Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 71 , Issue 2
Showing 1-27 articles out of 27 articles from the selected issue
  • Yasunori Yamada, Miki Hasegawa, Michio Kobayashi, Yutaka Fukuda, Toshi ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 2 Pages 305-313
    Published: 1998
    Released: August 01, 2005
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    The electronic structure and nature of the electronic transitions of copper(II) naphthalenediolate complexes, (2,2′-bipyridine) (2,3-naphthalenediolato) copper(II) ([Cu(ndo)(bpy)]) and (2,3-naphthalenediolato) (1,10-phenanthroline) copper(II) ([Cu(ndo)(phen)]), have been studied from the viewpoints of the polarization spectra and MO theory. The 339.0 and 296 nm bands of [Cu(ndo)(phen)] have been assigned to localized transitions of the naphthalenediolate (ndo) skeleton, and the 308, 275, and 269 nm bands on the phenanthroline (phen) skeleton. It has been clarified experimentally that the 400 nm band can be assigned to the CT transition between ndo and Cu(II). The total state wavefunctions show that the 293 and 282 nm bands are due to the intramolecular interligand CT (LL′CT) transitions from ndo to phen, thus indicating that the two π-electronic systems, separated by the central metal ion, can directly interact. The complex [Cu(ndo)(bpy)] shows the electronic transitions at 339.0, 256.0, 245, 238, and 210 nm localized on ndo, and at 315, 295, and 264 nm localized on the bipyridine (bpy) moiety. The 400 nm band of [Cu(ndo)(bpy)] is due to the intramolecular CT transition between ndo and Cu(II). In the case of [Cu(ndo)(bpy)], the LL′CT transition is not observed.
  • Osamu Koga, Tadanori Matsuo, Hiroki Yamazaki, Yoshio Hori
    1998 Volume 71 Issue 2 Pages 315-320
    Published: 1998
    Released: August 01, 2005
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    Adsorbed species on Ni and Fe electrodes were investigated by in-situ infrared spectroscopy in the electrochemical reduction of CO2 or CO. Two types of adsorbed CO on the Ni electrode and one type on the Fe electrode were detected in a CO atmosphere. The two types, assigned to linear and bridged CO molecules, were also formed on the Ni electrode in CO2 reduction. The negative polarization decreased the coverage of the adsorbed CO on Ni. The decay rate constants were evaluated from the spectroscopic data; the rate constant for the linear type was three times higher than that for the bridge one. Both constants agreed well with those determined from the formation rate of hydrocarbons in CO reduction, confirming that both adsorbed CO molecules were intermediate species to hydrocarbons. The high electrocatalytic activity of Cu in hydrocarbon formation from CO2 and CO was rationalized in terms of the adsorption strength of CO on metals by comparing the activity of Ni, Fe, and Cu electrodes with the infrared bands of adsorbed CO on these electrodes. The weaker adsorption of CO on Cu led to higher activity.
  • Nobuhiro Marubayashi, Takayuki Ogawa, Noriaki Hirayama
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 2 Pages 321-327
    Published: 1998
    Released: August 01, 2005
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    The solid-state photodimerization of three polymorphic crystal forms (forms I, II, and III) of a bulky olefin, methyl (RS)-1-phenyl-2-piperidinoethyl (RS)-1,4-dihydro-2,6-dimethyl-4-(2-thiazolyl)pyridine-3,5-dicarboxylate hydrochloride, was studied. Forms I and II are anhydrous crystals and form III is an isomorphous hydrate of form II. X-Ray analyses of these forms showed that forms II and III have the same geometrical characteristics suggesting high susceptibility to photodimerization according to the well-known topochemical rule. Although UV irradiation of from II affords a photodimer, 4a,8a-dimethoxycarbonyl-2,4b,6,8b-tetramethyl-3-[(RS)-1-phenyl-2-piperidinoethoxycarbonyl]-7-[(SR)-1-phenyl-2-piperidinoethoxycarbonyl]-(4RS,8SR)-4,8-di(2-thiazolyl)-1,4,4a,4b,5,8,8a,8b-octahydro-cis-transoid-4a,4b-cis-cyclobuta[1,2-b : 3,4-b′]dipyridine, in high yield, the photolysis of form III proceeds much more slowly than that of form II. A detailed inspection of the crystal structures revealed that there is a space to afford the mobility of molecules for dimerization in form II, whereas the space is occupied by the incorporated water molecule in form III. We have previously proposed that a buffer zone, which is a space in the crystal structure, controls the photodimerization of bulky olefins. The present study demonstrates that the buffer zone is an essential controlling factor for the solid-state photodimerization of bulky olefins.
