bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of ZSM-5 Using a TBP Template and an Oligomeric Silicic Ester
Authors: Lingappan Nachiappan , Krishnasamy V
Published: June 2006

The syntheses of pentasil zeolites were carried out using the system xNa2O·y(TBP)2O·Al2O3·zSiO2·1050H2O, keeping z = 50—600, y/z = 0.03 to 0.1, and x/z = 0.01 to 0.05 at 448 K. Pure ZSM-5 phase is found to form for any value of z in the range specified when y/z = 0.02 and x/z = 0.01. When these compositional ranges and ratios are altered either ZSM-11 or intergrowth of ZSM-5/11 or formation of ZSM-5 or ZSM-11 and quartz takes place. The decomposition of the templates, from the channels of ZSM-5 of different SiO2/Al2O3 ratio, showed differences in their patterns. After calcination of the samples phosphorus is retained in the zeolite channels in the form of a surface complex. Thermal analysis and FTIR studies support this observation. SEM pictures drive to the conclusion that a liquid–solid transformation mechanism operates in the crystallization of ZSM-5 under the conditions of the synthesis studied.
Conversion of Carbon and Alkali Metal Carbonates to Hydrocarbons Containing Aromatic Hydrocarbons by the Reaction with Copper Oxides and Aqueous Alkaline Solution
Authors: Akiyama Fuminori
Published: June 2006

Reaction of activated carbon and copper(II) oxide in the presence of aqueous potassium carbonate solution at 380 or 400 °C gave mainly carbon dioxide, accompanied by the formation of hydrocarbons containing aromatic hydrocarbons such as benzene and toluene. The similar reaction of copper(I) oxide gave mainly methane, accompanied by formation of smaller amounts of carbon dioxide, benzene, and toluene than the reaction of copper(II) oxide. Although the reaction of copper(II) oxide with aqueous potassium carbonate solution did not give hydrocarbons in the absence of activated carbon, the reaction of copper(I) oxide with aqueous potassium carbonate solution gave hydrocarbons even in the absence of activated carbon.
Bacterial Reduction of Azo Compounds as a Model Reaction for the Degradation of Azo-Containing Polyurethane by the Action of Intestinal Flora
Authors: Ueda Tsutomu , Yamaoka Tetsuji , Miyamoto Masatoshi , Kimura Yoshiharu , Sasatani Haruhide , Kim Soon-Ih
Published: June 2006

Two types of model compounds containing an azo aromatic group were synthesized, and their reduction kinetics in an anaerobic culture of intestinal flora was investigated for insight into the degradation mechanism of the azo-containing polyurethane which can be specifically degraded by the action of azo reductases which are released by intestinal floras. A water-soluble azo compound, 3,3′ -azodibenzenemethanol (ADM), was readily reduced into its hydrazo form and then to the amine form, 3-aminobenzenemethanol (ABM). The reduction rate from azo to hydrazo was much faster than that from hydrazo to amine. In the case of a water-insoluble azo compound, 3,3′-azodibenzenemethanol bis(N-phenylcarbamate) (ADM-PC), in which the hydroxy groups of ADM were capped by N-phenylcarbamoyl groups, the reduction was stopped in the first step, and only the hydrazo form was produced. These data indicated that the azo-containing polyurethane which is hydrophobic in nature should be degraded by the azo-hydrazo reduction of the azo groups without the chain breakage occurring.
Magnetic Characterization of Magnetite Particles for MR Contrast Agents
Authors: Suzuki Motoshi , Shimizu Wataru , Kosugi Yoshio , Honda Hiroyuki , Kobayashi Takeshi
Published: June 2006

The proton spin relaxivities (R1, R2) of agarose phantom with magnetite particles were measured using an NMR spectrometer at 5.875 T, and compared with other magnetic substances. R2 for the polyethylene glycol-coated magnetite particle (PEG-magnetite) was 455 s−1 mM−1 (M = mol dm−3), 50- and 95-times larger than that for FeCl3 and Gd(H2dtpa), respectively. PEG-magnetite also showed a high R2/R1 ratio of 172, while the latter two substances had low R2/R1 ratios below 10. The core size greatly affected R2, the maximum R2 value being observed in the case of the intermediate size (10 nm) among three different core sizes of magnetite. The basic characteristics of magnetite were found to be derived from its magnetism. The optimization of such acquisition parameters as TR and TE for spin-echo pulse sequences was also examined. The differences in the calculated signal intensity obtained from a tumor with PEG-magnetite and from normal tissue without PEG-magnetite were compared. The image with the highest contrast was found to be obtained at TE = 40 ms and an appropriately long TR. PEG-magnetite is expected to work well as a negative-contrast agent under suitable acquisition conditions.
Chemistry of Azulenequinones and Their Analogues
Authors: Nozoe Tetsuo , Takeshita Hitoshi
Published: June 2006

