Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 68 , Issue 10
Showing 1-33 articles out of 33 articles from the selected issue
  • Takashi Shibahara, Genta Sakane, Yoshiyuki Naruse, Kazuhisa Taya, Haru ...
    1995 Volume 68 Issue 10 Pages 2769-2782
    Published: 1995
    Released: July 10, 2006
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    Reaction of the incomplete cubane-type cluster [Mo3S4(H2O)9]4+ (A) with iron gives a novel cubane-type aqua cluster [Mo3FeS4(H2O)10](CH3C6H4SO3)4·7H2O (B′). An ammonia coordinated derivative cluster [Mo3FeS4(H2O)(NH3)9]Cl4 (C′) is also synthesized. X-ray structural analyses of B′ and C′ revealed that the clusters, [Mo3FeS4(H2O)10]4+ (B) and [Mo3FeS4(H2O)(NH3)9]4+ (C), have an approximate symmetry of C3v. The iron atom has fairly regular tetrahedral geometry in both clusters. The effective magnetic moments of B′ at 2.16 K and 269.95 K are 2.78 and 3.26 B.M., respectively. 57Fe-Mössbauer spectroscopy showed that the oxidation states of iron in B′ and C′ were assignable to be +2.39 and +2.54, respectively, which indicates that the reaction is a reductive addition of an iron atom to the Mo3S4 core in A. The cyclic voltammograms of A, B, and [Mo3NiS4(H2O)10]4+ (D) show three consecutive one electron reductive steps, respectively, and the oxidation states of metals in B and D are assigned as MoIVMoIII2MII (M = Fe, Ni). Discrete variational (DV)-Xα calculation of B, C, and D explains the magnetic behavior, XPS spectra, and reactivity toward CO, C2H2, and C2H4.
  • Shigenori Nagatomo, Sadamu Takeda, Hatsue Tamura, Nobuo Nakamura
    1995 Volume 68 Issue 10 Pages 2783-2789
    Published: 1995
    Released: July 10, 2006
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    The crystal structure of 4,5-dicyanoimidazole ((CN)2Imd) was determined by an X-ray diffraction at room temperature; monoclinic, P21/a, a = 7.259(2), b = 7.529(1), c = 10.0972(9) Å, β = 102.74(1)°, V = 538.2(2) Å3, Z = 4, R = 0.043, and Rw=0.066 for 1090 observed reflections. Crystal structure of 4,5-dichloroimidazole (Cl2Imd) was redetermined; tetragonal, P41212, a = 6.843(4), c = 24.236(7) Å, V = 1134(1) Å3, Z = 8, R = 0.043, and Rw = 0.058 for 427 observed reflections. Molecules in Cl2Imd and in (CN)2Imd are linked by intermolecular N–H···N hydrogen bonds to form one-dimensional chains. The hydrogen bonds in Cl2Imd are formed between the ring nitrogen atoms, while those in (CN)2Imd are between the ring and the cyano nitrogens. The hydrogen bond distance (3.051(2) Å) of N···N in (CN)2Imd is long, compared with that (2.800(6) Å) in Cl2Imd. The weak hydrogen bond in (CN)2Imd was also indicated by IR and 15N CP/MAS NMR spectra.
  • Sylvie Parret, Fabrice Morlet-Savary, Jean-Pierre Fouassier, Kiyoshi I ...
    1995 Volume 68 Issue 10 Pages 2791-2795
    Published: 1995
    Released: July 10, 2006
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    Due to their very substantial fluorescence emission, pyrylium and thiopyrylium salts are widely used as laser dyes and photosensitizers. This paper deals with the fluorescence properties (quantum yields and wavelengths of the fluorescence maxima as well as the lifetimes of the singlet excited states) of eight pyrylium and ten thiopyrylium salts, with special emphasis on the effect of α and γ substitutions of the heterocycle.
  • Narayanasamy Rajendiran, Meenakshisundaram Swaminathan
    1995 Volume 68 Issue 10 Pages 2797-2802
    Published: 1995
    Released: July 10, 2006
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    Fluorescence solvatochromic shifts of 4,4′-diaminobiphenyl (DABP) were found to be less than those of 4-aminobiphenyl and the difference mainly occured in hydrogen bonding solvents. This shows that the net effect of hydrogen bonding interactions of two amino groups is less than that of one amino group. The unusual fluorescence red-shift observed for the monocation of DABP relative to the neutral form is not because of the amino group becoming more basic, but because of a large solvent relaxation in aqueous media. As the entire molecule becomes planar upon excitation, its behavior is found to be similar to that of 2,7-diaminofluorene in the S1 state. pKa values for various prototropic reactions in the S0 and S1 states were determined and are discussed.