  • Jun Okubo, Hiraku Shinozaki, Toshiyuki Koitabashi, Ryo Yomura
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 2 Pages 329-335
    Published: 1998
    Released: August 01, 2005
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    The UV absorption spectra of some pyridylacetylenes were measured in various media at room temperature and 77 K, and the origin of the electronic absorption bands of these compounds was clarified compared with the results of MO calculations. For instance, it has been found that the 304.6, 271.7, 221, and 216 nm bands of 1-(2-pyridyl)-2-phenylethyne in cyclohexane can be assigned to the calculated S1 ← S0, S5 ← S0, S9 ← S0, and S10 ← S0 transitions, respectively, in which the observed 271.7 nm band (S5 ← S0) is ascribed as a new type transition from the n orbital on the aza-nitrogen atom of the pyridine ring to the in-plane π* orbital on the sp-carbon atoms of the ethynylene group. Furthermore, it is revealed that the observed 259.6 nm band of 1,2-di(2-pyridyl)ethyne (D2PE) can also be assigned to a new type of transition caused by weak interactions between the n orbitals and the in-plane π orbital of the ethynylene group. This result indicates that two n orbitals of the terminal pyridine rings of D2PE may interact with each other via the central in-plane π orbital.
  • Akihiro Ito, Aya Taniguchi, Kazunari Yoshizawa, Kazuyoshi Tanaka, Toki ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 2 Pages 337-343
    Published: 1998
    Released: August 01, 2005
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    Ab Initio CASSCF results of 1,3,5-tris(methylene)benzene (TMB) and 1,3,5-benzenetriamine trication (BTA3+), which are model molecules of the actively researched triradicals with star-branched topology, are presented. This study included a geometry determination of the four low-lying states (4A1″, 4A2, 2A2, 2B1) of TMB and BTA3+. The doublet–quartet splitting energies (ΔED–Q) of TMB and BTA3+ were calculated to be 12.7 and 3.1 kcal mol−1, respectively. Furthermore, the doublet-doublet splitting energies of TMB and BTA3+, which arise from a Jahn–Teller distortion of the doubly degenerate 2E″ state, were suitably estimated to be 2.5 and 6.8 kcal mol−1, respectively, due to obviation of the spin-contamination problem. As a result of configuration mixing, it was found that the doublet states for TMB and BTA3+ have to be represented at least by two configurations or more. In addition, the doublet states of TMB were regarded as being a doublet triradical, while those of BTA3+ were close to a doublet monoradical; associated with this result, the lowest doublet states of TMB and BTA3+ were found to be 2A2 and 2B1, respectively.
  • Yoshihiro Yokoyama, Yuji Ohashi
    1998 Volume 71 Issue 2 Pages 345-348
    Published: 1998
    Released: August 01, 2005
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    Structure analysis of acrylonitrile, which is a low-melting-point (189.5 K) material, was performed using an imaging-plate-Weissenberg-camera-type-diffractometer at 153 K. The crystal was grown on the diffractometer. The molecule is almost planar and the molecular planes are stacked at regular distances along the a axis. The molecule takes a disordered structure since the N atom and the approximate center of the C=C double bond lie on the crystallographic mirror plane. This causes the C=C bond to be aligned to be in parallel or perpendicular arrangements to the neighboring ones along the stacking. If the solid state polymerization induced by radiation is carried out, the isotactic structure may be obtained for the parallel stacking and the syndiotactic structure may be obtained for the perpendicular stacking. Since the crystal structure is disordered, either structure or a structure with the two structures mixed (atactic structure) should be formed in the solid state polymerization.
