Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 73 , Issue 9
Showing 1-30 articles out of 30 articles from the selected issue
  • Mitsuhiko Shionoya, Kentaro Tanaka
    2000 Volume 73 Issue 9 Pages 1945-1954
    Published: 2000
    Released: December 27, 2001
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    Novel synthetic approaches for incorporation of metal complexes into nucleic acids and peptides are described. First, novel artificial β-C-nucleosides bearing a chelator nucleobase (2-aminophenol, catechol, or o-phenylenediamine) have been synthesized. These artificial nucleobases were introduced for alternative base pairing through metal coordination instead of the hydrogen bonding in natural DNA. 1H NMR and mass spectral studies clearly showed that o-phenylenediamine-type nucleoside forms a stable 2 : 1 square-planar complex with a PdII ion, providing an alternative DNA base pairing through metal complexation. Secondly, an efficient strategy for the liquid-phase synthesis of cyclic metallopeptides having a repeating Gly-L-Cys(terpyPtII) sequence, cyclo[-Gly-L-Cys(terpyPtII)-]nCln (n = 3, 4), has been developed. These cyclic metallopeptides were obtained by cyclization of the corresponding linear peptides, H2[-Gly-L-Cys(terpyPtII)-]nOH·(CF3CO2)n+1 (n = 3, 4), in moderate yields. The former cyclic hexapeptide was found to act as a positively charged anion receptor. This synthetic approach would provide a powerful tool for arraying metal centers on cyclopeptide frameworks.
  • Hiroko Satoh, Kimito Funatsu, Keiko Takano, Tadashi Nakata
    2000 Volume 73 Issue 9 Pages 1955-1965
    Published: 2000
    Released: December 27, 2001
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    The classification and prediction of the roles for reagents in reactions are presented. The same dimensional representation of various reagents independent of the number of atoms was achieved by selecting representative factors by the FRAU (Field-characterization for Reaction Analysis and Understanding) system. Training of a self-organizing model considering both negative and absent data was accomplished by modifying the original counter-propagation (CP) type of Kohonen neural network to treat absent data differently from negative data. The modified CP Kohonen neural network successfully classified the reagents and produced a reagent-roles correlation model that gives good answers predicting roles of the reagents.
  • Kentaro Sugawara, Yasuo Kameda, Takeshi Usuki, Osamu Uemura, Toshiharu ...
    2000 Volume 73 Issue 9 Pages 1967-1972
    Published: 2000
    Released: December 27, 2001
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    Time-of-flight (TOF) neutron diffraction measurements have been carried out on the alkaline aqueous 2 mol% glycine solution in heavy water. The isotopic substitution technique has been applied to both nitrogen and hydrogen atoms within glycine molecules in order to obtain information concerning the hydration structure around the amino- and methylene group in the glycine molecule under the high-pH condition. Results revealed that the nitrogen atom in the amino group forms a hydrogen bond of the N…D-O type with ca. one D2O molecule (rN…D = 1.97(3) Å, ∠N…D-O = 174(5)°), and simultaneously forms bonds of N-D…OD2 type with ca. two D2O molecules (rN…O = 2.92(3) Å) in the present alkaline aqueous solution. This behavior is in contrast to the hydration structure around the amino group in the glycine molecule reported for the neutral aqueous solution, in which the amino group forms the hydrogen bonds of N-D…OD2 type with ca. three D2O molecules. The first hydration shell around the methylene group in the glycine molecule involves ca. two D2O molecules per one glycine molecule. The orientational correlation between the methylene-hydrogen atoms and neighboring D2O molecules is weak.
  • Seiko Nakagawa, Toshinari Shimokawa
    2000 Volume 73 Issue 9 Pages 1973-1978
    Published: 2000
    Released: December 27, 2001
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    The temperature dependence of the formation of negative ions from C6F6, C5F5N, C6F5CN, C6F5CF3, and C6F5C6F5 was studied by using negative chemical ionization mass spectrometry. Parent negative ion and fragment ions: F- and (M-F)- (M = Parent Molecule) were observed. Secondary product ions: C5F4- and C5F2- for C6F6 and C5F6N- and C4FN- for C5F5N were also observed at temperatures higher than 523 K. A cluster of the parent molecule and F- is produced for C6F6 and C5F5N. The intensity of parent negative ions increases, while that of fragment ions and secondary ions decreases with decreasing temperature. Such results show that electron detachment from the parent anions will occur. Geometry of parent negative ions and cluster anions of C6F6, C5F5N, C6F5CN, and C6F5CF3 were also calculated using the Hartree-Fock method. The structure and the distribution of the spin density are almost the same for all these molecules. This similarity means that the production of negative ions from them and the reaction mechanisms are almost the same.
