bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetic Study of Interconversion between Two Geometrical Isomers of the Methoxy-Bridged Bis(silylene)iron Complex, (η-C5Me5)(OC)Fe{(SiMe2)···OMe···(SiMeOMe)}
Authors: Ueno Keiji , Ogino Hiroshi
Published: July 2006

Isomerization between two geometrical isomers of the methoxy-bridged bis(silylene)iron complex, anti-and syn-Cp*(OC)Fe{(SiMe2)···OMe···(SiMeOMe)} (Cp* = η5-C5Me5), was investigated by means of a variable-temperature 1H NMR experiment. The equilibrium constant (K) for the isomerization and its thermodynamic parameters were determined to be K = [syn-isomer]/[anti-isomer] = 0.53 at 293 K in toluene-d8, ΔG°298 = 1.5 ± 0.5 kJ mol−1, ΔH° = 3.8 ± 0.2 kJ mol−1, and ΔS° = 7.7 ± 1.0 J mol−1 K−1. Computer simulation of the VT spectra and calculation using Eyring equation yielded activation parameters, ΔH‡ = 83.8 ± 3.2 kJ mol−1, ΔS‡ = 42.3 ± 9.6 J mol−1 K−1, and ΔG‡298 = 71.2 ± 6.0 kJ mol−1, for the isomerization from the anti-isomer, in which the terminal OMe group is located on the opposite side of the Cp* group with respect to the Fe–Si–O(bridged)–Si ring, to the syn-isomer. A mechanism in which the bridging OMe group is replaced by the terminal OMe group is proposed for the isomerization.
Synthesis and Dynamic Stereochemistry of a Tri(1-azulenyl)methyl Cation Containing a Different Substituent on Each Azulene Ring
Authors: Ito Shunji , Morita Noboru , Asao Toyonobu
Published: July 2006

The first example of a tri(1-azulenyl)methyl cation (2) containing a different substituent on each azulene ring was synthesized, and the dynamic stereochemistry was studied by temperature-dependent 1H NMR spectra. The dynamic behavior of 2 supported a one-ring flip mechanism and the validity of the flip mechanism for the analysis of the conformational change of the tri(1-azulenyl)methyl cations.
A Novel Enzymatic Decarboxylation Proceeds via a Thiol Ester Intermediate
Authors: Kawasaki Takayasu , Watanabe Masakatsu , Ohta Hiromichi
Published: July 2006

It is proposed that arylmalonate decarboxylase (AMDase)-catalyzed decarboxylation proceeds via a thiol ester intermediate. Kinetics and CD spectra indicated that α-bromophenylacetate is a competitive inhibitor. TOF mass data indicated that the inhibitor bound with the enzyme through a thiol ester bond which was formed between a cysteine residue of the enzyme and the carboxyl group of the inhibitor. This result was also supported by reactivation of the enzyme by the addition of 2-mercaptoethanol, which is expected to cleave the enzyme–inhibitor bond via nucleophilic attack on the thiol ester linkage.
Effect of a Liquid–Liquid Phase Separation on the Slopes of Density vs. Concentration Plots
Authors: Inamura Isamu , Jinbo Yuji , Akiyama Yoriko , Kubo Yasuo
Published: July 2006

The densities were measured for dextran (Dex)–polyethylene glycol (PEG)–water, poly(1-vinyl-2-pyrrolidone (PVP)–PEG–water, and poly(vinyl alcohol) (PVA)–PEG–water systems. In all cases, the linear relationship of the density vs. concentration plots was not affected by the occurrence of liquid–liquid phase separation. The partial specific volumes were calculated from the slopes of the straight lines of the density.
Direct C≡C Triple Bond Formation from the C=C Double Bond and Direct Hydroxylation into the o-Position of a Nitro Group on the Benzene Nucleus with Potassium t-Butoxide in N,N-Dimethylformamide in the Air
Authors: Akiyama Shuzo , Tajima Kunihiko , Nakatsuji Shin’ichi , Nakashima Kenichiro , Abiru Kazuko , Watanabe Miwa
Published: July 2006

A novel and facile method for direct C≡C acetylenic bond formation from the C=C double bond by treatment with potassium t-butoxide (t-BuOK) in N,N-dimethylformamide in the air has been found in a 9,10-bis(4-substituted styryl)anthracene series, in 4-substituted 4′-nitrostilbene series, and in 1-(p-nitrophenyl)-4-(p-substituted phenyl)-1,3-butadiene series; its scope and limitations have been examined. The ESR spectrum of the reaction against 4-diethylamino-4′ -nitrostilbene was measured to identify an anion radical species expected for explanation of the mechanism of the dehydrogenation reaction. Further, cyclic voltammetric measurements of a series of stilbenes and diphenylacetylenes were carried out in connection with the above mechanism. In many cases, interestingly, the use of a large excess of t-BuOK brought about succeeding hydroxylation into the ortho-position of a nitro group on the benzene nucleus. The simple hydroxylation is useful for the synthesis of substituted 5-(arylethynyl)-2-nitrophenols, which are expected to function as non-linear optical materials with the corresponding non-hydroxy compounds. The ultraviolet-visible and fluorescence spectral properties were measured and discussed also with those of the related compounds.
Hafnium(IV) Trifluoromethanesulfonate, An Efficient Catalyst for the Friedel–Crafts Acylation and Alkylation Reactions
Authors: Hachiya Iwao , Moriwaki Mitsuhiro , Kobayashi Shu
Published: July 2006

Hafnium(IV) trifluoromethanesulfonate (hafnium(IV) triflate, Hf(OTf)4) was synthesized from hafnium tetrachloride and trifluoromethanesulfonic acid. The triflate thus prepared was found to be effective in the catalytic Friedel–Crafts acylation reactions of various substituted benzenes with acid anhydrides in lithium perchlorate–nitromethane (LiClO4–MeNO2). Lithium perchlorate–nitromethane is an excellent solvent system, and the catalytic activity of the Lewis acid was much improved in this medium. The product was obtained in up to 250000% molar amounts based on the catalyst. Hafnium(IV) triflate was also found to be quite effective in the catalytic Friedel–Crafts alkylation reactions of aromatic compounds with alkyl chlorides. The reactions proceeded smoothly in the presence of 5% molar amount of Hf(OTf)4 and 50% molar amount of LiClO4 by using a slow addition procedure.
Studies on the Complex Formation between Iron(III) or Copper(II) and Poly(vinyl alcohol) in Terms of Inclusion of the Metal Hydroxide-Like Clusters by the Polymer
Authors: Yokoi Hiroshi , Mori Yasuyoshi , Fujise Yutaka
Published: July 2006

