bluuebunny/crossref_metadata_2025 huggingface dataset:
Conjugated Systems with Identical Circuit Resonance Energies
Authors: Gutman Ivan , Mizoguchi Noriyuki
Published: July 2006

Circuit resonance energy CE defined by Aihara is one of indices for local aromaticity. The CE for a circuit of a polycyclic conjugated molecule is calculated from the roots of the reference polynomial and circuit characteristic polynomial. It is reported that there exist polycyclic conjugated molecules which have identical reference polynomials and identical circuit characteristic polynomials and thus identical circuit resonance energies.
Substituent Effects. XX. Highly Electron-Deficient Carbocation Solvolyses
Authors: Murata Akihisa , Sakaguchi Shin-ichi , Fujiyama Ryoji , Mishima Masaaki , Fujio Mizue , Tsuno Yuho
Published: July 2006

The solvolysis rates of 1-aryl-2,2,2-trifluoroethyl tosylates (1-OTs) and m-nitrobenzenesulfonates (1-ONs) were determined conductometrically in aqueous ethanol and aqueous TFE. While the Brown ρ+σ+ equation does not give a simple linear plots, but a remarkably split pattern, there is a linear free energy relationship between the solvolyses of 1-OTs and 1-aryl-1-(trifluoromethyl)ethyl tosylates (2) with a slope of unity over a wide range (108 in reactivity) of substituents from p-MeO to unsubstituted derivatives. The substituent effect on the solvolysis of 1 should be closer to that on the solvolysis of 2, rather than to the σ+ substituent effect. The ρ value for this system was estimated to be identical to the value of −6.3 assigned for 2, and the r value in the LArSR correlation to be comparable with or even higher than the r=1.4 of 2. The enhanced r value of this system must be caused from a strong destabilization of the transition state by the α-CF3 substituent. Extremely high ρ+ values have recently been pointed out for many solvolyses generating highly electron-deficient carbocations; however, in no case is the ρ+ value equally high for the electron-attracting region of the substituent. In fact, they all resulted in significantly concave σ+ plots, suggesting a mechanistic transition. All of the conflicts must be attributed to the inadequacy of the simple application of σ+. The use of the Brown σ+ scale must be the only cause of a curve break in the correlation plot of such a system having a significantly different resonance demand.
Electron Spin Resonance Spectra of Sulfinamidyl Radicals and a Comparison of Hyperfine Splitting Constants with Sulfenamidyl and Sulfonamidyl Radicals
Authors: Miura Yozo , Nakamura Yuji
Published: July 2006

An ESR spectroscopic study of N-arylsulfinyl- and N-alkylsulfinyl-3,5-di-t-butylphenylaminyls (2) is described. The sulfinamidyls 2, generated by the reaction of the corresponding sulfinamides (7) with di-t-butyl diperoxyoxalate (DBPO) in benzene at 21 or 40°C, give hyperfine splitting (hfs) constants which indicate that the unpaired electron is slightly delocalized onto the sulfinyl group. A comparison of the hfs constants for 2 with those for structurally related sulfenamidyl and sulfonamidyl radicals indicates that the abilities of –SR, –S(O)R, and –S(O2)R to delocalize the unpaired electron are in the order –SR>–S(O)R>–(O2)R. The reaction of 7 with DBPO has been examined on the basis of product analyses. The mechanism accounting for the formation of the isolated products is briefly discussed.
Syntheses and Properties of the Copper(II) Complexes of the Amphoteric Surfactants, N-Alkyl-β-alanine
Authors: Nakamura Akio , Koshinuma Masakatsu , Tajima Kazuo
Published: July 2006