  • Shinsaku Fujita
    2000 Volume 73 Issue 9 Pages 1979-1986
    Published: 2000
    Released: December 27, 2001
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    A chiral replacement criterion has been proposed to characterize stereochemical equivalence. This criterion is effective to determine holotopic and hemitopic relationships, which are sub-relationships of a homotopic relationship. The criterion has been shown to be complementary to the membership criterion based on the sphericity concept.
  • Tooru Atake, Hitoshi Kawaji, Takeo Tojo, Koji Kawasaki, Yasushiro Oots ...
    2000 Volume 73 Issue 9 Pages 1987-1991
    Published: 2000
    Released: December 27, 2001
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    We measured the heat capacities of 2-butoxyethanol (abbreviated as nBE), 2-isobutoxyethanol (iBE) and 2-t-butoxyethanol (tBE) from 13 to 300 K by adiabatic calorimetry, and glass transition was found for all three: 140 K (nBE), 146 K (iBE) and 150 K (tBE). We were successful in crystallizing nBE and tBE, and determined thermodynamic functions for fusion for the first time. The temperatures of fusion and their enthalpy changes are 199.53 K, 11.8 kJ mol-1 for nBE and 223.09 K, 11.4 kJ mol-1 for tBE. Where possible, we calculated thermodynamic functions. The total entropy in the liquid state at fusion is almost the same, within 1%, between nBE and tBE. However, the values of the liquid heat capacity are about 10% different at the melting point. This indicates that the entropy fluctuation is different while the global average of the entropy remains the same. We measured the density of the liquid and supercooled liquid states for all three samples, and calculated the amplitude, as well as the amplitude plus wavelength of the entropy fluctuation.
  • Kazutoshi Kobayashi, Shin'ichiro Imabayashi, Katsuhiko Fujita, Kazuhid ...
    2000 Volume 73 Issue 9 Pages 1993-2000
    Published: 2000
    Released: December 27, 2001
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    Thiolated heme derivatives were synthesized and their self-assembly behaviors on gold surfaces together with that of native heme were studied. The kinetics of this adsorption and the thickness of the formed monolayer were investigated by surface plasmon resonance spectroscopy. Native heme shows a different adsorption behavior compared to that of the synthesized derivatives. Though the heme derivatives were found to form monolayers, native heme formed only irregular aggregates on gold surfaces. IR spectroscopy was used to reveal the molecular structure of the adsorbates in the vicinity of the peptide linkage in the heme molecules on the gold surfaces. UV spectroscopy was employed to determine the tilt angle of the porphyrin rings relative to the gold surface normal. Cyclic voltammograms and potential-modulated UV-vis reflectance spectra of heme derivatives were observed in order to estimate the adsorbed amount and the redox behaviors of heme derivatives on gold surfaces.
  • Hiroshi Ichikawa, Hirotaka Kagawa, Chikara Kaneko
    2000 Volume 73 Issue 9 Pages 2001-2008
    Published: 2000
    Released: December 27, 2001
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    The minimal linear-combination-of-atomic-orbitals (LCAO) has a clear chemical meaning, namely, that a molecular orbital consists of atomic orbitals of the member atoms. In organic chemistry, this concept has been applied to graphical expression of orbital interactions. However, the minimal LCAO method is inadequate to illustrate such interatomic interactions. Based on a general idea in quantum chemistry, we have proposed pictorial ``in-bond orbitals'' to compensate for the shortcomings of the minimal LCAO scheme without destroying its simple concept. In-bond orbitals well express the qualitative electronic structures of bonding and antibonding internuclear regions. Furthermore, they are continuously correlated with the AOs of the united atom. In this paper, (1) we discuss the conceptual problems of the minimal LCAO expression in interaction between atoms, (2) we show the importance of the contribution of AOs with higher quantum numbers to the chemical interaction nominally given by AOs with the lowest quantum number, (3) we show that the introduction of a minimal number of in-bond orbitals is a simple method to solve the continuity problem of the correlation diagram and to improve the electronic structure, (4) a selection scheme for in-bond orbitals is proposed, and (5) as an example, the concept of the in-bond orbital is applied to the prediction of the direction of pyramidalization of the olefinic carbon atoms of norbornene.
