Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 69 , Issue 5
Showing 1-41 articles out of 41 articles from the selected issue
  • Tetsuo Nozoe, Hitoshi Takeshita
    1996 Volume 69 Issue 5 Pages 1149-1178
    Published: 1996
    Released: June 21, 2006
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    Azulenequinones have been attracting great interest in recent years. After a brief introduction concerning an earlier study of azulenequinones we review recently developed areas of azulenequinone chemistry, which became possible by the discovery of a facile one-pot synthesis of azulenequinones, or their bromo derivatives, by means of the bromine oxidation of various azulene derivatives in an aqueous solvent. Various functionalized, and some annulated, azulenes are used as substrates to determine the scope and limitations of this method. The bromoazulenequinones can be used as synthons, from which various azulenequinones can be derived by nucleophilic displacement. In a hope to encourage other chemists to develop new azulenequinone chemistry, we herein describe the process of the discovery, starting from the original motivation. In addition, we touch on remarkable and mysterious products whose structures remain undetermined and our speculation concerning their reaction paths. Some physical and chemical properties of azulenequinones, together with those of azulenequinone methides and diazoazulenequinones, are also described. This is the first complete review of the field of newly developing azulenequinones.
  • Xincheng Hu, Norimichi Takenaka, Masaru Kitano, Hiroshi Bandow, Yasuak ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1179-1185
    Published: 1996
    Released: June 21, 2006
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    The reaction kinetics, the chemiluminescence spectra, the products, and the lifetimes of emission species for the chemiluminescence reaction between hypobromite and ammonia or urea in an alkaline aqueous solution were investigated. Results show that the reaction mechanism for ammonia chemiluminescence is different from that for urea. The reaction of ammonia and hypobromite produces NO2 in the gaseous phase and NO2 in solution; however, the reaction of urea and hypobromite does not. For the reaction of ammonia and hypobromite, chemiluminescence intensity obeys 1.5 order kinetics for hypobromite concentration when ammonia is in excess, but the reaction of urea and hypobromite obeys second order kinetics for hypobromite when urea is in excess. The spectrum of the chemiluminescence from the ammonia and urea with hypobromite shows a maximum intensity at 710, and at 510 nm, respectively. The chemiluminescence lifetimes of the emission species were 0.056 and 0.092 s for the reaction of ammonia and the reaction of urea, respectively. The chemiluminescence species of the reaction between hypobromite and ammonia seems to be excited NO2, that for urea seems to be excited N2.
  • Haruo Nakayama, Chihiro Hayashi, Masato Endou
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1187-1190
    Published: 1996
    Released: June 21, 2006
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    In order to observe more directly the structural organization of water molecules around a nonpolar molecule in an aqueous solution, the supercooling temperatures and enthalpies of mixing with various solvents were measured using two kinds of aqueous solutions (solutions I and II) of tetrabutyl(or isopentyl)ammonium chloride, which were subjected to different treatments. Solution I was made by melting a hydrate solid formed from the ammonium salts and water and by keeping its temperature only one degree Celsius higher than its dissolution temperature; solution II was made by irradiating solution I with ultrasonic waves (38 kHz) for 20 min at the same temperature as solution I. The supercooling temperatures of solution I were found to be about 10 degrees Celsius higher than those of solution II. The differences in the enthalpies of mixing between solution I and solution II in the same solvent, ΔHI − ΔHII, were found to be about 3 kJ per mole of (n-C4H9)4NCl for most of the solvents. It has been concluded that these results directly reflect the difference in the stability of hydrogen-bonded water networks around either a butyl or an isopentyl chain of the ammonium cation in aqueous solutions.
  • Tetsuji Tatsumi, Hiromi Matsuhashi, Kazushi Arata
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1191-1194
    Published: 1996
    Released: June 21, 2006
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    Solid superacids of sulfated zirconia were prepared by the sulfation of zirconia gels, which were obtained from mother solutions with different pH values. The gel precipitated at pH = 8 gave the sulfated zirconia, which showed the highest catalytic activity and selectivity for the skeletal isomerization of n-pentane. The active superacid was obtained with high reproducibility upon heating the mother solution, followed by washing the precipitate with hot water; this preparation procedure provided the oxide of small particle size. The catalytic activity of sulfated zirconia could be estimated from the exothermal peak caused by crystallization of the zirconia gel in DTA.
  • Kumi Yunoki, Atsumu Tezaki, Keiichi Yokoyama, Hiroyuki Matsui
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1195-1199
    Published: 1996
    Released: June 21, 2006
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    Gas-phase reactions of NH(a1Δ, v = 0,1) + H2 (1) and NH(a1Δ, v = 0,1) + D2 (2) were studied in the photolysis of HNCO/H2 (or D2) mixtures. NH(a1Δ) and product H (D) atom were detected by UV and vacuum-UV laser-induced fluorescence. The observed rate constants at room temperature (295 ± 2K) and activation energies in the range of 295 — 407 K were;

    in units of 10−12 cm3 molecule−1 s−1 and kJ mol−1. The product branching ratio in reaction 2 was determined to be [D]/[H] = 3.2 ± 0.76, in which no temperature dependence was indicated. These results are consistent with insertion mechanism having a loose entrance transition state structure, which is suggested by ab initio CI calculations. In contrast, the contribution of direct abstraction channel is supposed to be negligibly small.
