bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ruthenium Complex-Catalyzed Silylation of Olefins. Selective Synthesis of Allylsilanes
Authors: Hori Yoji , Mitsudo Take-aki , Watanabe Yoshihisa 
Published: July 2006

Abstract
(1-2; 5-6-η-Cyclooctadiene)(1-6-η-cyclooctatriene)ruthenium catalyzes the silylation of olefins at 60–140 °C to give allylsilanes with good selectivity in high yields. The reactions of trialkylsilane with 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene give the same product, 3-methyl-1-trialkylsilyl-2-butene. Silylation of ethyl (E)-2-butenoate gives ethyl (E)-4-trialkylsilyl-2-butenoate in high yield.
A Tin-Mediated One-Step Synthesis of (+)-Dicrotaline, an 11-Membered Dilactonic Pyrrolizidine Alkaloid
Authors: Niwa Haruki , Okamoto Osamu , Ishiwata Hiroyuki , Kuroda Akio , Uosaki Youichi , Yamada Kiyoyuki 
Published: July 2006

Abstract
A new synthesis of (+)-dicrotaline (1), an 11-membered dilactonic pyrrolizidine alkaloid of retronecine (6) type has been achieved in one step by utilizing a tinmediated lactonization process.
A Peculiar Conformation of Normal-Chain Dicarboxylic Acid Salts in Aqueous Solutions
Authors: Fukushima Kunio , Adachi Koichi , Watanabe Kiyohisa 
Published: July 2006

Abstract
The Raman spectra of adipic acid, pimelic acid, and their salts were observed for various states. The spectra of the acids in aqueous sodium hydroxide solutions were found to be very different from those of the acids in organic solvents. The difference was interpreted, on the basis of normal vibration calculations, as being due to the helix formation of molecules in the former solutions. This tendency toward helical coiling is consistent with the same tendency found for the salts of azelaic acid and suberic acid in our previous study.
The Temperature Dependence of the Conductivities and Ion-Association Constants of Potassium Nitrate and Potassium Perchlorate in Water
Authors: Yokoyama Haruhiko , Ohta Tomoko 
Published: July 2006

Abstract
The electric conductivities of potassium nitrate and potassium perchlorate in water have been measured at eleven temperatures from 0 to 50 °C and analyzed in order to obtain the ion-association constants and the limiting molar conductivities of these salts. It was found that the observed ion-association constants have a minimum value at 30 °C for KNO3 and at 36 °C for KClO4. Such a characteristic temperature dependence was considered to be due to the presence of specific short-range interactions within contact ion pairs, although the weak hydration of the ions seemed to help the formation of the contact ion pairs. The experimental standard enthalpies and entropies of ion association were discussed in comparison with the theoretical ones. The limiting molar conductivities of NO3− and ClO4− at each temperature were also evaluated and expressed as cubic equations of the temperature.
Monolayers of Triple Long-Chain Salts on the Concentrated Sodium Chloride Solution
Authors: Shibata Osamu , Kaneshina Shoji , Matuura Ryohei 
Published: July 2006

Abstract
The surface pressure–area (π–A) curves for monolayers of four kinds of cation-anion triple long-chain salts [dialkyldimethylammonium alkanesulfonates] on the aqueous solution of 4.4 M NaCl were measured at various temperatures by the Langmuir method. Some π–A curves of these salts showed two transition points. Judging from the apparent molar entropy change on the transition, the first was assigned to the transition from the expanded state (E phase) to the condensed state (C-I phase) and the second to the transition from the C-I phase to another condensed state (C-II phase). In this paper, another condensed phase (C-I′) was newly observed over a certain temperature range on the phase diagram, which is the intermediate phase between the C-I phase and the C-II phase. There exist two triple points on the phase diagram at which three phases (i.e., E, C-I, and C-I′, and C-I, C-I′, and C-II) coexist. From the apparent molar entropy change, limiting area, compressibility, and phase diagram, the orientation of (2–1) long-chain salts in the monolayer state was assumed.
A Facile Synthesis of 3-Hydroxymethyl- and 3-Formylindoles from o-Nitrotoluene
Authors: Tanaka Hideo , Murakami Yasuo , Okamoto Koichi , Aizawa Takao , Torii Sigeru 
Published: July 2006