  • Tetsuji Yumura, Makoto Koga, Hironori Hoshikawa, Yoshinori Nibu, Ryoic ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 2 Pages 349-354
    Published: 1998
    Released: August 01, 2005
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    The temperature effect on the depolarization degree of the Raman bands of the totally symmetric vibrations of some benzene derivatives belonging to point groups D6h and D3h was studied. In these molecules a direct field due to incident light gives rise to an intrinsic depolarization, and an indirect field causes by dipoles induced in the surrounding molecules by the incident light gives rise to depolarization due to intermolecular interactions. It was observed that although the depolarization degree increases with increasing temperature for all vibrational modes, the relationship between the temperature and depolarization degree is different, depending on the vibrational modes as well as the substituents. These observations are qualitatively explained by a change in the intermolecular interaction due to thermal fluctuations of the intermolecular distance caused by molecular vibrations.
  • Shilin Liu, Akiyoshi Hishikawa, Kaoru Yamanouchi
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 2 Pages 355-362
    Published: 1998
    Released: August 01, 2005
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    The rotational predissociation of water molecules in the vibrationless level of the B1 state was investigated under jet-cooled conditions (27—154 K) by exciting them with a tunable VUV laser in the wavelength range of 124.3—123.7 nm and by detecting the total fluorescence from electronically excited photofragments OH(A2Σ+). Due to the simple one-photon selection rule and the efficient rotational cooling, individual low-J rotational transitions of the B1A1 origin band were observed with almost no overlap in the laser-induced photofragment fluorescence (LIPF) spectrum. The widths and intensities of these rotational transitions exhibited pronounced dependence on the parent rotational levels in the B1 state. The least-squares analysis of the observed line-widths (FWHM) of the resolved rotational transitions, Γ ’s, showed that they are well described by the formula, Γ = Γ0 + αa<Ja2>, with optimized parameters Γ0 = 2.5(1) cm−1 and αa = 0.63(1) cm−1, indicating that (i) the homogeneous interaction couples the B1 state with the B1 state to form OH fragments in the electronically ground 2Πi state and (ii) the heterogeneous (a-axis orbital-rotation) interaction couples the B1 state with the A1 state to form OH fragments in the electronically excited A2Σ+ state. By taking account of the rotational line-broadening effect, the least-squares analysis was also performed to fit the observed spectral intensities to derive the branching ratio of the OH(A2Σ+) formation via the A1 state of H2O. It was found that the OH(A2Σ+) formation branching ratio can be expressed by an exponential form, exp (−γ<Ja2>), which was proposed first by Hodgson et al. [Mol. Phys., 54, 351 (1985)], and reproduces well the observed rotational intensity pattern when γ = 0.097(7). By using this branching ratio and the previous data for the absorption oscillator strength, the absolute cross section to yield OH(A2Σ+) photofragments was obtained as a function of the excitation energy.
  • Junichi Tachibana, Taira Imamura, Yoichi Sasaki
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 2 Pages 363-369
    Published: 1998
    Released: August 01, 2005
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    The molybdenum(VI) porphyrin dioxygen complex, [MoVIO(O2)(tmp)] (tmp = 5,10,15,20-tetramesitylporphyrinato), prepared from the reaction of [MoIVO(tmp)] with dioxygen at room temperature is characterized in detail. Bulky mesityl substituents on the porphyrin rings enable the isolation of the dioxygen complex. Photoirradiation of the toluene solution of the dioxygen complex with visible light regenerated [MoIVO(tmp)] immediately. Upon heating the solid sample of the dioxygen complex, dioxygen gas was liberated around 40—90 °C, leaving [MoIVO(tmp)]. The solid and a toluene solution of [MoIVO(tmp)] thus formed, again absorbed O2 from air to make [MoVIO(O2)(tmp)]. The IR and 1H NMR data confirmed that O2 was coordinated as a peroxide mode to the central molybdenum(VI) ion from the same side of the porphyrin plane with the oxo ligand and that both the axial ligands (peroxo and oxo) eclipsed the trans-N atoms of the porphyrin rings. The second-order rate constant for the formation of the dioxygen complex in toluene was evaluated to be (3.9 ± 0.1) × 10−1 dm3 mol−1 s−1 at 20 °C. The rate constant is extremely small as compared with those of the oxygenation of iron(II) porphyrins, by at least a factor of 10−5.
