Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 70 , Issue 11
Showing 1-34 articles out of 34 articles from the selected issue
  • Naomichi Furukawa
    1997 Volume 70 Issue 11 Pages 2571-2591
    Published: 1997
    Released: June 15, 2006
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    1,5-(Dithia and diselena)cyclooctanes gave the dithia and diselena dications. Their structures were determined by X-ray crystallographic analyses. Similarly, dithia and diselena dications were produced on oxidation with 2 equiv of NOBF4 or NOPF6 or on treatment of the corresponding monooxides with Tf2O or concd H2SO4 from the sterically congested bis-sulfides or bis-selenides, such as 1,9-bis(thio- or seleno-substituted)dibenzochalcogenophene, 1,8-bis(thio- or seleno-substituted)naphthalenes and 2,2′-(thio- or seleno-substituted) 1,1′-biphenyls. These dications, however, were found to be unstable and to release the substituents attached at the chalcogen atoms. These either generated reactive species, i.e., quinodimethane and alkyl cations or demonstrated new reactions such as thio-Claisen rearrangement or photochemical conversion of naphtho[1,8-de]-1,3-dithiin derivatives.
    Diphenyl chalcogenides bearing 2,6-bis(methylthiomethyl), 2,6-bis(methylselenomethyl) and 2,6-bis[(dimethylamino)methyl] substituents produced the hypervalent chalcogenuranes(λ4). Their structures were determined by X-ray crystallographic analyses and their charge distributions were estimated by the ab initio MO-calculation and 77Se- or 125Te-NMR spectroscopy. Methyl 2,6-bis[(dimethylamino)methyl]phenyl selenide and telluride gave stable monoselenenium and monotellurenium cations on oxidative demethylation by the reaction with t-BuOCl. These are the first monovalent selenenium and tellurenium cation species.
  • Makoto Ogawa, Kazuyuki Kuroda
    1997 Volume 70 Issue 11 Pages 2593-2618
    Published: 1997
    Released: June 15, 2006
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    Recent developments in the study of the intercalation of organoammonium ions into layered silicates are reviewed. The new developments of the applications of the organoammonium-exchanged layered silicates include the selective adsorption of toxic compounds from water, the immobilization of photo and electroactive species to construct novel photo and electrofunctional materials, and the complexation with organic polymers for the enhancement of the mechanical properties. The conversion of the layered solids to three dimensional nanoporous solids with novel microstructures and adsorptive properties has also been successfully done. The novel controlled properties achieved by the modification with the adsorption of organoammonium ions open new opportunities to tailor the properties of the inorganic-organic nanostructured materials.
  • Hidekazu Watanabe, Toshio Asada, Suehiro Iwata
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 11 Pages 2619-2629
    Published: 1997
    Released: June 15, 2006
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    A recently developed hybrid procedure of ab initio molecular orbital (MO) calculations and Monte Calro (MC) samplings is applied to investigate the intracluster reactions of B+(H2O)n (n = 2 and 3). In this procedure we do not assume the potential energy functions during MC samplings. At every step the ab initio MO method is directly used to evaluate the electronic energy. The procedure makes it possible to deal with the intra-cluster reaction involving any rearrangement of atoms such as isomerization and dissociation. The many-body effects on the energy are taken into account within the approximation used in the MO calculation. During the MC samplings at room temperature, the B+(H2O)2 cluster undergoes a series of isomerization reactions, and eventually forms the most stable isomer, sp2 type of trans HBOH+(H2O). For B+(H2O)3, the reactions turn out to be more complicated, and a few times simulations suggest that there are several reaction products as well as intermediates in the reactions. The MO-MC procedure is proved to be a powerful tool to search for many isomers, reaction intermediates, and the products as well as the transition state structures between them although it is still very time-consuming.
  • Rafie Abu-Eittah, Mohamed Abdou, Maher Hamed, Yahya El Nady
    1997 Volume 70 Issue 11 Pages 2631-2641
    Published: 1997
    Released: June 15, 2006
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    The electronic absorption spectra of some 1,4-benzoquinone diazides were investigated in different solvents. The results indicate that the studied molecules pertain to the quinonoid structure. A common feature of the observed spectra is the overlap of the spectral bands. A Gaussian analysis was used to resolve the overlapping bands, and the minimum residue method was used to obtain the best fit between the analyzed and observed spectra. The observed spectra were assigned to π–π* transitions, and none of the n–π* transitions were observed. Molecular-orbital calculations with geometry optimization were performed using the ab initio method and different basis sets through the GAMESS package, whereas excited-state calculations were performed using the SCF-AM1-CI procedure through the MOPAC 5 package. For a comparison, MO-calculations were performed on 1,4-benzoquinone.