Copper(II) complexes of amphoteric surfactants, N-alkyl-β-alanine (NAA) (the number of carbon atoms in the alkyl chains: n=2, 4, 6, 8, 10, 12), Were synthesized from NAA and copper(II) chloride dihydrate by mixing in aqueous solutions. The properties and structures of these bluish flaky complexes were investigated by elemental analyses, infrared and far-infrared spectroscopy, electronic diffuse reflection spectroscopy, X-ray diffractometry, and thermal analyses. As a result, all of these complexes were found to be composed of one copper(II) ion and two NAA molecules, regardless of the chain length in the alkyl group, (Cu(NAA)2·2H2O), and were also found to have a laminated structure in the crystalline state. A linear relationship was found between the long spacings (d/nm) of the laminated structure and the numbers of carbon atoms (n) in the N-alkyl substituents; d=0.135n+0.62. From these results it was concluded that copper(II) complex molecules have a trans configuration, and are extended and parallel to the normal line of the laminated planes in the crystal. A multiunilayer model for the molecular arrangement of these copper(II) complexes has been proposed, which is quite different from those so far proposed to explain the long spacings observed for metal soap crystals, lyotropic liquid crystal and so on. Also, the role of the alkyl substituents in complex formation has been indicated.
Dynamic NMR as a Nondestructive Method for the Determination of Rates of Dissociation. XVII. Dissociation of the N–B Bond in the Coordinated Form of 2-[2-(Dimethylaminomethyl)phenyl]-4,4-diphenyl-1,3,2-dioxaborolane and Related Compounds
Authors: Toyota Shinji , Oki Michinori
Published: July 2006

The rates of dissociation of the N–B bonds in the title compounds were reexamined by the dynamic NMR technique to get further insight into the mechanism of dissociation. Entropies of activation were fairly large positive to suggest that the dissociation of a bond of ionic characters is the rate-limiting step. The rates of dissociation were generally larger in nonpolar solvents than in polar solvents, suggesting that the stabilization of the ground state by solvation was important in determining the activation energy for dissociation. Diethyl ether, tetrahydrofuran, and acetone gave larger rate constants of dissociation than those expected from their polarity. Participation of solvent molecules in the dissociation is discussed on the basis of these results. Introduction of various substituents indicated that steric effects as well as electronic effects affect the N–B bond energy.
Diastereoselective Reduction of α,α-Difluoro β-Hydroxy Ketones to syn- and anti-2,2-Difluoro-1,3-diols
Authors: Kuroboshi Manabu , Ishihara Takashi
Published: July 2006

While reduction of α,α-difluoro β-hydroxy ketones with diisobutylaluminium hydride gave a mixture of syn- and anti-diols in various ratios, the reduction in the presence of zinc bromide or zinc chloride-N,N,N′,N′-tetramethylethylenediamine was highly selective and gave syn-2,2-difruoro-1,3-diols predominantly, anti-2,2-Difluoro-1,3-diols were obtained by the reduction of α,α-difluoro β-hydroxy ketones with aluminium isopropoxide.
Octacarbonyldicobalt(0)-Catalyzed Ring-Opening Cyanation of Tetrahydrofuran Derivatives with Trimethylsilyl Cyanide
Authors: Okuda Fumio , Watanabe Yoshihisa
Published: July 2006

Tetrahydrofuran, less strained cyclic ether was effectively cyanated by trimethylsilyl cyanide ((CH3)3SiCN) with its ring-opening to give 5-(trimethylsiloxy)pentanenitrile in 82% yield at 120°C for 23 h in the presence of a catalytic amount of Co2(CO)8. Several tetrahydrofuran derivatives having methyl and alkoxyl groups also reacted with trimethylsilyl cyanide to give the corresponding 5-siloxy nitriles in 25–88% yields. On using oxiranes or oxetanes, which are more strained cyclic ethers, however, no reaction proceeded under the same conditions. In the present reaction, (CH3)3SiCN would firstly coordinate to the cobalt metal center as its isocyanide form to give a cobalt-isocyanide complex, which would be a precursor of active catalyst species in the reaction.
The Production of Methacrylic Acid by the Vapor-Phase Aldol Condensation over V–Si–P Ternary Oxide Catalyst
Authors: Ai Mamoru
Published: July 2006

The vapor-phase aldol condensation of propionic acid with formaldehyde was performed over a V–Si–P ternary oxide catalyst of atomic ratio of 1:2:2.2. The one-pass yield of methacrylic acid was 55 mol% on the charged formaldehyde basis at the propionic acid/formaldehyde molar ratio of 2. The maximum yield of methacrylic acid remained unchanged with the variation in temperature and the dilution of reactants, but it increased with the propionic acid/formaldehyde ratio; the yield reached 82 mol% at the propionic acid/formaldehyde ratio of 6. The effects of reaction variables such as temperature, concentrations of propionic acid, formaldehyde, water vapor, methacrylic acid, and oxygen, and propionic acid/formaldehyde ratio were examined.
Association of Halobenzenes with Cyclodextrins in Aqueous Medium
Authors: Takuma Tatsuyoshi , Deguchi Toshio , Sanemasa Isao
Published: July 2006