  • Ken-ichi Iimura, Noboru Suzuki, Teiji Kato
    1996 Volume 69 Issue 5 Pages 1201-1211
    Published: 1996
    Released: June 21, 2006
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    Long-chain alkylchlorosilanes (trichloro(octadecyl)silane; TCOS, dichloro(methyl)(octadecyl)silane; DCMOS, and chloro(dimethyl)(octadecyl)silane; CDMOS) form stable spread monolayers on water surfaces. From the experimental fact that X-ray photoelectron spectra of the LB films showed no chlorine peak, it is estimated that chlorosilyl residues were hydrolyzed rapidly just after spreading on the water surface. Brewster angle microscopic observation of the monolayers gave information on the molecular tilt and phase transitions in these monolayers with compression. It is expected that dimerization or polymerizations of resultant hydroxysilane residues could proceed by condensation among the hydroxyl groups in monolayers. However, condensation reactions were very slow in neutral conditions and the film molecules exist mainly as monomeric or dimeric hydroxysilanes and not in polymeric forms, based on the comparison of the atomic ratios of Si to O estimated from the X-ray photoelectron spectroscopy measurements of LB films of the three compounds and those of the polymers of TCOS and DCMOS, and the dimer of CDMOS.
  • Sung-Kil Lee, Yoshinori Kumasaka, Joe Otsuki, Koji Araki
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1213-1221
    Published: 1996
    Released: June 21, 2006
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    The Ni(II) complex of 6,6′-bis(hexylbenzoylamino)-2,2′-bipyridine (LH2) in square-planar symmetry underwent a reversible and simultaneous deprotonation of the two amide units. The non-deprotonated complex (NiLH22+) showed high SCN selectivity by the preferential axial coordination of two SCN molecules (log KSCN = 8.11 ± 0.03 in CH2Cl2 at 20 °C), while the deprotonated complex showed little affinity toward anions. Deprotonation-induced affinity-switching of the complex by the external aqueous layer mediated an efficient SCN-selective up-hill transport across a CH2Cl2 liquid membrane by coupling with the symport of protons from pH 4.0 to 6.0 aqueous solutions. Equilibrium at the aqueous/organic interface could be represented by the equation Kapp = ([Ni(LH2)(SCN)2]org)/([NiL]org[H+]2aq[SCN]2aq), where Kapp is the equilibrium constant (log Kapp = 13.6 at 20 °C). However, the rates of protonation and deprotonation of the complex at the interface were dependent mostly on the concentration of the complex in the organic layer. Based on these results, detailed mechanisms of the transport are discussed.
  • Hiroki Akutsu, Masamichi Ogasawara, Masahiko Saburi, Kozo Kozawa, Toki ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1223-1226
    Published: 1996
    Released: June 21, 2006
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    The molecular structure of 9,10-diethyl-9,10-diphospha-9,10-dihydroanthracene (PEPP) was determined by X-ray analysis. The central six-membered ring takes a boat conformation with two phosphorus atoms being the stem and stern, and the condensed tricyclic skeleton forms a butterfly-like structure. Of the two ethyl groups, which are attached to two P atoms in the central ring, the one is placed toward outside the skeleton (extra), and the other is located toward the inside of the ‘butterfly’ (intra). The observed redox potential of 0.63 V vs. Ag/AgCl suggests that this molecule has a fairly good electron-donating characteristics. From the spectroscopic observation and a quantum-chemical calculation, the donating orbital is estimated to be that of lone pair electrons at the P atom that attaches to the intra ethyl group.
  • Hiroshi Yao, Noboru Kitamura
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1227-1232
    Published: 1996
    Released: June 21, 2006
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    CdS nanocrystals were prepared in micrometer-sized chelate polymer particles by nucleation of Cd2+ ions with an aqueous Na2S solution. Simulation of the absorption spectral band shapes of CdS under an effective mass approximation was conducted on the basis of the size distributions of the crystals in the polymer, which were estimated by the relevant transmission electron micrograph images. The optical properties and the size distributions of CdS were dependent on the diameter of the polymer particle, when the concentration of an added S2− solution was sufficiently high for rapid nucleation. In the case of the reaction of Cd2+ with a diluted S2− solution, contrarily, the formation of CdS was confined in the surface layer of the host polymer particle with layer-by-layer size distributions. Effects of the host polymer particle size and the concentration of the Na2S solution on the size distributions and the optical properties of CdS are discussed in terms of the apparent rate of nucleation of Cd2+ to CdS.
  • Mohamedally Kurmoo, Peter Day, Tadaoki Mitani, Hiroshi Kitagawa, Hideo ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1233-1240
    Published: 1996
    Released: June 21, 2006
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    We report the crystal and electronic band structures and the electrical, magnetic, and optical properties of {bis(ethylenedithio)tetrathiafulvalene}2dicyano-silver and -gold, η-(BEDT–TTF)2M(CN)2, M = Ag or Au. The compounds belong to the monoclinic system; space group C2/c, a = 36.28(8), b = 4.286(2), c = 22.02(6) Å, β = 110.62(9)° and V = 3205 Å3, and a = 36.44(8), b = 4.256(2), c = 22.16(6) Å, β = 111.3(1)° and V = 3201 Å3, respectively. The structure consists of pairs of stacks with parallel BEDT–TTF molecules along b. Molecules in neighboring pairs of stacks are tilted by 55.3°. There are several short S···S contacts between stacks to form layers, which are separated by the anions along a. The transfer integrals suggest a highly dimerized system. The band structure calculation, however, predicts metallic behavior contrary to the semiconducting properties observed (σRT ≈ 10−1—10 S cm−1 and EA = 0.15(2) eV). The static (SQUID magnetometry) and spin (EPR) susceptibilities are modelled to a singlet–triplet system with an energy gap of 315(5) K (39(1) meV). This is one of two phases in the BEDT–TTF family to exhibit an activated susceptibility for a spin dimer model.