  • Mohammad Hadi Ghatee, Mohammad Mehdi Papari, Ali Boushehri
    1997 Volume 70 Issue 11 Pages 2643-2646
    Published: 1997
    Released: June 15, 2006
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    The interaction potential energy between CH4 and He has been determined from the extended law of corresponding states for viscosity using the inversion technique. Lennard–Jones (12-6) and BBMS potential functions have been checked as the initial model potentials required by the technique. The resulting potential energy from L–J potential is in excellent agreement with the one obtained from crossed molecular beam experimental results. The interaction potential energies from inversion reproduce the viscosity within 1%, the binary diffusion coefficient within 5%, and the thermal diffusion within 25%.
  • Akira Miyazaki, Isao Ichikawa, Toshiaki Enoki, Gunzi Saito
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 11 Pages 2647-2655
    Published: 1997
    Released: June 15, 2006
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    The crystal structures and phase transition nature of (BEDT-TTF)2BF4Sol0.5 (Sol = TCE, DBE, and DCE) are investigated by means of X-ray diffraction, electrical conductivity, ESR, and magnetic susceptibility measurements. As the size of the neutral molecules become smaller (TCE > DBE > DCE), the metal-insulator transition temperature rises (60 K < 100 K < 110 K), showing that their transitions are governed mainly by the structural degrees of freedom. For the DBE and DCE salts, these transitions are simple metal-insulator transitions, whereas the transition of the TCE salt occurs only when the sample is cooled slowly, and the Fermi surfaces survive in the resulting low-temperature phase. For this salt, the anomaly of the interplanar resistivity appears at ca. 160 K for the slow cooling process, and the difference of the ESR line width between the slow and rapid cooling processes is also observed below this temperature. These phenomena are due to the disorder enhanced by the generation of the in-plane superlattice.
  • Yoshifumi Kimura, Kohei Sugihara, Masahide Terazima, Noboru Hirota
    1997 Volume 70 Issue 11 Pages 2657-2664
    Published: 1997
    Released: June 15, 2006
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    Transient grating (TG) spectroscopy, photoaccoustic spectroscopy, and transient adsorption spectroscopy have been applied to studying the nongeminate recombination of photodissociated diphenyl disulfide (DPDS) in liquids. The photolysis quantum yield can be easily determined by an analysis of the time profile of the thermal grating signal, if the contribution of the population grating can be neglected. The quantum yield of the photodissociation for DPDS in isooctane has been determined to be 0.43 ± 0.02, which coincides with the values evaluated from the acoustic strength in the TG signal and the acoustic intensity in an ordinary photoacoustic measurement. This result is compared with a pico-second transient absorption measurement (T. W. Scott and S. N. Liu, J. Phys. Chem., 93, 1393 (1989)).
  • Hideo Ohkita, Wataru Sakai, Akira Tsuchida, Masahide Yamamoto
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 11 Pages 2665-2670
    Published: 1997
    Released: June 15, 2006
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    The charge recombination of electron–cation pairs produced in a poly(butyl methacrylate) film through two-photon ionization was examined at 20 K by emission spectroscopy and absorption spectroscopy. Both the isothermal luminescence (ITL) decay and the absorbance decay of the radical cation obeyed the same kinetics at 20 K: the tm law, I(t) ∝ tm with m ≈ 1. The temperature dependence of the ITL decay kinetics remained the same from 20 to 200 K far below the glass-transition temperature (293 K). These findings show that the ITL decay at low temperatures can be explained in terms of a long-range electron transfer by electron tunneling. Multi-shot photoirradiation was found to cause a deviation of the ITL decay from the tm law. Multi-shot photoirradiation probably induces a larger separation of a photoejected electron from the parent cation and/or a deepening of the trap depth.
  • Kotohiro Nomura, Masaru Ishino, Gohfu Suzukamo
    1997 Volume 70 Issue 11 Pages 2671-2676
    Published: 1997
    Released: June 15, 2006
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    A nickel-phosphine catalyst system consisting of nickel naphthenate, P(cyclo-C6H11)3, AlEt3, and 2,4,6-trichlorophenol (TCP) in the presence of sulfonic acids (CF3SO3H and MeSO3H) or dialkyl sulfates (Me2SO4 and Et2SO4) exhibits remarkable catalytic activity for the dimerization of propene. The catalytic activity (turnover number (TON) for the formation of C6 olefins or 2,3-dimethylbutenes) was enhanced when the catalyst was combined with effective additives, such as Et2SO4 and MeSO3H. The reaction products consisted of 2,3-dimethyl-1-butene (DMB-1) and/or 2,3-dimethyl-2-butene (DMB-2) in high yields (selectivity of dimers based on the reacted propene = 70—80%: selectivity of 2,3-dimethylbutenes in C6 olefins = 78—80%). The ratio of DMB-1/DMB-2 could be controlled by varying the molar ratios of the catalyst ingredients without decreasing in the turnover numbers. Although CF3SO3H was found to be the best additive as far as the catalytic activity and the selectivity of dimers (94—99%) are concerned, the selectivity of 2,3-dimethylbutenes in C6 olefins decreased. The addition of a small amount of water was also effective to enhance the catalytic activity: The turnover number for the formation of 2,3-dimethylbutenes was raised from 7050 to 30360.