Abstract
A synthesis of 3-hydroxymethyl- and 3-formylindoles has been performed by manipulation of the side chain of 3-hydroxymethylindoline derived from o-nitrotoluene. Electro-reductive cyclization of 2-(2-nitro-phenyl)-1,3-bis(methylsulfonyloxy)propane to 3-(benzyloxymethyl)indole, is also discussed.
Mössbauer Spectroscopic Characterization of Iron Supported on Y Type Zeolites after Sulfiding
Authors: Hidaka Setsuo , Iino Akira , Nita Kenji , Morinaga Kenji , Yamazoe Noboru 
Published: July 2006

Abstract
Iron supported on zeolite catalysts, prepared by treating NH4Y with aqueous solutions containing Fe3+ or Fe2+ ions followed by calcination in air, were subjected to Mössbauer spectroscopic investigations before and after sulfiding treatments to elucidate the states and properties of Fe species supported. At least three types of Fe3+ species could be distinguished in the prepared samples. The first Fe3+ species were those located at the cation-exchange sites of zeolite. This type was reduced easily to Fe2+ species with the H2S treatment, but was resistant to aggregation to form Fe1−xS. The second Fe3+ species were those which had precipitated on the surface of zeolites as hydroxides. These were sulfided to crystalline Fe1−xS after H2S treatment. Finally, the third Fe3+ species were those which were quite resistant to both reduction to Fe2+ and sulfiding to Fe1−xS. These species were preferentially supported under the conditions where dealumination from zeolite framework took place simultaneously. Thus it was speculated that these species were bonded to zeolite framework to be stabilized. The distribution of the three Fe3+ species were quite different depending on the sample preparation. Comparison with the catalytic data clearly indicated that the third Fe3+ species acted as highly active sites for the toluene disproportionation reaction in the presence of H2S.
Diastereoselective Hydrogenation of Methyl 2-[α-(Methoxycarbonylamino)benzyl]acrylate Catalyzed by Ru(II) or Rh(I) Complexes
Authors: Yamamoto Keiji , Takagi Masatoshi , Tsuji Jiro 
Published: July 2006

Abstract
The title compound was prepared and hydrogenated by using a Ru(II)- or Rh(I)-phosphine catalyst precursor with excellent anti-selectivity, the results indicating that a ligating group, NHCO2Me, may direct the addition of hydrogen to an olefinic diastereoface proximate to this group which binds the catalyst.
XANES of Aqua Complexes of 3d Transition Metal in Solid Solution
Authors: Miyanaga Takafumi , Watanabe Iwao , Ikeda Shigero , Tashiro Kouji , Fujiwara Takashi 
Published: July 2006

Abstract
A characteristic second peak appears at about 10 eV from a main peak in the XANES (X-ray Absorption Near Edge Structure) spectrum of aqueous 3d transition metal complex of divalent state. This second peak is prominent in solid samples. The peak intensity depends on the kind of central metal or counter anion in solid. Theoretical calculations based on the full multiple scattering formalism provide the information regarding the origin and property of the second peak in XANES. The second peak can be reproduced by the multiple scattering calculation considering only six first coordinating oxygen atoms. The intensity and the position of the peak vary with the charge on the first coordinating oxygen atoms which is affected by the ions or solvent molecules contacting with the metal complex.
A Novel Chiral Stationary Phase for Optical Resolution of Amino Acids and Their Derivatives by Ligand-Exchange High-Performance Liquid Chromatography
Authors: Saigo Kazuhiko , Yuki Yoichi , Kimoto Hiroki , Nishida Toru , Hasegawa Masaki 
Published: July 2006

Abstract
A novel chiral stationary phase, [(1R,2S)-2-hydroxy-1-methyl-2-phenylethylamino]acetic acid, was prepared from (−)-norephedrine, and its sodium salt was bound to silica gel pretreated with [3-(glycidyloxy)propyl]trimethoxysilane. The chiral stationary phase was found to be effective for the optical resolution of amino acids and their derivatives by ligand-exchange high-performance liquid chromatography using aq copper(II) sulfate solution as an eluent.
Synthetic Photochemistry. XLII. Total Synthesis of Cycloaraneosene, a Fundamental Hydrocarbon of 5–8–5-Membered Tricydic Diterpenoid from Sordaria araneosa
Authors: Kato Nobuo , Tanaka Shinya , Takeshita Hitoshi 
Published: July 2006