  • Shinsaku Fujita
    2000 Volume 73 Issue 9 Pages 2009-2016
    Published: 2000
    Released: December 27, 2001
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    The concept of size-invariant subductions has been proposed to design prochiral molecules. Thus, an even-membered homospheric orbit has been proved to be desymmetrized into an enantiospheric orbit, where the sizes of the relevant orbits remain invariant. The concept has been applied to methanes, allenes, adamantanes, and biphenyls. It has proved effective in designing a wide variety of prochiral molecules. These prochiral molecules have been shown to be extrinsic meso compounds. Intrinsic meso compounds have also been discussed as another type of prochiral molecule.
  • Yasuo Izumi, Hiroyuki Oyanagi, Hiroyasu Nagamori
    2000 Volume 73 Issue 9 Pages 2017-2023
    Published: 2000
    Released: December 27, 2001
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    A Rowland-type fluorescence spectrometer was designed to measure site-selective XAFS spectra by utilizing the chemical shift of emission peak for each site. The positions of Johansson-type cylindrically-bent Ge(111) crystal and scintillation counter were controlled independently by five-channel stepping motors, thereby satisfying precise Rowland condition. Thus, measurements of many fluorescence lines over wide ranges of Bragg angle 55.6—83.9° and Rowland radius 127.7—240.9 mm are made feasible. The Cu Kα peak shifted by +1.6 eV on going from Cu to CuCl and by -0.6 eV on going from CuCl to CuCl2. The Cr 1 peak shifted by +0.8 eV on going from Cr to Cr2O3 and by -1.6 eV on going from Cr2O3 to K2CrO4. The FWHM of Cu peaks was as small as 3.0 eV. The major factor to control the energy resolution of this spectrometer was found to be geometrical angle width (slit size). The effects of Rowland radius and X-ray penetration depth into the bent crystal were smaller in the range of slit size in this paper [slit length (horizontal) in front of I0 ion chamber was 0.5—2.0 mm and two slit lengths (vertical) in Rowland circle were 0.5—5.5 mm].
  • Yoichi Kitamura, Leona Yano, Kazuya Fujimori, Ryuji Mizuki, Masayuki H ...
    2000 Volume 73 Issue 9 Pages 2025-2032
    Published: 2000
    Released: December 27, 2001
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    Acid-catalysed hydrolysis has been studied by a stopped-flow method at 25 °C, ionic strength of 2.0 (NaClO4) and oxonium ion concentration of 0.02—1.0 M for monodentate carbonato complexes ( [Co(CO3)(NH3)5]+, [Rh(CO3)(NH3)5]+, and [Ir(CO3)(NH3)5]+) and for didentate carbonato complexes ( [Co(CO3)(NH3)4 ]+, [Co(CO3)(en)2]+, α, β-[Co(CO3)(trien)]+, [Co(CO3)(tren) ]+ and [Co(CO3)(nta)]2- (M = mol dm-3, en = ethylenediamine, trien = 1,8-diamino-3,6-diazaoctane, tren = tris(2-aminoethyl)amine, and H3nta = nitrilotriacetic acid) ). The experimental first-order rate constant of decarboxylation from the monodentate hydrogencarbonato intermediate depends on the acidity of the solution, which we ascribe to its amphiprotic character. The deprotonation constant depends critically on an aqua ligand cis to the hydrogencarbonato ligand: 0.004—0.6 M with it, whereas about 10-6 M without it. We interpret that the former strong acidity originates from the stability of the aquacarbonato complex, owing to a strong (21—33 kJ mol-1) intramolecular hydrogen bond. The basicity has been confirmed by the acidity dependent zero-time spectra, the protonation constant being 0.1—0.7 M-1. The hydrolysis rate constant of the monodentate carbonic acid complex has been estimated to be smaller than 0.3 s-1 at 25 °C.
