Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 74 , Issue 5
Showing 1-27 articles out of 27 articles from the selected issue
  • Hisaharu Hayashi, Yoshio Sakaguchi, Masanobu Wakasa
    Type: scientific monograph
    2001 Volume 74 Issue 5 Pages 773-783
    Published: 2001
    Released: September 01, 2002
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    A pulsed magnet which is useful for the research of chemical reactions has recently been constructed by our group. Here, the world record of the maximum magnetic field (30 T) has been attained in this research area. An optical detected X-band ESR apparatus has also been developed by our group. The world’s best sensitivity and resolution have been realized in this apparatus. In this account, we review our recent results on new magnetic field effects and spin dynamics obtained with such novel methods as described above for radical reactions at room temperature in solution. In Section 1, typical mechanisms of MFEs on radical pairs such as the Δg mechanism and the relaxation mechanism are explained as the introduction of this review. In Section 2, the saturation of MFEs due to the Δg mechanism observed for radical pairs generated from the photoreduction of 4-methoxybenzophenone with benzenethiol in fluid solutions under ultrahigh fields are described. In Section 3, the saturation and reversion of MFEs due to the relaxation mechanism observed for radical pairs generated from the photoreduction of carbonyl and quinone compounds in micellar solutions under ultrahigh fields are reviewed. In Section 4, the first observation of MFEs on the reactions of three-spin systems generated photochemically in solution are introduced. In Section 5, we describe spin dynamics of radical pairs studied with our optically detected ESR apparatus for radical pairs generated from the photoreduction of carbonyl and quinone compounds in micellar solutions.
  • Toshikazu Kitagawa, Ken’ichi Takeuchi
    Type: scientific monograph
    2001 Volume 74 Issue 5 Pages 785-800
    Published: 2001
    Released: September 01, 2002
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    Though numerous investigations have appeared on the reduced and oxidized forms of parent C60, investigations on C60 ions that contain exohedral functional group(s) have been rather few. This account deals with the chemistry of such ions, in particular, the chemistry of monofunctionalized species RC60 and RC60+. Studies of the anions RC60 were initiated early in the history of the fullerene chemistry, and they are generally considered appreciably stable carbanions. This account focuses on our recent synthesis of a hydrocarbon salt and ionically dissociable hydrocarbons which contain the C60 framework. These are unusual classes of hydrocarbons that could be obtained by making use of the high thermodynamic stability of a hydrocarbon anion t-BuC60. Some of the properties which are characteristic of these hydrocarbons are also discussed. In contrast, studies of the chemistry of the cation RC60+ have only recently been launched. In this account, advances in the studies of these cations, including observations of their existence, the evaluation of their stabilities, and the role of these cations as a reactive intermediate, are described.
  • Aritomo Yamaguchi, Takafumi Shido, Yasuhiro Inada, Toshihiro Kogure, K ...
    Type: technical report
    2001 Volume 74 Issue 5 Pages 801-808
    Published: 2001
    Released: September 01, 2002
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    The reduction process of Cu–ZSM-5 was investigated by a time-resolved energy-dispersive XAFS (DXAFS) technique. The spectra were recorded every second and the entire spectra were analyzed to elucidate the dynamic change of the local structure around the Cu species. Two Cu–ZSM-5 samples with different Cu loadings were prepared by an ion-exchange method followed by calcination. In the low-loading sample (84% ion-exchanged), Cu2+ cations dispersed isolatedly in the channels of ZSM-5, while in the high-loading sample (104% ion-exchanged) CuO particles were formed. The isolated Cu2+ cations were reduced to isolated Cu2+ cations at 400–450 K and the Cu+ ions were reduced to Cu0 at 550–650 K. The curve fitting analysis of the DXAFS data revealed that Cu4–6 clusters were initially formed in the reduction process. The clusters went out to the outer surface and grew into big particles. On the contrary, the CuO particles on the outer surfaces were reduced directly to Cu0 metallic particles at ca. 450 K. The dynamic structure change around the Cu species in the zeolite during the reduction with H2 was monitored in situ by DXAFS technique for the first time.