  • Takayuki Sasaki, Shigeo Umetani, Masakazu Matsui, Shigekazu Tsurubou, ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 2 Pages 371-377
    Published: 1998
    Released: August 01, 2005
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    A new type of water-soluble crown ether (3′-sulfobenzo-12-crown-4 (SB12C4), 3′-sulfobenzo-15-crown-5 (SB15C5), 3′-sulfobenzo-18-crown-6 (SB18C6), di(3′-sulfo)dibenzo-18-crown-6 (DSDB18C6), di(3′-sulfo)dibenzo-21-crown-7 (DSDB21C7), and di(3′-sulfo)dibenzo-24-crown-8 (DSDB24C8)) has been prepared. The complex formation constants (β) of lanthanide ions with sulfonated crown ethers in aqueous solution were determined via the solvent-extraction method. The stability of the resulting complexes increases with the number of sulfonic acid groups, 18C6 < SB18C6 < DSDB18C6. For mono and disulfonated crown ether complexes, the stability varies as SB18C6 < SB15C5 < SB12C4 and DSDB18C6 < DSDB21C7 < DSDB24C8. The β values of all the complexes of lanthanide ions decrease with the atomic number, which is a characteristic of macrocyclic ligands, and is quite opposite to the conventional complexing tendency. The extractive separability of lanthanide ions was found to improve by adding sulfonated crown ethers into the aqueous phase as ion-size selective masking reagents. The number of water molecules in the first coordination sphere of the central Eu3+ in the complex was determined by a laser-induced luminescence study. In addition, the fluorescence spectra were measured in order to evaluate the structure of the complexes. The stabilization of the complexes formed is discussed while taking into account an outer-sphere electrostatic attraction between the sulfonic acid group and the metal ion.
  • Kazuhiro Manseki, Motoko Kumagai, Masatomi Sakamoto, Hiroshi Sakiyama, ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 2 Pages 379-383
    Published: 1998
    Released: August 01, 2005
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    The first heteronuclear copper(II)–lanthanide(III) complexes, CuLn(fsal-2,2)(NO3)3(H2O)n (n = 2 for Ln = Nd and n = 1 for Ln = Eu and Gd), of a symmetric macrocyclic dinucleating Schiff base ligand, H2fsal-2,2, which is a condensation product of two molecules of 2,6-diformyl-4-methylphenol and two molecules of ethylenediamine, were synthesized by the reaction of [N,N′-bis(3-formyl-5-methylsalicylidene)ethylenediaminato]copper(II) and ethylenediamine in the presence of lanthanide(III) ion as a template, where fsal-2,2 denotes the dianion formed by the deprotonation of two phenolic hydroxyl groups in H2fsal-2,2. The absorption spectra suggested that substrates possessing N- and O-donor groups, such as amino alcohols, are specifically bound at the Cu–Ln center through nitrogen-coordination to the copper site and through oxygen-coordination to the lanthanide site. The fluorescence intensity of Eu(III) decreased drastically upon forming the Cu–Eu complex. A cryomagnetic susceptibility measurement indicated a ferromagnetic spin-spin interaction between Cu(II) and Gd(III) ions.
  • Mitsuaki Narita, Koji Sode, Shokichi Ohuchi, Yuka Murakawa, Mitsuo Hit ...
    1998 Volume 71 Issue 2 Pages 385-395
    Published: 1998
    Released: August 01, 2005
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    Based on the definition of a helix region in terms of dihedral angles φ and ψ, 681 helices could be easily extracted from 125 kinds of analyzed proteins by using two-dimensional φ and ψ diagrams of their three-dimensional structures. The 8000 (203) possible kinds of amino acid residues in the middle of triplets consisting of consecutive residues were used for a precise analysis of helical segments in globular proteins. They correspond to the 8000 kinds of amino acid residues in a sequence of proteins. The 681 helices were built up from 8836 amino acid residues, which could be classified into 11 kinds of helix elements (a—k). Each of the amino acid residues in a sequence of helical segments could be allotted to one of 11 helix elements (a—k). Glycine residues in the proteins were used for its precise assignment as internal standards. The 11 kinds of helix elements could be statistically characterized with amino acid residues in the middle of triplets. Amino acid residues, observed as a specific helix element 3-times or more often in the total helical segments, were evaluated regarding their propensities for a specific helix element by using their inherent preference (IP)-values for the specific helix element, which had been defined in a previous paper. Amino acid residues found 13-times or more often in the data set are also listed to show their propensities for specific helix elements.