Abstract
A 5–8–5-membered tricyclic diterpene, cycloaraneosene, has been totally synthesized via a stereoselective condensation of two units of optically active iridoids, a Cope rearrangement, a chemical reduction of the tetrasubstituted double bond, and the formation of an eight-membered ring. The proposed structure of natural hydroxycycloaraneosene should be revised to 8β-hydroxycycloaraneosene, judging from the NMR spectral data.
Regio- and Stereoselective Ring Opening of ω-Alkenyllactones Using Organocopper Reagents
Authors: Kawashima Masatoshi , Sato Toshio , Fujisawa Tamotsu 
Published: July 2006

Abstract
New synthetic methods are described for the preparation of (E)-3-, (E)-4-, and (E)-5-alkenoic acids by the regio- and stereoselective ring opening of β, γ, and δ-lactones with unsaturated substituents at the ω-position using organocopper reagents such as halomagnesium diorganocuprates or Grignard reagents in the presence of copper(I) iodide. Both the organocopper reagents with primary, secondary, tertiary alkyl, and phenyl groups gave the corresponding carbon homologated alkenoic acids in good yields. Alkadienoic acids were also obtained in good yields by the reactions of ω-alkenyllactones with divinyl- and diallylcuprates. Utilizing the ring opening of β-isopropenyl-β-propiolactone, homoterpenoid carboxylic acids were easily obtained in good yields. The ring opening of β-(1-chlorovinyl)-β-propiolactone afforded 4-chloro-3-alkenoic acids which were easily transformed to 4-oxoalkanoic acids and 4-oxo-2-alkenoic acids.
Apparent Molal Volumes of Urea Derivatives in Water–Methanol Mixtures
Authors: Mizutani Kiyoshi , Yasuda Motoo 
Published: July 2006

Abstract
Apparent molal volumes (φv) at 25 °C have been obtained for the following urea derivatives in water–methanol mixtures from measurements of the density using an Anton Paar digital densimeter: urea (U), methylurea (MU), ethylurea (EU), 1,1-dimethylurea (1,1-DMU), 1,3-dimethylurea (1,3-DMU), 1,1-diethylurea (1,1-DEU), and 1,3-diethylurea (1,3-DEU). The limiting values φv° were calculated by linear extrapolation using the least-squares method. A plot of φv° vs. X2, the mole fraction of methanol, showed a minimum for each alkylurea studied at low methanol concentrations (X2\simeq0.1), but none for unsubstituted urea: the more alkyl-substituted the urea was, the sharper the minimum. Inspection of the data shows that the assumption of independent solvation on both sides of the urea molecules also holds to a good approximation to the apparent molal volumes both in the pure solvents and in the mixtures.
Facile Conversion of Aldehydes into 1-Substituted 2-Chloro-3,3-difluoro-2-propen-1-ols with 1,1-Dibromo-1-chloro-2,2,2-trifluoroethane/Magnesium Reagent
Authors: Fujita Makoto , Hiyama Tamejiro 
Published: July 2006

Abstract
Aldehydes RCHO are converted in excellent yields into chlorodifluoroallyl alcohols RCH(OH)CCl=CF2 upon treatment with CClBr2CF3 and magnesium in tetrahydrofuran at 0 °C.
Helix Formation of Poly(l-ornithine) in Decyl and Dodecyl Sulfate Solutions
Authors: Takeda Kunio , Yamamoto Kazuo 
Published: July 2006

Abstract
Structural changes in poly(l-ornithine)[(Orn)n] were studied in solutions of sodium decyl sulfate (NaDecSO4) by the curve-fitting method of circular dichroism. In the NaDecSO4 concentration range from 4 to 9 mmol dm−3, only the β-structure was found. Below and above this concentration range, however, the α-helical structure was formed slightly, its fraction being less than 20%. The addition of 1-octanol enhanced the helix formation in the (Orn)n–NaDecSO4 complex.
Electrical Properties of the Organic Conductor, (BEDT-TTF)3(ClO4)2
Authors: Imaeda Kenichi , Enoki Toshiaki , Saito Gunzi , Inokuchi Hiroo 
Published: July 2006