  • Nobuhiro Saito, Akihiko Kudo, Tadayoshi Sakata
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1241-1245
    Published: 1996
    Released: June 21, 2006
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    A simple and new synthetic method of tungstate thin films (CaWO4, MgWO4, PbWO4, ZnWO4) was developed. The absorption and luminescence spectra of tungstate thin films synthesized on quartz substrates were measured; the optical properties were also studied. It was found that CaWO4 has Eg = 5.4 eV of a direct transition nature. Tungstate thin films were strongly luminescent when irradiated with UV-light. Excitation at around 290 nm was interpreted as a singlet–triplet transition.
  • Mostafa El-Behairy
    1996 Volume 69 Issue 5 Pages 1247-1254
    Published: 1996
    Released: June 21, 2006
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    New examples of thermal tetrahedral-to-octahedral transformation were discovered and studied in the thermal reactions of disodium tetrakis(aryloxo)cobaltate(II) complexes, of the formula Na2[Co(OAr)4(thf)mnthf (OAr = o-chloro-, o-bromo-, m-chloro-, p-bromo-, 2,4-dichloro-, 2,4-dimethyl- or 2,6-dichlorophenoxo; m = 2 for all complexes except for 2,4-dimethylphenoxo complex where m = 0; thf: tetrahydrofuran; n = 1—3), in the solid phase. With one exception, the original complexes were all violet colored and have octahedral configurations. The exception is Na2[Co(2,4-Me2C6H3O)4]·thf, which has an intense blue color and its electronic and magnetic data are characteristic of tetrahedral cobalt(II). The aryloxo complexes of 2,6-dichloro-, m-chloro-, and p-bromophenoxo show a two-step thermochromism, violet → blue → rose, upon heating. These steps correspond to structural changes to tetrahedral thf-free complexes and then to aryloxo bridged polymers with octahedral cobalt(II) ions, respectively. o-Chloro- and o-bromophenoxo complexes underwent only thermal desolvation–polymerization, which occurs in one step, changing directly into the rose aryloxo-bridged polymers. 2,4-Dichlorophenoxo complex shows only one-step thermochromism, violet → blue, thus changing from the octahedral to tetrahedral configuration. The remainder complex, of 2,4-dimethylphenoxo, does not show any color changes and retained its tetrahedral configuration until it decomposed. The reverse changes of the thermal products to the original complexes proceed on standing under dry thf atmosphere, for some hours or days.
  • Yoshinari Baba, Yoshinobu Kawano, Hiroyuki Hirakawa
    1996 Volume 69 Issue 5 Pages 1255-1260
    Published: 1996
    Released: June 21, 2006
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    Crosslinked N-(2-pyridylmethyl)chitosan, N-(2-thienylmethyl)chitosan, and N-[3-(methylthio)propyl]chitosan were newly synthesized. The amino group of the active adsorption site of chitosan was protected by Schiff’s base formation prior to being crosslinked by 2-(chloromethyl)oxirane. The final chitosan derivatives were obtained by reducing the imine moiety of the Schiff’s bases with sodium borohydride. The adsorption behavior of metal ions on the chitosan derivatives was examined from a solution containing hydrochloric acid using a batchwise method. These chitosan derivatives exhibited high selectivities and excellent loading capacities for gold(III), palladium(II), and platinum(IV) over base metals in hydrochloric acid. In order to elucidate the adsorption species of palladium(II) on the chitosan derivatives, the effect of the chloride ion concentration on the distribution ratio in the adsorption of palladium(II) was examined. The adsorption capacities of these chitosan derivatives for palladium(II) were found to be about 2.5—3 times greater than that of the cross-linked original chitosan. The desorption of palladium(II) was performed to an extent of 70% by a single batchwise treatment with aqueous thiourea solution.
  • Ryuji Nakata, Masatoshi Yano, Yukari Ochi, Naomi Hatanaka, Hisaya Oki
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1261-1264
    Published: 1996
    Released: June 21, 2006
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    Racemization between fac-Λ-(+)546- and fac-Δ-(−)546-[Cr(val)3] (1 and 2) was studied in N,N-dimethylformamide (DMF). These complexes were preferentially converted into bis-type complexes, Λ-(+)546- and Δ-(−)546-[Cr(val)2(val-N)DMF] (4 and 3), and an equilibrium comprising these four species was established. In order to determine the equilibrium constants, rate constants, and activation parameters in a proposed square-network reaction system, the mole fractions of four species with time in reacting solutions at 40, 50, and 60 °C were determined by liquid chromatography. The reaction processes are discussed based on the obtained values.
  • Toyofumi Itoh, Yuki Fujii, Toshiji Tada, Yuzo Yoshikawa, Hiroyuki Hisa ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1265-1274
    Published: 1996
    Released: June 21, 2006
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    The formation constant (KZnL), enthalpy and entropy changes (ΔH and ΔS), and deprotonation constant (Ka) of coordinated water for hydrated zinc(II)–triamine (1 : 1) complexes (N3–Zn-(OH2)n (N3 = diethylenetriamine (dien), N-(2-aminoethyl)-1,3-propanediamine (epd), dipropylenetriamine (dpt), cis,cis-1,3,5-triaminocyclohexane (tach), and 1,5,9-triazacyclododecane ([12]aneN3)) were determined by potentiometry. The pKa linearly increased along with an increase in -ΔH, and was explained in terms of a ligand–ligand interaction through the N3–Zn-O bond on the bases of a thermodynamic analysis and strain-energy calculation (MM2). The zinc(II) complex-promoted hydrolysis of 2,4-dinitrophenyl diethyl phosphate was investigated in 1% (v/v) methanol–water; the rate constants linearly increased along with decreases of pKa and −ΔH. This fact indicates that the hydrolysis proceeds via a concerted direct nucleophilic attacking mechanism of the coordinated hydroxide ion, in which the phosphate ester coordinates to the zinc(II) ion. X-ray structure analyses for synthesized model complexes, [Zn(OAc)(dien)](ClO4), [{Zn(dpt)}3(CO3)](ClO4)4·NaClO4, and [Zn(OAc)(tach)](ClO4), are also reported.