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.
Supercooling and Enthalpy of Mixing of Aqueous Solutions of Tetrabutyl(or isopentyl)ammonium Chloride Subjected to Irradiation with Ultrasonic Waves
Authors: Nakayama Haruo , Hayashi Chihiro , Endou Masato
Published: June 2006

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.
A Study of the Preparation Procedures of Sulfated Zirconia Prepared from Zirconia Gel. The Effect of the pH of the Mother Solution on the Isomerization Activity of n-Pentane
Authors: Tatsumi Tetsuji , Matsuhashi Hiromi , Arata Kazushi
Published: June 2006

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.
Studies on Spread Monolayers and LB Films of Long-Chain Alkylchlorosilanes by Brewster Angle Microscopy and X-Ray Photoelectron Spectroscopy
Authors: Iimura Ken-ichi , Suzuki Noboru , Kato Teiji
Published: June 2006

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.
Nickel(II) Complex of 6,6′-Bis(hexylbenzoylamino)-2,2′-bipyridine as a Functional Carrier: pH-Induced Affinity-Switching and Mechanism of the SCN−-Selective Up-Hill Transport
Authors: Lee Sung-Kil , Kumasaka Yoshinori , Otsuki Joe , Araki Koji
Published: June 2006

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.
Structure and Characterization of 9,10-Diethyl-9,10-diphospha-9,10-dihydroanthracene as an Electron Donor
Authors: Akutsu Hiroki , Ogasawara Masamichi , Saburi Masahiko , Kozawa Kozo , Uchida Tokiko
Published: June 2006

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.
CdS Nanocrystals in Chelate Polymer Microparticles: Polymer Size Dependence of The Optical Properties
Authors: Yao Hiroshi , Kitamura Noboru
Published: June 2006

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.
Crystal Structure and Physical Properties of {Bis(ethylenedithio)tetrathiafulvalene}2dicyano-Silver and -Gold
Authors: Kurmoo Mohamedally , Day Peter , Mitani Tadaoki , Kitagawa Hiroshi , Shimoda Hideo , Yoshida Den , Guionneau Philippe , Barrans Yvette , Chasseau Daniel , Ducasse Laurent
Published: June 2006

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.
Synthesis of Tungstate Thin Films and Their Optical Properties
Authors: Saito Nobuhiro , Kudo Akihiko , Sakata Tadayoshi
Published: June 2006

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.
Highly Selective Adsorption Resins. I. Preparation of Chitosan Derivatives Containing 2-Pyridylmethyl, 2-Thienylmethyl, and 3-(Methylthio)propyl Groups and Their Selective Adsorption of Precious Metals
Authors: Baba Yoshinari , Kawano Yoshinobu , Hirakawa Hiroyuki
Published: June 2006

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.
Studies of the Hydrous Titanium Oxide Ion Exchanger. VII. Effects of pH at Precipitation on the Isotopic Exchange Rate of Na+ and Cs+ Ions between the Exchanger in the Relevant Ionic Form and Aqueous Solutions
Authors: Kasuga Fuminori , Yamazaki Hiromichi , Inoue Yasushi , Tochiyama Osamu
Published: June 2006

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.
Spectroscopic Properties of One-Electron-Reduced Species of Dichloro(phthalocyaninato)antimony(V) Cation
Authors: Isago Hiroaki , Kagaya Yutaka
Published: June 2006

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.
Conglomeratic Solid Solutions in trans(N,t-N)-[Co(leucinato)(tren)]I2 and trans(N,t-N)-[Co(norleucinato or norvalinato)(tren)][ClO4]2 [t-N = tertiary amine nitrogen; tren = tris(2-aminoethyl)amine]
Authors: Yamanari Kazuaki , Fuyuhiro Akira
Published: June 2006

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.
The Influence of Protecting Groups on the β-Sheet-Structure Stability of Protected Peptides
Authors: Oh-uchi Sho-kichi , Lee Jin-Shik , Narita Mitsuaki
Published: June 2006