Abstract
Electrical conductivity and thermoelectric power have been measured for (BEDT-TTF)3(ClO4)2. The electrical conduction is two-dimensional in the be plane. The metal–insulator transition temperature is lowered by pressure at a rate of −8 K kbar−1. The negligible thermopower at high-temperatures indicates that (BEDT-TTF)3(ClO4)2 is the system with large on-site Coulomb repulsion.
Photosensitized Reduction of Methylviologen through the Energy Transfer from Triplet Dyes to 9-Anthracenecarboxylate Anion
Authors: Usui Yoshiharu , Sasaki Yoshimi , Ishii Yukie , Tokumaru Katsumi 
Published: July 2006

Abstract
The reaction mechanism for photosensitized reduction of methylviologen, MV2+ through the triplet–triplet energy transfer from organic dyes to 9-anthracenecarboxylate, AC− was investigated. From the kinetic analysis on MV\underset.+ formation, it was estimated that both efficiencies of the energy transfer and of the electron transfer from 3AC− to MV2+ were close to unity.
The Second Dissociation Constant of Sulfuric Acid at Elevated Temperatures from Potentiometric Measurements
Authors: Matsushima Yoshiyuki , Okuwaki Akitsugu 
Published: July 2006

Abstract
The second dissociation constant of sulfuric acid in 1 m KCl media has been determined from 25 to 200 °C using Debye–Hückel equation from the data on the electromotive force of a hydrogen ion-concentration cell. The thermodynamic values for the HSO4−=H++SO42− reaction and the KSO4− ion-pair association constant are also presented.
Synthesis of Mixed Trialkyl Phosphates: Oxidative Phosphorylation of Alcohols with Dialkyl Phosphonates in the Presence of Copper(II) Chloride
Authors: Okamoto Yoshiki , Kusano Tetuya , Takamuku Setsuo 
Published: July 2006

Abstract
Mixed trialkyl phosphates were synthesized by oxidative phosphorylation of alcohols with dialkyl phosphonates and oxygen in the presence of copper(II) chloride in fairly good yields.
One-Step Synthesis of 1,4-Diketones by Nucleophilic Reaction to Tricarbonyl Complexes of α,β-Unsaturated Ketones
Authors: Kitahara Haruo , Tozawa Yasuyuki , Fujita Seikou , Tajiri Akio , Morita Noboru , Asao Toyonobu 
Published: July 2006

Abstract
Tricarbonyliron complexes of 3-buten-2-one, 3-penten-2-one, and 4-phenyl-3-buten-2-one reacted with organolithium and Grignard reagents to afford 1,4-diketones in one step, some of the products are amenable to convertion to natural products.
Solid-Phase Synthesis of C-Terminal Hexapeptide Analogs of Substance P
Authors: Sofuku Shosuke , Ishikawa Atsushi , Muramatsu Ichiro , Shibata Kensuke 
Published: July 2006

Abstract
C-Terminal hexapeptide analogs of substance P (SP) were synthesized by a solid-phase method. These analogs, [Dab6]-SP(6-11), [Orn6]-SP(6-11), and [Lys6]-SP(6-11), showed a contractile activity on an isolated guinea-pig ilum.
A Facile Method for the Preparation of γ-Alkenyl-γ-butyrolactones
Authors: Kawashima Masatoshi , Fujisawa Tamotsu 
Published: July 2006

Abstract
Methyl substituted γ-alkenyl-γ-butyrolactones were prepared from easily available α,β-unsaturated aldehydes such as acrylaldehyde, methacrylaldehyde, crotonaldehyde, and 3-methyl-2-butenal.
Time-Dependent Metastable Fragmentations. The \dotCH2OH Loss from Methyl Acetate Ions
Authors: Arakawa Ryuichi 
Published: July 2006