  • Jianhua Hu, Wesley Min-Da Chiang, Peter Westh, Daniel Heng Chi Chen, C ...
    Type: Others
    Subject area: TP
    2001 Volume 74 Issue 5 Pages 809-816
    Published: 2001
    Released: September 01, 2002
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    Excess chemical potential, μ1PE, partial molar enthalpy, H1PE and volume of 1-propanol, V1PE, were determined as a function of mole fraction of 1-propanol, x1P, in mixed solvents of aqueous 2-propanol with various initial mole fraction of 2-propanol, x2P0. The 1-propanol–1-propanol interaction functions, H1P–1PEN(∂H1PE/∂n1P), and V1P–1PEN(∂V1PE/∂n1P), were evaluated by graphical differentiation. The x1P-dependence of all these quantities indicates that 1-propanol and 2-propanol modify the molecular organization of H2O in the same and additive manner in the water-rich region. The additive effect of 1-propanol and that of 2-propanol are in the ratio of (0.07/0.08).
  • Xin Xu, Song-Yun Kang, Tokio Yamabe
    Type: Others
    Subject area: TP
    2001 Volume 74 Issue 5 Pages 817-825
    Published: 2001
    Released: September 01, 2002
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    Dissociative adsorption of ammonia on the Si(100)-(2×1) surface has been investigated using the hybrid density functional B3LYP method and the Si9H12 one-dimer cluster model of the surface. The adsorption geometries and the reaction energetics from NH3(a) to NH2(a) and H(a) have been studied with Si basis sets varying from the standard all electron 6-31G(d) to the LanL2DZ with effective core potential, while keeping NH3 basis sets as 6-31G(d,p) in all cases. It was found that B3LYP/LanL2DZ is a reasonable level of theory for the calculations of not only the geometries, but also the reaction energetics. This provides a cost-effective way to extend the size of the Si cluster models and to study in details the energetics of the whole reaction path. Based on the experimental and theoretical results available, we recommend an “optimal” bond geometry of NH2(a) and H(a) on the Si(100)-(2×1) surface to be: Si–Si (symmetric dimer) 2.42 Å, Si–N 1.75 Å, Si–H 1.50 Å, N–H 1.01 Å, Si–Si–N 115°, Si-N-H 118°, Si–Si–H 111°, H–N–H 109°. The calculated results on the reaction energetics are in general agreement with the experimental findings as well as the previous theoretical ones.
  • Ryoka Matsushima, Shuichi Fujimoto, Kunihiro Tokumura
    Type: Others
    Subject area: TP
    2001 Volume 74 Issue 5 Pages 827-832
    Published: 2001
    Released: September 01, 2002
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    4-Dialkylamino-2-hydroxychalcones [3-(4-dialkylamino-2-hydroxyphenyl)-1-(substituted phenyl)-2-propen-1-ones] undergo reversible E/Z-photoisomerization in good quantum yields (0.2–0.4) in neutral aprotic solvents. The absorption bands of the photo-Z-isomers are significantly red-shifted from the E-isomers. By addition of acid, the photo-Z-isomers are converted to the flavylium ions with competitive reversion to the E-isomers. In aqueous ethanol solution, photochromic interconversion between chalcones and flavylium ions takes place rather slowly and less extensively.
  • Masanobu Aragaki, Shinya Kimura, Mao Katsuhara, Hiroyuki Kurai, Takehi ...
    Type: Others
    Subject area: TP
    2001 Volume 74 Issue 5 Pages 833-838
    Published: 2001
    Released: September 01, 2002
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    A novel selenium-containing bis-fused tetrathiafulvalene donor, C2TET-TS-TTP (2-[4,5-bis(ethylthio)-1,3-dithiol-2-ylidene]-5-(4,5-ethylenedithio-1,3-diselenol-2-ylidene)-1,3,4,6-tetrathiapentalene), has been synthesized. The ClO4, BF4, and PF6 salts of C2TET-TS-TTP are isostructural, having uniform β-type structures. These salts are essentially metallic down to low temperatures.