  • Koichi Iwata, Hiro-o Hamaguchi
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 11 Pages 2677-2683
    Published: 1997
    Released: June 15, 2006
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    A new photochemical reaction has been found between trans-stilbene and carbon tetrachloride. In carbon tetrachloride, the first excited singlet (S1) state of trans-stilbene decays with a time constant of 3.1 ± 0.2 ps, a factor of ten or more faster than in alcohols and hydrocarbons. The mechanism of this anomalous lifetime shortening has been studied by using four time-resolved spectroscopies: sub-microsecond infrared, picosecond Raman, sub-picosecond visible absorption, and picosecond fluorescence. After photoexcitation to the S1 state, a bimolecular reaction occurs between trans-stilbene and the solvent carbon tetrachloride to form a stilbene-Cl adduct and the trichloromethyl (·CCl3) radical. Then, the stilbene-Cl adduct and the ·CCl3 radical are likely to react further in about 100 μs, following second-order reaction kinetics. The newly found photochemical reaction between trans-stilbene and carbon tetrachloride can serve well as a prototype for studying the microscopic mechanism of bimolecular reactions in solution.
  • Tomoharu Ama, Motoo Shiro, Akiyoshi Takeuchi, Toshiaki Yonemura, Hiros ...
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 11 Pages 2685-2692
    Published: 1997
    Released: June 15, 2006
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    Four isomers (T0, T1, T2, and T3) of [Co3(edma)3(μ-OH)3(μ3-O)]Cl (edma: ethylenediamine-N-acetate) containing a partial cubane Co3O4 core were isolated and optically resolved. The geometrical structures and absolute configurations of optically active -T2 chloride–water (1/7) and -T3 chloride–water (1/7) were determined by the X-ray diffraction method. The absolute configurations of optically active T0 and T1 were assigned on the basis of the NMR, UV, and CD spectral data. Each isomer was stable for at least 5 d in its neutral aqueous solution. Reversible protonation accompanying a color change was observed for each isomer in the pH range 2—7; this protonation did not accompany the cleavage of its partial cubane core. However, slow decomposition of each isomer was observed in its 60% HClO4 solution.
  • Nagao Kobayashi, Ryuji Higashi, Tatsuya Tomura
    1997 Volume 70 Issue 11 Pages 2693-2698
    Published: 1997
    Released: June 15, 2006
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    Some phthalonitriles and 1H-isoindole-1,3(2H)-diimines containing silicon(s) in their alkoxy substituent groups are prepared and used for phthalocyanine formation reactions. Silicon–carbon bonds often survive under the reaction conditions using K2CO3 in N,N-dimethylformamide (DMF), but are often broken in the presence of sodium hydride. Silicons in the alkoxy groups do not affect the electronic absorption spectra of phthalocyanines in solution significantly. The Q band of films of phthalocyanines (Pcs) with alkyl or alkoxy groups attached to benzene carbons furthest from the Pc core lies to the blue compared to the Pcs in solution, while films of Pcs with eight alkoxy groups closest to Pc core have a Q band shifted to the red.
  • Masaru Kimura, Aki Takahashi, Hiroko Kayanoki, Tomomi Sakata, Keiichi ...
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 11 Pages 2699-2702
    Published: 1997
    Released: June 15, 2006
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    The chromate (VI) ion HCrO4 at pH 2—4 was not appreciablly reduced by the phosphinate ion PH2O2 in the absence of molecular oxygen (O2), but was reduced in the presence of O2, forming peroxodiphosphate ions (denoted by PDP and meaning all forms of P2O84−, HP2O83− etc.) in much higher concentrations than those of the added chromate(VI). Both the rates of the chromate decay and the PDP formation increased with decreasing pH. When the chromate(VI) ion disappeared completely, PDP formation stopped and its concentration remained constant. However, such PDP once formed in the presence of O2 began to decompose after the solution was saturated with N2 gas; its decomposition ceased again when the solution was again saturated with air. Such behaviors are discussed while presenting the reaction mechanisms.
