerer-type ring fission of the rings was performed by treating with trifluoroacetic anhydride or trifluoromethanesulfonic anhydride at −78 °C to give α,β-unsaturated esters and ketones in modest yields. Thus, this reaction sequence was regarded as being a new method for the two-carbon homologation of aldehydes and ketones.
  • Masaharu Tsuji, Masato Aizawa, Yukio Nishimura
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 1055-1063
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    The gas-phase ion–molecule reactions of CF3+ with five monosubstituted benzenes carrying a carbonyl group (PhCOX: X = H, CH3, C2H5, OCH3, OC2H5) have been studied at near-thermal energies using an ion-beam apparatus. The major product channel for PhCHO, PhCOCH3, and PhCOOCH3 is electrophilic addition to the O-atom leading to initial adduct ions, which are 80.3—95.0% of the total product ions. Although no initial adduct ions are observed for PhCOC2H5 and PhCOOC2H5, major product ions are formed by electrophilic addition to the O-atom followed by dissociation and molecular eliminations. The reaction mechanism is discussed based on product ion distributions and semi-empirical calculations of the energies of intermediates and products. The results obtained are compared with reported ion-cyclotron-resonance data for aliphatic carbonyl compounds.
  • Masato Sakamoto, Isao Shimizu, Akio Yamamoto
    1996 Volume 69 Issue 4 Pages 1065-1078
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    The direct activation of the C–O bonds in allylic alcohols catalyzed by palladium complexes has been accelerated by carrying out the reactions under CO2. On reaction with diethylamine, allyl alcohol can be converted into N,N-diethylallylamine in the presence of palladium complexes at room temperature under normal pressure of carbon dioxide. Allylation of various carbon nucleophiles such as β-keto esters and β-diketones can be achieved by using allylic alcohols directly in the presence of palladium complexes and CO2. Direct carbonylation of allylic alcohols into unsaturated carboxylic acids can be catalyzed by palladium complexes under the pressure of CO and CO2. Disproportionation of diallylamine into triallylamine and allylamine is also catalyzed by palladium complexes in the presence of CO2. On the basis of studies on the behavior of η3-allylpalladium hydrogencarbonate complexes with the nucleophiles, mechanisms are proposed to account for the palladium-catalyzed allylation processes influenced by CO2.
  • Kaoru Nakamura, Masashi Kawasaki, Atsuyoshi Ohno
    1996 Volume 69 Issue 4 Pages 1079-1085
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    Lipase-catalyzed transesterifications of aryl-substituted alcohols with vinyl acetate in organic solvents have been investigated. Vmax of (R)-1-phenylethanol is much larger than its (S)-counterpart, although their Kms are similar each other. It is proposed that a lipase from Pseudomonas cepacia can form a complex easily with each enantiomer, although the complex with the (S)-enantiomer is abortive. Enantioselectivity for the ortho-substituted 1-phenylethanol is smaller than those for the others. A three-dimensional model for the active domain of the lipase has been proposed to explain the enantioselectivity and substrate selectivity of the lipase.
  • Fumihiko Akutsu, Mari Inoki, Nozomu Nishimura, Yoshio Kasashima, Kiyos ...
    1996 Volume 69 Issue 4 Pages 1087-1091
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    The thermal reaction in the solid state of binary salts, obtained from an equimolar mixture solution, of lithium 3-methyl-3-butenoate/methacrylate (3-MBA/MA) or potassium 3-MBA/MA, after esterification, produced mainly dimethyl (Z)-3,6-dimethyl-2-heptenedioate as a novel cross-coupled dimer. The cross-coupled dimer was obtained from the potassium salts in 35.5% yield upon heating at 230 °C for 2 h. Similary, a methyl ester of the cross-coupled dimer, dimethyl (Z)-3-methyl-2-heptenedioate, was given from sodium 3-methyl-3-butenoate/acrylate (3-MBA/AA) or potassium 3-MBA/AA after esterification. The cross-coupled dimer was obtained from potassium 3-MBA/AA in 57.5% yield upon heating at 230 °C for 2 h. The X-ray diffraction pattern of potassium 3-MBA/MA or potassium 3-MBA/AA indicates the formation of a new phase, that is different from that of the individual salts. The crystal system of K–(3-MBA/AA) was transformed to a more stable state by initial heating for 20 min. The selective cross-coupled dimerization was caused by the new phase of binary salts and maintaining the crystal state of the reaction system by the formation of solid-solution crystals.
  • Atsuyoshi Ohno, Norimasa Yamazaki, Mutsuo Okamura, Yasushi Kawai, Akih ...