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  values of the protected peptide are almost independent of the kinds of their protecting group.
Cycloreversion of 1-(1-Naphthyl)-5-phenylbicyclo[3.2.0]hept-6-ene to 1-(1-Naphthyl)-4-phenyl-1,3-cycloheptadiene by Triplet Sensitization and Direct Irradiation
Authors: Nakabayashi Kenichi , Arimura Junichi , Yasuda Masahide , Shima Kensuke , Takamuku Setsuo
Published: June 2006

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.
Intramolecular “Through-Bond” and “Through-Space” Electron Transfer Pathways in Covalently Linked Porphyrin-Quinone Molecules
Authors: Higashida Suguru , Tsue Hirohito , Sugiura Ken-ichi , Kaneda Takahiro , Sakata Yoshiteru , Tanaka Yoshinori , Taniguchi Seiji , Okada Tadashi
Published: June 2006

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.
Hydrocarbonylation of Enol Esters Catalyzed by a Palladium(II) Complex
Authors: Kudo Kiyoshi , Oida Yuji , Mitsuhashi Koichi , Mori Sadayuki , Komatsu Koichi , Sugita Nobuyuki
Published: June 2006

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.
Chain Extension of Carbohydrates VI. Synthesis of the Two C-6 Epimers of the 6-Acetylamino-4,6-dideoxyheptopyranosiduronic Acid Present in Amipurimycin by Means of Stereocontrolled Ethynylation of Methyl 2,3-Di-O-benzyl-4-deoxy-α-d-xylo-hexodialdo-1,5-pyranoside
Authors: Czernecki Stanislas , Valery Jean-Marc , Wilkens Roland
Published: June 2006

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.
New Method for Derivatization of Squaric Acid to Highly Substituted Cyclobutenones: Lewis Acid-Catalyzed Reaction of Cyclobutene-1,2-dione Monoacetal and Its Vinylog with Unsaturated Organosilanes, and Subsequent Ring Transformation of the Adducts
Authors: Yamamoto Yoshihiko , Ohno Masatomi , Eguchi Shoji
Published: June 2006

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.
Synthesis of 3-Chloro-Δ3-cephem-4-carboxylate by Addition/Cyclization of Allenecarboxylate. Copper(II)-Promoted Aerobic Oxidation of Arenesulfinic Acids
Authors: Tanaka Hideo , Kikuchi Ryo , Torii Sigeru
Published: June 2006

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.
Kinetics of Oxidation of Cyclic Alcohols by Quinolinium Dichromate
Authors: Nongkynrih Irona , Mahanti Mahendra K
Published: June 2006

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.
Magnetic Properties of 1,3,5-Tris[bis(p-methoxyphenyl)amino]benzene Cation Radicals
Authors: Yoshizawa Kazunari , Hatanaka Masashi , Ago Hiroki , Tanaka Kazuyoshi , Yamabe Tokio
Published: June 2006

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.
Relationships between the Molecular Structures and Stabilities of Functional Dyes with a Phenothiazine Skeleton
Authors: Fujii Isao , Hirayama Noriaki , Aoyama Norihito , Miike Akira
Published: June 2006

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.
Characteristics of Alkali-Exchanged Y Zeolites, Montmorillonite, and Al-Pillared Montmorillonite, Studied by Physical and Chemical Methods
Authors: Hannus István , Pálinkó István , Tasi Gyula , Béres Attila , Kiricsi Imre
Published: June 2006

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.
Liquid Crystalline Properties of 4-Alkoxyphenyl 4-Thiocyanatophenyl Terephthalates
Authors: Okamoto Hiroaki , Hayashi Mitsuaki , Takenaka Shunsuke
Published: June 2006

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.
Toward Direct Synthesis of Organonitrogen Compounds from Dinitrogen: The Chemistry of Diazoalkane Complexes Derived from Dinitrogen Complexes
Authors: Hidai Masanobu , Ishii Youichi
Published: June 2006