  • Masayasu Iida, Akie Sakamoto, Taeko Yamashita, Kaori Shundoh, Shiho Oh ...
    2000 Volume 73 Issue 9 Pages 2033-2041
    Published: 2000
    Released: December 27, 2001
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    The aggregation of novel type cobalt(III) surfactants, such as [Co(en)2{NH2(CH2)2S(1-CnH2n+1)}]3+ (n = 6, 8, and 12) and [(en)2Co{NH2(CH2)2 S(CH2)mS(CH2)2NH2}Co(en)2]6+ (m = 8 and 12), was studied in water using multinuclear NMR spectroscopies, 1H NMR self-diffusions, and 1H NMR chemical shifts. The 59Co linewidths of the surfactants were useful to monitor the premicellar and micellar formation. It was revealed that the tripositive mononuclear surfactants have comparable cmc (critical micelle concentration) values to those for the usual monovalent surfactants having the same alkyl chains. The 35Cl longitudinal relaxation rates for the counterions were useful to monitor the two kinds of ionic interactions, i.e., those with the surfactant monomers and with the micelles. We determined the cmcs for the premicellar formation in the hexyl mononuclear and octyl dinuclear complex systems. The determination of this kind of cmc has become possible by using such highly charged complexes as the cystam complex and by measurements of the 59Co linewidths and of the 35Cl longitudinal relaxation rates. The self-diffusion coefficient for the surfactants revealed that the aggregation behavior is similar in comparison between the hexyl mononuclear and octyl dinuclear complexes or between the octyl mononuclear and dodecyl dinuclear complexes.
  • Sen-ichi Aizawa, Yasushi Sone, Siti Khajar, Yuuki Ohishi, Shinkichi Ya ...
    2000 Volume 73 Issue 9 Pages 2043-2050
    Published: 2000
    Released: December 27, 2001
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    Sparingly soluble neutral fac(S)-[Rh(aet)3] was newly optically resolved in order to apply the optically active isomer as a CD-inducing reagent to the circular dichroism (CD) spectrophotometric determination of the transition metal ions. Simple determinations of cobalt(II) and nickel(II) and a simultaneous determination for the binary solution were successful by using an excess of powdery Λ-fac(S)-[Rh(aet)3] with the dissolution equilibrium. A more sensitive determination of the transition metal ions, such as iron(III), iron(II), cobalt(III), cobalt(II), and nickel(II), was possible by using a homogeneous solution of ΔLLL-fac(S)-[Rh(L-cys-N,S)3]3- without the dissolution equilibrium. The latter CD spectrophotometric determination is quite effective for a simultaneous determination of the transition metal ions in binary and ternary solutions of metal ions, such as iron(III)-cobalt(III), cobalt(III)-cobalt(II), and cobalt(II)-nickel(II)-zinc(II).
  • Chang-Shik Choi, Lallan Mishra, Toshiki Mutai, Koji Araki
    2000 Volume 73 Issue 9 Pages 2051-2058
    Published: 2000
    Released: December 27, 2001
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    7-Amino-dipyrido[3,2-a : 2,3-c]phenazine (dppz-NH2) has a diimine coordination site, a rigid and extended π conjugation system, and a reactive amino group within the molecule, and [Ru(bpy)2(dppz-NH2)]2+ was synthesized as a useful photosensitizing unit for the construction of photoinduced energy-transfer systems. Anthraquinone, anthracene, and [Os(bpy)3]2+ derivatives having a carboxylic acid function were used as energy-accepting units, and were successfully connected to [Ru(bpy)2(dppz-NH2)]2+ through an amide bond. Electronic spectral and electrochemical studies of the resultant complexes were carried out, and it was shown that effective excited electron or energy transfer took place from the Ru(II) polypyridyl center to these units. In the case of the heterodinuclear Ru(II)/Os(II) complex, emission from the Ru(II) polypyridyl center was effectively quenched and that from the Os(II) polypyridyl center was increased compared to the reference Os(II) polyimine complex. The rate of energy transfer from the Ru(II) to the Os(II) polypyridyl center through the dppz-amide connector was estimated to be 1.0 × 108 s-1 in acetonitrile.