The complex formation between iron(III) or copper(II) and poly(vinyl alcohol) (PVA) in aqueous solution has been investigated in some detail by using many PVAs ranging in degree of polymerization (DP) from 33 to 500. The minimum concentration of PVA required to form soluble complexes has been found to be inversely proportional to its DP, as expressed by the constancy of (DP of PVA) × [PVA]; the constants were 13 and 15 M in 10 mM iron(III) and copper(II) solutions (1 M = 1 mol dm−3), respectively. It has been revealed that iron(III) and copper(II) ions in the complexes exist in the form of metal hydroxide-like clusters comprising, at most, 120 metal ions per PVA chain. Transmission electron micrographs for the cast films of an iron(III) complex solution have shown the cluster size to be about 30 Å. Poly(vinyl methyl ether), a methyl ether derivative of PVA, was similar to PVA in complex formation with iron(III) up to pH 5. This fact also supports the conclusion that the present PVA complexes are of an inclusion type due to a hydrophobic interaction.
Study on the Interaction between Iron(III) Hydroxide Oxide and Cation Exchange Resins
Authors: Inami Ichiro , Baba Takao
Published: July 2006

In some nuclear power plants, ion exchange resins for condensate purification systems show increasing rust removal efficiency year by year. In order to clarify this phenomenon, resin properties and rust behavior after adsorption on the resins have been studied. An adsorption test, a dissolution test and an ion exchanging test were performed in this study, using strongly acidic cation exchange resins, amorphous iron(III) hydroxide oxide and 55Fe tracer. It was found that aged cation exchange resins showed obvious property changes due to oxidative swelling, which induced better water mobility in the micropores. According to the property change, amorphous iron(III) hydroxide oxide, one of the iron rust components, is easily dissolved and diffused into resin beads, and consequently adsorption sites on aged resins are recovered rapidly compared with fresh resins. This is the reason for the superiority of the aged cation exchange resins in rust removal.
Formalized Drawing of Fullerene Nets. 2. Applications to Mapping of Pyracylene Rearrangements, C2-Insertion/Elimination Pathways, and Leapfrog/Carbon Cylinder Operations
Authors: Yoshida Mitsuho , Osawa Eiji
Published: July 2006

The net drawing method of fullerenes presented in the preceding paper has been applied to the predictive studies on the movements of pentagonal rings accompanying skeletal transformations in fullerenes. The products of pyracylene rearrangements have been systematically generated to examine low-energy isomers containing abutting pentagons (so-called anti-IPR isomers) by performing the rearrangement only once on all the pyracylene units in each of the C60 to C100 isomers. The Endo-Kroto mechanism of C2-insertion into the carbon framework of fullerene has been likewise shown to be executable on paper. In this way, several energetically favorable pathways of growth have been found for C76 to C90. Potential applications of net drawing to the leapfrog and carbon cylinder operations and C2-elimination are also mentioned.
C–H···π Hydrogen Bonding between Electron-Rich Benzene Rings and Polarized C–H Bonds: Selectivity in the Complexation of Highly Hydrophilic Guest Molecules with Calix[4]resorcarene Hosts in Water
Authors: Fujimoto Takako , Yanagihara Ryoji , Kobayashi Kenji , Aoyama Yasuhiro
Published: July 2006

Tetrasulfonate derivatives of calix[4]resorcarene (calix[4]arene derived from resorcinol) (1) form 1 : 1 complexes with highly hydrophilic guest molecules, such as ethers, alcohols, ketones, and sulfoxides, in water. The affinities of three types of the guests increase in the order CH3–X–CH3 < (–CH2CH2–X–)2 < CH3–X–CH2CH2–X–CH3 (X = O, CH(OH), C=O, or S=O), reflecting the importance of multiple host-guest interactions. The binding constants (K) with respect to X increase in the order O < CH(OH) < C=O < S=O or CH(OH) < O < C=O < S=O. As for the effects of substituents Y on 2-C of the benzene rings of the host, both 1b (Y = CH3) and 1c (Y = OH) exhibit higher binding capabilities than does the parent host 1a (Y = H). Thus, the present complexation is promoted by electron-withdrawing residue (X) in the guests and electron-donating substituents (Y) in the host. The binding of CH3–X–CH3 (X = C=O or S=O) to hosts 1a—c is characterized by favorable enthalpy changes and unfavorable entropy changes. These results, coupled with NMR data, indicate that the driving force of the present complexation is a C–H···π interaction between C–H bonds of a guest as soft acids and benzene rings of the host as soft bases.
Basic Properties of Polylactic Acid Produced by the Direct Condensation Polymerization of Lactic Acid
Authors: Ajioka Masanobu , Enomoto Katashi , Suzuki Kazuhiko , Yamaguchi Akihiro
Published: July 2006

The direct condensation polymerization of lactic acid has been studied, and polylactic acid having a high molecular weight was obtained in an organic solvent without any isolation of the intermediate, dilactide. The molecular weight was raised up to 300000 through the examination of several reaction conditions, e.g., solvent, catalyst, etc. Thus-obtained high-molecular-weight polylactic acid can be processed into films and molded products having sufficient strength and toughness. The characteristic features of polylactic acid obtained by this direct process were compared to that obtained by the conventional ring-opening polymerization process. In addition, copolymerization of lactic acid with a variety of d/l ratios is discussed.
Stability of Colloidal Alumina in the Presence of Various Inorganic Anions
Authors: Petkovic Milan Dj , Milonjic Slobodan K , Dondur Vera T
Published: July 2006