  • Ryoichi Nakagaki, Osamu Takahira, Masaharu Yamaoka, Noriko Kashima
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 10 Pages 2803-2808
    Published: 1995
    Released: July 10, 2006
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    No appreciable magnetic field effects were observed on the relative quantum yield for photochemical reactions of 4-methyl-2-quinolinecarbonitrile with (R)-(−)-2-phenylpropionic, diphenylacetic, and 2,2-diphenylpropionic acids in benzene. Observed results were reasonably explained in terms of kinetic parameters which are dependent on and independent of an external magnetic field. (S)-(+)- and (R)-(−)-α-methoxyphenylacetic acids exhibit equivalent reactivity toward the excited state of 4-methyl-2-quinolinecarbonitrile in acetonitrile. No unusual phenomena were observed under well controlled conditions with sufficient repetitions.
  • Kaoru Ohta, Masahide Terazima, Noboru Hirota
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 10 Pages 2809-2815
    Published: 1995
    Released: July 10, 2006
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    Translational diffusion of MBBA (N-(4-methoxybenzylidene)-4-n-butylaniline) in the nematic and isotropic phases is investigated by the transient grating (TG) method. The origin of the TG signal due to the population grating is attributed to the spatial variation of the order parameter and, as a result, the time dependence of the signal reflects the diffusion of the cis form of MBBA, not of the trans form. In the nematic phase, the diffusion constant parallel to the director orientation, D||, is always larger than the perpendicular one, D. The obtained values are 2.2—2.5 times larger than previously reported ones measured by using a photosensitive probe molecule in the liquid crystal. The anomaly previously reported near the nematic–isotropic phase transition temperature is not observed, and the diffusion constant in the isotropic phase is close to the average value of the both components, 1/3(D + 2D). The experimental values are also compared with the ones calculated from two theoretical expressions by Franklin, and Chu and Moroi.
  • Rajesh Kumar Vatsa, Awadhesh Kumar, Prakash Dattatray Naik, Kuchimanch ...
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 10 Pages 2817-2822
    Published: 1995
    Released: July 10, 2006
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    Photodissociation of CF2Br2 at 248 nm has been studied in the gas phase using time-resolved optical absorption spectroscopy. A transient absorption spectrum in the range of 200—320 nm with λmax ≈ 260 nm is observed and has been assigned to the primary photodissociation product, the CF2Br radical. The absorption cross section of this radical at 260 nm has been found to be (1.05 ± 0.2) × 10−18 cm2 molecule−1. The rate constant for CF2Br dimerization is evaluated to be (3.0 ± 0.6) × 10−12 cm3 molecule−1 s−1. Laser fluence dependence in the secondary photodissociation of CF2Br radical is discussed.
  • Xiao-Min Chen, Kiminori Itoh, Masayuki Murabayashi
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 10 Pages 2823-2829
    Published: 1995
    Released: July 10, 2006
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    A K+ ion-exchanged glass optical waveguide (OWG) was combined with an Ag+ ion-exchanged glass OWG on one substrate by tapered velocity coupling to obtain a low loss and highly sensitive ion-exchanged OWG system. The relative sensitivity of the Ag+-doped region was more than 1000 times per unit length (the reference here being spectroscopic measurements with normal incidence of monitoring light). The attenuation of the guided light was 3—5 dB cm−1 at the highly sensitive part. Stability against heat and against UV-irradiation were investigated also.
  • Hidefumi Sakamoto, Junichi Ishikawa, Makoto Otomo
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 10 Pages 2831-2836
    Published: 1995
    Released: July 10, 2006
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    Dithiazacrown, tetrathiazacrown, and two tetrathiadiazacrown ether derivatives, bearing a phenyl group on each nitrogen atom at the periphery, were synthesized, and the solvent extractions of some transition metal ions with these compounds were carried out using an H2O–1,2-dichloroethane system. All of the thiazacrown compounds employed exhibited Ag+ selectivity, and formed 1 : 1 : 1 complexes of Ag+ : ligand : laurate ion as a counter anion to be extracted into a 1,2-dichloroethane solution. The extractabilities (extraction constants, Kex) for Ag+ decreased in the order: 7,16-diphenyltetrathia-7,16-diaza-18-crown-6 (3) (log Kex = 1.18 ± 0.13) > 13-phenyltetrathia-13-aza-15-crown-5 (2) (0.75 ± 0.09) > 7-phenyldithia-7-aza-9-crown-3 (1) (−0.47 ± 0.06) > 13,16-diphenyltetrathia-13,16-diaza-18-crown-6 (4) (−0.62 ± 0.16).