The hydrazido complexes trans-[MX(NNH2)(dppe)2]+ (3) and cis,mer-[MX2(NNH2)(PMe2Ph)3] (4) (M = Mo, W; X = halogen; dppe = 1,2-bis(diphenylphosphino)ethane), which are readily derived from dinitrogen complexes trans-[M(N2)2(dppe)2] (1) and cis-[M(N2)2(PMe2Ph)4] (2) by protonation with acid, undergo condensation with aldehydes or ketones (RR′C=O) to give a series of diazoalkane complexes, trans-[MX(NNCRR′)(dppe)2]+ and cis,mer-[MX2(NNCRR′)(PMe2Ph)3]. The diazoalkane ligand in those complexes has a singly-bent structure with the N–N–C bond angle of ca. 120° and the essentially linear N–N–M bond, and may be regarded as a four-electron-donating ligand. Owing to the conjugate structure including the metal center M≡N–N=CRR′, the diazoalkane complexes exhibit various reactivities including nucleophilic addition, deprotonation, conjugate addition, and reductive dimerization. Condensation of hydrazido complexes 3 and 4 with dialdehydes or their equivalents leads to complexes with nitrogen heterocyclic ligands incorporating the terminal nitrogen atom by way of the cyclization of intermediary diazoalkane complexes. By this method are prepared complexes containing phthalimidine, 1,3-dihydro-2H-pyrrol-2-one, 1,5-dihydro-2H-pyrrol-2-one, and pyrrole moieties. Interestingly, the (1-pyrrolyl)imido complexes with dppe ligands (26; M = Mo, W) undergo unusual electrophilic substitution reactions at the β-position of the pyrrole ring. Various types of organonitrogen compounds such as acetone azine, pyrazoles, phthalimidines, pyrroles, and N-aminopyrrole are liberateded from the above complexes in good yields. As a typical reaction, pyrrole and N-aminopyrrole are formed by the LiAlH4 reduction of complexes 26. In this reduction, tetrahydrido complexes [MH4(dppe)2] (M = Mo, W) are obtained as the metal products, which can be converted back to the starting dinitrogen complexes 1. Thus, a synthetic cycle for the formation of pyrrole and N-aminopyrrole from dinitrogen has been accomplished by using dinitrogen complexes 1.
Synthesis of Bifunctional Polycyclic Compounds and Their Application to Mechanistic Studies of Solvolysis Reactions
Authors: Takeuchi Ken’ichi , Ohga Yasushi
Published: June 2006

The 1-adamantyl cation reacts with carbon monoxide and adamantane in the presence of a superacid to give 3-hydroxy-4-homoadamantyl 1-adamantanecarboxylate in good yields. This finding has permitted the development of a synthetic route by using ring-expansion of bridgehead aldehydes with benzoic trifluoromethanesulfonic anhydride to give various bicyclic and tricyclic 1,2-diols having different ring flexibility. The diols are transformed to bridgehead compounds having an oxo or a methylene substituent on the vicinal position, which can be used as substrates showing different degrees of π-conjugation between these substituents and the bridgehead cationic center in the transition state of solvolysis. The solvolysis rate ratio of 2-methylene vs. parent bridgehead compounds markedly increases with the ring-flexibility, indicating that the allylic conjugation can be enhanced by increasing ring flexibility. However, the rate ratios for 2-oxo (or α-carbonyl) vs. parent bridgehead compounds are essentially constant, irrespective of the ring flexibility, suggesting the unimportance of π conjugative stabilization of α-carbonyl carbocations. On the contrary, 3-oxo (or β-carbonyl) bridgehead compounds solvolyze markedly faster than expected and support the proposal of pC(1)+ ↔ σC(2)C(3) ↔ n(CO) hyperconjugative interaction. The comparison of the solvolysis rates of (Z)- and (E)-2-ethylidene bridgehead compounds having a rigid structure provides a new method to evaluate the importance of F-strain effects in solvolysis.
Attractive Potential Effect on the Rotational Correlation Times for Benzene-d6 in Organic Solvents
Authors: Wakai Chihiro , Nakahara Masaru
Published: June 2006

2H NMR spin-lattice relaxation times have been measured to obtain the rotational correlation times τ2R for benzene C6D6 (50 mol m−3) in various organic solvents, such as benzene (C6H6), hexane, decane, carbon tetrachloride, chloroform, dichloromethane, methanol, ethanol, 1-propanol, 1-butanol, and acetonitrile over the widest possible range of temperature. Plots of the determined values of τ2R against solvent viscosity η divided by temperature T are linear in the apolar and polar aprotic solvents, as predicted by the Stokes–Einstein–Debye (SED) law. However, the plots of τ2R vs. η/T in the alcohols are concave upward, the slope in the high temperature region being ca. 2 times as large as that in the low temperature region. The nonlinearity and the decrease in the slope reflect the influence of the hydrogen-bonded solvent structure. For the benzene rotation in solutions, fairly good positive linear correlations are found between the slopes and the negative dissolution enthalpies at infinite dilution at room temperature. These results indicate an important role played by attractive solute–solvent interactions in controlling the molecular rotation in solution.
Isolation and Structural Characterization of Complexes Formed in the Reactions of [{C5H4(SiMe3)}2Fe2(CO)4] and [{1,3-C5H3(SiMe3)2}2Fe2(CO)4] with Elemental Sulfur
Authors: Yamada Mikiya , Tobita Hiromi , Inomata Shinji , Ogino Hiroshi
Published: June 2006