  • Hiroshi Fukuoka, Hideo Imoto
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 11 Pages 2703-2708
    Published: 1997
    Released: June 15, 2006
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    Mixed-valence ruthenium diphosphates with a tunnel structure, ARu2(P2O7)2 (A = Li, Na, Ag, and Cu), were prepared by the reaction of an amorphous ruthenium phosphate, H2RuP3O10, with Li2CO3, NaNO3, AgNO3, and Cu3(PO4)2·3H2O, respectively. The structure has a three-dimensional network constructed with RuO6 and P2O7 groups, and has large tunnels where A cations reside. In the sodium system, two isotypic compounds were obtained. One was obtained as single crystals and the X-ray structure analysis showed ruthenium and sodium vacancies. Another was obtained as powder and Rietveld analysis did not indicate ruthenium vacancies. It is paramagnetic and shows an antiferromagnetic transition at around 5.5 K. The phosphate with no cation in the tunnel, Ru2(P2O7)2, was obtained as a powder upon heating amorphous ruthenium phosphate (atomic ratio P/Ru is 4).
  • Yasuo Miki, Yoshikazu Sugimoto
    1997 Volume 70 Issue 11 Pages 2709-2718
    Published: 1997
    Released: June 15, 2006
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    Recycle solvents were obtained in 50 d of continuous operation of a 1 ton/day coal-liquefaction plant at Kimitsu. Acidic fractions were obtained by base extraction for the starting solvent and final solvent, and their components were analyzed in detail by gas chromatography/mass spectrometry. The application of a selected ion monitoring technique has allowed the assignment of the atomic compositions to practically all compounds despite many of their presence as overlapping peaks on the chromatogram: 327 individual compounds for 142 peaks.
    These compounds have been classified into nine of compound types: phenols, indanols/tetrahydronaphthols, naphthols, biphenylols/acenaphthenols, hexahydroacenaphthylenols, fluorenols, phenanthrenols/anthracenols, phenylnaphthols, and pyrenols/fluoranthenols. As compared to the initial solvent, the final solvent contains higher concentrations of indanols/tetrahydronaphthols and hexahydroacenaphthylenols and contains a lower concentration of pyrenols/fluoranthenols.
  • Takashi Yasukochi, Koichi Fukase, Yasuo Suda, Keiichi Takagaki, Masahi ...
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 11 Pages 2719-2725
    Published: 1997
    Released: June 15, 2006
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    Fluorescence labeled trisaccharide, Gal(β1-3)Gal(β1-4)Xyl(β)–MU [MU = 4-methyl-2-oxo-2H-chromen-7-yl (4-methylumbelliferyl)], and tetrasaccharide, GlcA(β1-3)Gal(β1-3)Gal(β1-4)Xyl(β)–MU, corresponding to the linkage region between glycosaminoglycans and core proteins in proteoglycans were synthesized from Xyl–MU by stepwise enzymatic transglycosidation using β-galactosidase (Escherichia coli) and β-glucuronidase (bovine liver). Introduction of the second galactosyl residue at the 3′-position of Gal–Xyl–MU was achieved by minimal protection of the disaccharide intermediate whose reactive primary hydroxy function was selectively protected with an acetyl group by using lipase catalyzed transacetylation. Regioselective β-glucuronylation was effected by the high substrate specificity of the β-glucuronidase without any protection of the glycosyl acceptor.
  • Katsuaki Inoue, Takako Sekido, Takayuki Sano
    1997 Volume 70 Issue 11 Pages 2727-2736
    Published: 1997
    Released: June 15, 2006
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    In order to clarify the mechanism of the shape change of human erythrocytes induced by anionic surfactants, kinetic experiments were performed using the stopped-flow technique and the conventional spectroscopic method. In the time range from 0.1 s to a few dozen minutes, four kinetic processes were observed. In the dead time of the stopped-flow apparatus (within 10 milli seconds), a decrease in the intensity of the transmitting light was observed. Based on an analysis of the dependence of the relaxation time of each process on the surfactant concentration for various reaction schemes, we propose a most plausible reaction model that includes four kinds of binding processes of the surfactant and three intramolecular processes. In the present paper, based on this model, we discuss the detailed mechanism of the shape change of the erythrocytes.
  • Masanori Wada, Hideki Konishi, Katsuhiko Kirishima, Hiroshi Takeuchi, ...