  • Yuki Tanaka, Masaharu Tsuji
    Type: Others
    Subject area: TP
    2001 Volume 74 Issue 5 Pages 839-849
    Published: 2001
    Released: September 01, 2002
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    Chemical ionization of 1-olefins (CxH2x : x = 8–18) by the CH5+, C2H5+, and C3H5+ ions has been studied under a reactant-ion selective mode of an ion-trap type of GC/MS. In all the reactions, alkyl CyH2y+1+ (y = 3–x) and alkenyl CyH2y−1+ (y = 3–x) ions were observed. For long-chain reagents (x = 11–18), the CyH2y+1+ and CyH2y−1+ distributions peaked at C4 or C5 and C7, respectively, which were essentially independent of the reactant hydrocarbon ions. On the basis of observed distributions and calculated thermochemical data, it was concluded that the major reactions for the formation of CyH2y+1+ were proton transfer to a C=C bond and hydride-ion abstraction from the alkyl portion in the CH5+ reactions, proton transfer to a C=C bond in the C2H5+ reactions, and addition to a C=C bond in the C3H5+ reactions, while the major reactions for the formation of CyH2y−1+ were hydride-ion abstraction in the CH5+ reactions, alkanide-ion abstraction in the C2H5+ reactions, and addition to a C=C bond in the C3H5+ reactions.
  • Takashiro Akitsu, Seiko Komorita, Akio Urushiyama
    Type: Others
    Subject area: AI
    2001 Volume 74 Issue 5 Pages 851-860
    Published: 2001
    Released: September 01, 2002
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    Square planar [CuN4] copper(II) complexes, Rb2[Cu(succim)4]•2H2O (1), trans-[CuL2(R-chea)(S-chea)] (2), trans-[CuL2(R-chea)2] (3), (succim = succinimidate, L = 5,5-diphenylhydantoinate, and chea = 1-cyclohexylethylamine) were prepared and crystal structures were determined. Crystal data for 1 are monoclinic with space group C2/m; a = 16.279(4), b = 8.382(3), c = 8.297(3) Å; β = 93.13(3) °; V = 1130.4(6) Å3; Z = 2. Crystal data for 2 are monoclinic with space group P21/c; a = 8.485(2), b = 9.7854(8), c = 26.334(4) Å; β = 92.83(1) °; V = 2183.8(5) Å3; Z = 2. Crystal data for 3 are monoclinic with space group P21; a = 8.472(2), b = 9.803(2), c = 26.331(6) Å; β = 92.67(2) °; V = 2184.6(8) Å3; Z = 2. The polarized crystal electronic spectra were determined for square planar [CuN4] 1, 2, and 3 and distorted square planar [CuN4] trans-[CuL2(R-phenea)(S-phenea)] (4) and trans-[CuL2(R-phenea)2][CuL2(S-phenea)2] (5) (phenea = 1-phenylethylamine). These spectra were deconvoluted by Gaussian curve fitting by considering selection rules for electric dipole transitions. The 3d orbital orders were determined to be dx2−y2 > dxy > dz2 > dyz,dzx for 1, dx2−y2 > dxy > dz2 > dyz > dzx for 2 and 3, and dx2−y2 > dxy > dz2 > dyz > dzx for 4 and 5 by means of polarized crystal spectra and angular overlap model (AOM) calculations. Since the dz2 → dx2−y2 transition could be observed separately for 4 for the first time, the present assignment could be established certainly. Distortion of [CuN4] chromophores decreases the peak wave numbers for a series of trans-[Cu(imidate)2(amine)2] complexes. The results of 1, 2, and 3 suggest that lone pairs of imidate ligands destabilize the dxy orbital by distributing in the [CuN4] plane.