  • Ken-ichi Tominaga, Yoshiyuki Sasaki, Taiki Watanabe, Masahiro Saito
    1995 Volume 68 Issue 10 Pages 2837-2842
    Published: 1995
    Released: July 10, 2006
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    Methanol, together with methane, is formed for the first time by homogeneous hydrogenation of CO2 using a catalytic system consisting of Ru3(CO)12 and alkaline iodides in N-methylpyrrolidone (NMP) solution at 240 °C. The time course of the reaction indicates the successive formation of CO, methanol, and then methane. The FT-IR analysis of the resulting reaction solutions reveals the formation of several species of ruthenium carbonyl anion and their mutual interchanges during the reaction. A mechanism for the overall reaction is proposed, based on these results.
  • Shigehiro Kagaya, Joichi Ueda
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 10 Pages 2843-2846
    Published: 1995
    Released: July 10, 2006
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    Gallium(III) phosphate coprecipitates quantitatively 0.2—7.5 μg of chromium(III) from 100 to 500 cm3 of a sample solution at pH 4.5—6.0. Although chromium(VI) is hardly coprecipitated with gallium(III) phosphate, it can be collected as chromium(III) after reduction by hydroxylamine. The calibration curve is linear from 8 to 300 ng cm−3 for chromium. The detection limit (signal/noise = 2) is 0.11 ng cm−3 of chromium(III) or chromium(VI) in 500 cm3 of the initial sample solution.
  • Mannar R. Maurya, Deena C. Antony, Sarada Gopinathan, Vedavati G. Pura ...
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 10 Pages 2847-2852
    Published: 1995
    Released: July 10, 2006
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    A general method for the preparation of dioxotungsten(VI) complexes of the type [WO2L(MeOH)] (where LH2 = the Schiff’s base derived from salicylaldehyde or o-vanillin and benzoylhydrazide, salicylhydrazide, furoylhydrazide, and isonicotinoylhydrazide) using [WO2(acac)2] (acacH = acetylacetone) as a precursor, is described. These complexes have been characterized by elemental analysis, electrical conductance, IR, electronic, and NMR spectral, electrochemical, and magnetic susceptibility measurements. The structure of [WO2(o-C6H4CH=NN=C(O)C6H5)(MeOH)]·MeOH (1a·MeOH) has been determined by single-crystal X-ray diffraction analysis. 1a·MeOH crystallizes in the space group Pbc21 with a = 6.992(2), b = 16.190(2), c = 31.390(4) Å, V = 3553.4(12) Å3, Z = 8, RF = 0.050, and Rw = 0.054. The tungsten atom has a highly distorted octahedral coordination in which anionic oxygen atoms of the tridentate ligand are mutually trans and are cis to the cis-dioxo group.
  • Masaru Kimura, Tomoko Hara, Keiichi Tsukahara
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 10 Pages 2853-2857
    Published: 1995
    Released: July 10, 2006
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    The kinetics of the oxidation of iodide ion to iodine by molecular oxygen catalyzed by VO2+ ions were studied in sulfuric acid solutions in the dark. After an induction period during which time the I2−• radical anion forms, the rate of formation of iodine increased due to catalysis by VO2+ ions. The rate of reaction depended on the concentrations of VO2+, H+, and I, and was independent of the ionic strength. The reaction was inhibited by either radical scavengers or the complex-forming substances of ethylenediaminetetraacetic acid and chloride ions. A chain mechanism containing I2−•/I2, VO2+/V3+, and O2/HO2 redox cycles is presented.
  • Toshiaki Yonemura, Sayuri Nakahira, Tomoharu Ama, Hiroshi Kawaguchi, T ...