The stability of colloidal alumina in the presense of selected inorganic anions (NO3−, Cl−, I−, SO42−, and [Fe(CN)6]3−) has been studied by a potentiometric titration technique. The dependencies of the critical concentrations of coagulation on the solution pH were determined for all studied anions, as well as the regions of coagulation and stability of the system. It has been shown that the critical concentrations of coagulation decrease along with an increase in the pH, which is interpreted by coagulation theory and the electrical layer model. Differences between the critical concentrations of coagulation at the same pH value for monovalent anions are explained based on their hydration degree differences, while the discrepancies between the experimental data and the theoretical values given by the Schultze–Hardy law are interpreted in light of specific sorption of sulfate anions and the general specificity of the investigated system. Based on a parallel stability study of colloidal alumina prepared in the laboratory and of a commercial product, the same stability behavior in the presence of KCl has been found.
The Physicochemical Properties of a Nonaqueous Microemulsion: Cyclohexane/Triton® X-100/Dimethylformamide at 40 °C
Authors: Tessy Elavathingal Itteera , Rakshit Animesh Kumar
Published: July 2006

The phase diagram of a nonaqueous microemulsion system containing cyclohexane/Triton® X-100/DMF was determined at 40 °C. The one-phase microemulsion area increased in the presence of a cosurfactant. Physical properties like viscosity, adiabatic compressibility, specific conductance, and contact angle are discussed at a surfactant concentration of 15% to explain the microstructure. A cyclohexane/TX 100+1-propanol/DMF system shows percolation, though not high, with ca. 0.15 mole fraction of DMF. Contact angle measurements of cyclohexane/TX 100/DMF at various cyclohexane/DMF ratios show a DMF continuous system. In the presence of a cosurfactant, the contact angle values show a continuous change indicating an 0/DMF to bicontinuous to DMF/0 structure. NaI does not introduce a three-phase liquid system.
Rotational Effects on Radiationless Transition IV: Hyperfine Interaction and Deuterium Isotope Effects
Authors: Kanamaru Nobuaki
Published: July 2006

The theory of the rotational effects on radiationless transitions in typical azines is extended to include the hyperfine (hf) interaction term, while examining their deuterium (isotope) effects on the decay behaviors after excitation into the rotational levels belonging to their S10 levels, i.e. their ground vibrational levels of S1 states. The Fermi-contact hf term is shown to be enough to endorse the coupling between rotational levels that are different either in symmetries or in some angular-momentum quantum numbers. The deuterium (D) effect is found to be not simply described as a conventional isotope effect: Changes by D substitution are brought about in densities of triplet states and hf coupling terms, as well as molecular symmetry groups. While interpreting the experimental data, modifications of the schemes are made from those presented earlier in this series.
Dielectric Characterization of Binary Solvents Containing 1,2-Dichloroethane and 2-Chloroethanol
Authors: Corradini Fulvio , Marchetti Andrea , Tagliazucchi Mara , Tassi Lorenzo , Varini Alessandra
Published: July 2006

Static dielectric constants (ε) were determined for the 1,2-dichloroethane (DCE, 1)/2-chloroethanol (CE, 2) binary solvent system at 19 temperatures ranging from −10 to +80 °C and in the whole composition range expressed by the mole fraction 0 ≤ X1 ≤ 1. The experimental values have been fitted to some equations that could be usefully employed for predictive ε calculations. Furthermore, the excess mixing properties (εe) have been evaluated in order to point out the presence of solvent–cosolvent adducts in the binary mixtures mentioned above. The values of εe have been generally found to be negative and only slightly positive under a few experimental conditions in the CE rich-region, thus giving evidence of a close interaction network probably via hydrogen bonding as well as other interactions of every kind in this solvent system.
Investigation of Spin-Correlated Ion Pairs in Distance-Fixed Triads by Time-Resolved Electron Paramagnetic Resonance
Authors: Nakamura Hirofumi , Terazima Masahide , Hirota Noboru , Nakajima Satoshi , Osuka Atsuhiro
Published: July 2006

Charge separated ion-pair (IP) states formed from three distance-fixed photosynthetic triads were studied by the time-resolved EPR method. Upon photoexcitation of the triads in THF at 77 K, small and narrow signals were observed at the central parts of broad EPR spectra due to the excited triplet states of the chromophores. These signals were assigned to secondary, fully charge separated IP states by the simulation based on the spin-correlated radical pair mechanism. Time dependence of the TREPR signals indicates that charge separation occurs in the singlet manifold as in the case of the photoexcited state dynamics at room temperature. Estimated electron exchange interactions, J, are in the order of 10−2—10−3 mT, which is in line with the observed long lifetimes of the IP states.
Molecular Conformation of Tetragastrin in Aqueous Solution by the Monte-Carlo Simulation
Authors: Kuroda Masataka , Yamazaki Kazuto , Taga Tooru
Published: July 2006

A conformational analysis of tetragastrin in an aqueous solution was carried out by a Monte-Carlo simulation, assuming a molecular model in a continuous media. The hydration energy of the peptide was evaluated from a calculations of the peptide–water accessible surface area. The tetrapeptide conformers in the low-energy state take an extended form, in which the two aromatic rings on both termini of the peptide are apart. The extended conformation in which the hydrophilic portions are exposed to solvent water is quite different from that in DMSO.
Electrocatalytic Behavior of Poly(2,5-dihydroxyaniline) Synthesized by Electropolymerization in Aqueous Solutions
Authors: Morita Masayuki , Takase Hironari , Ishikawa Masashi , Matsuda Yoshiharu
Published: July 2006

Poly(2,5-dihydroxyaniline), or poly[imino(2,5-dihydroxy-1,4-phenylene)] (PAn(OH)2), films were prepared by electropolymerization of 2,5-dimethoxyaniline (DMA), followed by electrochemical hydrolysis of methoxyl groups in an acidic solution. The films gave responses characteristic of a hydroquinone/quinone couple in aqueous solutions, suggesting that many hydroquinone units are introduced in the polymer structure. Although the polymer in the reduced state consisted of aniline units with substitutions by hydroxyl groups, its redox process is based on the reaction of hydroquinone/quinone couple in its structure, not on the doping/undoping in the aniline unit. Electrochemical redox processes were examined on the PAn(OH)2-modified platinum electrode. The polymer films showed electrocatalytic activities for such redox reactions as the oxidation of [Fe(CN)6]4−, Fe2+, and [Co(NH3)6]2+ in aqueous solutions. Some interactions were suggested between the hydroquinone/quinone site or the aniline unit in the polymer and the redox active metal complexes in the solution and/or in the polymer.
The Role of Nonadiabatic Coupling in Bond-Selective Dissociations: Two-Dimensional Model Calculations
Authors: Takayanagi Toshiyuki , Yokoyama Atsushi
Published: July 2006