  • Nami Saeki, Yuji Hirano, Yasunari Sasamoto, Ichiro Sato, Tsuyoshi Tosh ...
    Type: Others
    Subject area: AI
    2001 Volume 74 Issue 5 Pages 861-868
    Published: 2001
    Released: September 01, 2002
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    The following successive axial ligand substitution reactions of the head-to-head (HH) 2-pyridonato-bridged cis-diammineplatinum(III) dinuclear complex ([(H2O)Pt(NH3)2(μ-C5H4NO)2Pt(NH3)2(H2O)]4+) with halide ions X (X = Cl and Br) to give monohalogeno and dihalogeno complexes were studied kinetically:
    [(H2O)Pt(NH3)2(μ-C5H4NO)2Pt(NH3)2(H2O)]4++X [(H2O)Pt(NH3)2(μ-C5H4NO)2Pt(NH3)2(X)]3++H2O,
    [(H2O)Pt(NH3)2(μ-C5H4NO)2Pt(NH3)2(X)]3++X [(X)Pt(NH3)2(μ-C5H4NO)2Pt(NH3)2(X)]2++H2O.
    The acid dissociation constant (Kh1) of the axial aqua ligand in the HH dimer and the formation constants (K1X and K2X) of the monohalogeno and dihalogeno complexes were determined spectrophotometrically to be −log(Kh1/M) = 1.71 ± 0.04; log(K1Cl/M−1) = 5.93 ± 0.02, log(K2Cl/M−1) = 3.71 ± 0.00 for the reaction with Cl, and log(K1Br/M−1) = 6.20 ± 0.05, log(K2Br/M−1) = 4.55 ± 0.01 for the reaction with Br. The two platinum atoms are nonequivalent in the HH dimer, in which the first deprotonation occurs selectively to the water molecule on the Pt(N4) atom and the first nucleophilic substitution with X occurs preferentially to the Pt(N2O2) atom, where the atoms in parentheses are the coordinating atoms. The first water substitution with X proceeds via two similar substitution paths, whereas the second substitution proceeds through two dissimilar paths: one is a simple substitution path and the other is via dissociation of the water molecule, providing a coordinatively unsaturated complex. These reaction paths are reasonably explained by the relative strength of the trans effect of the water, hydroxide, and halide ions in the monohalogeno complexes.
  • Kenichi Oyaizu, Masayoshi Ueno, Hong Li, Eishun Tsuchida
    Type: Introduction
    Subject area: AI
    2001 Volume 74 Issue 5 Pages 869-870
    Published: 2001
    Released: September 01, 2002
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    The oxygenation of (2,9-dimethyl-1,10-phenanthroline)copper(I) chloride in THF, followed by a treatment with DMF and acidification with HCl, afforded dichloro[2-(dimethylamino)(hydroxy)methyl-9-methyl-1,10-phenanthroline]copper(II) and (aqua)dichloro(2,9-dimethyl-1,10-phenanthroline)copper(II) quantitatively.
  • Masahiro Mikuriya, Kenichi Minowa, Nobuyuki Nagao
    Type: Introduction
    Subject area: AI
    2001 Volume 74 Issue 5 Pages 871-872
    Published: 2001
    Released: September 01, 2002
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    A vanadium(IV) complex with 2-hydroxy-N,N′-bis(1-methyl-3-hydroxy-3-phenyl-2-propen-1-ylidene)-1,3-propane-diamine (H3L), [(VO)2(L)(pz)] (Hpz = pyrazole), was synthesized and characterized by measurements of the magnetic moment and the electronic spectra. The X-ray crystal structure analysis shows that the compound has a dinuclear structure with two square-pyramidal N2O3 coordination environments, which are bridged by the alkoxo and the pyrazolato groups. The antiferromagnetic interaction between the two metal atoms is fairly weak.