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 11 Pages 2737-2741
    Published: 1997
    Released: June 15, 2006
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    2,4,6-Trimethoxyphenyllithium, Φ′Li[Φ′ = 2,4,6-(MeO)3C6H2], reacted with diphenyl carbonate and with ethyl formate to give tris(2,4,6-trimethoxyphenyl)methanol, Φ′3COH (1), and bis(2,4,6-trimethoxyphenyl)methanol, Φ′2CHOH (2), respectively. Compound 1 reacted with a slight excess of perchloric acid in 2-propanol to give very dark-purple crystals of the triarylcarbenium salt, [Φ′3C]X (3, X = ClO4), which were inert even in hot ethanol. However, a treatment of 3 (X = Cl), prepared in situ in 1 M (1 M = 1 mol dm−3) hydrochloric acid, with 1 M sodium hydroxide resulted to give 4-bis(2,4,6-trimethoxyphenyl)methylene-3,5-dimethoxy-2,5-cyclohexadienone. Compound 2 also reacted with a slight excess of perchloric acid in methanol to give dark-red crystals of the diarylcarbenium salt, [Φ′2CH]X (5, X = ClO4). Compound 5 was considerably inert even in hot methanol, but was easily reduced in primary and secondary alcohols to give bis(2,4,6-trimethoxyphenyl)methane, Φ′2CH2. Measurements of the half-lives of 5 in these alcohols showed that 5 was more labile in secondary alcohols, such as 2-propanol and 2-butanol, than in primary alcohols. When a suspension of 5 (X = Cl), prepared in situ in 1 M hydrochloric acid, was heated, tris(2,4,6-trimethoxyphenyl)methane, Φ′3CH (7), was obtained. Analogous reactions to give 7 were observed in methanol containing a slight excess of hydrochloric acid or nitric acid in place of perchloric acid. The possible paths of these reactions are discussed.
  • Tatsuo Ohmichi, Naoki Sugimoto
    1997 Volume 70 Issue 11 Pages 2743-2747
    Published: 1997
    Released: June 15, 2006
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    The roles of two different 2′-hydroxyls near to a catalytic site of a leadzyme (Pb2+ ribozyme), CUGGGAGUCC, have been investigated kinetically. These roles of two different 2′-hydroxyls were clearly distinguished upon a cleavage reaction of an RNA substrate. One 2′-hydroxyl of G of the leadzyme in an asymmetry internal loop contributed to only the binding constant for the leadzyme with the substrates. The other 2′-hydroxyl of A in the asymmetry loop contributed to only the cleavage rate constant. On the basis of the results, we propose the possibility of the formation of a hydrogen bond between the 2′-hydroxyl of G of the leadzyme and the substrate and the binding between Pb2+ ion and the 2′-hydroxyl of A.
  • Masafumi Unno, Ryoji Tanaka, Toshie Kuribara, Mina Saito, Hideyuki Mat ...
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 11 Pages 2749-2756
    Published: 1997
    Released: June 15, 2006
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    The reaction of dichloro(diethylamino)thexylsilane (thexyl = 1,1,2-trimethylpropyl) with lithium gave 1,2,3-tris(diethylamino)-1,2,3,4-tetrathexylcyclotetrasilane (2) as a mixture of four diastereomers (r-1,t-2,c-3,t-4-2, r-1,t-2,t-3,t-4-2, r-1,t-2,c-3,c-4-2, and r-1,c-2,t-3,t-4-2). The isomers were separated and identified by 1H, 13C, and 29Si NMR, IR, Mass, and UV spectroscopy. The structures of r-1,t-2,c-3,t-4-2, r-1,t-2,t-3,t-4-2, and r-1,t-2,c-3,c-4-2 were confirmed by X-ray crystallography. The Si–Si bond lengths are 2.391(1)—2.499(2) Å for r-1,t-2,c-3,t-4-2, 2.389(2)—2.478(1) Å for r-1,t-2,t-3,t-4-2, and 2.397(2)—2.485(2) Å for r-1,t-2,c-3,t-4-2. In these molecules, there is a significant change in the structures of the Si4 frameworks; the dihedral angles were 18° for r-1,t-2,c-3,t-4-2, 34° for r-1,t-2,t-3,t-4-2, and 3° for r-1,t-2,c-3,t-4-2. The chlorodeamination or bromodeamination of 2 with HCl or HBr afforded 1,2,3-trichloro-1,2,3,4-tetrathexylcyclotetrasilane or 1,2,3-tribromo-1,2,3,4-tetrathexylcyclotetrasilane, respectively. Also, a tetrachlorocyclotetrasilane, 1,2,3,4-tetrachloro-1,2,3,4-tetrathexylcyclotetrasilane was obtained via cyclotetrasilanyllithium.