  • Shigeyuki Hirose, Shinya Hayami, Yonezo Maeda
    2000 Volume 73 Issue 9 Pages 2059-2066
    Published: 2000
    Released: December 27, 2001
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    New spin-crossover Iron(III) complexes [Fe(salten)(trans-stpy)]BPh4·(CH3)2CO·0.5H2O 1 and [Fe(salten)(cis-stpy)]BPh42 with cis-trans photoisomerizable ligands have been synthesized and characterized, where trans-stpy is trans-4-styrylpyridine and cis-stpy cis-4-styrylpyridine, and salten denotes bis(3-salicylideneaminopropyl)amine, which is a quinquedentate Schiff base derived from the condensation of salicylaldehyde and di(3-aminopropyl)amine. The data of the variable-temperature magnetic susceptibility measurements for the complexes show that 1 and 2 exhibit spin-crossover phenomena in a solid. The spin-state transition temperature of 1 is lower than that of 2. The temperature dependencies of the Mössbauer spectra for the complexes also provide evidence that spin-state transitions between the high- and low-spin states take place, and that the rates of the spin interexchange at 298 K are faster than the inverse of the lifetime (1×10-7 s) of the Mössbauer nucleus. A temperature dependence of the UV-visible spectra suggesting spin-equilibrium in acetonitrile solution was obtained. The X-ray diffraction structures of single crystals of 1 and 2 were determined. Crystal data for 1: C60H61N4O3.5FeB, space group P1 (#2), Z = 2, a = 14.83(1), b = 17.98(1), c = 11.31(2) Å, α = 103.71(8), β = 110.60(8), γ = 94.31(7)°, V = 2702(5) Å3, R = 14.0%, Rw = 17.2%. Crystal data for 2: C57H54N4O2FeB, space group P21/n (#14), Z = 4, a = 14.823(9), b = 17.417(7), c = 18.37(1) Å, β = 95.331(8)°, V = 4722(3) Å3. The coordination cores of both complexes have trans coordination in oxygen atoms. Although light irradiation to 1 in acetonitrile brings about isomerization from trans- to cis- of styrylpyridine, the change in the spin-state of the complexes is not clear.
  • Yasunori Yamada, Kiyoshi Fujisawa, Ken-ichi Okamoto
    2000 Volume 73 Issue 9 Pages 2067-2073
    Published: 2000
    Released: December 27, 2001
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    The reaction of [Pd(aet)2] (aet = 2-aminoethanethiolate) with [Pd(NO3)2(diimine)] (diimine = 2,2-bipyridine (bpy), 4,4-dimethyl-2,2-bipyridine (dmbpy), 1,10-phenanthroline (phen), 4,7-dimethyl-1,10-phenanthroline (dmphen)) gave a new type of S-bridged tetranuclear complex [{Pd(diimine)}2{Pd(aet)2}2]4+. The crystal structures of these complexes were determined by X-ray crystallography. In these complexes, the two intramolecular diimine moieties are aligned so as to overlap each other and the PdN2S2 planes in the {Pd(aet)2} units are almost perpendicular to those in the {Pd(diimine)} moieties. In the case of diimine = bpy and dmbpy, furthermore, the complex cations exist in the dimeric structure with a coplanar stacking arrangement, in which the diimine moieties of the two distinct complex cations are antiparallel to each other. In the case of diimine = phen and dmphen, on the other hand, the complex cations exist in the linear-chain-like structure with an alternate coplanar stacking arrangement, in which the diimine moieties of the neighboring complex cations are antiparallel to each other. All of the complexes were characterized on the basis of the electronic absorption, diffuse reflection, and 13C NMR spectra.
  • Shigeru Ohba, Hiroyuki Hosomi, Koichi Tanaka, Hisakazu Miyamoto, Fumio ...
    2000 Volume 73 Issue 9 Pages 2075-2085
    Published: 2000
    Released: December 27, 2001
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    X-Ray structure analyses of the inclusion complexes indicated that the high stereo- and enantioselectivities in photocyclization of cyclohex-1-enecarboic acid methyl-phenyl-amide (3), N-methyl, N-{(E)-methylmethacryloyl}anilide (5), N-methyl, N-(methacryloyl)anilide (8), and N-ethyl-N-methylbenzoylformamide (10) are the result of their chiral conformations in the clathrate crystalline environment with the title chiral hosts [(-)-1 and (-)-2, respectively]. The chirality of acrylanilides and benzoylformamide can be indicated by the sign of the torsion angle in the backbone of the molecule, C-N-C(=O)-C and O=C(-Ph)-C(=O)-N, respectively. A partial single-crystal-to-single-crystal transformation of 1 : 1 complex of 10 with (-)-1 was performed by photoirradiation to observe in situ the photoproduct.