  • László Somogyi
    Type: Others
    Subject area: OB
    2001 Volume 74 Issue 5 Pages 873-881
    Published: 2001
    Released: September 01, 2002
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    Several substituted isatin 3-acylhydrazones (e.g. 1ak, n, p, t) have been synthesized. Under acetylating conditions they were transformed into selectively acetylated derivatives (e.g., 1l, n, o, qs) and into the novel, title spiroheterocycles (2ai). Some side reactions occurring under various acetylating conditions are also discussed.
  • Andrew Robertson, Masato Ikeda, Masayuki Takeuchi,, Seiji Shinkai
    Type: Others
    Subject area: OB
    2001 Volume 74 Issue 5 Pages 883-888
    Published: 2001
    Released: September 01, 2002
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    A benzocrown-appended lanthanum(III) porphyrin double decker has been synthesized which is capable of binding simple K+ in a cooperative, allosteric fashion to form a 1 : 4 complex. Analysis of this system by means of the Hill equation gave an overall binding constant (Kb) of 1.0 × 1014 (mol dm−3)−4 and a Hill coefficient of 4.0. This same system, however, binds Na+ in a conventional, linear fashion. These results indicate that the novel allosteric binding occurs as the result of 1 : 2 sandwich complexes between K+ and appended crown ether moieties of the two joined porphyrins. The suitability of lanthanum(III) over cerium(IV) for preparing this highly crowded double decker porphyrin is also noted.
  • Hiroyuki Higuchi, Takashi Ishikura, Kazumine Mori, Yukari Takayama, Ko ...
    Type: Others
    Subject area: OB
    2001 Volume 74 Issue 5 Pages 889-906
    Published: 2001
    Released: September 01, 2002
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    An extended π-electronic conjugation system of dihexylbithiophene–octaethylporphyrin [OEP–(DHBT)nOEP; n = 1–5], all the chromophores in which are connected with the linkage of 1,3-butadiyne (diacetylene), was synthesized by an oxidative cross-coupling reaction of the corresponding terminal acetylenes. Absorption spectral and electrochemical properties of the OEP–(DHBT)n–OEP system were examined. The results proved that the orientation of two 3-hexylthiophene (3HTh) rings of DHBT plays an important role in electronic communications between the two terminal OEP rings.
  • Toshihiro Tanaka, Ken Endo, Yasuhiro Aoyama
    Type: Others
    Subject area: OB
    2001 Volume 74 Issue 5 Pages 907-916
    Published: 2001
    Released: September 01, 2002
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    The Ni(II) complex of monoresorcinol derivative of a sterically unhindered tetraalkylporphyrin (3) affords adducts 3•(methanol) and 3•1.5(acetophenone). In the crystals, porphyrin 3 forms hydrogen-bonded (O–H···O–H) polyresorcinol chains with the porphyrin residues sticking out of the chains. The chains are self-assembled in such a manner as to give closely stacked interchain porphyrin columns, while the guest molecules are either firmly bound to the hydrogen-bonding sites (in the case of methanol) or incorporated in the channels running in parallel with the porphyrin stacks (in the case of acetophenone). The formation of such a stacked porphyrin array is not observed when the guest is changed to 4-heptanone or when the porphyrin is changed to a sterically hindered one 4 or 5 with full substitution at the meso- or the β-positions. The mode of interchain porphyrin stacking is discussed in light of the crystal structures of adducts 3•(4-heptanone), 4•pyridine, and 5•(2-nonanone).
  • Michihiko Noguchi, Hirofumi Okada, Masayuki Tanaka, Satoshi Matsumoto, ...
    Type: Others
    Subject area: OB
    2001 Volume 74 Issue 5 Pages 917-925
    Published: 2001
    Released: September 01, 2002
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    3-(Alk-2-enylamino)- and 3-(acryloylamino)-2,2-dimethylpropionaldehyde oximes underwent thermally induced 1,3-dipolar cycloaddition under mild conditions, leading to perhydroisoxazolo[4,3-c]pyridine derivatives. The features of the intramolecular oxime–olefin cycloaddition in this system and the roles of the geminal methyl groups at the 2-position and the alkenylamino nitrogen in the oxime–nitrone isomerization process are discussed based on kinetic studies.