The complex formation of cyclodextrin (CyD) with fluoro-, chloro-, bromo-, and iodobenzene has been studied in aqueous medium at 25 °C. It was found that van der Waals force is the main factor to stabilize the complex. Formation constsnts for α and β-CyDs increase with the size of halogen atom, while those for γ-CyD are almost independent of the size.
Aluminium-Containing Polymethylsiloxane as a New Solid Acid Catalyst
Authors: Mishima Shozi , Matsuzaki Isao , Nakajima Tsuyosi , Hiki Toshimichi
Published: July 2006

An aluminium-containing polymethylsiloxane (AMS) was prepared in an aqueous system using methyltrichlorosilane, dimethyldichlorosilane, and aluminium hydroxide as the starting materials, and its applicability as a new solid acid catalyst was examined. AMS is an amorphous hydrophobic solid with a high surface area (ca. 250 m2 g−1) and a relatively high thermal stability (max. 573 K in air). The adsorption of basic indicators indicated that acid sites with a medium strength (pKa=1.5) exist on AMS, and protic acid sites were detected on AMS by the IR spectra of adsorbed pyridine. These acid sites differ from the aprotic sites found on alumina. Though those on AMS are able to catalyze the dehydration of pinacol in the vapor phase, they are inactive for the hydrolysis of methyl acetate in an aqueous system.
Synthesis and Inclusion Properties of “Neutral” Water-Soluble Calixarenes
Authors: Shinkai Seiji , Kawabata Hirosuke , Matsuda Tsutomu , Kawaguchi Hirofumi , Manabe Osamu
Published: July 2006

“Neutral” water-soluble calix[n]arenes, 1n (n=6 and 8) were synthesized for the first time. Below the critical micelle concentrations, they formed host–guest-type complexes with naphthalenesulfonate derivatives used as fluorescence probes. The binding sites showed the hydrophobicity comparable with those of cyclodextrins, and the cavities showed the shape selectivity for these guest molecules.
Studies on the Reactivity of Dicyanodihydroborate with Some Lewis Base Hydrochlorides
Authors: Das M K , Bandyopadhyay S N
Published: July 2006

The reactions of sodium dicyanodihydroborate with various Lewis base hydrochlorides produce mainly the metathesis reaction products in contrast to those of sodium cyanotrihydroborate, which produces cyanoborane adducts. This has been established with the help of IR, 1H and 11B NMR data.
Acid-Catalyzed Hydrolysis of Methoxymethyl Phenyl Sulfoxide without Concomitant Racemization
Authors: Okuyama Tadashi , Toyoda Masayoshi , Fueno Takayuki
Published: July 2006

Methoxymethyl phenyl sulfoxide 1 undergoes acid-catalyzed hydrolysis to give S-phenyl benzenethiosulfinate 5, which is formed rapidly from a primary product, benzenesulfenic acid 3. Formation of 5 follows pseudo-first-order kinetics. Rate constants obtained spectrophotometrically in perchloric acid show that the reaction is dependent on the protonated substrate with the Bunnett–Olsen φ=−0.15. Rate constants for the loss of optical activity of the enantiomeric 1 measured in 80 vol% aqueous dioxane are identical with those obtained spectrophotometrically for the formation of 5. Racemization of the substrate does not take place more rapidly than the fragmentation. The reaction is accelerated by chloride and bromide ions. The halide reaction is first order in acid concentration.
Resolution of Enantiomers by Supercritical Fluid Chromatography with Cellulose Tris(phenylcarbamate) Coated on Silica Gel
Authors: Nitta Tomoshige , Yakushijin Yoshiki , Kametani Takefumi , Katayama Takashi
Published: July 2006

The solvent characteristics of super- and subcritical carbon dioxide for the chromatographic resolution of enantiomers (tarns-stilbene oxide) by chiral cellulose tris(phenylcarbamate) were investigated by altering the pressure (10, 15, 20, and 40 MPa), the temperature (0, 25, and 40 °C), and the concentrations of the modifiers. Among methanol, ethanol, and 2-propanol used as modifiers, methanol is the most effective in terms of the resolution of enantiomers, though 2-propanol gives a slightly high value for the separation factor. When the concentration of alcohol increases, the capacity ratio decreases substantially, but the separation factor decreases only a little. At 40 °C, an increase in pressure results in a decrease in the capacity ratio and a slight increase in the separation factor. These pressure effects may be attributed to the enhanced solubilities of both the solute and the modifier with an increase in the mobile-phase density. The temperature is the most effective variable for the separation factor of enantiomers; it increases as the temperature lowers. Therefore, the resolution becomes higher at 0 °C (subcritical conditions) than at 40 °C on the basis of the same analysis time.
Simple and Convenient Method for Synthesis of 3-O-Sulfonyl- γ-cyclodextrin
Authors: Tahara Tsutomu , Fujita Kahee , Koga Toshitaka
Published: July 2006