  • Ryo Yamanishi, Kazuki Okada, Norihusa Tamugi, Makoto Iwashima, Kazuo I ...
    2000 Volume 73 Issue 9 Pages 2087-2091
    Published: 2000
    Released: December 27, 2001
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    A new maleic anhydride derivative 1 (FR222398) was isolated from fermentations with the fungus Talaromyces sp. No. 10092. The structure of 1 was determined based on spectroscopic analysis and chemical conversion. The sodium salt of 1 exhibited a dispersant activity toward kaolin suspension.
  • Masafumi Unno, Koichi Higuchi, Koji Furuya, Hiroaki Shioyama, Soichiro ...
    2000 Volume 73 Issue 9 Pages 2093-2097
    Published: 2000
    Released: December 27, 2001
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    Octathexyloctagermacubane (1, thexyl = 1,1,2-trimethylpropyl) was synthesized by the condensation of trichlorothexylgermane with Mg/MgBr2, and structurally characterized by X-ray crystallography. As in the case of the thexyl-substituted octasilacubane, a ring-opening reaction followed by skeletal rearrangement of 1 took place with PCl5 to give endo, exo- and exo,exo-4,8-dichlorooctathexyltetracyclo[3.3.0.02,7.03,6]octagermanes. Treatment of these dichlorides with sodium afforded octagermacubane 1.
  • Katsuma Hiraki, Takayuki Ishimoto, Hiroyuki Kawano
    2000 Volume 73 Issue 9 Pages 2099-2108
    Published: 2000
    Released: December 27, 2001
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    A dihydridoruthenium(II) complex, [RuH2(CO)(PPh3)3], reacts with styrene to give two species: a bis(styrene)ruthenium(0) complex, [Ru(CO)(CH2=CHPh)2(PPh3)2], and a cyclometallated hydridoruthenium(II) one, [Ru(C6H4PPh2)H(CO)(PPh3)2]. The complex [RuH2(CO)(PPh3)3] reacts with isoprene to give a piano-stool type ruthenium(0) complex [Ru(η4-CH2=CMeCH=CH2)(CO)(PPh3)2]. In reactions among [RuH2(CO)(PPh3)3], styrene, and 3-(trifluoromethyl)acetophenone, three cyclometallated hydridoruthenium(II) complexes: P,P-cis-C,H-cis-, P,P-trans-C,H-trans-, and P,P-trans-C,H-cis-[Ru{C6H3(CF3)C(=O)Me}H(CO)(PPh3)2] are detected by NMR spectroscopy. The 1H NMR spectra of the reaction mixture exhibit the catalytic formation of 2-(2-phenylethyl)- and 2-(1-phenylethyl)-5-(trifluoromethyl)acetophenones. On the basis of these findings, a mechanism for the C-H/olefin coupling reaction is discussed. The first of the three complexes is assigned to an active intermediate in the catalytic coupling reaction, whereas the other two are assigned as quasi-stable ruthenium(II) complexes which are in equilibrium with active species.
  • Tetsuya Enomoto, Naoki Nishigaki, Hiroyuki Kurata, Takeshi Kawase, Mas ...
    2000 Volume 73 Issue 9 Pages 2109-2114
    Published: 2000
    Released: December 27, 2001
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    A number of hexaphenyl[3]radialene derivatives were synthesized in modest to good yields by the reaction of tetrachlorocyclopropene with diarylmethyl anion followed by oxidation with oxygen. That the acidity of diarylmethane is higher than that of diphenylmethane is found to be an important factor for the successful synthesis. Lithiation and protonation of hexa(4-iodophenyl)[3]radialene thus obtained leads to the first synthesis of hexaphenyl[3]radialene. These hexaaryl[3]radialenes are stable, orange to red, crystalline substances. An X-ray crystallographic analysis of hexa(4-cyanophenyl)[3]radialene reveals a double three-bladed propeller conformation. The effects of substituents in the phenyl groups on their properties are most clearly seen in their electrochemical reduction potentials; among hexaphenyl[3]radialenes here obtained, hexa (4-nitrophenyl)[3]radialene (1Ered = -0.30 V, 2Ered = -0.45 V) is found to be a good electron acceptor stronger than p-benzoquinone.