  • Kunio Kawamura, Masatosi Umehara
    Type: Others
    Subject area: OB
    2001 Volume 74 Issue 5 Pages 927-935
    Published: 2001
    Released: September 01, 2002
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    A kinetic study of the temperature dependence of the template-directed formation of oligoguanylate (oligo(G)) on polycytidylic acid (poly(C)) from the 5′-phosphorimidazolide of guanosine (ImpG) has been carried out in the presence of Zn2+ at 40–80 °C. It is surprising that a large amount of oligo(G) was formed at 40–60 °C and a small amount of oligo(G) was detected even at 80 °C. The rate constants of the template-directed formation of oligo(G) were determined at 40–60 °C, and the same trend, the rate constants increase with the chain length, was observed as that at lower temperatures. Besides, second-order rate plots of the hydrolyses of ImpG and oligo(G) were consistent with pseudo-second-order processes in the presence of 0.04 M Zn2+. The apparent activation energy determined from the Arrhenius plots decreases in the order hydrolysis of oligo(G) > formation of 4-mer ≈ formation of 3-mer ≈ hydrolysis of ImpG > formation of 2-mer. The kinetic analysis and computer simulations demonstrate the importance of the rate of 2-mer formation to determine the efficiency of the oligo(G) formation.
  • Hitoshi Sashiwa, Yoshihiro Shigemasa, Renè Roy
    Type: Others
    Subject area: OB
    2001 Volume 74 Issue 5 Pages 937-943
    Published: 2001
    Released: September 01, 2002
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    Chitosan–sialic acid conjugates were prepared using p-formylphenyl α-sialoside by reductive N-alkylation. The degree of substitution (DS) of conjugates could be controlled from 0.06 to 0.53 by the amount of sialoside. With the use of p-isothiocyanatophenyl α-sialoside, chitosan–sialic acid conjugates were also prepared with excellent efficiency. Chitosan–melibiose conjugates having α-galactosyl epitope were also prepared by reductive N-alkylation. These conjugates were transformed into water-soluble forms by N-succinylation and their protein binding property was tested using wheat germ agglutinin (WGA) or Griffonia simplicifolia (GSI-B4) lectin. Strong immunodiffusion bands were observed in all of conjugates, thus demonstrating the specific binding of epitope in conjugate to each lectins.
  • Tiaoling Dong, Takayoshi Fujii, Satoro Murotani, Huagang Dai, Shin Ono ...
    Type: Others
    Subject area: OB
    2001 Volume 74 Issue 5 Pages 945-954
    Published: 2001
    Released: September 01, 2002
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    A kinetic investigation on the hydrolysis of aryl(fluoro)(phenyl)-λ6-sulfanenitriles was carried out in some aqueous and mixed aqueous-organic solutions. The pH-rate profiles showed that the hydrolysis consists of pH-independent, acid-catalyzed and base-catalyzed reactions. The neutral hydrolysis of fluoro-λ6-sulfanenitriles was found to proceed via an SN1 or an S-nitrilosulfonium cation-like transition state, which is characterized by a large negative Hammett ρ-value (ρ = −1.76 in water; −1.85 in CH3CN/H2O(1/4, v/v); −2.35 in TFE/H2O (1/1, v/v)), relatively large m-values (ca. 0.83 for fluoro(diphenyl)-λ6-sulfanenitrile; ca. 0.82 for fluoro(p-nitrophenyl)(phenyl)-λ6-sulfanenitrile against the solvent ionizing power YOTs-values in acetonitrile–water), a common ion effect in TFE/H2O, and a small salt effect. The large negative activation entropies (−60 – −101 J K−1 mol−1) were presumed to be due to strong solvation of F with H2O in the reaction systems. The ease of ion dissociation of the S–F bond was examined by a theoretical calculation in a DFT method, to show that the SN1-like transition state is caused by a facile tendency of dissociation of the S–F bond of fluoro-λ6-sulfanenitriles. The acid-catalyzed hydrolysis was found to proceed via a more cation-like transition state involving a concerted proton transfer to the fluorine atom and breaking of the sulfur-fluorine bond in the λ6-sulfanenitrile. The alkaline hydrolysis probably takes place via an SN2 mechanism.