3-O-(2-Naphthylsulfonyl)-γ-cyclodextrin was prepared together with 2-O-(2-naphthylsulfonyl)-γ-cyclodextrin by a reaction of γ-cyclodextrin with 2-naphthalenesulfonyl chloride in aqueous CH3CN, isolated, and structurally determined.
Characterization of the Surface Oxide Layer on Iron Particles for Magnetic Recording by Mössbauer Spectrometry
Authors: Makishima Akio , Yamamoto Yukihiro , Watanabe Kohji
Published: July 2006

The average valency of iron in the oxide layer on iron particles for magnetic recording and the saturation magnetization of the oxide layer were estimated to be 2.8 and 39 emu g−1, respectively, by examining the Debye temperature and the recoilless fraction of oxide layer which were calculated with the Mössbauer parameters.
PPS Preparation. A Kinetic Study and the Effect of Water on the Polymerization
Authors: Ito Masato M , Onda Masahiro , Ona Seiichi , Inoue Hakuai
Published: July 2006

A kinetic study on poly (p-phenylene sulfide) formation from p-dichlorobenzene (1) and sodium sulfide reveals that the initiation rection is first order with respect to 1 and sodium sulfide, respectively. Reaction on the surface of solid sodium sulfide has proved to be negligible when the reaction is carried out in the presence of the solid. The time course of the concentration of 1 and its dimer can be explained with a simplified eight step kinetic model for the initial stage, in which each of the step is firest order with respect to the reactant in concern. Kinetic parameters for each of the steps were estimatied. Increase in [Na2S]/[1] ratio causes the increase both in polymer yield and in the degree of polymerization. Presence of a small amount of water enhances cosiderably the rate of polymerization and increases the polymer yield, but the highest degree of polymerization was observed in the presence of water approximately equimolar to 1.
Chemistry of Organic Eutectics: p-Phenylenediamine–m-Nitrobenzoic Acid System Involving the 1:2 Addition Compound
Authors: Rai U S , Mandal K D
Published: July 2006

The phase diagram of p-phenylenediamine–m-nitrobenzoic acid system, determined by the thaw-melt method, show the formation of two eutectics and a 1:2 addition compound. The linear velocity of crystallization of pure components, eutectics and addition compound, measured by determining the rate of movement of growth front in a capillary, suggests that crystallization data obey the Hillig–Turnbull equation. Using experimental values of heats of fusion, determined by the DTA method, entropy of fusion, heat of mixing and excess thermodynamic functions were calculated and the results are explained on the basis of cluster formation in the melts. Microscopic studies reveal that the eutectics have different characteristics microstructures as compared to those of parent components. X-Ray diffraction data suggest that there is preferential ordering of atomic planes in the formation of the eutectics.
The Kinetics and Mechanism of the Decomposition Reaction of the Bis(oxalato)manganese(III) Complex in an Aqueous Solution
Authors: Kimura Masaru , Ohota Miwako , Tsukahara Keiichi
Published: July 2006

The kinetics and mechanism of the decomposition of the bis(oxalato)manganese(III) complex ion ([Mn(ox)2]−) were studied in acid solution in the absence and in the presence of oxygen at temperatures from 10 to 35°C. The decomposition reaction of [Mn(ox)2]− in the absence of oxygen was described by the first-order rate law of −d[[Mn(ox)2]−]/dt=kobsd[[Mn(ox)2]−], where the observed rate constant, kobsd, increased proportionally with the increasing hydrogen-ion concentrations, being expressed as kobsd=k[H+] in the [H+] range of 0.006–0.1 M. The enthalpy and entropy changes of activation(ΔH\eweq and ΔS\eweq) were 73.4±2.0 kJ mol−1 and −8.6±0.2 J K−1 mol−1 respectively. The rate of the decomposition of [Mn(ox)2]− decreased greatly upon the addition of a radical scavenger for CO2\ewdot such as [Co(NH3)6]3+, [CoCl(NH3)5]2+, or molecular oxygen. In the presence of oxygen, the rate deviated greatly from the first-order rate law. On the other hand, the addition of [Co(NH3)6]3+ or [CoCl(NH3)5]2+ in the absence of oxygen did not change the first-order rate law, but did decrease the rate of reaction up to 40% of that in the absence of the radical scavenger. The mechanisms for the decomposition reaction of [Mn(ox)2]− are discussed in the light of the results obtained.
Liquid/Solid Extraction of Acetylacetone Chelates with Supercritical Carbon Dioxide
Authors: Saito Norio , Ikushima Yutaka , Goto Tomio
Published: July 2006