Abstract
The metastable ion intensity for the loss of \dotCH2OH from ionized methyl acetate has been measured as a function of the ion-source residence time up to 100 μs by means of the ion-trapping technique. The decay of the metastable ion intensity was adequately interpreted by the use of a prior isomerization mechanism on the basis of RRKM calculations. It was suggested that the intermediate precursor for the generation of CH3CO+ and \dotCH2OH from ionized methyl acetate is not a hydrogen-bridged complex structure, CH3CO–H–OCH2+·, but a distonic ion structure, CH3\overset+C(OH)O\dotCH2.
Electronic Structure of Poly(dimethylsilane) and Polysilane Studied by XPS, UPS, and Band Calculation
Authors: Seki Kazuhiko , Mori Takehiko , Inokuchi Hiroo , Murano Kentaro 
Published: July 2006

Abstract
The valence electronic structures of poly(dimethylsilane)(PDMS) (Si(CH3)2)n and polysilane (SiH2)n were studied. PDMS was experimentally studied by X-ray photoelectron spectroscopy (XPS) and UV photoelectron spectroscopy (UPS), and band calculations were performed for both compounds. The observed spectral features and calculated band structures were assigned and discussed through a comparison with theoretical and experimental results for oligomers and other polymers. These analyses have demonstrated how the electronic structures of these compounds are correlated through factors such as (i) change in the chain length, (ii) methylation, and (iii) the substitution of Si by C. PDMS has a small ionization energy (5.9 eV) almost as low as that of poly(p-phenylene) (5.6 eV). This small value comes from the combined contribution from the small electronegativity of silicon, σ-conjugation, and the inductive effect of methyl groups. The small ionization energy and large σ-conjugation explain the reported high conductivity of PDMS and its derivatives upon acceptor doping.
Inversion of Stereoselectivity by Hydrophobic Interligand Interactions. Preparation, Structure, and Stereoselectivity of {N,N′-Ethylenebis(1,1,1-trifluoro-4-amino-2-pentanonato)}(l-amino acidato)cobalt(III)
Authors: Fujii Yuki , Shinohara Homare , Mikuriya Masahiro , Kida Shigeo , Konishi Yoshie 
Published: July 2006

Abstract
Ternary cobalt(III) complexes with a general formula β2-[Co(tfac2en)(l-aa)], where tfac2en is the titled Schiff base ligand and l-aa denotes l-ala, l-leu, l-phe, l-tyr, and l-trp, were synthesized and separated into two diastereoisomers. On the bases of X-ray crystal analysis of the l-phe complex, CD, and 1H and 19F NMR spectra, the structure of (−)435- and (+)435-isomers was determined to be Λ- and Δ-cis-β2-forms, respectively, and preferred conformation of the coordinated l-amino acidates was assummed to be h-form in solution. All the complexes showed stereoselectivity for the Λ-isomer in acetone and methanol, but the selectivity decreased or reversed with addition of water. The solvent-dependent stereoselectivity was explained in terms of steric repulsion and hydrophobic interligand interactions between CF3 group of tfac2en and side chain of l-aa.
Synthesis and Cation-Complexing Ability of Ferrocene or Ruthenocene Functionalized Crown Ethers Possessing 2,6-Pyridino Moieties
Authors: Izumi Taeko , Murakami Satoshi , Kasahara Akira 
Published: July 2006

Abstract
Keto crown ethers that contain ferrocene or ruthenocene and 2,6-disubstituted pyridine unit as part of the major ring have been reported. These keto crown ethers were synthesized by a reaction of 1,1′-metallocenedicarbonyl dichloride (ferrocene or ruthenocene) with 2,6-bis[ω-hydroxyoligo(oxyethylene)-α-ylmethyl]pyridine by using a high-dilution method. Their complexing ability with metal cations was measured by a solvent-extraction method, and was found to be poor with alkali metal cations but excellent with Ag+, In3+, and Zr4+ cations.
Synthesis, Structure, and Hypochromism of Pyrimidinopurinophanes
Authors: Doyama Kazuo , Higashii Takayuki , Seyama Fumio , Sakata Yoshiteru , Misumi Soichi 
Published: July 2006