The photodissociation dynamics of the model CH2XY (X and Y are halogen atoms) molecule was studied using a time-dependent quantum mechanical method in two dimensions. Simple functional forms were employed as two diabatic potential energy surfaces which correspond to the excited states of C–X (n–σ*) and C–Y (n–σ*). Bond selectivity in the photodissociation is quantitatively examined in terms of the coupling strength between the two surfaces. A method to predict the bond selectivity in the photodissociations is also discussed on the basis of the results of ab initio molecular orbital calculations.
Electrochemical Properties of Carbon-Paste Electrodes Spiked with Some 1,4-Naphthoquinone Derivatives
Authors: Raoof DJahan B , Golabi Seyed M
Published: July 2006

The preparation and aqueous electrochemistry of a carbon-paste electrode, modified by 1,4-naphthoquinone and some of its derivatives are described. From a calculation of the half-wave potential as a function of the pH, potential-pH diagrams were constructed for each compound. The values of the formal potentials and the pKa′ of some different redox and acid-base couples involved at various solution pHs were obtained. The influence of such substituents as methyl-, hydroxy-, chloro-, and amino- concerning the electrochemical behavior of surface 1,4-naphthoquinone is described. The electrochemical behavior of such electrodes was examined in buffered borate solutions and the formation of a complex between borate anion and o-naphthalenediols was characterized. Finally, the range of the pH at which the electrode function is consistent was determined.
Steric Trans Influence of Aminomethane Ligand in trans-Aminomethanechlorobis(1,2-diaminoethane)cobalt(III)
Authors: Mizuta Tsutomu , Kusakari Kenji , Hashimoto Mari , Miyoshi Katsuhiko
Published: July 2006

The trans isomer of aminomethanechlorobis(1,2-diaminoethane)cobalt(III), trans-[CoCl(NH2Me)(en)2]2+, was prepared from trans-[CoCl(NO2)(en)2]+ by a two-step reaction in which Cl− was replaced with an NH2Me and then the remaining NO2− was replaced with a Cl−. The configuration was confirmed by X-ray crystal analysis, and structural comparison was made with its cis isomer. The crystals have the formulae, trans-[CoCl(NH2Me)(en)2]Cl(ClO4) and cis-[CoCl(NH2Me)(en)2]Cl2. The crystallographic data are as follows; Monoclinic, P21/c, a = 11.515(1), b = 7.421(2), c = 17.257(1) Å, β = 99.220(8) °, V = 1455.6(5) Å3, Z = 4, and R = 0.043 for the former, and Orthorhombic, Fdd2, a = 26.64(1), b = 27.26(1), c = 7.570(2) Å, V = 5497(3) Å3, Z = 16, and R = 0.057 for the latter. The Co–Cl bond of the trans complex is longer than that of the cis complex. It was found that the bulkiness of the Me group effects the trans Co–Cl bond through one of the two flexible equatorial en chelate rings. The kinetic data of an aquation reaction of the trans and the cis complexes show that the Cl− of the trans complex is substituted more readily than that of the cis is.
Analysis of d–d Transitions in trans-[Cr(CN)2(NH3)4](ClO4) as Inferred from Polarized Optical Spectra and Angular Overlap Model Calculations
Authors: Schönherr Thomas , Itoh Mutsuyoshi , Urushiyama Akio
Published: July 2006

The polarized absorption spectra of trans-[Cr(CN)2(NH3)4](ClO4), which crystallizes in the orthorhombic space group Pna21, were measured in spin-allowed quartet ( → ) and intraconfigurational spin-forbidden doublet ( → ) transition regions. Gaussian deconvolution of the quartet bands and detailed vibronic assignments of the spin-forbidden doublet transitions yielded a total of seven electronically excited states. These have been used for ligand field calculations in terms of the angular overlap model. By using a π-orbital reduction factor of τ = 0.984 as well as a negative eπ value for the acceptor ligand CN− (−930 cm−1) we were able to reproduce the d-level scheme in high accuracy. The results compare well with our findings for the related monocyano complex.
Reactivity of Five-Coordinate Intermediate Generated by Laser Photolysis of Monoligated Chloro(5,10,15,20-tetraphenylporphinato)chromium(III) in Toluene
Authors: Inamo Masahiko , Hoshino Mikio , Nakajima Kiyohiko , Aizawa Sen-ichi , Funahashi Shigenobu
Published: July 2006

The Cr(III) porphyrin complexes [Cr(tpp)(Cl)(H2O)] (1) and [(Cr(tpp)(Cl)(py)] (2) (tpp represents the dianion of 5,10,15,20-tetraphenylporphine) crystallized from a chloroform–toluene mixture in the tetragonal space group I4, Z = 2, a = 13.559(5), b = 13.559(5), c = 9.770(3) Å, V = 1796(3) Å3, and from a dichloroethane–toluene mixture containing a small amount of pyridine (py) in the monoclinic space group P21/n, Z = 4, a = 14.655(5), b = 23.498(4), c = 13.152(2) Å, β = 101.54(1)°, V = 4437(2) Å3, respectively. The axial Cr–O bond length for 1 and the axial Cr–N bond length for 2 are 2.239(3) and 2.140(5) Å, respectively. Laser irradiation of the toluene solution of [Cr(tpp)(Cl)(L)] causes the photodissociation of the axial ligand L, where L represents H2O or 3-cyanopyridine, to give the five-coordinate intermediate [Cr(tpp)(Cl)]. The rate constant of the axial ligand recombination reaction falls into a narrow range around 1 × 109 mol−1 kg s−1 at 25.0 °C for both reactions. The activation parameters indicate the very high reactivity of the five-coordinate intermediate. The diffusion-controlled process is regarded as a rate-determining step for the recombination.
Dissolution Behavior of Optical Isomers of fac-Tris(aniono)cobalt(III) of Some α-Amino Acids in Water
Authors: Yoshimura Yasuki
Published: July 2006