The solubilities of the acetylacetone chelates in supercritical CO2 (SC-CO2) at 333 K and 9.8–29.4 MPa were strongly influenced by the extraction pressure, and by the nature of the metals and the number of acetylacetone ligands in the chelates. It was found that acetylacetone chelates could be extracted selectively by SC-CO2 treatment because of significant differences in their solubilities in SC-CO2.
Dideoxygenation on the 3′,4′-Positions of an α-Linked Disaccharide Derivative: A Key Intermediate for New Aminoglycoside Synthesis
Authors: Hayashida Mitsuo , Sakairi Nobuo , Kuzuhara Hiroyoshi
Published: July 2006

A 2′,6′-diamino-1,6-anhydro disaccharide derivative (6) was prepared from maltose. The 3′,4′-diol system of 6 was successfully converted into the 3′-ene system by application of the Corey–Winter procedure, giving the hex-3′-enopyranose derivative (8). Catalytic hydrogenation of 8 gave the dideoxy derivative, a key intermediate for the synthesis of a new aminoglycoside.
Adsorption Behavior of Some Metal Ions onto Octadecylsilica Gel in the Presence of Acetylacetone
Authors: Kato Masanao , Shimofuruya Hiroshi
Published: July 2006

Adsorption of 11 metal acetylacetonate complexes onto an octadecylsilica(ODS) gel from an aqueous solution was measured as a function of pH. It was found that the pH dependencies regarding adsorption are almost consistent with those of a solvent-extraction system, except for Zn(II) which is unextracted into benzene. Plots of the adsorption ratio against pH indicates the 1:1 complexes are adsorbed onto ODS gel, except for Al(III) whose composition is 1:2.
Photochromism of a Furylfulgide, 2-[1-(2,5-Dimethyl-3-furyl)ethylidene]-3-isopropylidenesuccinic Anhydride in Solvents and Polymer Films
Authors: Yokoyama Yasushi , Hayata Hirofumi , Ito Hiroshi , Kurita Yukio
Published: July 2006

The quantum yields of the photochromic reaction between (E)- and (Z)-2-[1-(2,5-dimethyl-3-furyl)ethylidene]-3-isopropylidenesuccinic anhydride and the cyclized valence isomer were determined in various solvents and polymers. In both media the ring-opening quantum yield (ΦCE) depended on the dielectric constant of the media. In some polymer films, ΦCE were larger, and the cyclization quantum yield (ΦEC) and olefinic isomerization quantum yields (ΦEZ) and (ΦZE) were smaller than those in the corresponding solvents.
Cis Selective Wittig Olefination of α-Alkoxy Ketones and Its Application to the Stereoselective Synthesis of Plaunotol
Authors: Inoue Seiichi , Honda Kiyoshi , Iwase Norimichi , Sato Kikumasa
Published: July 2006

Several Wittig olefinations between α-heterosubstituted acetones and a phosphorus ylide were investigated concerning the product stereoselectivity. Benzyloxyacetone and tetrahydropyranyloxyacetone furnished trisubstituted (Z)-olefins exclusively. The stereoselective preparation of oxygenated acyclic terpenoids was practical by use of the direct Wittig olefination toward α-alkoxy ketones, and it facilitated a total synthesis of plaunotol from geraniol derivatives in short steps with high stereoselectivity.
Photochromic Properties of Unsymmetric Mono- and Bis(phenylazo)naphthalenes
Authors: Yoshida Katsuhira , Koujiri Tetsunao , Horii Taeko , Kubo Yuji
Published: July 2006