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 10 Pages 2859-2866
    Published: 1995
    Released: July 10, 2006
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    Novel S-bridged dinuclear cobalt(III) complexes having different absolute configurations in [Co(didentate-N,S)3] moieties, Λ- and Δ-[Co{Co(didentate-N,S)3}(D-pen-N,O,S)]+ or 2− (didentate = 2-aminoethanethiolate (aet), L-cysteinate (L-cys), and D-penicillaminate (D-pen)), were prepared stereospecifically. The dinuclearizing reaction of ΔLLL-fac(S)-[Co(L-cys-N,S)3]3− with [CoCl(NH3)5]2+ and D-penicillaminate proceeded with configurational retention in the [Co(L-cys-N,S)3] moiety, while the reaction using the Co(II) ion instead of [CoCl(NH3)5]2+ was accompanied by a configurational inversion in the [Co(L-cys-N,S)3] moiety. The occurrence of the configurational inversion was related to the intramolecular N–H···O hydrogen bonds between two ligands in the formation process of the dinuclear complexes. The newly prepared dinuclear complexes were characterized on the basis of their electronic absorption, CD, 13C NMR, and IR spectral data. Electrochemical measurements of [Co{Co(didentate-N,S)3}(D-pen-N,O,S)]+ or 2− gave two redox waves at ca. −0.61 V and −0.85 to −1.04 V (vs. Ag/AgCl). The former wave corresponds to the Co(III)/Co(II) redox of the [Co(S)3(D-pen-N,O,S)] moiety, and the latter one to that of the [Co(didentate-N,S)3] moiety.
  • Quyen T. H. Le, Shigeo Umetani, Takayuki Sasaki, Takeshi Tomita, Masak ...
    1995 Volume 68 Issue 10 Pages 2867-2873
    Published: 1995
    Released: July 10, 2006
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    The synergistic extraction of alkaline earth (Mg2+, Ca2+, Sr2+, and Ba2+) and alkali metals (Li+ and Na+) with a highly acidic extractant, 4-benzoyl-3-phenyl-5-isoxazolone (HPBI), combined with a synergist, trioctylphosphine oxide (TOPO) or bis(diphenylphosphinyl)methane (BDPPM), has been examined. The results were compared with those of the analogous extractants, 4-benzoyl-3-methyl-1-phenyl-5-pyrazolone (HPMBP) and 3-methyl-1-phenyl-4-trifluoroacetyl-5-pyrazolone (HPMTFP) which are also highly acidic extractants derived from heterocyclic compounds. Owing to the strong acidity of HPBI (pKa = 1.23), alkaline earths were extracted quantitatively from a very low pH region. Especially, alkaline earths were readily extracted at pH 2—3 with the bidentate phosphine oxide, BDPPM, as a synergist. The extraction of Li+ and Na+ with HPBI and TOPO was inferior to that with HPMBP and HPMTFP, though their acidity is weaker. In contrast to the excellent extractability of HPBI, its separation was poor. The extractability and separability are discussed in terms of the molecular structure, particularly the distance of the two donating oxygens.
  • Kenji Nomiya, Hiroshi Yokoyama, Hitomi Nagano, Munehiro Oda, Sadatoshi ...
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 10 Pages 2875-2883
    Published: 1995
    Released: July 10, 2006
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    Sodium salt of anionic Au(I) complex with a trianion of thiomalic acid tma3− (H3tma = HOOCCH(SH)CH2COOH), known as an effective antiarthritic drug, was prepared in highly pure form by one-step synthesis from NaAuCl4 and tma3− in aqueous solution. The reaction consisted of a reduction of Au(III) by tma3− and the following complexation of Au(I) with tma3− ligand. The disulfide species of tma3− formed by this reduction was removed by passing through an anion-exchange resin column and the contaminating NaCl by passing through a gel filtration column. The tma–Au(I) complex was also prepared by another reaction based on ligand exchange of the intermediate complex AuCl(thiodiglycol) with tma3−. It was purified using the anion-exchange resin and gel filtration columns. The target compound, finally isolated in 30% yield in highly pure form, has been characterized by complete elemental analyses, TG/DTA, FT-IR, 1H and 13C NMR spectroscopies, and molecular weight was determined in aqueous solution by molmass measurement based on the cryoscopic method combined with dissociation degree determination based on the [Na+] measurement in equilibrium state using a Na+-ion selective electrode. This Au(I) complex was an oligomer with a formula of {Na2[Au(tma)]·1.75H2O}n (n = 3—10; MW = 1260—4220). This polymerization degree, low in comparison with previously proposed data, was determined in the neutral aqueous solution without any other electrolytes under the concentration range CNa = 0.914—182.9 mmol dm−3. The tma–Au(I) complex exists in an oligomeric form both in the solid and in aqueous solution. The properties of the oligomeric tma–Au(I) complex were compared with those of the previously reported complex and a commercially available sample, and also with those of the recently prepared, oligomeric tma–Ag(I) complex with antimicrobial activity.