fac-Tris(aniono)cobalt(III) of d-alanine, d-valine, d-leucine, l- and d-prolines, and l- and d-serines was synthesized, and the separation of the diastereoisomers of these chelates was attempted. The solubilities of these isomers in water were determined over the temperature range of 5 to 55 °C. The thermodynamic parameters of solution at 25 °C, such as the free energy (ΔGs°), enthalpy (ΔHs°), and entropy (ΔSs°), were estimated from the temperature dependence of the solubilities. Also, the dissolution behavior of these chelate in water was considered in terms of these thermodynamic parameters. Plot of ΔHs° against TΔSs° gave separate correlation lines for the groups comprising less soluble chelates and more soluble chelates. An increase in the solubility within the respective groups was caused by an increase in TΔSs°. Both ΔHs° and TΔSs° for the chelates of less hydrophobic glycine and serine were larger than those for the chelates of more hydrophobic amino acids.
Reaction of Vinylphosphonium Salts with Sulfoxonium Ylides. Synthesis of Cyclopropylphosphonium Salts
Authors: Okuma Kentaro , Ikari Komei , Ono Masaaki , Sato Yasunari , Kuge Seiji , Ohta Hiroshi , Machiguchi Takahisa
Published: July 2006

Reactions of (dimethylamino)phenylsulfoxonium methylide with triphenylvinylphosphonium salts gave the corresponding cyclopropyltriphenylphosphonium salts (E-form) in high yields, when 1,8-diazabicyclo[5.4.0]undec-7-ene was used as a base. Reactions of cyclopropyltriphenylphosphonium salts with sodium hydride in the presence of tris[2-(2-methoxyethoxy)ethyl]amine afforded the corresponding ylides, which further reacted with aldehydes to give alkylidenecyclopropanes in high yields.
Efficient Oxidation of Organic Compounds with Sodium and Silver Bromates NaBrO3, AgBrO3, in Non-Aqueous Solvents in the Presence of Lewis Acids
Authors: Firouzabadi Habib , Mohammadpoor-Baltork Iraj
Published: July 2006

The synthetic utility of sodium and silver bromates in the presence of Lewis acids as catalysts in organic solvents is described. They are efficient for the oxidation of alcohols, acyloins, and hydroquinones to their corresponding carbonyl compounds. The oxidation coupling of thiols performs well in the absence of the catalysts. Silver bromate is able to transform primary benzylic and saturated alcohols, aldehydes, and primary benzylic carbon–hydrogen bonds to their carboxylic acids efficiently. Secondary benzylic carbon–hydrogen bonds are oxidized to their carbonyl compounds with sodium and silver bromates.
Synthesis of Glucose-Containing Linear Oligosaccharides Having α(1→4) and α(1→6) Linkages Using Stereoselective Dehydrative Glycosylation
Authors: Koto Shinkiti , Haigoh Hisamitsu , Shichi Sonoko , Hirooka Motoko , Nakamura Teiko , Maru Chika , Fujita Misuzu , Goto Ayano , Sato Tomoko , Okada Masato , Zen Shonosuke , Yago Kazuo , Tomonaga Fumiya
Published: July 2006

Glycogen-storage-disease-relating linear tetra-, hexa-, and octasaccharides of d-glucose having α(1→4) and α(1→6) linkages were synthesized using a stereoselective dehydrative glycosylation with a reagent mixture of p-nitrobenzenesulfonyl chloride, silver trifluoromethanesulfonate, N,N-dimethylacetamide, and triethylamine. A cross-condensation of a quasi-stoichiometric amount of a donor and an acceptor of an octasaccharide, followed by deprotection, afforded a glucohexadecasaccharide.
Topochemical Photopolymerization of 4-[2-(Unsubstituted and Methyl-Substituted Pyrazinyl)ethenyl]cinnamates and -thiocinnamates in the Crystalline State
Authors: Saigo Kazuhiko , Sukegawa Makoto , Maekawa Yasunari , Hasegawa Masaki
Published: July 2006

Topochemical photopolymerization of 4-[2-(unsubstituted and methyl-substituted pyrazinyl)ethenyl]cinnamates and -thiocinnamates were carried out in the crystalline state. Upon photoirradiation, ethyl 4-[2-(unsubstituted and methyl-substituted pyrazinyl)ethenyl]cinnamates and S-ethyl 4-[2-(unsubstituted and methyl-substituted pyrazinyl)ethenyl]thiocinnamates gave α-hetero-type crystalline linear polymers, whereas methyl 4-[2-(methyl-substituted pyrazinyl)ethenyl]cinnamates afforded mixtures of β-type oligomers. The X-ray crystallographic analyses of the monomers revealed that the thioesters were more favorable monomers than the corresponding esters from the viewpoint of close packing in a crystal. The following factor(s) would play an important role in determining their molecular arrangements: 1) The close contact between the central 1,4-phenylene ring and the alkoxy oxygen of the ester group or the alkylthio sulfur of the thioester group, 2) the hydrogen bond between the interstacked pyrazinyl groups, and/or 3) the gearing of the alkyl group in the ester moiety with the methylpyrazinyl group.
Friedel–Crafts Acylation of Arenes Catalyzed by Bromopentacarbonylrhenium(I)
Authors: Kusama Hiroyuki , Narasaka Koichi
Published: July 2006

The intermolecular Friedel–Crafts acylation of aromatic compounds (such as toluene, m-xylene, and anisole) with various acid chlorides proceeds by using a catalytic amount of bromopentacarbonylrhenium(I) to afford aryl ketones. Intramolecular acylation is also catalyzed by the above-mentioned catalyst to give indanone and tetralone derivatives.
A Practical Synthesis of Mannosaminyl-β(1→4)-glucosyl-α(1→2)-rhamnose, the Trisaccharide Repeating Unit of a Streptococcus pneumoniae Capsular Polysaccharide
Authors: Kaji Eisuke , Lichtenthaler Frieder W , Osa Yumiko , Takahashi Keiko , Zen Shonosuke
Published: July 2006