To utilize the reversible photochromic system of phenylazonaphthalenes in a design of functional molecule, the photochromic behaviors of various substituted phenylazonaphthalenes have been investigated. Introduction of substituents onto ortho positions with respect to the azo group retarded the rate of thermal cis-to-trans isomerization. The retardation effects were greatly dependent on both the number and position of the ortho substituents. To investigate the reterdation effects of ortho substituents, the activation parameters were determined; the results suggest that the steric hindrance among the ortho substituents and the two nitrogen lone pairs of the azo group becomes far more severe in an inversional transition-state than in the ground cis-state, which leads to the remarkable slow cis-to-trans isomerization. On the basis of the kinetic data of various phenylazonaphthalenes, the complicated isomerization behaviors of unsymmetric bis(phenylazo)naphthalenes have been elucidated.
Catalysis of Pd(II)-Catalyzed Acetalization of Alkenes with Diols
Authors: Hosokawa Takahiro , Ataka Yoshiharu , Murahashi Shun-Ichi
Published: July 2006

Alkenes bearing electron-withdrawing substituents are catalytically acetalized with 1,3-propanediol only by the use of PdCl2(MeCN)2 catalyst under O2 atmosphere. When a combination of BiCl3 and LiCl is used as co-catalyst, the acetalization proceeds effectively. These results indicate that a hydroperoxopalladium(II) species is most likely an active catalyst in the present reaction.
Dual Channels for Nucleophilic Displacements on Benzoyl Chlorides: Tetrahedral and Trigonal-Bipyramidal Transition States
Authors: Yamabe Shinichi , Koyama Tetsuji , Minato Tsutomu , Inagaki Satoshi
Published: July 2006

Nucleophilic substitutions on carbonyl carbons initiated by Cl−, Ph–CO–Cl+Cl−→Cl−+Ph–CO–Cl, were studied with ab initio MO calculations. Two transition states (TS’s) were found. One is the “tetrahed-ral” TS caused by the π attack of the nucleophile. The other is the “trigonal-bipyramidal” TS initiated by the σ attack. The coexistence of two TS’s is in accord with the proposals of Bentley and Cevasko et al. based on kinetic analyses. Two independent reaction paths are interpreted in terms of the frontier-orbital theory.
Novel Nematogenic Benzene Derivatives: N,N′-Dialkanoyl-2,5,6-trimethyl-4-alkanoyloxy-1,3-benzenediamines
Authors: Kawada Hiromitsu , Matsunaga Yoshio
Published: July 2006

A series of N,N′-dialkanoyl-2,5,6-trimethyl-4-alkanoyloxy-1,3-benzenediamines has been synthesized. The mesophases appearing in the octanoyl to octadecanoyl derivatives adopt a schlieren texture and are transformed into isotropic liquids, with enthalpy changes as small as from 1 to 4 kJ mol−1. Their X-ray diffraction patterns consist of only two diffuse peaks, fully confirming that the phases are nematic in type. The spacing deduced from the inner diffraction peak is markedly shorter than the molecular length and is similar to the spacings, d100, found for the hexagonal disordered columnar phases exhibited by closely-related benzene derivatives. This is strong evidence for the alignment with their normals to the average molecular planes parallel. In other words, the mesophase is classified as discotic even though the molecular shape is far from disk-like. Another viscous birefringent phase is found below the nematic phase when the molecule carries octanoyl to hexadecanoyl groups.
The Total Synthesis of 8β-Hydroxycycloaraneosene by Means of an Eight-Membered Ring-Formation via a Lewis Acid-Catalyzed Ene Reaction. Confirmation of Its Natural Occurrence
Authors: Kato Nobuo , Wu Xue , Tanaka Shinya , Takeshita Hitoshi
Published: July 2006

An improved eight-membered ring closure by means of a Lewis-acid-catalyzed ene reaction was applied to the synthesis of cycloaraneosene and its congener, “hydroxycycloaraneosene.” Comparisons of the NMR spectral data of the synthetic and natural compounds established that the natural product possesses an 8β-hydroxy structure, not the originally proposed 9α-hydroxy one.
Effect of Azoles as a Nucleotide Activating Group on Uranyl (Vl)-Ion Catalyzed Synthesis of Oligoadenylate in Aqueous Solution
Authors: Sawai Hiroaki , Shibusawa Takashi , Kuroda Kensei
Published: July 2006