  • Fuminori Kasuga, Hiromichi Yamazaki, Yasushi Inoue, Osamu Tochiyama
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1275-1279
    Published: 1996
    Released: June 21, 2006
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    The isotopic exchange rate of Na+ and Cs+ between hydrous titanium(IV) oxide in the relevant ionic form and aqueous solutions was measured radiochemically. Four kinds of exchangers were precipitated at various pH’s: pH 4, 6, 8, and 10. The rate of each alkali metal ion was controlled by the diffusion of the ions in the exchanger particles at any pH of the surrounding solutions. At high pH of the solution, the diffusion of Cs+ in the exchangers precipitated at pH 4 and 6 was faster than that of Na+, but the difference of diffusion coefficients between two ions was negligible in the exchangers precipitated above pH 8. The diffusion coefficient in a particular exchanger decreased with increasing amount of ions taken up on the exchanger, owing to the increase of frequency of the electrostatic interaction between ions and dissociated ion-exchange sites. The difference of diffusion coefficients among exchangers was interpreted in terms of the difference in the microstructure of the exchanger matrix.
  • Hiroaki Isago, Yutaka Kagaya
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1281-1288
    Published: 1996
    Released: June 21, 2006
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    Electrochemical properties of the titled complex in dichloromethane (DCM) solutions have been investigated by cyclic and rotating-disk-electrode voltammetry. Two successive reversible one-electron reduction waves (E1/2 = −0.23 and −0.65 V vs. ferrocene/ferricinium+, respectively) and one irreversible oxidation wave (Epa = 1.32 V) have been observed. These were assigned as phthalocyaninate-ring-centered. Ring-reduced species of the titled complex was generated by both chemical and electrochemical reduction of the complex in DCM solutions and was characterized by electronic absorption (UV; 250—1100 nm), magnetic circular dichroism (MCD; 250—800 nm), and ESR spectroscopy. A quite sharp ESR signal was observed at g = 2.0041 (with a width of 0.5 mT) for the electrochemically-generated species, confirming the formation of monomer but not of dimer. The reduced species showed some prominent bands in its UV spectra, at 328 (B1; π → π*), 382 (LMCT), 553 (n → π*), 599 (π* → π*), and 1059 nm (Q; π → π*). The MCD spectra showed sharp bands at 328 and 599 nm as Faraday C-terms, indicating that the ground state of the reduced species is orbitally degenerated. Thus the phthalocyanine-ring is not significantly Jahn–Teller-distorted and is approximately D4h in symmetry even upon reduction.
  • Kazuaki Yamanari, Akira Fuyuhiro
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1289-1296
    Published: 1996
    Released: June 21, 2006
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    Ternary solubility isotherms of trans(N,t-N)-[Co(leu)(tren)]I2, trans(N,t-N)-[Co(n-leu)(tren)][ClO4]2, and trans(N,t-N)-[Co(n-val)(tren)][ClO4]2 [t-N = tertiary amine nitrogen; leu = leucinate(1−), n-leu = norleucinate(1−), n–val = norvalinate(1−), and tren = tris(2-aminoethyl)amine] were determined at 25 °C. Each isotherm consists of two branches of the solubility curve and one eutectic point; the tie lines do not converge to any apex of the pure enantiomers, but diverge widely. These facts mean that the three complexes simultaneously form a conglomerate and a solid solution. X-Ray crystal analyses were carried out for crystals grown from the three racemic aqueous solutions. All of the crystals were isomorphous to each other in spite of having different amino acidates and counter ions. The crystal structures clearly demonstrated the coexistence of D-amino acidate and L-amino acidate at one site of the crystal lattice, that is, a solid solution. Furthermore, all of the crystals were partially optically active: D : L = 63 : 37 for leu complex (space group P32), D : L = 32 : 68 for n-leu one (P31), and D : L = 44 : 56% for n-val one (P31). Head-to-tail hydrogen bonding contacts, which form spiral chains along the c-axis, were commonly found for these complexes.
  • Masatoshi Kanesato, Toshiro Yokoyama, Osamu Itabashi, Toshishige M. Su ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1297-1302
    Published: 1996
    Released: June 21, 2006
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    The preparation and characterization of praseodymium(III) and neodymium(III) complexes of heptadentate (N4O3) ligand trensal, tris[2-(salicylideneamino)ethyl]amine (H3L1), have been studied. These complexes (PrL1 and NdL1) were prepared by the reaction of the praseodymium(III) or neodymium(III) complex of 1,9-bis(2-aminoethyl)-1,4,6,9,12,14-hexaazacyclohexadecane with salicylaldehyde in acetonitrile. Alternatively, the reaction of tris(2-aminoethyl)amine and salicylaldehyde in the presence of praseodymium(III) or neodymium(III) salt in acetonitrile also gave praseodymium(III) and neodymium(III) complexes of trensal. The molecular structures of PrL1 and NdL1 were determined by X-ray structural analysis; these are rare examples of lanthanide heptadentate complexes in which the metal ions are coordinated by the four nitrogen atoms and the three oxygen atoms. The crystals of Pr(C27H27N4O3)·0.5CH3CN and Nd(C27H27N4O3)·0.5CH3CN are both trigonal, space group , a = 13.713(2), c = 8.093(3) Å, U = 1318.0(7) Å3, Z = 2 for [PrL1]·0.5CH3CN, and a = 13.724(3), c = 8.067(3) Å, U = 1315.8(7) Å3, Z = 2 for [NdL1]·0.5CH3CN. The structures were solved by heavy-atom Patterson methods and expanded using Fourier techniques; they were then refined by full-matrix least-squares procedures to R = 0.033 and Rw = 0.043 for 1547 observed reflections with I ≥ 3σ(I), R = 0.028 and Rw = 0.039 for 1923 observed reflections with I ≥ 3σ(I) for [PrL1]·0.5CH3CN and [NdL1]·0.5CH3CN, respectively. The individual metal ions and the apical nitrogen atoms lie on a 3-fold axis in each crystal; the molecules possess a C3 molecular symmetry.