    1996 Volume 69 Issue 4 Pages 1093-1098
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    The molecular structure of an enantiomer of nicotinamide coenzyme analog 1 has been determined by X-ray crystallography with the absolute configuration being established by the anomalous dispersion effects of all non-hydrogen atoms: (+)-1 exhibits (S)-form sticking the sulfinyl S–O out of the re face. The stereochemistry of the hydride-transfer reaction between the chiral coenzyme analogs, 1 and MenPNPH, was studied. The hydride from (S)- or (R)-MenPNPH, respectively, transfers to (S)- or (R)-1, affording the dihydropyridine compound syn-2 predominantly: That is, the reaction takes place in the face occupied by the sulfinyl oxygen. On the other hand, the transfer to (R)- or (S)-1 mainly takes place so as to afford anti-2. It has been deduced that (S)-1 reacts with (S)-MenPNPH more than twice as fast as (R)-1 does or vice versa. It has also been elucidated that the amide oxygen in MenPNPH points to 1 exclusively at the transition state of the reaction, regardless the configuration of the reagents. The intermolecular arrangement at the transition state of the reaction is discussed.
  • Takashi Nakata, Masaru Nakatani, Masatoshi Takahashi, Jiro Okai, Yoshi ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 1099-1106
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    Some (p-hydroxyphenyl)benzylmethylsulfonium salts were prepared. These compounds generated a benzyl cation and converted not only N-acylamino acids but also N-acylpeptides into their corresponding benzyl esters without causing the racemization.
  • Morifumi Fujita, Shunichi Fukuzumi, Gen-etsu Matsubayashi, Junzo Otera
    1996 Volume 69 Issue 4 Pages 1107-1116
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    β,β-Dimethyl-substituted ketene silyl acetal (1a) reduces p-chloranil and other activated quinones with electron-withdrawing substituents to produce the carbon–oxygen adduct, the hydrolysis of which yields the corresponding hydroquinone ether. The structure of the hydroquinone ether has been determined by the X-ray crystal analysis. The reactions are significantly slowed down in benzene where the charge-transfer spectra of electron donor–acceptor complexes formed between 1a and the activated quinones are observed. The comparison of the observed rate constant with that predicted for the electron transfer process from 1a to p-chloranil indicates that the addition of 1a to p-chloranil proceeds via the electron transfer from 1a to p-chloranil. Although no reaction takes place between 1a and p-benzoquinone, the electron affinity of which is significantly smaller than that of p-chloranil, the reduction of p-benzoquinone by 1a occurs efficiently in the presence of magnesium ion. The kinetic expression of the Mg2+ catalysis changes from the first-order to second-order in [Mg2+] under the conditions that Mg2+ forms the 2 : 1 complexes with the corresponding radical anions. The catalytic effects of Mg2+ are approximately the same as those observed for the electron transfer reduction of these oxidants, demonstrating the important contribution of the Mg2+-catalyzed electron transfer process in the addition of 1a to p-benzoquinone. On the other hand, the reaction of a nonsubstituted ketene silyl acetal (1d) with p-fluoranil yields the carbon–carbon adduct rather than the carbon–oxygen adduct. The much larger rate constants of 1d than those of 1a despite the higher oxidation potential of 1d suggest that the 1,2-addition to p-fluoranil occurs via the nucleophilic attack of 1d, which is much less sterically hindered than 1a, to the positively charged carbonyl carbon of p-fluoranil rather than an alternative electron transfer pathway.
  • Yukio Kawanami, Keiji Yamamoto
    1996 Volume 69 Issue 4 Pages 1117-1124
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    Rh(I)-catalyzed dehydrogenative silylation was selectively carried out by using divinylsilanes and half an equimolar amount of trialkylsilanes under ambient conditions to give 1,2-disilylethene and ethylvinylsilane derivatives in equimolar amounts. The mechanistic aspects for the dehydrogenative silylation were discussed in terms of the consecutive migratory insertions of the alkene moiety into both Rh–Si and Rh–H bonds which are formed by an oxidative addition of the hydrosilane to the Rh(I) catalyst precursor.
  • Nachiappan Lingappan, V. Krishnasamy
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 1125-1128
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    The syntheses of pentasil zeolites were carried out using the system xNa2y(TBP)2O·Al2O3·zSiO2·1050H2O, keeping z = 50—600, y/z = 0.03 to 0.1, and x/z = 0.01 to 0.05 at 448 K. Pure ZSM-5 phase is found to form for any value of z in the range specified when y/z = 0.02 and x/z = 0.01. When these compositional ranges and ratios are altered either ZSM-11 or intergrowth of ZSM-5/11 or formation of ZSM-5 or ZSM-11 and quartz takes place. The decomposition of the templates, from the channels of ZSM-5 of different SiO2/Al2O3 ratio, showed differences in their patterns. After calcination of the samples phosphorus is retained in the zeolite channels in the form of a surface complex. Thermal analysis and FTIR studies support this observation. SEM pictures drive to the conclusion that a liquid–solid transformation mechanism operates in the crystallization of ZSM-5 under the conditions of the synthesis studied.