The reactions of [CpS12Fe2(CO)4] and [CpS22Fe2(CO)4] with elemental sulfur afforded a tetrairon cluster containing two end-on type S2 ligands [CpS14Fe4S6] (1) and a diiron complex containing an end-on type S2 and a side-on type S2 ligands [CpS22Fe2S4] (2), respectively, where CpS1 and CpS2 stand for mono- and bis(trimethylsilyl)cyclopentadienyl ligands, respectively. From these results and the previously reported results which were obtained for the reactions of [Cp2Fe2(CO)4] and [Cp*2Fe2(CO)4] with elemental sulfur, it is suggested that [Cp′2Fe2S4] is an intermediate to give tetrairon sulfur clusters, where Cp* and Cp′ denote pentamethylcyclopentadienyl and substituted cyclopentadienyl ligands, respectively. X-Ray crystal structure analysis was carried out for the compounds 1 and 2. Crystallographic data are as follows: 1: Monoclinic, P21/c, a = 17.302(6), b = 18.646(3), c = 15.310(4) Å, β = 120.71(2)°, V = 4246(2) Å3, Z = 4, and R = 0.061 for 5850 reflections with |Fo| > 3σ(Fo); 2: Triclinic, space group , a = 12.602(2), b = 12.891(2), c = 11.401(1) Å, α = 114.52(1), β = 95.45(1), γ = 88.39(1)°, V = 1677.5(4) Å3, Z = 2, and R = 0.046 for 7343 reflections with |Fo| < 3σ(Fo).
Effects of the Molar Mass of a Solute on Permeability through Poly(vinyl alcohol) Gel Membranes
Authors: Yonese Masakatsu , Kondo Masatoshi , Miyata Isamu , Kugimiya Sin-ichi , Sato Shizuko , Inukai Masao
Published: June 2006

The effects of the molar masses of solutes on permeability through poly(vinyl alcohol) PVA gel membranes were studied using polyethylene glycol having a wide range of molar masses and other solutes, such as electrolytes, glucose, and maltose. Furthermore, the effects of the network structure and fixed charges on the permeability were studied using opaque, transparent, and charged PVA gels. The permeability coefficients of solutes through PVA gel membranes (P) depended on the hydrodynamic radius of the solute (d0) and the mesh sizes of the network (ξ). When interactions between the matrix and the solute were negligible, the normalized permeability coefficients (P/D0) were found to be the scaling function of ξ/d0.
Adsorption of CO2, CH3OH, and H2O on Fe(III)-Substituted Calcium Hydroxyapatites
Authors: Ishikawa Tatsuo , Saito Hiroshi , Yasukawa Akemi , Kandori Kazuhiko
Published: June 2006

Calcium hydroxyapatites (CaHAP) substituted with Fe3+ ions of different atomic ratios Fe/(Ca + Fe) = XFe from 0 to 0.23 were synthesized and characterized by various methods. The number of Ca2+ ions in CaHAP substituted by one Fe3+ ion was higher than one, implying that the formation of cation vacancies and the protonation of PO43− ions are caused by Fe(III)-substitution. XFe of the surface layer of the particles determined by XPS was less than the total XFe. IR spectra of Fe(III)-substituted CaHAP contain a band at 3707 cm−1 assigned to the surface Fe–OH groups in addition to the surface P–OH bands at 3688, 3677, and 3658 cm−1. With an increase in XFe, the amount of irreversible adsorption of CO2 decreased whilst those of CH3OH and H2O first decreased and then increased. IR results showed that the surface Fe–OH groups act as stronger irreversible adsorption sites for CO2 and CH3OH compared to the surface P–OH groups.
Unimolecular Dissociation Kinetics of Benzene Cluster Ions
Authors: Ohashi Kazuhiko , Adachi Kei , Nishi Nobuyuki
Published: June 2006