  • Mitsuhiro Yanagita, Izuo Aoki, Sumio Tokita
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 11 Pages 2757-2763
    Published: 1997
    Released: June 15, 2006
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    The equilibrium between the colorless lactone (L) and the colored zwitterion (Z) forms of the fluoran compound 1, which has been widely used as a typical black color former in data-recording systems, has been studied by 13C NMR and electronic absorption spectroscopies. Fluoran 1 showed no visible absorption in aprotic solvents, while a black color appeared in phenolic solvents. The 13C NMR and signal of the spiro carbon of 1 in CDCl3 appeared at 84.2 ppm, indicating that 1 exists substantially as L in aprotic solvents. In phenol d6 at 50 °C, the signal of the spiro carbon in 1 shifted to a lower magnetic field and appeared in the sp2-hybridization region (δ = 162.7), suggesting that in phenol-d6 a cleavage of the C(spiro)–O bond in the lactone ring occurs and that the ring-opened Z form is produced. The equilibrium between L and Z depended strongly on the temperature and solvents. The high temperature and inhibition of the solute (1)–solvent interaction by steric hindrance, self-association and intramolecular chelation of the solvent shifted the LZ equilibrium toward L. The thermodynamic parameters for the equilibrium reaction in phenolic solvents were also estimated.
  • Mamoru Miyazaki, Hitoshi Kakidani, Satoshi Hanzawa, Hiromichi Ohta
    1997 Volume 70 Issue 11 Pages 2765-2769
    Published: 1997
    Released: June 15, 2006
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    Arylmalonate decarboxylase (AMDase) catalyzes the asymmetric decarboxylation of α-aryl-α-methylmalonic acid. Since this enzyme is inhibited by SH-reagents, a cysteine residue is supposed to be involved at the catalytic site. Cloning of the gene which codes the enzyme revealed that this enzyme contains four cysteine residues. Titration of free SH groups by p-(chloromercurio)benzoate disclosed that all four Cys are in the reduced form. In this study, four mutant enzymes (C101S, C148S, C171S, and C188S) were prepared, in which one of four cysteines was replaced by serine. The CD spectra indicated that the conformational differences of C101S and C188S compared to that of the native enzyme are not so significant. The catalytic activities of the four mutants were measured. Among these mutant enzymes, only C188S showed a drastic decrease in enzyme activity, indicating that cysteine188 is located at the active center of the enzyme. The catalytic activities of the other mutants are also discussed.
  • Makoto Minato, Masatoshi Ikeya, Fumihiko Ohkubo, Takashi Ito
    1997 Volume 70 Issue 11 Pages 2771-2775
    Published: 1997
    Released: June 15, 2006
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    [MoH2(OMe)2(dppe)2] reacts with a series of phthalimide derivatives, each of which contains an electron-donor, an electron-acceptor, or redox-active center, to give the corresponding (substituted phthalimido)hydrido complexes in good yields. Investigation of spectroscopic properties suggests that some of these complexes have a polarized structure in a polar solvent.
  • Seiji Yamaguchi, Yoshihiko Sugioka, Yuzoh Kitagawa, Yoshinori Matsumot ...
    1997 Volume 70 Issue 11 Pages 2777-2780
    Published: 1997
    Released: June 15, 2006
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    An intramolecular anhydride formation in 5-isopropenyl-4,5-dihydrofuran-2,3-dicarboxylic acid caused a new ring expansion to give 4,7-dihydro-6-methyloxepin-2,3-dicarboxylic anhydride (2b). An aminolysis of 2b with benzylamine gave a mixture of two isomeric carboxamides, N-benzyl-4,7-dihydro-6-methyloxepin-2-carboxamide and trans-1-(benzyloxamoyl)-2-isopropenylcyclopropane. Also, the ring expansion and ring contraction are discussed.
  • Yasuo Tohda, Takeshi Yanagidani, Shin-ichi Hiramatsu, Nagatoshi Nishiw ...
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 11 Pages 2781-2790
    Published: 1997
    Released: June 15, 2006
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    The reaction of the sodium salt of 2-acylmethyl-4,4-dimethyl-2-oxazolines with α,β-acetylenic ketones in ethanol gave Michael adducts, which were easily transformed to 4,6-disubstituted 3-acyl-1-(2-hydroxy-1,1-dimethylethyl)-2-pyridones by silica gel. N-Dealkylation of the pyridones was performed using hydrochloric acid in good yields. Deacylation of the pyridones was performed using potassium hydroxide. A mild treatment of the pyridones with bases or silica gel gave 7-oxa-1-azabicyclo[4.3.0]non-3-en-2-one derivatives via intramolecular Michael addition. A similar reaction of 2-phenacyl-2-oxazoline with diphenylpropynone gave the corresponding 1-(2-hydroxyethyl)-2-pyridone derivative, which was inert against these 1-dealkylation, 3-deacylation, and intramolecular addition reactions.