  • Mahito Atobe, Tsutomu Nonaka
    1998 Volume 71 Issue 2 Pages 397-402
    Published: 1998
    Released: August 01, 2005
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    The ultrasonic effects on the electroreduction of methyl and allyl halides (RX) to the corresponding stannanes (R3SnSnR3 and R4Sn) at a reactive (consumable) tin cathode were examined. The current efficiency and product selectivity for the reduction were found to be greatly affected by ultrasonic irradiation. For instance, the selectivity for (CH3)3SnSn(CH3)3 to (CH3)4Sn from CH3I was significantly increased under irradiation. This fact is rationalized as being due to because the intermediate species [(CH3)3Sn·] formed by the primary one-electron reduction of CH3I are activated for their coupling by mobilization on/from the cathode surface under irradiation. On the other hand, the ultrasonic effects on the reduction of CH3Br and C3H5Br seemed to be slightly different from those in the reduction of CH3I.
  • Saburo Nakanishi, Seiji Memita, Toshikazu Takata, Keiji Itoh
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 2 Pages 403-412
    Published: 1998
    Released: August 01, 2005
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    [Fe(η3-allyl)(CO)2(NO)] complexes were prepared by the reaction of tetrabutylammonium tricarbonylnitrosylferrate with tosylates, trifluoroacetates and phosphonates of allylic alcohols and with allylic halides. However, acetates and carbonates of the allylic alcohols are ineffective for the preparation of the complexes. The reaction of [Fe{η3-(1-substituted allyl)}(CO)2(NO)] with phosphorus ligands (L) gave a mixture of diastereomeric [Fe{η3-(1-substituted allyl)}(CO)(NO)(L)] complexes, which have planar chirality and central chirality of the iron atom. Variable-temperature 1H NMR spectroscopy revealed that no isomerization between these diastereomers occurred upon heating up to 80 °C. Also, neither synanti isomerization of the allylic ligand nor isomerization of planar chirality of the complexes took place. The unsubstituted allylic ligand rotates about the iron-allyl ligand axis at room temperature, while η3-(1-substituted allylic) ligands do not.
  • Tadashi Mizutani, Takuya Horiguchi, Hiroshi Koyama, Ippei Uratani, His ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 2 Pages 413-418
    Published: 1998
    Released: August 01, 2005
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    A cationic porphyrin host, [5,10,15,20-tetrakis(1-pentyl-3-pyridinio)porphyrinato]zinc(II), binds benzenecarboxylates, in water. The temperature dependence of the binding affinity showed that the binding was entropically driven: for the binding of 1,2,4,5-benzenetetracarboxylate, ΔH° = 4.36 kJ mol−1 and ΔS° = 95.4 J K−1 mol−1. The atropisomerization rates of the porphyrin were investigated by 1H NMR, and were decelerated by the addition of either anionic guests or simple inorganic salts. Electrostatic interactions and accompanying desolvation mainly controlled these equilibrium and kinetic behaviors.
  • Tomotaka Nakamura, Katsuhiko Takagi, Yasuhiko Sawaki
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 2 Pages 419-424
    Published: 1998
    Released: August 01, 2005
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    The irradiation of iodide salts of stereo isomeric stilbazolium cyclodimers in their CT bands (ca. 355 nm) resulted in a one-electron transfer induced photocycloreversion, which led to the formation of stilbazolium ions; the quantum yields (Φ) being highly sensitive to their structures, i.e., the Φ for syn-Head-to-Head (syn-HH) was found to be 0.35, for syn-Head-to-Tail (syn-HT) 0.0026, and for anti-Head-to-Head (anti-HH) 0.00095, respectively. This reaction shows a distinct contrast to photocycloreversion by irradiation at 255 nm, which resulted in a highly efficient, but nonselective, splitting, the Φ’s being in the range of 0.3—0.8. In the photosensitized cycloreversion of methyl sulfate salts of dimers using 9,10-dimethoxyanthracene (DMA) as a sensitizer, the quantum efficiencies show a structural dependence similar to the above case of irradiation at their CT bands. Cosensitization with DMA and 1-cyanonaphthalene as an electron mediator resulted in relative quantum yields showing a close coincidence to the yields in the irradiation of the CT band, i.e., 254 : 2.6 : 1 for syn-HH, syn-HT, and anti-HH, respectively. This implies that the one-electron transfer mechanism can be initiated both by CT band irradiation as well as DMA sensitization. It can be concluded that the structural dependence of the quantum efficiencies is attributed to the through-bond interaction of two pyridinium rings, which facilitates the splitting of the C–C bond in the cyclobutane ring.