  • Monica Nijhawan, Rakam Singh Chauhan, Lajpat Rai Kakkar
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 10 Pages 2885-2889
    Published: 1995
    Released: July 10, 2006
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    5,7-Diiodo-8-hydroxyquinoline (diiodo-oxine) has been used as an analytical reagent for the spectrophotometric determination of zirconium with which it forms a yellow colored complex (1 : 2) in dilute hydrochloric acid solution. The complex is extractable into chloroform from 0.1—0.2 mol dm−3 HCl showing an absorption maximum at 417.5—421 nm with a molar absorptivity of 1.87 × 104 dm3 mol−1 cm−1 and Sandell sensitivity equal to 4.8 × 10−3 μgZr cm−2. Beer’s law holds good in the range 0—5 μgZr cm−3, with a standard deviation ±0.006 and relative mean error ±0.36%. The method is simple, selective and sensitive.
  • Mutsuo Kodama
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 10 Pages 2891-2896
    Published: 1995
    Released: July 10, 2006
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    With polarographic and potentiometric methods, the complexation equilibria of 15,15′-trimethylenebis(1,4,7,10,13-pentaazacyclohexadecane-14,16-dione) [abbreviated to bis(dioxo[16]aneN5)] with Cu2+, Cd2+, Hg2+, and Pb2+ ions were investigated systematically. It was found that bis(dioxo[16]aneN5) reacts with Cu2+ ion affording a 2 : 1 ratio binuclear complex, designated Cu2L4+ or [Cu2H−4L]°, but in the reactions with Cd2+, Hg2+, and Pb2+ ions it forms 1 : 1 ratio complexes, ML2+. Comparison of formation constants for the complexes of the latter bivalent metal ions with those of the parent 1,4,7,10,13-pentaazacyclohexadecane-14,16-dione [abbreviated to dioxo[16]aneN5] showed that the attachment of the second dioxo[16]aneN5 moiety always enhances the complexation ability of the dioxo[16]aneN5 ligand considerably, suggesting the formation of sandwich-type complexes, where the metal(II) ion is located between the two cyclic pentaamine moieties.
  • Dai Ooyama, Noriharu Nagao, F. Scott Howell, Masao Mukaida, Hirotaka N ...
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 10 Pages 2897-2904
    Published: 1995
    Released: July 10, 2006
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    A one-electron oxidation species of the title complex, [Ru(NO)Cl5]({RuNO}5-type nitrosyl complex), converted into cis-[Ru(NO)Cl4(CH3CN)]({RuNO}6-type nitrosyl complex) at low temperature (5 °C) in the dark. The product species could be isolated and characterized. An X-ray structure determination showed a remarkably short N–O bond distance of the Ru–NO moiety: l(N–O) = 0.998 Å, l(Ru–N) = 1.787(5) Å, ∠Ru–N–O = 175.1(6)°. Under room light at 25 °C, the complex underwent a facile nitrosyl photoelimination to give trans-[RuCl4(CH3CN)2], the structure of which was also established. During the course of the reactions, two other unidentified species were confirmed to exist by cyclic voltammetry.
  • Ikuo Naito, Yoshihisa Fujiwara, Yoshifumi Tanimoto, Akito Ishida, Sets ...
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 10 Pages 2905-2908
    Published: 1995
    Released: July 10, 2006
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    1,3-Dipolar additions of a nitrile ylide (NY) with carbonyl compounds were studied by means of the laser flash photolyses of 3-(biphenyl-4-yl)-2H-azirine in the presence of various types of carbonyl compounds: i.e. ketones, aldehydes, and esters. NY decays according to psuedo first-order kinetics. The rate constant of the 1,3-dipolar addition reaction of NY with carbonyl compound is increased with increasing the ionizing potential of the π-electron on the carbonyl double bond. NY reacts also with carbon dioxide (k = 5.3 × 105 dm3 mol−1 s−1 in acetonitrile).
  • Atsuhiro Osuka, Shinji Marumo, Yukihisa Wada, Iwao Yamazaki, Tomoko Ya ...