  • Ryukichi Takagi, Toshiki Manabe, Akiko Shiraki, Arata Yoneshige, Yoshi ...
    2000 Volume 73 Issue 9 Pages 2115-2121
    Published: 2000
    Released: December 27, 2001
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    Catalysts, oligo-L-leucine, for the Juliá-Colonna asymmetric epoxidation of chalcone with defined degrees of polymerization were prepared by a stepwise elongation method. The yield and enantioselectivity in the epoxidation increased with the degree of polymerization of the catalyst. The presence of an unprotected amine moiety at the N-terminus proved to be essential for high asymmetric induction. The IR characteristic absorption bands (the amide I region) of the catalysts suggested that helical structure in the catalyst is related to asymmetric induction.
  • Takehisa Dewa, Toshiyuki Saiki, Yuki Imai, Ken Endo, Yasuhiro Aoyama
    2000 Volume 73 Issue 9 Pages 2123-2127
    Published: 2000
    Released: December 27, 2001
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    When immersed in an aqueous solution of alcohol or alkyl acetate as a guest, 9,10-bis(3,5-dihydroxyphenyl)anthracene 1 as a hydrogen-bonded solid host incorporates two mols of the guest together with 5—8 mols of water. The binding isotherm shows a sharp threshold guest concentration characteristic of guest-induced phase-transition. The threshold concentrations as a measure of affinities are highly dependent on the hydrophobicities of the guests. Host 1 also catalyzes the Diels-Alder reaction of acrylaldehyde and 1,3-cyclohexadiene in an aqueous environment. The preserved 1 : 2 (host-to-guest) stoichiometry, spectroscopic evidence (ΔνC=O), guest-desorption behaviors, and X-ray powder-diffraction studies indicate that host-guest hydrogen-bonding in collaboration with apolar interactions is responsible for the selective guest-binding and catalysis under the present aqueous conditions.
  • Tsukasa Matsuo, Hidetoshi Fure, Akira Sekiguchi
    2000 Volume 73 Issue 9 Pages 2129-2137
    Published: 2000
    Released: December 27, 2001
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    The reaction of 3,3,6,6,8,8,11,11,14,14,16,16,19,19,21,21-hexadecamethyl-3,6,8,11,14,16,19,21-octasilacyclohenicosa-1,4,9,12,17-pentayne with an excess molar amount of [Mn(CO)3(Me-Cp)] in tetrahydrofuran (THF) under photochemical and refluxing conditions produced 2,2,4,4,9,9,11,11,13,13,15,15,17,17,21,21-hexadecamehyl-2,4,9,11,13,15,17,21-octasilahexacyclo[10.5.3.15,8.06,18.07,20.014,19]henicosa-1(18),5,7,12(20),14(19)-pentaene (2) as silyl-substituted [5]radialene derivative. This was reacted with lithium metal in THF to give dark red crystals of the tetralithium salt (4) of 2. The molecular structure of tetraanion of 2 with a novel ten-center, fourteen-electron π-system was established by X-ray crystallography. The tetralithium salt 4 has a monomeric structure and forms contact ion pairs (tetrakis-CIPs) in the crystals. The structural parameters of 4 are discussed in comparison with those of the neutral starting molecule 2. The structure of 4 in solution is also discussed on the basis of NMR spectroscopic data.
  • Hirotada Kakiya, Hiroshi Shinokubo, Koichiro Oshima
    2000 Volume 73 Issue 9 Pages 2139-2147
    Published: 2000
    Released: December 27, 2001
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    Treatment of trialkyl(dibromomethyl)silanes with trialkylmanganates, derived from manganese(II) chloride and three molar amounts of Grignard reagents or alkyllithiums, provided (E)-1-trialkylsilyl-1-alkenes with high stereoselectivity in good yields. The reaction of trialkyl(dibromomethyl)silanes with alkylmagnesium halides proceeded in the presence of a catalytic amount of manganese(II) chloride. Treatment of 1,2-bis(dibromomethyl)benzene with triphenylmanganate gave 1,2-diphenyl-1,2-dihydrobenzocyclobutene.