Various adenosine-5′-phosphorazolides were prepared from adenosine-5′-phosphate and azoles such as 2-methylimidazole, 4-methylimidazole, 1,2,4-triazole, 3-nitro-1,2,4-triazole, benzimidazole and 2-methylbenzimidazole. The adenosine-5′-phosphorazolides obtained were then polymerized in neutral aqueous solution using uranyl(VI) ion as a catalyst. Oligoadenylates up to the hexadecamer with 2′-5′-internucleotide linkage were formed in high yields under the optimum condition. The azoles worked as adenylate activating group, and had a large effect on the rate of polymerization, the yield and the chain length of the resulting oligonucleotides. Imidazolides showed the moderate reactivity and gave oligoadenylates of the longest chain length. From the phosphortriazolides, only short-chained oligoadenylates were obtained, as they are susceptible to the hydrolysis. Polymerization and hydrolysis reaction of the benzimidazolides were retarded.
Phenylmercury Dithio Complexes as Ligands: Preparation and Spectroscopic Characterization of Heterobimetallic Complexes Obtained from Bisdithio Complexes of Ni(II), Pd(II), and Pt(II) as Lewis Acids
Authors: Singh Nanhai , Singh Nand Kishore , Kaw Chetna
Published: July 2006

Reaction of PhHgX [X=ethylxanthate (xant) or N,N′-diethyldithiocarbamate (dtc)] with MX2 [M=Ni(II), Pd(II) or Pt(II)] occurs, to afford a new class of golden green to yellowish brown organo heterobimetallic complexes, PhHgXMX2 with MS4 coordination geometry. The precursor PhHgX, have also been characterized. All the complexes are quite stable in solid and solution and are non-conducting species. In PhHgX, IR and NMR spectral studies suggest that dithio ligands are bound to phenylmercury in a linear fashion with additional Hg···S linkage in monodentate manner. Diamagnetism and electronic spectra indicate square planar geometry around M(II) in all the heterobimetallic complexes. IR and NMR spectral studies suggest the presence of monodentate and symmetrical bidentate dithio groups in heterobimetallic complexes.
ESR Studies of the Adsorption Behavior of Polystyrene at the Solid–Liquid Interface
Authors: Kobayashi Kazutoshi , Yajima Hirofumi , Imamura Yoshio , Endo Ryuichi
Published: July 2006

The adsorption of spin-labeled polystyrene on the silica surface from a carbon tetrachloride solution was studied by ESR spectroscopy. The fraction of train segments in the adsorbed polymer was determined from ESR spectrum analysis. The adsorption behavior of polystyrene is discussed as a function of surface coverage.
ESR Spectra of Radical Ions Generated from 5,10-Dihydroindeno[2,1-α]indene
Authors: Ogawa Keiichiro , Suzuki Hiroshi , Higuchi Jiro , Tajima Kunihiko , Ishizu Kazuhiko
Published: July 2006

While each the ESR hyperfine coupling constants (hfc’s) for the aromatic protons of the anion radical derived from 5,10-dihydroindeno[2,1-a]indene (2−·) is similar to that of the corresponding protons of the cation radical of the same compound (2+·) as well as of the radical ions of (E)-stilbene (1−· and 1+·), the methylene protons of 2−· shows an unusually large hfc value, which is much larger than that of 2+·. This is interpreted in terms of the so-called “Whiffen Effect.”
The Crystal and Molecular Structure of cis-Dichloro[3,11-dimethyl-3,11,17,18-tetraazatricyclo[11.3.1.15,9]octadeca-1(17),5,7,9(18),13,15-hexaene]rhodium(III) Cation
Authors: Sakaba Hiroyuki , Kabuto Chizuko , Horino Hiroshi , Arai Mannosuke
Published: July 2006

The crystal and molecular structure of the title compound has been determined by the use of the X-ray diffraction method. The central metal atom coordinates all four of the nitrogen atoms of N,N′-dimethyl 2,11-diaza[3.3](2,6)-pyridinophane and two additional chloride atoms in an approximately octahedral geometry.
Synthesis of Substituted Azaindenes: Synthesis of New Pyrazolo[1,5-a]pyrimidine Derivatives
Authors: Elnagdi Mohamed Hilmy , Erian Ayman Wahba
Published: July 2006