    1995 Volume 68 Issue 10 Pages 2909-2915
    Published: 1995
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    1,3-Dioxane-bridged pyropheophorbide–diimide dyads and pyropheophorbide dimer were synthesized by simple acid-catalyzed reactions of methyl pyropheophorbide d with diimide-substituted diols and with pentaerythritol, respectively. 1,3-Dioxane-bridged bacteriopyropheophorbide–diimide was similarly prepared from bacteriopyropheophorbide a. Intramolecular electron-transfer and energy-transfer reactions in these models have been studied by picosecond fluorescence measurements.
  • Sigeru Torii, Kouji Akiyama, Hidetoshi Yamashita, Tsutomu Inokuchi
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 10 Pages 2917-2922
    Published: 1995
    Released: July 10, 2006
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    Vanadium(II)-assisted cross-coupling of 1,4,5,8-tetramethoxynaphthalene-2-carbaldehyde and 3-methyl-2-butenal was employed for introduction of the side chain of dl-shikonin. 2-(1-Hydroxy-4-methyl-3-pentenyl)-1,4,5,8-tetramethoxynaphthalene was prepared by the pinacol coupling and the subsequent palladium-catalyzed hydrogenolysis of the carbon–oxygen bond at the allylic position of the diol carbonate. Electrochemical oxidation of the 2-substituted 1,4,5,8-tetramethoxynaphthalene, followed by reductive acetylation with zinc and the subsequent electrooxidation of the resulting 5,8-diacetoxy-1,4-dimethoxynaphthalene, afforded the corresponding 5,8-diacetoxy-1,4-naphthoquinone, whose alkaline hydrolysis furnished dl-shikonin.
  • Takeo Imai, Kazuya Kamata, Hiroshi Saito, Akio Urushiyama
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 10 Pages 2923-2930
    Published: 1995
    Released: July 10, 2006
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    Addition of potassium hexacyanoferrate(III) to Mycobacterium smegmatis 7Fe ferredoxin resulted in the formation of a new 6Fe(2 × [3Fe–4S]) ferredoxin, which was verified by the iron content and resonance Raman spectra of the highly purified preparation. The results suggest that the 4Fe cluster in the native ferredoxin was converted into a 3Fe cluster. The new 3Fe cluster produced was found to be similar in structure to the native 3Fe cluster as judged by the Raman spectra. The produced 6Fe(2 × [3Fe–4S]) ferredoxin was further degraded into apoferredoxin upon application of additional hexacyanoferrate(III).
  • Seiji Sakamoto, Hisakazu Mihara, Eitarou Matsuo, Takuro Niidome, Kazun ...
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 10 Pages 2931-2939
    Published: 1995
    Released: July 10, 2006
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    The 24-peptide 46, designed to take an amphiphilic α-helix structure, had strong activity toward phospholipid membranes and could form ion-channels selective for cations on a planar membrane [J. Biol. Chem., 266, 20218 (1991)]. Four, six, and eight segments of the peptide 46 were bundled (4α-46, 6α-46, and 8α-46) on dendrimers consisting of Lys residues. These bundled peptides had highly α-helical structures with an enhanced α-helicity compared with the original 46 peptide. These peptides had hydrophobic pockets inside the bundle structures in aqueous solution in which the fluorescent hydrophobic probe, 1-anilino-8-naphthalenesulfonate (ANS), bound strongly. The peptides caused much leakage of carboxyfluorescein from small unilamellar vesicles of phospholipids at much lower concentrations of peptides than 46 did. Furthermore, the peptides induced the vesicle fusion at lower concentrations than those of the leakage. Four segments of the analogous 24-peptide 46S, in which six Ser residues were introduced instead of Ala and Leu residues in 46, were bundled by the same method (4α-46S). The fluorescent properties of the Trp residues incorporated at the 1 and 12 positions in 4α-46S, respectively, indicated that the centers of the helices were in more hydrophobic conditions than the N-terminal was. These facts caused us to conclude that the bundled conformation increased the perturbation of the phospholipid membrane, and as a result, the peptides were embedded in the membrane.
  • Toshikazu Ibata, Mu-Hong Shang, Tetsuo Demura
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 10 Pages 2941-2949
    Published: 1995
    Released: July 10, 2006
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    An aromatic nucleophilic substitution (SNAr) reaction of p-chloronitrobenzene with N-substituted pyrrolidines under high pressure gave p-pyrrolidinonitrobenzene and ring-opening products through quaternary ammonium salt. The selectivity of dealkylation and ring-opening depends on the electronic and steric factors of N-substituents. The reactions with N-methylaziridine and N-methylazetidine gave ring-opening products without affording any demethylation product.