  • Michinori Oki, Hiroshi Ikeda, Kazuya Kodama, Shinji Toyota
    1997 Volume 70 Issue 11 Pages 2791-2799
    Published: 1997
    Released: June 15, 2006
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    Rates of topomerization of substituted 9-fluorenyllithiums and α-(benzylthio)benzyllithium were determined in various ether-type solvents by the dynamic NMR technique. The rates are small in solvents of bulky molecules in comparison with those of less-bulky molecules. UV-vis spectra of these compounds in the solvents indicate that the compounds tend to exist as solvent-separated ion pairs in solvents of small molecular size, whereas they exist as contact ion pairs in solvents of bulky molecules. 1H NMR spectra did not show signals attributable to two species at the lowest temperature of study. From these results, it is concluded that the observed process is the tumbling of the anion in solvent-separated ion pairs with a rapid pre-equilibrium between contact ion pairs and solvent-separated ion pairs, further intervention of solvent molecule(s) into the observed solvent-separated ion pairs being the rate-limiting step. A term, dimensiosolvatic effect, is proposed for the effects where the solvent molecular size plays important roles in determining rates of reaction or equilibria.
  • Yoshihiko Ito, Yutaka Kojima, Masahiro Murakami, Michinori Suginome
    1997 Volume 70 Issue 11 Pages 2801-2806
    Published: 1997
    Released: June 15, 2006
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    Racemization of optically active oligo- and poly(quinoxaline-2,3-diyl) derivatives with a single screw-sense, prepared by the polymerization of 3,6-diaryl-1,2-diisocyanobenzenes catalyzed by methylpalladium(II) initiator, was investigated. Pentameric and hexameric oligomers with a living palladium terminus were reluctant to undergo racemization in solution at room temperature. However, the (oligoquinoxalinyl)bis(phosphine)palladium(II) complexes underwent a phosphine exchange reaction in the presence of an excess of phosphine ligand with partial racemization at room temperature. Oligomers without palladium terminus, prepared by a treatment of the corresponding palladium derivatives with methylmagnesium bromide, underwent racemization more rapidly, the rate of which depended upon the bulkiness of the substituents at the 5,8-positions of the quinoxaline rings and oligomerization degree, i.e., the number of the quinoxaline units in the oligomer chain. Starting from the racemic polymers with a living palladium terminus, substantial deracemization of the helical poly(quinoxaline-2,3-diyl) was induced by means of optically active 2,3-O-isopropylidenedioxy-1,4-bis(diphenylphosphino)butane ligand, which coordinated to the palladium terminus.
  • Ryoichi Kuwano, Masaya Sawamura, Satoshi Okuda, Tomohito Asai, Yoshihi ...
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 11 Pages 2807-2822
    Published: 1997
    Released: June 15, 2006
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    New chiral peralkyldiphosphines (S,S)-2,2″-bis[(R)-1-(dialkylphosphino)ethyl]-1,1″-biferrocenes ((R,R)-(S,S)-alkylTRAPs) were synthesized from (R)-N,N-dimethyl-1-ferrocenylethylamine in four steps in 38—68% overall yields (MeTRAP: 38%, EtTRAP: 68%, PrTRAP: 53%, BuTRAP: 56%, i-BuTRAP: 51%, i-PrTRAP: 42%). The reactions of alkylTRAP (Et-, Bu-, i-Bu, and i-PrTRAP) with 1 molar amount of PdBr2 gave trans-[PdBr2(alkylTRAP)] in good yields. The X-ray crystal structures of these palladium complexes revealed that alkylTRAPs coordinated to a palladium atom in a trans-chelating manner regardless of the P-alkyl substituents. The structures of palladium complexes of Et-, Bu-, and i-PrTRAP had nearly C2-symmetry, but that of i-BuTRAP was deviated from C2-symmetry significantly. AlkylTRAPs also reacted with [PtCl2(MeCN)2] and [RhCl(CO)2]2, giving the corresponding trans-chelate platinum and rhodium complexes. The crystal structure of trans-[RhCl(CO)(BuTRAP)] revealed that the conformation of the BuTRAP ligand in the complex was almost the same as that in the palladium complex trans-[PdBr2(BuTRAP)].