An efficient chemical synthesis is described for the title trisaccharide repeating unit of the capsular polysaccharide of Streptococcus pneumoniae Type 19F. The key intermediate was a well-accessible indirect β-d-mannosaminyl donor, i.e. 2-(benzoyloxyimino)-2-deoxy-α-d-arabino-hexopyranosyl bromide, which underwent glycosidations with 20 : 1 β-selectivities; the benzoyloxyimino group was reduced with essential manno specificity. The ManNAc-β(1→4)-Glc disaccharide, thus obtained in suitably blocked form, was subsequently converted into 1-fluoride, with which a l-rhamnosyl acceptor was glycosylated by an α(1→2) linkage to yield the target trisaccharide in an altogether 6% overall yield for the 13 steps required from d-glucose.
Photodissociation and Vibrational Dynamics of OCS in the VUV Region
Authors: Yamanouchi Kaoru , Ohde Kyoko , Hishikawa Akiyoshi , Pibel Charles D
Published: July 2006

The photofragment excitation (PHOFEX) spectrum of jet-cooled OCS was remeasured for the 154.5 nm peak in the 1Σ+–1Σ+ transition by scanning a tunable vacuum ultraviolet (VUV) laser wavelength in the deep VUV region and by probing the S(1S) product with a second laser. Due to the efficient cooling of the sample in the free-jet expansion and the high-resolving power of the VUV laser, the homogeneous broadening of the dissociative state was derived directly from the observed PHOFEX spectrum. Based on the measured peak width, the lifetime (τ) of the dissociative state was determined to be τ   0.14 ps. The profile of the PHOFEX peak was found to be asymmetric and was fit to a Fano line profile to derive the value of the asymmetry parameter, q = −3.5(9), which indicates a considerable mixing of the continuum and discrete states in that particular energy region. A Fourier-transform analysis was also performed for the whole distinct absorption feature in the 160—140 nm region measured by McCarthy and Vaida [J. Phys. Chem., 92, 5875 (1988)], and the period of the vibrational motion on the dissociative potential-energy surface was derived to be 41 fs. Using these pieces of experimental evidence, the dissociation dynamics on the repulsive 1Σ+ surface in the 154.5 nm region was inferred.
A Zinc(II)–Cyclen Complex Attached to an Anthraquinone Moiety that Acts as a Redox-Active Nucleobase Receptor in Aqueous Solution
Authors: Tucker James H R , Shionoya Mitsuhiko , Koike Tohru , Kimura Eiichi
Published: July 2006

Recently, we demonstrated that a zinc(II) macrocyclic tetraamine complex, ZnII–cyclen (cyclen = 1,4,7,10-tetraazacyclododecane), could bind to thymidine (dT) and uridine (U) selectively among the DNA/RNA bases in aqueous solution at physiological pH. This paper describes the design and synthesis of the zinc(II) complex of an anthraquinone-pendant cyclen. The interaction of this complex with a variety of nucleosides has been studied by potentiometric pH titration, 1H NMR, and a polarographic technique. The effect of the anthraquinone functionality in this complex is an enhanced 1 : 1 association with N(3)-deprotonated dT (log K = 6.6 ± 0.1against 5.6 for ZnII–cyclen system at 25 °C with I = 0.10 (NaNO3)) and its congeners, implying an additional anthraquinone-thymine aromatic stacking π–π interaction. This complex, moreover, can electrochemically recognize thymidine and other related organic substrates in aqueous solution, and is therefore a new prototype for electrochemical oligonucleotide recognition.
Thermal Dissociation of Disilenes into Silylenes
Authors: Suzuki Hiroyuki , Tokitoh Norihiro , Okazaki Renji
Published: July 2006

Extremely hindered and stable disilenes (Tbt(Mes)Si=Si(Mes)Tbt {Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl, Mes = 2,4,6-trimethylphenyl. (Z)-1: cis-isomer, (E)-1: trans-isomer}) underwent dissociation under very mild conditions (ca. 70 °C) into a divalent silicon species (Tbt(Mes)Si: (2)), which was trapped by methanol, triethylsilane, 2,3-dimethyl-1,3-butadiene, elemental sulfur, and elemental selenium to afford the corresponding adducts in good yields. Silylene 2 reacted with some carbon–carbon multiple-bond compounds to afford the corresponding [1 + 2] cycloadducts, among which the adduct with 3,3,6,6-tetramethylthiacyclohept-4-yne was established by an X-ray diffraction analysis. Silylene 2 also reacted with naphthalene and benzene to give the corresponding adducts, 15 and 17, respectively, the molecular structures of which were confirmed by X-ray crystallographic analyses. The formation of 15 and 17 represents the first example of [1 + 2] cycloaddition of silylenes to aromatic compounds. The thermolysis of 15 and 17 regenerated silylene 2, which was trapped with triethylsilane. A kinetic study of the thermal dissociation of 1 gave the activation parameters, which were compared with those for E    Z isomerization of previously reported disilenes.
Photoelectrochemical Properties of RuS2-Coated TiO2 Electrodes
Authors: Ashokkumar Muthupandian , Kudo Akihiko , Sakata Tadayoshi
Published: July 2006

Photoelectrochemical studies of RuS2-coated TiO2 electrodes showed semiconductor sensitization by RuS2 fine particles on TiO2. RuS2 particles of ca. 100 nm size were observed from a scanning electron micrograph of the RuS2/TiO2 electrode surface. RuS2-coated TiO2 electrodes showed continuous wide absorption in the visible spectral region. Photoelectrochemical measurements of several RuS2/TiO2 electrodes, prepared under different conditions, were carried out. The electron-transfer efficiency from RuS2 to TiO2 was affected by the number of RuS2 colloid coatings and the preparation temperature of the RuS2 colloids. A schematic study was carried out on the effect of a heat treatment in order to find the optimum temperature for the maximum sensitization efficiency. A comparison of the absorption and action spectra of the RuS2/TiO2 electrode showed that only small RuS2 particles with a critical size distribution could transfer the photo-generated electrons to TiO2. A band-gap value of ca. 2.8 eV was evaluated (from the photocurrent action spectrum) for the RuS2 particles with high sensitization efficiency. A scheme which shows the energy diagram for RuS2 fine particles has been proposed by considering the flat-band potential values derived from the photocurrent onset potentials and the above-mentioned band-gap value.
Critical Demicellization Concentration of Diethylammonium Perfluorononanoate and Diethylammonium Tetradecyl Sulfate Mixture in Aqueous Solution
Authors: Asakawa Tsuyoshi , Shiraishi Tsugunori , Sunazaki Shinichi , Miyagishi Shigeyoshi
Published: July 2006