  • Susumu Takeuchi, Yutaka Ukaji, Katsuhiko Inomata
    Type: Others
    Subject area: OB
    2001 Volume 74 Issue 5 Pages 955-958
    Published: 2001
    Released: September 01, 2002
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    A palladium-catalyzed asymmetric bis(alkoxycarbonylation) reaction of terminal olefins in the presence of copper(I) triflate was achieved by using a chiral bioxazoline ligand, (4S,4′S)-4,4′-dibenzyl-4,4′,5,5′-tetrahydro-2,2′-bioxazole, under normal pressure of carbon monoxide and oxygen at 25 °C to give the corresponding optically active mono-substituted succinates with enantioselectivity up to 66% ee.
  • Yoshihito Inai, Tatsuo Oshikawa, Mitsuji Yamashita, Tadamichi Hirabaya ...
    Type: Others
    Subject area: OB
    2001 Volume 74 Issue 5 Pages 959-966
    Published: 2001
    Released: September 01, 2002
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    In this paper we attempted to reveal how a large β-substituent (pyrenyl group) of dehydroresidue affects the structural and conformational preferences of (Z)-β-substituted α,α-dehydroalanine. An X-ray crystallographic analysis was carried out for Boc–L-Ala–ΔZPyr–L-Val–OMe (Boc = t-butyloxycarbonyl; OMe = methoxy) possessing a novel (Z)-β-(1-pyrenyl)dehydroalanine (ΔZPyr) residue. Single crystals were obtained by slow evaporation from an ethanol solution in the monoclinic space group P21. The bond lengths and bond angles of the ΔZPyr residue were essentially similar to other β-substituted dehydroalanines. The tripeptide took a type II β-turn conformation involving an intramolecular hydrogen bond between CO(Boc) and NH(Val), like small peptides possessing a (Z)-β-(1-naphthyl)dehydroalanine or a (Z)-β-phenyldehydroalanine residue. The similarity between ΔZPyr and other dehydroalanines in structural property and conformational preference should be responsible for the non-planarity of the ΔZPyr residue to give an extremely high energy in the planar orientation of the pyrenyl group relative to the Cα=Cβ-Cγ plane; the non-planarity should weaken the π-conjugation effect of the pyrenyl group on the structural property and conformational preference of the ΔZPyr residue. The pyrenyl rings were packed in a partially overlapped face-to-face orientation with the shortest center-to-center distance of 5.96 Å. The CD spectrum of a KBr disk prepared from the crystal showed strong excitonic interactions between pyrenyl groups, reflecting a regular arrangement of the pyrenyl groups in the crystal structure.
  • Tetsuya Eguchi, Yukio Hoshino
    Type: Others
    Subject area: OB
    2001 Volume 74 Issue 5 Pages 967-970
    Published: 2001
    Released: September 01, 2002
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    Chromones were regioselectively reduced to 2H-1-benzopyrans through the 1,2-addition of 9-borabicyclo[3.3.1]nonane. Although transition-metal complexes did not have a catalytic effect on the reaction, only by using palladium(II) chloride, could both 2H-1-benzopyran and dihydro-1-benzopyran be obtained to a similar extent. Also, the reduction of chromone using other organoboranes led not to 2H-1-benzopyran, but rather to chromanone through the reduction of only an olefin moiety.
  • Yukinori Wada, Junji Ichikawa, Tadayuki Katsume, Tomoko Nohiro, Tatsuo ...