Abstract
Seventeen pyrimidinopurinophanes in which a pyrimidine and a purine ring are fixed with different mode of stacking were prepared. The synthesis was carried out by stepwise introduction of two bridging chains. In the final ring closure reaction, two isomers, i.e., isomers bridged at 9-position of a purine ring and those having the bridge at 7-position of a purine ring were obtained. The structures of the isomers were determined on the basis of 1H NMR, IR, and UV spectra and X-ray analysis. In 1H NMR spectra the bridge protons of the pyrimidinopurinophanes show complex multiplets, in contrast to the first order splittings in singly bridged reference compounds. This shows clearly the fixation of the conformations of the present cyclic compounds at room temperature. All of the pyrimidinopurinophanes show relatively large hypochromism (H) values. Even the compounds 2a–2d, 4, and 6 where the two base rings are not stacked in parallel, but inclined with the dihedral angle of around 50°, show H values of 10–20%. The H values did not change among the compounds 1c, 1e–1g, and 3 which have similar parallel-stacking structures of the two base rings. The results are well explained by the simplified equation of Ts′o et al.
On the Mechanism of Reductive Cleavage of the Carbon–Nitrogen Bond of Aliphatic Nitro Compounds with Tributyltin Hydride
Authors: Kamimura Akio , Ono Noboru 
Published: July 2006

Abstract
Denitrohydrogenation reaction of aliphatic nitro compounds with tributyltin hydride (Bu3SnH) is accelerated in the presence of radical initiators. ESR and electrochemical measurements reveal that the reductive cleavage of the carbon–nitrogen bond proceeds not via anion radicals of nitro compounds such as SRN1 reaction but via β-scission of (tributylstannyloxy)nitroxyl radicals. The relative reactivities of tin radicals toward substituted α-nitrocumenes, α-nitroethylbenzenes, and α-nitropropiophenones exhibits excellent Hammett correlations with positive ρ values. This tendency has also been found in the reaction of benzyl halides with tin radical. These results suggest that the carbon–nitrogen bond breaking from nitroxyl radical intermediates should take place in rate-determining step for the reaction.
Studies on Dielectric Permittivities, Refractive Indices for 1,1′-Bicyclohexyl Liquid Crystals in the Nematic and Isotropic Phases
Authors: Sen Sushmita , Kali Krishnakoli , Roy Subir K 
Published: July 2006

Abstract
The dielectric permittivities ε|| and ε⊥ and the refractive indices ne, no of five 4-cyano-4′-alkyl-1,1′-bicyclohexyls (CCH 2, CCH 3, CCH 4, CCH 5, CCH 7 where 2, 3, 4, 5, 7 means ethyl, propyl, butyl, pentyl, heptyl respectively) have been measured at different temperatures in the nematic and isotropic phases. The orientational order parameter from the refractive indices data, calculated from (1) Vuks’ method and (2) Neugebauer’s method were in good agreement. At any reduced temperature, the order parameter for CCH 2 is largest and that of CCH 7 is smallest and those for the others are in between them. Unlike for cyanobiphenyls or cyclohexylbenzenes, the dielectric permittivity ε|| is obtained for \overset→E⊥\overset→H and ε⊥ for E||H, where \overset→E is the electric and \overset→H is the magnetic field, and has been explained as due to these molecules having negative diamagnetic anisotropy. The dielectric anisotropy, Δε and optical anisotropy Δn for all the CCH’s is much less than that of the corresponding CB or PCH molecules. All the CCH’s show pretransitional permittivity just above the transition temperature TNI.
Conductivity of Iron(II) Sulfate in Aqueous Solution at Various Temperatures
Authors: Kubota Eiji , Mochizuki Yoshiaki , Yokoi Masatoki 
Published: July 2006

Abstract
The molar conductivity of iron(II) sulfate, FeSO4, in water was measured in the temperature range 10–35°C. Data were analyzed by the Quint–Viallard equation, and the resulting ion association constant, KA, was applied to the Bjerrum equation to determine the contact ion size, RB. The limiting ionic molar conductivity of iron(II) at 25°C is λ0(1⁄2Fe2+)=53.8 S cm2 mol−1. Thermodynamic properties of ion association reactions are ΔG298°=−13.7 kJ mol−1, ΔH°=9.7 kJ mol−1, and ΔS298°=78.0 J K−1 mol−1.