The micellar pseudophase diagram of diethylammonium perfluorononanoate (DEAPFN) and diethylammonium tetradecyl sulfate (DEATS) was determined by both conductivity and fluorescence probe methods. The conductivity measurements gave unusually low dissociation degrees of counter ion for DEAPFN-rich regions in contrast to those for DEATS-rich region. The micelles in a DEAPFN-rich region have high microviscosities, suggesting a micellar growth. The existence of the second cmc indicated the presence of two types of mixed micelles, but the mutual solubility of fluorocarbon and hydrocarbon surfactants in micellar pseudophase showed significant differences between DEAPFN–DEATS and LiPFN–LiTS systems. Third inflection points on both conductivity and fluorescence intensity curves were observed for DEAPFN–DEATS system. This suggests the presence of a critical demicellization concentration (CDC).
Molecular Dynamic Study of Conformational Properties of Cyclopenta[a]phenanthren-17-ones. Comparison of Theoretical Structures to X-Ray Structures
Authors: Kingsford-Adaboh Robert , Kashino Setsuo
Published: July 2006

The conformational analysis of a group of carcinogenic cyclopenta[a]phenanthren-17-ones has been done using quenched molecular dynamics to simulate built models. Optimum energy conformers have been searched within 300 to 600 K. The results are presented and compared to structures derived from X-ray experiments. While the pattern of distortion is similar for the simulated molecules to the crystalline state, the conformers corresponding to minimum energy show more molecular distortions in the free state than the crystalline at the bay regions. From the results, it emerges that the observed out-of-plane distortions are an inherent feature of the bay region substituted compounds.
Solid Solutions in Metal Complexes. Solubility Phase Diagrams and X-Ray Crystal Structures of trans(N,t-N)-[Co(norleucinato)(tren)]I2 and trans(N,t-N)-[Co(methioninato)(tren)]I2 [tren = tris(2-aminoethyl)amine]
Authors: Yamanari Kazuaki , Fuyuhiro Akira
Published: July 2006

Ternary solubility diagrams of trans(N,t-N)-[Co(n-leu)(tren)]I2 and trans(N,t-N)-[Co(met)(tren)]I2[t-N = tertiary amine nitrogen, n-leu = norleucinate(1-), met = methioninate(1-), and tren = tris(2-aminoethyl)amine] were determined at 25.0 °C. A single isotherm was found; the tie lines do not converge to any apexes of the enantiomers in either system. The solid phases are variable over the entire region from d : l(%) = 100 : 0 to 0 : 100, and both systems form a solid solution. The X-ray crystal structures of trans(N,t-N)-[Co(Dl-n-leu)(tren)]I2 (1; d : l = 50 : 50) and trans(N,t-N)-[Co(Dl-met)(tren)]I2 (3; d : l = 50 : 50) were determined from 3600 and 4699 reflections to R = 0.036 (Rw = 0.046) and R = 0.045 (Rw = 0.068), respectively: space group P21/c with a = 9.204(4), b = 11.057(2), c = 19.576(3) Å, β = 95.95(2)°, and Z = 4 for 1 and space group P21/n with a = 13.032(4), b = 11.210(4), c = 13.535(2) Å, β = 92.62(2)°, and Z = 4 for 3. The results confirm the co-existence of the d- and l-amino acidato complex ions in each site of the unit cell in both complexes. Furthermore, the unit cell comprises two d-rich sites and two l-rich sites: The unequal occupancy of the d- and l-amino acidato complex ions in each site is found irrespective of the racemic composition.
Preparations and 13C and 195Pt NMR Spectra of Platinum(II) Peptide Complexes and Their Growth-Inhibitory Activity against Mouse Meth A Solid Tumor in Vivo
Authors: Watabe Masatoshi , Takayama Toshio , Kuwahara Akira , Kawahashi Takako , Koike Yoshio , Horiuchi Akira , Suzuki Masuko , Watanabe Toshihiko , Mikami Ken , Matsumoto Tatuji , Narusawa Yoshio
Published: July 2006

Several dipeptide complexes of the form K[Pt(x-gly or gly-x)Cl], where x-gly or gly-x stands for a dipeptide anion (where x is glycine, alanine, valine, or leucine) moieties, were synthesized, purified, and characterized by various analytical and spectroscopic techniques (13C, 195Pt NMR and MS(FAB)). The complexes of the form K[Pt(x-gly)Cl] were pale brown and those of K[Pt(gly-x)Cl] were light yellow in solid form or in solution. The former was more labile than the latter in H2O solution. Growth inhibition assays of K[Pt(alagly)Cl], K[Pt(glyala)Cl], and cis-diamminedichloro platinum(II) (Cisplatin) against methylcholanthrene induced Meth A fibrosarcoma (Meth A) solid tumors transplanted in BALB/c mice were measured. In mice in the group administered K[Pt(glyala)Cl] doses of 26 mg kg−1 d−1, 28.9% of slight growth inhibition was observed. The side effects related to the decrease of body weight were mild. Cisplatin did not show any antitumor activity under the present administration conditions. The toxicities of the dipeptide complexes against normal mouse bone marrow cells were measured. All of them exhibited toxicity against bone marrow cells, but K[Pt(alagly)Cl] and K[Pt(glyala)Cl] were 1000 times less toxic than Cisplatin.
Syntheses, Characterization, and Properties of Vanadium(III) Complexes Containing Tripodal Tetradentate Ligands with Single Pyridyl Groups
Authors: Kanamori Kan , Kameda Eiji , Kabetani Takatsugu , Suemoto Taiko , Okamoto Ken-ichi , Kaizaki Sumio
Published: July 2006