  • Duc Hai Dao, Yasushi Kawai, Kouichi Hida, Sander Hornes, Kaoru Nakamur ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 2 Pages 425-432
    Published: 1998
    Released: August 01, 2005
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    Alkyl 2-oxo-4-phenylbutyrates are reduced to the corresponding alkyl (R)-2-hydroxy-4-phenylbutyrates, versatile chiral building blocks in organic synthesis, in high chemical yield (80—90%) with excellent stereoselectivity ( > 90%ee). The reaction has been run in aqueous diethyl ether at 30 °C for 24 h under the catalysis of bakers’ yeast (Saccharomyces cerevisiae) which was preincubated for 6 h in the presence of phenacyl chloride. The amount of water in the medium should be controlled strictly not to exceed 0.8 mL (g yeast)−1.
  • Hiroshi Ogawa, Yasutake Kodera, Shigeyoshi Kanoh, Akihiko Ueyama, Masa ...
    1998 Volume 71 Issue 2 Pages 433-442
    Published: 1998
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    Polyoxetanes anchoring a pendant spacer-separated mesogen at the tertiary-like C-3 carbon of the oxetane unit were prepared by cationic ring-opening polymerization of the corresponding oxetane derivatives. The resulting polymers were liquid-crystalline substances showing textures assignable to the nematic or smectic mesophase over a wide temperature range from about 260 °C to room temperature. These mesogens also behaved in the manner similar to that of the mesogens in the analogous polyoxetanes attached by a methyl side chain at the quaternary C-3 carbon, although the less bulky polymer backbone in the present work indicated a somewhat higher isotropic phase-transition temperature than that of the methyl-substituted analogs. In both types of the polyoxetanes, their mesophase patterns were influenced by the core structure and alkoxy tail length in the pendant mesogen, but not by the bulkiness of the second side chains, H and CH3, attached at the C-3 carbon of the polyoxetane unit.
  • Tadashi Ema, Juka Kobayashi, Soichi Maeno, Takashi Sakai, Masanori Uta ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 2 Pages 443-453
    Published: 1998
    Released: August 01, 2005
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    The stereoelectronic considerations and the molecular modeling using an X-ray structure of Rhizomucor miehei lipase suggested that the lipase-catalyzed reactions proceed under the stereoelectronic control. This suggestion was supported by the semiempirical MO (MNDO-PM3) calculations carried out on the imidazole-catalyzed transesterification as a model reaction. The stereoelectronic effect operates at the transition state (TS) more effectively than at the tetrahedral intermediate (THI). The stabilization energy due to the stereoelectronic effect operating at the TS was estimated to be ca. 5 kcal mol−1. The enantioselectivities for 1-phenylethanol, 1-phenyl-2-propanol, and 1-cyclohexylethanol were estimated in terms of the lipase-induced strain caused at the TS. A TS model generally applicable to chiral secondary alcohols is proposed. The kinetic study supported the TS model. The result that the enantioselectivity in the lipase-catalyzed transesterifications arises from the difference in Vmax between the two enantiomers rather than from the difference in Km indicates that the ability of lipases to discriminate between the enantiomers at the TS is high, while the ability to recognize the chirality in the binding step is poor. Furthermore, the difference in Vmax between the enantiomers was found to result not from the enhanced reactivity of the (R)-enantiomers but from the reduced reactivity of the (S)-enantiomers.