    Type: Others
    Subject area: OB
    2001 Volume 74 Issue 5 Pages 971-977
    Published: 2001
    Released: September 01, 2002
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    β,β-Difluorostyrenes bearing an oxygen (OH) or a sulfur (SH, SCOCH3) nucleophile linked by a methylene unit to the ortho carbon are prepared from 2,2,2-trifluoroethyl p-toluenesulfonate via the in situ generation of 2,2-difluorovinylboranes and their palladium-catalyzed cross-coupling reaction with aryl iodides. These styrene derivatives readily undergo intramolecular nucleophilic substitution of the oxygen and sulfur with loss of fluorine under basic conditions, leading to 3-fluoroisochromenes and 3-fluoroisothiochromenes in high yields.
  • Naoto Sumi, Hidetaka Nakanishi, Shinpei Ueno, Kazuo Takimiya, Yoshio A ...
    Type: Others
    Subject area: OB
    2001 Volume 74 Issue 5 Pages 979-988
    Published: 2001
    Released: September 01, 2002
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    A series of the longest class of oligothiophenes extended at intervals of seven thiophene units from the 6-mer up to the 48-mer has been synthesized by a combination of the random Eglinton coupling reaction of mono- and di-ethynylsexithiophenes and a subsequent sodium sulfide-induced cyclization reaction of the resulting oligo(sexithienylene-diethynylene)s. Their structures were well characterized by MALDI-TOF MS and 1H NMR spectroscopy. The molecular weights of the oligothiophenes and oligo(sexithienylene-diethynylene)s, measured by gel-permeation liquid chromatography using the polystyrene standard, are nearly double the actual ones, indicating that they keep highly rigid rod-type shapes. According to a molecular model, the molecular lengths of the longest oligothiophene 48-mer and the longest oligo(sexithienylene-diethynylene) reach approximately 18.6 nm and 25.0 nm, respectively. In the electronic absorption and emission spectra, the π–π* transitions of the oligothiophenes demonstrate progressive red shifts with increasing chain length up to the 20-mer. In the cyclic voltammograms, furthermore, the first oxidation potentials tend to continue negative shifts up to the 34-mer. In accordance with these spectral changes, the doped conductivities steadily increase and approach that of a structurally related polymer.
  • Tomomi Nagasawa, Nozomi Kudo, Yoshiyuki Hida, Kazuaki Ito, Yoshihiro O ...
    Type: Introduction
    Subject area: OB
    2001 Volume 74 Issue 5 Pages 989-990
    Published: 2001
    Released: September 01, 2002
    JOURNALS RESTRICTED ACCESS
    A chiral solid catalyst as a heterogeneous Lewis acid prepared from trimethylaluminum, menthol and tetrachlorobisphenol A has been found to promote the asymmetric Diels–Alder reaction of 2-methyl-2-propenal with cyclopentadiene and is a reuseable catalyst.
  • Naoki Yasuda, Shigeyuki Yamamoto, Hiroshi Adachi, Suguru Nagae, Yuji W ...
    Type: Others
    Subject area: AM
    2001 Volume 74 Issue 5 Pages 991-996
    Published: 2001
    Released: September 01, 2002
    JOURNALS RESTRICTED ACCESS
    A negative working photosensitive silicone ladder polymer (PVSQ) based on polyphenylsilsesquioxane with vinyl groups as a reactive substituents in the side chain, and 2,6-bis(azidobenzylidene)-4-methylcyclohexanone (BA) as a photocrosslinker, has been developed. The monodisperse PVSQ was synthesized by co-polymerization of trichlorophenylsilane and trichloro(vinyl)silane with potassium hydroxide in isobutyl methyl ketone. The PVSQ film showed excellent transparency above 280 nm and high solubility in organic solvents. The photosensitive PVSQ containing 3 wt% of BA showed the sensitivity of 40 mJ cm−2 when it was exposed to 365 nm light (i-line) followed by development with a mixture solution of anisole and xylene at 25 °C. The photosensitive PVSQ film also showed high thermal stability (decomposition temperature: 520 °C) and low dielectric constant (3.2/1 MHz), demonstrating a high potential for application to LSI production.
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