The syntheses, characterization, and properties of [V(pda)(OH)(H2O)] (1a), [V2(μ-O)(pda)2(H2O)2] (1b), [V2(μ-O)(bpg)2Br2] (2), and [V2(μ-O)Br2(tpa)2]Br2 (3) are described, where pda (N-(2-pyridylmethyl)iminodiacetate), bpg (N,N-bis(2-pyridylmethyl)glycinate), and tpa (tris(2-pyridylmethyl)amine) are tripodal tetradentate ligands with single pyridyl groups. Complexes 1a, 1b, and 2 were characterized on the basis of their electronic and Raman spectra. The structure of 3 was determined by X-ray crystallography. Complex 3 crystallizes in the space group with the following unit cell dimensions: a = 11.505(5), b = 11.509(5), c = 16.348(7) Å, α = 103.73(2)°, β = 103.71(2)°, γ = 93.26(3)°, and Z = 2. The V–O–V angle is 175.3(2)° and the V–μ-O distances are 1.783(2) and 1.784(2) Å. In complex 3, the four unpaired electrons are ferromagnetically coupled. It was found that there is a positive correlation between 2 × νas(V–O–V) and the energy of the oxo-to-V(III) charge-transfer transition for single oxo-bridged dinuclear vanadium(III) complexes including the present complexes. This correlation is discussed in terms of the π character of the V(III)–μ-O bond that is affected by the remaining donor groups.
Modified Borohydride Agents, 1-Benzyl-4-aza-1-azoniabicyclo[2.2.2]octane Tetrahydroborate (BAAOTB) versus Tetrabutylammonium Tetrahydroborate (TBATB). Efficient, Selective, and Versatile Reducing Agents
Authors: Firouzabadi Habib , Afsharifar Gholam Reza
Published: July 2006

1-Benzyl-4-aza-1-azoniabicyclo[2.2.2]octane tetrahydroborate (BAAOTB) and tetrabutylammonium tetrahydroborate (TBATB) are used for the selective reductions of aldehydes, ketones, α,β-unsaturated carbonyl compounds, acid chlorides, azides, epoxides, and disulfides in t-BuOH and hexane/chloroform. ABBOAB with its rigid and bulky structure reacts more selectively than its analogue TBATB.
Solvent Effects on Anchimerically Assisted Solvolyses. II. Solvent Effects in Solvolyses of threo-2-Aryl-1-methylpropyl p-Toluenesulfonates
Authors: Fujio Mizue , Saeki Yoshihiro , Nakamoto Kenichiro , Yatsugi Ken-ichi , Goto Naomi , Kim Sung Hong , Tsuji Yutaka , Rappoport Zvi , Tsuno Yuho
Published: July 2006

The solvent effects on the solvolysis of threo-2-aryl-1-methylpropyl p-toluenesulfonates were analyzed with the aid of the extended Winstein–Grunwald Equation. The aryl-assisted kΔ solvolysis of 2-(p-methoxyphenyl)-1-methylpropyl and 2-methyl-2-phenylpropyl p-toluenesulfonates failed to give a single linear correlation with the YOTs parameter. The dispersion against YOTs cannot be due to nucleophilic solvent assistance. The m values from the plots of 2-(p-methoxyphenyl)-1-methylpropyl and 2-methyl-2-phenylpropyl p-toluenesulfonates against YOTs were significantly lower than m = 1.0 for the limiting kc solvolysis. Significantly improved correlations (R > 0.99; SD < 0.14) were obtained for the p-methoxy, 3-chloro-4-methoxy, and p-methyl derivatives with the YΔ scale based on the solvolysis of 2-(p-methoxyphenyl)-2-methylpropyl p-toluenesulfonate, instead of with YOTs. No improvement by the YΔ treatment was obtained for the unsubstituted compound (R = 0.97; SD = 0.22). A new similarity comparison analysis in terms of YOTs and YΔ, i.e., log (k/k80E) = mcYOTs + mΔYΔ, was applied successfully to the present kΔ solvolyses. The degree of YΔ character relative to the YOTs one, scaled by mΔ/(mc + mΔ), varies for 1-methyl-2-phenylpropyl tosylates in the range from 1.0 to 0.00 in the consistent manner expected if the dispersion in the YOTs plot becomes less pronounced for solvolyses of less significant anchimeric assistance. There is a continuous spectrum of behavior between the extreme pure kc mechanism and the extreme pure kΔ one.
Solvent Effects on the Solvolysis of Benzyl Tosylates. Behavior of Derivatives with Electron-Donating Substituents
Authors: Fujio Mizue , Susuki Toshihiro , Yatsugi Ken-ichi , Saeki Yoshihiro , Goto Mutsuo , Kim Sung Hong , Tsuji Yutaka , Rappoport Zvi , Tsuno Yuho
Published: July 2006

Solvolysis rates of p-methylbenzyl and 3-bromo-4-(methylthio)benzyl p-toluenesulfonates were measured in a wide variety of solvents and the solvent effects were compared with those for less activated benzyl tosylates and other related benzylic substrates. Plots of the dual parameter Winstein–Grunwald Equation failed to give satisfactory correlations using the ordinary 2-adamantyl YOTs parameter. m Values close to unity for both derivatives were obtained but the linearity of the correlations was unsatisfactory. Although the high response (m value) to the solvent polarity and the low l value may indicate a nearly limiting mechanism, the pattern of dispersion observed in binary solvent mixtures cannot be interpreted in terms of nucleophilic solvent assistance. The use of the polarity scale YΔ derived from 2-methyl-2-(p-methoxyphenyl)propyl tosylate solvolysis instead of YOTs significantly improved the correlations. The dispersion can be ascribed to the varying solvation-desolvation interactions characteristic of highly delocalized cationic centers in binary solvent mixtures. We used extended similarity comparison analysis, log (k/k80E) = mcYOTs + mΔYΔ + (lN). Based on the resulting characteristic susceptibility parameters, the mechanisms of benzyl solvolysis and the structures of relevant benzylic solvolyses transition states are discussed.
Synthesis of an Artificial HMG-CoA Reductase Inhibitor NK-104 via a Hydrosilylation–Cross-Coupling Reaction
Authors: Takahashi Kyoko , Minami Tatsuya , Ohara Yoshio , Hiyama Tamejiro
Published: July 2006

The hydrosilylation of t-butyl (3R,5S)-3,5-isopropylidenedioxy-6-heptynoate with ClMe2SiH and a platinum catalyst, t-Bu3P·Pt(CH2=CHSiMe2)2O, gave an (E)-vinylsilane in high yield with high regioselectivity. A subsequent cross-coupling reaction with an aryl halide afforded t-butyl (3R,5S,6E)-7-aryl-3,5-isopropylidenedioxy-6-heptenoate. This sequence was applied to the synthesis of a potent HMG-CoA reductase inhibitor, NK-104.