The “unimolecular” dissociation processes of benzene cluster ions prepared by resonant 2-photon ionization (R2PI) of neutral clusters were investigated by using a time-of-flight mass spectrometer equipped with a reflectron. The dissociation rates were determined for fast-decay processes (kfast) in the acceleration region and slow dissociations (kslow) in the drift region of the spectrometer. The ejection of one neutral molecule was a dominant dissociation channel of small (C6H6)n+ in the drift region; in addition, the ejection of two molecules was observed for n − 2 ≥ 14. These size-specific dissociation channels and the size dependence of the kslow values imply a closing of the first shell of (C6H6)n+ at n = 14. The magnitude of both kfast and kslowwas found to be independent of the excess energy upon R2PI, suggesting rapid cooling of the nascent hot ions by prompt dissociation within the laser focus. For slow dissociation within a well-defined time window, the measured values of kslow were compared with those calculated according to a statistical theory of unimolecular reaction. The comparison deduced the average internal energies of (C6H6)n+ at ca. 1 μs after preparation.
Pressure Effect on Inter- and Intramolecular Vibrations of the p-Xylene Crystals
Authors: Shimizu Fumio , Yoshikai Kazumasa , Kawano Hiroshi , Nibu Yoshinori , Shimada Hiroko , Shimada Ryoichi
Published: June 2006

The Raman active inter- and intramolecular vibrations of the [1H10]- and [2H10]p-xylene crystals were studied under various pressures between 1 atm and 7.5 GPa. The pressure effect of the frequency of the Raman bands due to the intermolecular vibrations indicates that the coupling between the intramolecular torsional vibration of the methyl group and the intermolecular rotational vibrations takes place under about 1 and 2.5 GPa in the [1H10]- and [2H10]p-xylene crystals, respectively. The calculated pressure-induced frequency shift of the intramolecular vibrations explains fairly well the observed frequency shifts and supports the conclusion given in the previous work that the contribution of the first-order differential of the intermolecular potential to the pressure-induced frequency shift is vanishingly small when the potential is well approximated.
Spectroscopic Characterization and Biological Potential of Palladium(II) Complexes of Benzylidenehydrazinecarboxamide or -carbothioamide
Authors: Fahmi Nighat , Saxena Chitra , Singh Ranvir V
Published: June 2006

In this article a brief account of the synthesis, stereochemistry, and biochemical behavior of palladium(II) complexes of benzylidenehydrazinecarboxamide or -carbothioamide is presented. The bimolar addition and substitution products have been characterized by elemental analyses, conductance measurements, molecular-weight determinations, magnetic susceptibilities, and spectral studies viz., IR, 1H NMR, 19F NMR, and UV. The data support the binding of sulfur or oxygen and nitrogen to the palladium in and (X is O or S) types of complexes. The square-planar geometry has been proposed. The representative free ligands () and their respective metal complexes were tested in vitro against a number of microorganisms to assess their antimicrobial properties and in vivo to test their sterilizing potential. The results are indeed positive.
Elucidation of Salt Effects on the Indicator Acidity in Acetonitrile
Authors: Hojo Masashi , Hasegawa Hiroshi , Yoneda Hitoshi
Published: June 2006

The salt effects on the proton-transfer from CF3COOH to an acid-base indicator, ‘Methyl Yellow’ [p-(dimethylamino)-azobenzene], were examined in acetonitrile by means of spectrophotometry. The addition of LiClO4 to the indicator (Ind) and CF3COOF mixture (both 2.0 × 10−4 mol dm−3) caused an increase and a successive decrease in the absorbance (λmax = 514 nm) of IndH+. The promoted increase of the IndH+ concentration with increasing concentration of LiClO4 was explained on a quantitative basis concerning the formation of a triple cation, CF3COO−(Li+)2, as well as an ion pair, CF3COO−Li+: Ind–CF3COOH + 2 Li+ IndH+ + CF3COO−(Li+)2. The successive decrease in the absorbance at 514 nm with a large excess of LiClO4 was attributed to an ion-exchange reaction: IndH+ + Li+ IndLi+ + H+. The addition of NaClO4 to Ind–CF3COOH caused only an increase in the IndH+ concentration, and no deprotonation from IndH+. Alkaline-earth metal ions (M2+ = Mg2+, Ca2+, Sr2+, and Ba2+) promoted protonation by the formation of complex species, CF3COO−M2+. Although distinct deprotonation from IndH+ was observed with Mg(ClO4)2, no deprotonation occurred with Ba(ClO4)2. The effects of the chloride ion (Et4NCl) on deprotonation from IndH+ (In + CF3SO3H) were explained by the formation of homoconjugated species (HCl2−), and not by the mere formation of HCl. The apparent changes in pH or the Hammett acidity function with the presence of various salts were elucidated by the ‘complex’ formation in acetonitrile.