  • Sho-kichi Oh-uchi, Jin-Shik Lee, Mitsuaki Narita
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1303-1307
    Published: 1996
    Released: June 21, 2006
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    The influence of protecting groups on the β-sheet-structure stability of protected peptides was studied in organic solvents. α-Amino groups, carboxyl groups, and side-chain functional groups of model peptides were protected by availably used protecting groups. The difference between the solubilities of model peptides was investigated by the solvent-titration method using infrared (IR) absorption spectra. The β-sheet-structure-stabilizing potentials (SPβ) of each protecting group showed similar behaviors, except for Npys, Mts, and Z2. The result exhibits that the <SPβ> values of the protected peptide are almost independent of the kinds of their protecting group.
  • Tetsuo Iwagawa, Yasuhisa Amano, Munehiro Nakatani, Tsunao Hase
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1309-1312
    Published: 1996
    Released: June 21, 2006
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    Seven new diterpenoids with an opened A-ring containing an aliphatic acid, called azamilides A—G (17), have been isolated from an acetone extract of Xenia sp. and their structures elucidated on the basis of spectroscopic analysis.
  • Kenichi Nakabayashi, Junichi Arimura, Masahide Yasuda, Kensuke Shima, ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1313-1317
    Published: 1996
    Released: June 21, 2006
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    The cycloreversion of 1-(1-naphthyl)-5-phenylbicyclo[3.2.0]hept-6-ene (1b) to 1-(1-naphthyl)-4-phenyl-1,3-cycloheptadiene (2b) upon benzophenone (BP) sensitization and direct irradiation has been investigated. The triplet sensitization of 1b in benzene gave 2b quantitatively up to a stationary state where the quantum yield was 0.96. The triplet state of 2b (λmax = 455 nm, τ = 4.6 μs) was formed by the pulse radiolysis of 1b in benzene. It has been found that cycloreversion proceeds by an adiabatic mechanism via a triplet state. The quantum yield for the formation of 2b by the irradiation of 1b at 313 nm was determined to be 0.17 in hexane. The fluorescence spectra of 1b and 2b indicated that diabatic cycloreversion occurred via a singlet state. The singlet and triplet energies of 1b, as well as those of 2b, were estimated to be 88, 60, 72, and 39 kcal mol−1, respectively. The effect of a substitution of the naphthalene chromophore on bicyclo[3.2.0]hept-6-ene was estimated.
  • Yukari Ikeda, Bing Zhu Yin, Nobuo Kato, Akira Mori, Hitoshi Takeshita
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1319-1327
    Published: 1996
    Released: June 21, 2006
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    The rotational barriers of the exocyclic double bonds of a series of methyl 8-cyanoheptafulvene-8-carboxylates were measured to evaluate the steric effect and the contribution of the polarized structures. An incorporation of five-membered heterocycles lowered the activation energies sufficiently to allow the study of steric and electronic factors. Thus, the Type I compounds, 8-[cyano(methoxycarbonyl)methylidene]-2-methyl-8H-cyclohepta[b]furan and its sulfur and nitrogen analogues, which have a different extent of steric effect, had rates of rotation in the order of N > S > O. On the other hand, the Type II derivatives, 6-(1-cyano-1-methoxycarbonylmethylidene)-2-methylcyclohepta[b]furan and its sulfur and nitrogen analogues, for which the steric factor is unimportant, showed an order of N > O > S. This was also the case for the Type III derivatives, methyl 8-cyano-3-methoxyheptafulvene-8-carboxylate, methyl 8-cyano-3-(methylthio)heptafulvene-8-carboxylate, and methyl 8-cyano-3-(dimethylamino)heptafulvene-8-carboxylate. The unusually low values of ΔH for the nitrogen analogues indicated that the ground state structures were destabilized by the steric repulsions.
  • Suguru Higashida, Hirohito Tsue, Ken-ichi Sugiura, Takahiro Kaneda, Yo ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1329-1335
    Published: 1996
    Released: June 21, 2006
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    In order to understand electron transfer (ET) pathways through bonds and through space, a porphyrin-spacer-benzoquinone molecule, where the spacer is spiro[4.4]nonane and a phenyl group is inserted between the space of the redox pair, was prepared. On the basis of MM2 calculation, the edge-to-edge distances between the phenyl and the porphyrin or quinone rings are in the range of 2.5—4.2 Å. Therefore, it was expected that there are two possible intramolecular ET pathways in the compound, i.e., through bond and through space. The ET rates for charge separation process (kcs) were obtained on the basis of fluorescence lifetime. The kcs value of the above compound is almost identical with that of a reference compound in which no inserted phenyl ring is present. Therefore, it was concluded that the inserted π-system between the redox pair is not used as a stepping stone in ET pathways; in other words, ET in the present molecules takes place in a through-bond mechanism. To compete with fast ET with through-bond pathways in covalently linked donor–acceptor systems where the two ET pathways are possible, through-space ET may function under quite limited conditions.