  • Motohiro Akazome, Yukiko Yanagita, Ryo-ichi Sonobe, Katsuyuki Ogura
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 11 Pages 2823-2827
    Published: 1997
    Released: June 15, 2006
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    The crystallization of (R)-arylglycyl-(R)-phenylglycine (1, aryl = phenyl; 2, aryl = 1-naphthyl) in the presence of 1,2-dimethoxybenzene or its derivatives affords an inclusion compound. A single-crystal X-ray analysis has shown that, in a 1,2-dimethyoxybenzene inclusion compound, dipeptide molecules arrange in a sheet and the 1,2-dimethoxybenzene lies at the end in a void between the sheets by being anchored to an ammonio hydrogen on the sheet via three-center hydrogen bonding. The distance between the sheets was found to be variable according to the length of the guest 1,2-dimethoxybenzene derivatives, as if they were pillars that support the sheets.
  • Jayadevan Santhanalakshmi, Thirumalaiswamy Raja
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 11 Pages 2829-2831
    Published: 1997
    Released: June 15, 2006
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    Vapor-phase N-alkylation syntheses of imidazole were carried out with MeOH and EtOH over a series of calcined MgII–AlIII layered double hydroxides (LDHs) selectively produced in high yields of N-methyl (70%) and N-ethyl (63%) imidazoles only on the 3 : 1 atomic ratio of MgII–AlIII calcined LDH. Attempts on C-alkylation and dialkylation reactions over the same catalysts proved to be unsuccessful.
  • Makoto Ogawa, Takanori Igarashi, Kazuyuki Kuroda
    1997 Volume 70 Issue 11 Pages 2833-2837
    Published: 1997
    Released: June 15, 2006
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    Novel silica-alkyltrimethylammonium (with the alkyl groups of decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl) bromide nanocomposite films were synthesized by coating the precursor solutions containing prehydrolyzed tetramethoxysilane and alkyltrimethylammonium bromide. The composites are thought to be composed of aggregates of alkyltrimethylammonium bromides and thin silica layers. The d values of the products varied depending on the relative ratios of tetramethoxysilane and surfactants, suggesting that the microstructures of the products can be controlled by simply changing the compositions. Since the present composites are obtained as transparent films, they have potential applicability as a new class of functional materials, especially for photofunctional purposes.
  • Hideo Sawada, Yutaka Nakamura, Shinsuke Katayama, Tokuzo Kawase
    1997 Volume 70 Issue 11 Pages 2839-2845
    Published: 1997
    Released: June 15, 2006
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    New fluoroalkylated end-capped oligomers containing triol segments were prepared by the reactions of N-tris(hydroxymethyl)methylacrylamide and fluoroalkanoyl peroxides. Under the non-crosslinked conditions, these fluoroalkylated oligomers were found to cause a gelation, where the aggregations of fluoroalkyl segments and the hydrogen-bonding interaction are involved in establishing a physical gel network not only in water, but also in organic solvents. Therefore, it was demonstrated that the aggregation of the end-capped fluoroalkyl segments in water and/or in organic media become a new driving factor for gelation as well as such well-known interactions as the hydrogen bond and ionic interaction. These thus-obtained fluorinated oligomer hydrogels had a high Cr3+ or Co2+ binding power, and the metal ions were easily released from the metal ions-bound oligomers into water.
  • Atsushi Shimojima, Yoshiyuki Sugahara, Kazuyuki Kuroda
    1997 Volume 70 Issue 11 Pages 2847-2853
    Published: 1997
    Released: June 15, 2006
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    Triethoxy(alkyl)silanes containing 12—18 carbon atoms in the alkyl groups were hydrolyzed and polycondensed to form ordered structured materials. The XRD pattern of each condensed product showed sharp diffraction peaks with higher orders. The basal spacings approximately corresponded to twice the extended molecular length of the alkyl groups, and increased linearly as a function of the alkyl chain length. The SEM images of the products exhibited a platy morphology, and the 29Si CP/MAS NMR spectra revealed the formation of siloxane bonds with various silicon sites from T1 to T3 environments. All of these results indicated the formation of highly-organized inorganic–organic layered materials.
  • Yoshinobu Izumi, Shunichi Kawanishi, Nobutake Suzuki, Masaharu Maruo, ...
    1997 Volume 70 Issue 11 Pages 2855-2859
    Published: 1997
    Released: June 15, 2006
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    Poly(vinyl chloride) (PVC) film was irradiated with intense monochromatic UV light from ArF, KrF, and XeCl excimer lasers. The detachment of chlorine atoms was observed by X-ray photoelectron spectroscopy, and the formation of polyene structures was observed by optical absorption spectroscopy. The irradiation of ArF and KrF excimer laser light mainly caused the formation of diene and triene structures, respectively. The irradiation of XeCl laser light caused no significant reactions. Upon the consideration of the triplet energies of olefin and diene and the dissociation energy of allylic C–Cl bond, the wavelength dependence was explained by photochemical and photothermal effects of the ArF and KrF lasers, respectively.
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