  • Toshiaki Kamachi, Ichiro Okura
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 2 Pages 455-457
    Published: 1998
    Released: August 01, 2005
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    Effect of copper ion on the activity of the hydrogenase from Desulfovibrio vulgaris (Miyazaki) was studied. When the hydrogenase was incubated with Cu(II) ion, the hydrogenase activity did not change. The hydrogenase activity was inhibited when the hydrogenase was incubated with copper ion in the presence of sodium ascorbate, suggesting the effect of Cu(I) ion. ESR studies indicate that the signal intensity attributed to [3Fe–4S] cluster decreased with decreasing the activity. Copper contents of hydrogenase increased, but the contents of iron and nickel did not change. Results obtained demonstrate that incorporated Cu(I) affects the hydrogenase a activity by the perturbation of [3Fe–4S] cluster.
  • Shigeyasu Kuroda, Syuzi Hirooka, Mitsunori Oda, Hiroyuki Iwaki, Syuki ...
    1998 Volume 71 Issue 2 Pages 459-465
    Published: 1998
    Released: August 01, 2005
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    The thermolysis of 1-substituted 4-morpholino-3,3a,8,8a-tetrahydroazulene-5,6-dicarboxylates derivatives (7ac) under catalytic dehydrogenation conditions was studied. The reaction substrates were prepared by a several-step sequence involving the [2+2] cycloaddition of bicyclc morpholino enamines with dimethyl acetylenedicarboxylate, and a subsequent electrocyclic opening of the cyclobutene ring as a key skeletal construction, starting from bicyclo[3.3.0]octane-2,6-dione mono(ethylene acetal). Refluxing of a diphenyl ether solution of dimethyl 4-morpholino-3,3a,8,8a-tetrahydroazulene-5,6-dicarboxylate (7a) containing a catalytic amount of Pd–C gave a 10% yield of dimethyl azulene-5,6-dicarboxylate (8a), accompanied by a 10% yield of dimethyl azulene-4,6-dicarboxylate (9a), trace amounts of dimethyl azulene-5,7-dicarboxylate (10a), methyl azulene-5-carboxylate (12a), and methyl azulene-6-carboxylate (13a). Under the same thermolytic conditions, a 1-phenyl-substituted compound 7b gave corresponding similar types of phenyl-substituted azulenes (8b, 9b, 10b, 11b, and 14b), and a 1-cyano-substituted compound 7c gave a mixture of corresponding similar types of cyano-substituted azulenes (8c, 9c, 10c, and 11c). This sequence provides a new method for synthesizing substituted azulenes suffering from migration and removal of one ester group. Also the thermolysis of a similar system of dimethyl 3-(1-pyrrolidinyl)-2,7-cycloheptadiene-1,2-dicarboxylate (15), even in the absence of a catalyst, gave cycloheptatriene derivatives of dimethyl 1,3,5-cycloheptatriene-dicarboxylate (16, 17, 18, and 19), bearing no morpholine molecule.
  • Sommai Pivsa-Art, Tetsuya Satoh, Yoshiki Kawamura, Masahiro Miura, Mas ...
    1998 Volume 71 Issue 2 Pages 467-473
    Published: 1998
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    The reactions of iodobenzene with azole compounds, 1,2-disubstituted imidazoles and 2-substituted oxazoles and thiazoles, were examined in the presence of catalytic amounts of Pd(OAc)2 and PPh3 in DMF using alkali metal carbonates as bases. It was found that the coupling products, 5-arylazoles, could be selectively produced in good yields by using Cs2CO3. In the case that their 2-position is unsubstituted, the site could also be arylated. In reactions using bromobenzene in place of iodobenzene, K2CO3 was also as effective as Cs2CO3. The addition of a stoichiometric amount of CuI appeared to specifically promote the reactions of thiazoles as well as those of thiophene derivatives. The reactions of 2-unsubstituted azole compounds with aryl iodides could be mediated by CuI to some extent without using the palladium species to give 2-arylazoles.
  • Yuji Koga, Hiroyuki Kusama, Koichi Narasaka
    1998 Volume 71 Issue 2 Pages 475-482
    Published: 1998
    Released: August 01, 2005
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    By the catalytic use of a rhenium(I) nitrogen complex, [ReCl(N2)(PMe2Ph)4], α-keto radicals are generated from α-bromo ketones and react with vinyl ethers and silyl enol ethers intermolecularly. Various substituted furans, including tetrasubstituted furans such as furoguaiacin, are prepared by this method.