  • Kiyoshi Kudo, Yuji Oida, Koichi Mitsuhashi, Sadayuki Mori, Koichi Koma ...
    1996 Volume 69 Issue 5 Pages 1337-1345
    Published: 1996
    Released: June 21, 2006
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    The palladium(II)-catalyzed carbonylation of various enol esters in the presence of methanol under pressurized carbon monoxide was investigated. As typical results, the carbonylation of isopropenyl acetate afforded a cyclocarbonylation product, 2-methoxy-2,5,5-trimethyl-1,3-dioxolan-4-one, in 46% yield under carbon monoxide of 150 atm at 100 °C, whereas vinyl acetate selectively gave an α-hydroesterification product, methyl 2-acetoxypropionate, in 56% yield under 250 atm at 100 °C. On the contrary, the reaction of 3,3-dimethyl-1-buten-2-yl acetate gave exclusively a β-hydroesterification product, methyl 3-acetoxy-4,4-dimethylpentanoate, in 64% yield. The yields of these products show a maximum as a function of the base/palladium ratio and of the carbon monoxide pressure. The effects of the reaction variables, such as the MeOH/substrate ratio, the structure of the base, the base/Pd ratio, the CO pressure, and the reaction temperature, were examined for optimizing the process. The mechanisms for the unique cyclocarbonylation and highly regioselective hydrocarbonylation of enol esters involving hydridopalladium(II) intermediate are discussed.
  • Stanislas Czernecki, Jean-Marc Valery, Roland Wilkens
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1347-1351
    Published: 1996
    Released: June 21, 2006
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    The two C-6 epimers of 6-acetylamino-4,6-dideoxy-heptopyranosiduronic acid present in amipurimycin were prepared by selective reactions from methyl 2,3-di-O-benzyl-4,6,7,8-tetradeoxy-α-L-ido-7-ynopyranoside (4) in which the ethynyl group was employed as a precursor of the carboxylic acid function. The masked amino group was introduced at C-6 by reaction of 4 with zinc azide in the presence of triphenylphosphine and diisopropyl azodicarboxylate. The resulting methyl 6-azido-2,3-di-O-benzyl-4,6,7,8-tetradeoxy-α-D-gluco-oct-7-ynopyranoside (5) was transformed into benzyl[6-(acetylamino)-2,3-di-O-benzyl-4,6-dideoxy-α-D-gluco-heptopyranosid]uronate (7) by two different sequences of reactions: (1) oxidative cleavage of the triple bond, benzylation, reduction of the azido group, N-acetylation or (2) reduction of the azido group, N-acetylation, oxidative cleavage of the triple bond and treatment with phenyldiazomethane. The second sequence of reactions was found to be more efficient (33% overall yield versus 13%). The configuration at C-6 was unambiguously confirmed by X-ray diffraction with a single crystal of 7. Final hydrogenolysis of benzyl groups afforded methyl 6-(acetylamino)-4,6-dideoxy-α-D-gluco-heptopyranosiduronic acid (9). A Mitsunobu reaction on acetylenic alcohol 4 followed by saponification afforded the C-6 epimer 11. The same sequences of reactions was applied to 11 and methyl 6-(acetylamino)-4,6-dideoxy-α-L-ido-heptopyranosiduronic acid (16) was obtained.
  • Yoshihiko Yamamoto, Masatomi Ohno, Shoji Eguchi
    1996 Volume 69 Issue 5 Pages 1353-1362
    Published: 1996
    Released: June 21, 2006
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    Described herein is a novel method for regio-controlled synthesis of highly substituted cyclobutenones having an unsaturated substituent at 4-position, starting from commercially available squaric acid. Both cyclobutene-1,2-dione monoacetal (4,4-diethoxycyclobutenone) and its vinylog (2,4-diethoxycyclobutenone), which were easily obtained from diethyl squarate, reacted with allylsilanes in the presence of Et2O·BF3 to afford 4-allyl-4-ethoxycyclobutenones having various substituents at 2-position regioselectively. These products were efficiently transformed to highly substituted bicyclo[3.2.0]heptenones by refluxing in xylene. The synthetic utility of this process was demonstrated in the construction of tricyclic ring systems. Further extension of the Lewis acid-catalyzed reaction of the monoacetal using an allenylsilane, a silyl enol ether, and a silyl ketene acetal also afforded the corresponding 4-substituted products. In contrast to the above 4-allylated products, 4-propargylated and 4-acylmethylated products did not undergo an analogous ring transformation under the same conditions.
  • Masato Aizawa, Masaharu Tsuji, Yukio Nishimura
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1363-1369
    Published: 1996
    Released: June 21, 2006
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    The branching ratios of product ions for the reactions of CF3+ with furan and thiophene were determined by using an ion-beam apparatus. The main reaction channels proceed via α- and β-trifluoromethylated intermediates (C-adducts), followed by HF elimination, CO elimination, and CO + HF elimination for furan, and followed by HF elimination for thiophene. Semiempirical MNDO calculations of heats of formation of various intermediates and products were carried out to explore possible mechanisms. It was concluded that the CO and CO + HF eliminations for furan occur through a cleavage of a C–O skeletal bond of the C-adducts. The lack of CO and CO + HF elimination channels for thiophene was explained by the fact that the ring-opening and ring-contraction channels are energetically closed.