  • Takahiro Gunji, Tsutomu Kitakatsu, Yoshimoto Abe
    1995 Volume 68 Issue 10 Pages 2951-2954
    Published: 1995
    Released: July 10, 2006
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    Syntheses and characterization of titaniosiloxane and zirconiosiloxane compounds were investigated. Titaniosiloxane and zirconiosiloxane compounds were prepared by the reaction of di-t-butoxymethoxysilanol [DBMS] with titanium or zirconium alkoxides.
    DBMS was subjected to the reaction with bis(acetylacetonato)titanium diisopropoxide and titanium tetraisopropoxide to give titaniosiloxane compounds TS12 and TS14, respectively. Titaniosiloxane compounds were isolated by distillation or sublimation. TS12 was estimated to be cis-form from its 13C NMR spectrum in CDCl3. TS14 was stable in solution, but apt to decompose after isolation.
    ZS12 and ZS14 were prepared by the reaction of DBMS with bis(acetylacetonato)zirconium diisopropoxide and zirconium tetraisopropoxide, respectively. The isolation of ZS12 and ZS14 by distillation or recrystallization was difficult because of decomposition and high solubility, and the formation of ZS12 and ZS14 was confirmed by 1H, 13C, and 29Si NMR and IR spectra.
  • Tatsuo Yamamura, Kazuhiro Nishiwaki, Yasumitsu Tanigaki, Susumu Terauc ...
    Type: Accounts
    Subject area: AI
    1995 Volume 68 Issue 10 Pages 2955-2960
    Published: 1995
    Released: July 10, 2006
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    The antioxidant activities of dihydric phenols, such as catechol, resorcinol, and hydroquinone, and their twenty-three alkyl and benzyl substituted derivatives were evaluated by means of an oxygen-absorption method at 60 °C for determining the oxidation of tetralin. Catechols exhibited a much higher stoichiometric factor (2.0—2.3) compared with those of other compounds. The stoichiometric factors of hydroquinones (0.6—1.1) are almost half those of catechols, and are lower for the resorcinols (0.3—0.6). In addition, the rates of oxidation during the induction period (Rinh) were 1.1—1.6 × 10−6, 3.0—3.8 × 10−6, and 13.3—18.4 × 10−6 M min−1 for catechols, hydroquinones, and resorcinols, respectively. According to these results, catechols and hydroquinones are efficient antioxidants, and their activities may be dependent on the stability of phenoxyl radicals as oxidation products due to the formation of the quinone structure. Furthermore, the stability of phenoxyl radicals derived from catechols is higher than that of those from hydroquinones. In spite of having two OH substituents, resorcinols behave as monohydric phenols in the reaction with peroxyl radicals.
  • Soichi Uchida, Yasushi Yokoyama, Jitsuo Kiji, Tamon Okano, Hitoshi Kit ...
    1995 Volume 68 Issue 10 Pages 2961-2967
    Published: 1995
    Released: July 10, 2006
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    The attempt to synthesize N-p-tolylsulfonylindolylfulgide by Stobbe condensation was unsuccessful because hydrolysis of the Stobbe-condensation product eliminated the sulfonyl moiety to give, after several steps, the N-unsubstituted fulgide. Pd(II)-catalyzed carbonylation of 2-butyne-1,4-diol derivative bearing the N-p-tolylsulfonylindole, however, afforded the desired N-p-tolylsulfonylindolylfulgide. A comparison of absorption spectroscopic and photochromic properties of these fulgides with those of the known N-methylindolylfulgide gave the following results. The electron-withdrawing substituent on nitrogen (i) shortened the absorption maximum of the colored form, (ii) suppressed thermal EZ isomerization, and (iii) enlarged quantum yields of photochromic reactions.