  • Hiroyuki Higuchi, Yoshiyuki Uraki, Hiroki Yokota, Haruki Koyama, Juro ...
    1998 Volume 71 Issue 2 Pages 483-495
    Published: 1998
    Released: August 01, 2005
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    The unsymmetrically substituted bi- and quaterthiophene derivatives were synthesized. The unsymmetrically substituted bithiophenes carrying the electron-withdrawing substituent X on one of the outer thiophene rings exhibited the maxima of absorption bands at the longer wavelengths than the symmetrically disubstituted bithiophene derivatives, while the unsymmetrical quaterthiophenes had such maxima at the shorter wavelengths than the corresponding symmetrical ones. The trend of bathochromic shift of the longest wavelength absorption bands due to the electron-withdrawing substituent X was more pronounced in case of bi- or quaterthiophenes bearing push–pull substituents. The unsymmetrical quaterthiophenes exhibited the greater third-order nonlinear optical (TNLO) properties than the corresponding bithiophenes, similarly to the case between the symmetrical bi- and quaterthiophenes. However, the TNLO properties of the unsymmetrical bi- and quaterthiophenes showed no dependence on the electron-withdrawing strength of the substituent X, unlike those of the symmetrical ones.
  • Tomoshige Kobayashi, Hideki Sugawara, Behrooz Nikaeen
    1998 Volume 71 Issue 2 Pages 497-502
    Published: 1998
    Released: August 01, 2005
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    5,8-Dihydro-5,8-methanophthalazine, prepared by the reaction of bicyclo[2.2.1]hepta-2,5-diene-2,3-dicarbaldehyde with hydrazine, reacted with MCPBA to give an N-oxide. Further oxidation with MCPBA afforded the corresponding exo-6,7-epoxy derivative. Treatments of the epoxide and its diphenyl-substituted derivative with trifluoroacetic acid gave 6,9-bis(trifluoroacetoxy) derivatives by a regioselective ring-opening of the oxirane, accompanied by Wagner–Meerwein rearrangement. The bis(trifluoroacetoxy) derivatives were converted to the corresponding diols for elucidation of their regio- and stereochemistry.
  • Yasushi Tsurita, Keisuke Wada
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 2 Pages 503-511
    Published: 1998
    Released: August 01, 2005
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    A new method for preparing porous supports in the SiO2–ZrO2 system was investigated. A microspherical silica gel impregnated with ZrOCl2 and NaCl was heated and subsequently washed with water. Crystallization of silica proceeded in supports prepared by heating the mixture of silica gel and NaCl. In contrast, crystallization of supports as well as their sintering was suppressed in the case of the gel impregnated with ZrOCl2 in addition to NaCl, and porous supports with the SiO2–ZrO2–Na2O composition were formed. A porous-glass-like texture similar to the texture resulting from the phase-separation method was observed inside the microspherical particles as well as on their surface. Microspherical supports, whose pore volume was more than 1 cm3 g−1 and whose mode pore radii ranged from 270 to 640 Å, were obtained by controlling the synthetic conditions for the silica gel, the amount of ZrOCl2 added to the gel, and the temperature of the heat-treatment of the mixture.
  • Nobuaki Kodakari, Takeshi Sakamoto, Kouji Shinkawa, Hisato Funabiki, N ...
    1998 Volume 71 Issue 2 Pages 513-519
    Published: 1998
    Released: August 01, 2005
    JOURNALS RESTRICTED ACCESS
    A tin(IV) oxide surface was modified by the chemical vapor deposition (CVD) of tetramethoxysilane after the pre-adsorption of benzoate anion as a template to obtain a novel gas sensor with a molecular-sieving function. The sensitivity to large molecules was strongly suppressed by the modification, whereas the sensitivity to small molecules was relatively less modified. It is considered that the silica overlayer with pores whose size was controlled by the template molecule prevented large molecules from reacting with the exposed tin oxide surface, resulting in the molecular-sieving property. The catalytic activity for the oxidation of the alcohol was measured in order to support the idea that the reactivity of organic molecules was suppressed by silica.
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