  • David Barrett, Hiroshi Sasaki, Takayoshi Kinoshita, Hideo Tsutsumi, Ka ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1371-1376
    Published: 1996
    Released: June 21, 2006
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    A new and improved method for the preparation of the key cyclization precursors for novel pyrido[3,2,1-ij]cinnoline antibacterial agents that avoids the use of di-t-butyl methylenemalonate is described. The key process is the alkylation of 1-[N-(hydroxymethyl)-N-methylamino]-4-quinolones with di-t-butyl malonate via the intermediate chloromethyl derivatives. Unexpectedly, this process produced labile pyrazolo[1,5-a]quinoline derivatives that were subsequently shown to undergo ring opening and cyclization to C8 to produce the pyrido[3,2,1-ij]cinnoline key intermediates.
  • Nagatoshi Nishiwaki, Aya Tanaka, Mitsue Uchida, Yasuo Tohda, Masahiro ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1377-1381
    Published: 1996
    Released: June 21, 2006
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    cine-Substitution of 1-methyl-3,6,8-trinitro-2-quinolone by 1,3-dicarbonyl compounds in the presence of NEt3 occurred efficiently, affording 4-functionalized 6,8-dinitro-2-quinolone derivatives. The addition intermediate was isolated in the reaction with CH2(CO2Et)2 and EtONa. Conversion of the isolated intermediate into the cine-substituted product was performed. These results indicate that the present cine-substitution proceeds by the addition-elimination mechanism.
  • Toru Arai, Takashi Imachi, Tamaki Kato, H. Iyehara Ogawa, Tsutomu Fuji ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1383-1389
    Published: 1996
    Released: June 21, 2006
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    [Hexafluorovalyl1,1′]gramicidin S (8), in which two valine residues in the natural gramicidin S were replaced by L-hexafluorovaline (Hfv) residues, was synthesized by the solid-phase-synthesis and cyclization-cleavage method on benzophenone oxime resin. Though the racemic hexafluorovaline derivative was employed for the peptide synthesis, the desired product was isolated in moderate yield, probably reflecting the stable cyclic structure of 8. CD and 1H NMR spectra indicated that the conformation of 8 is similar to that of gramicidin S. The two β-turn structure and antiparallel β-sheet structure with four intramolecular hydrogen bondings were maintained in spite of introducing the hexafluorovaline residues. The dye-release experiment from lecithin vesicle and antimacrobial activity assay also indicated that 8 showed membrane-disturbing activity like gramicidin S, although the activity of 8 was somewhat weaker than gramicidin S.
  • Hideo Tanaka, Ryo Kikuchi, Sigeru Torii
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1391-1396
    Published: 1996
    Released: June 21, 2006
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    The selective transformation of allenecarboxylate derived from penicillin into 3-chloro-Δ3-cephem-4-carboxylate was successfully achieved by an addition/cyclization reaction with chloride salts in aerobic media containing a copper(II) catalysts, in which copper(II)-catalyzed aerobic oxidation of in situ generated benzenesulfinate ion into less nucleophilic sulfonate ion prior to the nucleophilic addition of the former ion to the allenecarboxylate would completely eliminate the formation of undesired 3-phenylsulfonyl-Δ3-cephem-4-carboxylate. Under similar aerobic conditions, arenesulfinates salts and arenesulfinic acids were smoothly oxidized to the corresponding sulfonate salts and sulfonic acids, respectively.
  • Naoaki Fukada, Tadashi Ohtsu, Masamichi Miwa, Masayuki Mashino, Yasuyu ...
    1996 Volume 69 Issue 5 Pages 1397-1401
    Published: 1996
    Released: June 21, 2006
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    The reaction of diethyl oxalate with ethereal oxygen-containing diamines under high-dilution conditions gave 2 : 2 reaction products, 22-, 28-, and 34-membered macrocyclic amides in good yields. From the 2 : 1-mixed reaction between diethyl oxalate and the diamines, acyclic 2 : 1 and 3 : 2 reaction products were isolated at a ratio of ca. 9 : 1. The intermediate 2 : 1 and 3 : 2 reaction products led to the 2 : 2 reaction products mentioned above and the 3 : 3 reaction products, 33-, 42-, and 51-membered macrocyclic amides, respectively, upon reaction with additional corresponding diamines. Also, other macrocyclic amides were synthesized by combining the 2 : 1 reaction products and diamines.
  • Irona Nongkynrih, Mahendra K. Mahanti
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1403-1407
    Published: 1996
    Released: June 21, 2006
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    When treated with quinolinium dichromate (QDC) in acid medium using dimethylformamide as the solvent, cyclic alcohols were converted to the corresponding cyclic ketones. Kinetic data have been presented. The order of reactivity was 8 > 7 > 5 > 6. The reaction proceeds via a cyclic transition state, with the subsequent cleavage of the carbon–hydrogen bond (kH/kD = 5.8) in the rate determining step. The electrocyclic mechanism involved six electrons, and being a Hückel-type system (4n + 2), this was an allowed process.
  • Chiaki Kuroda, Naoko Mitsumata, Chen Ying Tang
    1996 Volume 69 Issue 5 Pages 1409-1416
    Published: 1996
    Released: June 21, 2006
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    An acylative C(3)–C(4)-bond cleavage of ethyl 4,5-disubstituted 2-(trimethylsilylmethyl)penta-2,4-dienoate occurred to give an ethyl 2-(2-oxoalkyl)acrylate by treatment with trifluoromethanesulfonic acid in nitriles. A self-cyclization also occurred to give a 5,5-disubstituted 3-methylenetetrahydrofuran-2-one when the reactions were carried out in bulky nitriles. Only self-cyclization proceeded when the corresponding 4,5-disubstituted 2-(trimethylsilylmethyl)penta-2,4-dienoic acid was treated in acetonitrile. The reaction mechanism is described.