  • Toshiyuki Ohe, Takeshi Wakita, Shin-ichi Motofusa, Chan Sik Cho, Kouic ...
    2000 Volume 73 Issue 9 Pages 2149-2155
    Published: 2000
    Released: December 27, 2001
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    A variety of aryltin compounds can be employed for Michael-type hydroarylation reactions to α,β-unsaturated ketones and aldehydes in the presence of a catalytic amount of palladium(II) salt in acetic acid under air. Each reaction is much accelerated in the presence of a soluble metal chloride such as LiCl, MgCl2, and CaCl2. It is found that slightly fewer than four aryl groups of tetraaryltins can be transferred to the products in this arylation.
  • Keiji Wakita, Norihiro Tokitoh, Renji Okazaki
    2000 Volume 73 Issue 9 Pages 2157-2158
    Published: 2000
    Released: December 27, 2001
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    The crystal structure of the stable 2-silanaphthalene was refined more adequately by the separation of the disorder of overlapped two 2-silanaphthalene moieties. The bond lengths of the 2-silanaphthalene ring were in fairly good agreement with the theoretically calculated values which we previously reported.
  • Hidenori Kinoshita, Hirotada Kakiya, Koichiro Oshima
    2000 Volume 73 Issue 9 Pages 2159-2160
    Published: 2000
    Released: December 27, 2001
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    Treatment of 1-dodecyne with triphenylgermane in the presence of catalytic amounts of tributylmanganate at 25 °C provided 1-triphenylgermyl-1-dodecene in good yield. The reaction proceeded in a radical pathway and treatment of diene afforded the corresponding radical cyclization product.
  • Shinobu Nagase, Masato Ohshika, Shinya Ueda, Naoki Satoh, Kaoru Tsujii
    2000 Volume 73 Issue 9 Pages 2161-2167
    Published: 2000
    Released: December 27, 2001
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    A universal structural model for human hair has been proposed in order to understand the physical properties of hair. The model consists of two structural parts, both of which have two states (Two-part/two-state model). The transition temperature (Tc) between the two states of one part is about 70 °C, and that of the other part is about 0 °C in a water medium. These transition temperatures depend highly upon the water content of the hair. A higher transition temperature is observed in hair having a lower water content. Above the transition temperatures, both parts of the hair are soft and plastic (a melted state); they are hard and elastic (a solid state) below the transition points. One part of hair which has a higher transition temperature (ca. 70 °C in water) is assigned to be macrofibril and exo-cuticle consisting of keratinous proteins; the other part with a lower Tc (ca. 0 °C) is inter-macrofibrillar materials, a cell-membrane complex (CMC), and the endo-cuticle of non-keratinous proteins and lipids. This structural model was derived from the results of thermal-setting and relaxation experiments as well as TEM observations after permeating a dye with a high electron density (Erythrosin B).
  • Masahiko Sakai, Shinobu Nagase, Tomoyuki Okada, Naoki Satoh, Kaoru Tsu ...
    2000 Volume 73 Issue 9 Pages 2169-2177
    Published: 2000
    Released: December 27, 2001
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    The mechanical properties of human hair fiber and the permeation behaviors of some dye molecules into hair have been studied, and are here discussed based on a universal structural model proposed by the authors in the previous paper. The model consists of two structural parts, both of which have two states (Two-part/two-state model). One part of the hair, which has a higher transition temperature (Tc; ca. 70 °C in water), is assigned to be macrofibril and exo-cuticle; the other part with lower Tc (ca. 0 °C in water) is inter-macrofibrillar materials, a cell-membrane complex (CMC) and endo-cuticle. The temperature dependence of the elastic modulus of a human hair in the Hookean region clearly shows two break points, indicating the above-mentioned transition temperatures. We have proposed a viscoelastic model based on the two-part/two-state structural model to understand the mechanical behaviors in the Hookean, yield and post-yield regions. The permeation rate of some dye molecules into hair fiber starts to dramatically increase at the higher transition temperature. Such permeation behaviors can also be understood from a universal structural model. The molecular size of dye is a crucial factor in permeation behaviors. Dye molecules with a size smaller than 1.0 nm migrate much more easily into hair.
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