  • Masaru Tada, Kiyohiko Sugano, Takao Yoshihara
    1995 Volume 68 Issue 10 Pages 2969-2973
    Published: 1995
    Released: July 10, 2006
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    Photolysis of methyl(L)cobaloxime (L = trans ligand) (1) or methyl(L)-O,O′-bis(difluoroboryl)cobaloxime (2) in the presence of bis(4-chlorophenyl) disulfide gave 4-chlorophenyl methyl sulfide together with 4-chlorophenylthio(L)cobaloxime (5) or 4-chlorophenylthio(L)-O,O′-bis(difluoroboryl)cobaloxime (6). Similar photolysis in the presence of 2,2,6,6-tetramethyl-1-piperidyloxyl (TEMPO) gives 1-methoxy-2,2,6,6-tetramethylpiperidine. The reactivity of the cobaloximes 1 and 2 to the disulfide and TEMPO increases when the cobaloximes have a trans ligand (L) of larger steric requirement and low pka, or when the equatorial ligand is an electronegative O-(difluoroboryl)dimethylglyoxime. Two probable mechanisms are proposed for the reaction. The first is a direct radical substitution on the disulfide with a methyl radical, and the second involves the initial interaction between the disulfide and the (L)cobaloxime radical to afford arylthio(L)cobaloxime (5 or 6) and an arylthio radical. The latter radical reacts with methyl(L)cobaloxime to give aryl methyl sulfide.
  • Takahiro Gunji, Takayuki Kasahara, Akihiko Fujii, Yoshimoto Abe, Masak ...
    1995 Volume 68 Issue 10 Pages 2975-2979
    Published: 1995
    Released: July 10, 2006
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    The syntheses and characterizations of cyclotitanosiloxane (CTS) and cyclozirconosiloxane (CZS) were investigated. CTS and CZS were synthesized by the reaction of di-t-butoxysilanediol with bis(acetylacetonato)diisopropoxidotitanium(IV) or bis(acetylacetonato)diisopropoxidozirconium(IV) in benzene. The formation of CTS and CZS was confirmed by the NMR and IR spectra and elemental analysis. The X-ray structural analysis for single crystals revealed that CTS and CZS consist of an eight-membered ring of two titano- or zirconosiloxane linkages bearing two t-butoxy groups on a silicon atom and two acetylacetonato groups on a titanium or zirconium atom.
  • Akira Sekiguchi, Masaaki Ichinohe, Chizuko Kabuto, Hideki Sakurai
    1995 Volume 68 Issue 10 Pages 2981-2988
    Published: 1995
    Released: July 10, 2006
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    The intramolecular bissilylation of 3,3,6,6,7,7,10,10-octamethyl-3,6,7,10-tetrasilacyclodecyne (4a) at 110 °C with a catalyst of Pd(OAc)2/1,1,3,3-tetramethylbutyl isocyanide under 5000 bar produced 2,2,2′,2′,5,5,5′,5′ -octamethyl-2,2′,5,5′-tetrasilabicyclopentylidene (5a). 2,2,2′,2′,5,5,5′,5′ -Octamethyl-2,2′,5,5′-tetragermabicyclopentylidene (5b) was also synthesized by the same method. The reaction of 5a with alkali metals (Li, Na, K, Rb, and Cs) in THF gave the corresponding dianion dialkali metals. The structures of 5a, (2,2,2′,2′,5,5,5′,5′-octamethyl-2,2′,5,5′-tetrasilabicyclopentylidene)bis[(tetrahydrofuran)lithium(I)] (6a), and (2,2,2′,2′,5,5,5′,5′-octamethyl-2,2′,5,5′ -tetrasilabicyclopentylidene)bis[(tetrahydrofuran)sodium(I)] (6b) were studied by X-ray crystallography as well as NMR spectroscopic means. The central anionic C–C bond is not twisted for 6a, whereas it is twisted by 17.1° for 6b.
  • Hideo Tanaka, Ryo Kikuchi, Masakatsu Baba, Sigeru Torii
    1995 Volume 68 Issue 10 Pages 2989-2992
    Published: 1995
    Released: July 10, 2006
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    Electrooxidation of olefins in the presence of potassium osmate (0.04 molar amount) and periodic acid (0.5 molar amount) afforded the corresponding carbon–carbon double bond cleavage products in moderate to good yields, where the turnover number of periodic acid reached ca. 3.
  • Yasufumi Dan-oh, Kenji Uneyama
    1995 Volume 68 Issue 10 Pages 2993-2996
    Published: 1995
    Released: July 10, 2006
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    Dialkyl fumarates were electrochemically hydrotrifluoromethylated. The reaction was explained in terms of anodic bistrifluoromethylation and subsequent hydrolysis of one of the trifluoromethyl groups under the basic condition near cathode surface.
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