  • Fuminori Akiyama
    1996 Volume 69 Issue 4 Pages 1129-1132
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    Reaction of activated carbon and copper(II) oxide in the presence of aqueous potassium carbonate solution at 380 or 400 °C gave mainly carbon dioxide, accompanied by the formation of hydrocarbons containing aromatic hydrocarbons such as benzene and toluene. The similar reaction of copper(I) oxide gave mainly methane, accompanied by formation of smaller amounts of carbon dioxide, benzene, and toluene than the reaction of copper(II) oxide. Although the reaction of copper(II) oxide with aqueous potassium carbonate solution did not give hydrocarbons in the absence of activated carbon, the reaction of copper(I) oxide with aqueous potassium carbonate solution gave hydrocarbons even in the absence of activated carbon.
  • Hirohumi Arakawa, Norimoto Watanabe
    1996 Volume 69 Issue 4 Pages 1133-1137
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    Reaction mixtures containing constant amounts of water-extract from withered oak leaves and various concentrations of potassium chromate were incubated, and each reaction mixture was fractionated by a Sephadex G-25 column. The concentrations of the Cr-tannin obtained in the fractions were determined. Then the Cr-binding ability of the tannin was examined by apparent stability constants and Cr-complexing capacities, following construction of a Scatchard plot which adopts a two-site model. The tannin was shown to have two-classes of Cr-binding sites. Based on the Cr-complexing capacities, 1 mg tannin was shown to bind about 0.5 mg of reduced Cr. Moreover, functional groups contributing to the complexation with Cr were investigated by FTIR and pH titration. The relationship between the Cr-complexing ligans in the two sites and the functional groups in the tannin was also investigated. Finally, Cr ion species which emerged during the reaction between chromate and the tannin were determined by EPR. The spectra showed a sharp signal attributable to Cr(V) and a broad one assignable to Cr(III). Thus, it can be speculated that the tannin most probably forms a final Cr(III)–tannin via Cr(V) species.
  • Tsutomu Ueda, Tetsuji Yamaoka, Masatoshi Miyamoto, Yoshiharu Kimura, H ...
    1996 Volume 69 Issue 4 Pages 1139-1142
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    Two types of model compounds containing an azo aromatic group were synthesized, and their reduction kinetics in an anaerobic culture of intestinal flora was investigated for insight into the degradation mechanism of the azo-containing polyurethane which can be specifically degraded by the action of azo reductases which are released by intestinal floras. A water-soluble azo compound, 3,3′ -azodibenzenemethanol (ADM), was readily reduced into its hydrazo form and then to the amine form, 3-aminobenzenemethanol (ABM). The reduction rate from azo to hydrazo was much faster than that from hydrazo to amine. In the case of a water-insoluble azo compound, 3,3′-azodibenzenemethanol bis(N-phenylcarbamate) (ADM-PC), in which the hydroxy groups of ADM were capped by N-phenylcarbamoyl groups, the reduction was stopped in the first step, and only the hydrazo form was produced. These data indicated that the azo-containing polyurethane which is hydrophobic in nature should be degraded by the azo-hydrazo reduction of the azo groups without the chain breakage occurring.
  • Motoshi Suzuki, Wataru Shimizu, Yoshio Kosugi, Hiroyuki Honda, Takeshi ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 4 Pages 1143-1148
    Published: 1996
    Released: June 21, 2006
    JOURNALS RESTRICTED ACCESS
    The proton spin relaxivities (R1, R2) of agarose phantom with magnetite particles were measured using an NMR spectrometer at 5.875 T, and compared with other magnetic substances. R2 for the polyethylene glycol-coated magnetite particle (PEG-magnetite) was 455 s−1 mM−1 (M = mol dm−3), 50- and 95-times larger than that for FeCl3 and Gd(H2dtpa), respectively. PEG-magnetite also showed a high R2/R1 ratio of 172, while the latter two substances had low R2/R1 ratios below 10. The core size greatly affected R2, the maximum R2 value being observed in the case of the intermediate size (10 nm) among three different core sizes of magnetite. The basic characteristics of magnetite were found to be derived from its magnetism. The optimization of such acquisition parameters as TR and TE for spin-echo pulse sequences was also examined. The differences in the calculated signal intensity obtained from a tumor with PEG-magnetite and from normal tissue without PEG-magnetite were compared. The image with the highest contrast was found to be obtained at TE = 40 ms and an appropriately long TR. PEG-magnetite is expected to work well as a negative-contrast agent under suitable acquisition conditions.
feedback
Top