  • Kazunari Yoshizawa, Masashi Hatanaka, Hiroki Ago, Kazuyoshi Tanaka, To ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1417-1422
    Published: 1996
    Released: June 21, 2006
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    In order to pursue the possibility of charge-transfer organic ferromagnets, magnetic properties of the monocationic ClO4- and BF4-salts of a triaminobenzene derivative, 1,3,5-tris[bis(p-methoxyphenyl)amino]benzene (TBMAB), were characterized by means of ESR and a Faraday-type magnetic balance. MNDO-PM3 calculations predicted 1,3,5-tris(diphenylamino)benzene (TDAB) dication and trication to be ground-state triplet and quartet, respectively. Thus these triaminobenzenes fulfill the necessary precondition for the appearance of intermolecular ferromagnetic coupling based on so-called McConnell’s second model. Negative Weiss constants (−1 to 0 K) and low spin concentrations (7—8 %) were observed for TBMAB–ClO4 and TBMAB–BF4, although, according to this rule, intermolecular ferromagnetic coupling is expected to occur for these systems.
  • Isao Fujii, Noriaki Hirayama, Norihito Aoyama, Akira Miike
    1996 Volume 69 Issue 5 Pages 1423-1427
    Published: 1996
    Released: June 21, 2006
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    10-N-Methylcarbamoyl-3,7-bis(dimethylamino)-10H-phenothiazine (MCDP) is one of the functional dyes which are applied clinically as diagnostics. MCDP spontaneously decomposes to methylene blue while increasing the undesirable background of diagnosis. Understanding the mechanisms of spontaneous decomposition is essential for the molecular design of better functional dyes. X-Ray analyses of two derivatives of MCDP, 10-N-methylthiocarbamoyl-3,7-bis(dimethylamino)-10H-phenothiazine and 10-N-benzylthiocarbamoyl-3,7-bis(dimethylamino)-10H-phenothiazine, have been undertaken. Based on the three-dimensional structures the structure-property relationships between them were analysed.
  • István Hannus, István Pálinkó, Gyula Tasi, ...
    Type: Accounts
    Subject area: AI
    1996 Volume 69 Issue 5 Pages 1429-1435
    Published: 1996
    Released: June 21, 2006
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    Microporous catalytic materials with various surface acidities have been prepared and characterized with instrumental methods as well as chemical reactions. The catalysts were LiY, NaY, KY, CsY, RbY, Na-montmorillonite (Na-mor), and Al-pillared montmorillonite (Al-PILC). Structural characterization involved atomic absorption and X-ray fluorescence spectroscopies, X-ray diffractometry, infrared spectroscopy in the region of framework vibrations, and thermogravimetric and BET measurements. Infrared spectroscopy of adsorbed pyridine and the acid-catalyzed isomerization of cyclopropane was used for testing surface acidity. The instrumental methods suggested a decreasing acidity order with increasing cationic radii, while the chemical reaction showed that the acidity decreased in the Al-PILC > LiY > NaY > CsY > KY ≈ RbY sequence. On the first two catalysts oligomerization followed isomerization, and the activity of isomerization decreased in the above order.
  • Hiroaki Okamoto, Mitsuaki Hayashi, Shunsuke Takenaka
    1996 Volume 69 Issue 5 Pages 1437-1441
    Published: 1996
    Released: June 21, 2006
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    This paper describes the preparation and thermal properties of a homologous series of 4-alkoxyphenyl 4-thiocyanatophenyl terephthalates. The homologous series shows nematic and smectic A phases commencing from the pentyloxy homolog. The smectic A phase is immiscible with the smectic A phase of polar liquid crystals having a terminal cyano group. Interestingly, the smectic B phase is also formed from the hexyloxy homolog, while the compound has a polar group at the terminal position.
  • Kuniaki Takata, Fumio Hanada, Yasuhiro Kagiyama, Toshikatu Sata
    1996 Volume 69 Issue 5 Pages 1443-1448
    Published: 1996
    Released: June 21, 2006
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    In order to prepare a monovalent permselective anion exchange membrane, the surface of a precursor membrane, which was prepared from a membranous copolymer of chloromethylstyrene (CMS) and divinylbenzene (DVB) in the presence of poly(vinyl chloride), was treated with various amino compounds; the chloromethylphenyl groups in the membrane were then reacted with trimethylamine so as to introduce (trimethylammoniomethyl)phenyl groups. The anion exchange membranes which were modified with tetraethylenepentamine and 4-vinylpyridine showed a chloride anion permselectivity versus that of a sulfate one in electrodialysis. It was thought that the reaction between these amines and the chloromethylphenyl groups formed a higher crosslinking structure on the surface of the membrane.
  • Shinji Inagaki, Akihiko Koiwai, Noritomo Suzuki, Yoshiaki Fukushima, K ...
    1996 Volume 69 Issue 5 Pages 1449-1457
    Published: 1996
    Released: June 21, 2006
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    The synthetic conditions of highly ordered and thermally stable mesoporous molecular sieves from a layered silicate kanemite are established. We divided the formation process of the mesoporous materials from kanemite into two elemental processes: i) exchange of Na+ in the interlayer of kanemite for alkyltrimethylammonium cations and ii) condensation of silicates and formation of a three dimensional silicate framework. Higher pH (over 11.5) at the cation-exchange process and the subsequent pH adjustment at 8.5 at the condensation process were best suited for the formation of mesoporous products with high regularity and thermal stability. Removal of partially dissolved kanemite during the cation-exchange process avoided the formation of amorphous materials as a by-product. Structures of some intermediate silicate/surfactant complexes supported the proposed folded sheets mechanism for the formation of the mesoporous molecular sieves. Syntheses by using alkyltrimethylammonium with different alkyl-chain lengths are also reported.
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