Several new pyrazolo[1,5-a]pyrimidines were synthesized via the reaction of 4,5-disubstituted 3-aminopyrazoles 1a–d with 3-dimethylaminopropiophenone, cinnamaldehyde, benzylideneacetophenone and tetracyanoethylene.
Charge-Carrier Drift Mobilities and Phase Transition in Tetrakis(octylthio)tetrathiafulvalene, TTC8–TTF, Crystal
Authors: Li Yongfang , Nakano Chikako , Imaeda Kenji , Inokuchi Hiroo , Maruyama Yusei , Iwasawa Naoko , Saito Gunzi
Published: July 2006

Temperature dependence of the charge-carrier mobility in tetrakis(octylthio)tetrathiafulvalene crystals has been observed in the temperature range of −100–45°C by the time-of-flight measurement of transient photocarriers. The mobility shows a clear jump at the crystal phase transition which is found in the electrical conductivity measurement. This fact may lead a quantitative analysis of the correlation between the conductivity jump and the phase transition.
Stereoselective Syntheses of α-Substituted Cyclic Ethers and syn-1,3-Diols
Authors: Homma Koichi , Takenoshita Haruhiro , Mukaiyama Teruaki
Published: July 2006

In the presence of a catalytic amount of triphenylmethylium hexachloroantimonate or a catalyst system of antimony pentachloride, chlorotrimethylsilane and tin(II) iodide, α-substituted cyclic ethers are stereoselectively prepared from lactones by successive treatment with 1-(t-butyldimethylsiloxy)-1-ethoxyethene and silyl nucleophiles such as triethylsilane, allyltrimethylsilane and trimethylsilyl cyanide. These catalysts also promote the reaction of γ-, δ-, and ε-trimethylsiloxy carbonyl compounds with silyl nucleophiles resulting in the formation of α-substituted cyclic ethers. The former procedure is effectively applied to short syntheses of (−)-cis-rose oxide and (cis-6-methyltetrahydro-2-pyranyl)acetic acid, a constitutent of civet. Furthermore, syn-1,3-diols are also stereoselectively prepared from lactone analogue, 6-cis-substituted 2-trichloromethyl-1,3-dioxan-4-ones, easily prepared from β-hydroxy carboxylic acids.
Syntheses and Properties of Oligothymidylate Analogs Containing Stereoregulated Phosphoromorpholidate and Phosphodiester Linkages in an Alternating Manner
Authors: Ozaki Hiroaki , Kitamura Masanori , Yamana Kazushige , Murakami Akira , Shimidzu Takeo
Published: July 2006

Syntheses and some properties of undecathymidylate analogs containing stereoregulated phosphoromorpholidate and phosphodiester linkages in an alternating manner are described. These analogs were easily obtained by the phosphorobisamidite approach starting from pre-separated diastereomerically pure dithymidine phosphoromorpholidate derivatives. Both isomers were found to be high resistant to nucleases, in comparison with natural oligothymidylate; the phosphodiester linkages except 3’-end in the isomers were not cleaved by SI nuclease and both isomers were very slowly degraded by phosphodiesterase I and micrococcal nuclease. The rate of each degradation was dependent on the configuration of phosphoromorpholidate linkage in each isomer. The UV and CD spectral studies show that one of the isomer can interact with poly(dA) to give B-type duplex possessing the same thermal stability as natural oligothymidylate-poly(dA) duplex and the other isomer does not interact with poly(dA) under the comparable conditions.
Proton-Transferred Ion Pairs of p-Hydroxybenzaldehyde and p-Hydroxyacetophenone in Ethers at Low Temperature
Authors: Inoue Hiroyasu , Sakurai Tadamitsu , Hoshi Toshihiko , Okubo Jun
Published: July 2006

The self-associations of p-hydroxybenzaldehyde (HBA) and p-hydroxyacetophenone (HAP) have been studied from measurements of phosphorescence and the excitation spectra at 77 K. At appropriately high concentrations of HBA and HAP in ethereal matrices, such as 1,4-dioxane, these compounds exhibit dual phosphorescences around 430 and 470 nm with excitation at 290 and 330 nm, respectively. The shorter-wavelength emission is due to monomeric species of the substrates. The longer-wavelength emission can be interpreted as being due to ion pairs, in which the proton of the hydroxyl group of the substrate molecule is transferred intermolecularly to the formyl group of another substrate molecule. The phosphorescence excitation spectra show that the ion pairs are formed in the ground states of the phenolic compounds, being in equilibrium with the monomeric species at 77 K. The ion pair formation is strongly dependent on the medium.
Thienylpyridines as a New Fluorescent Reagent. I. Determination of Primary Alkylamines with 5-(4-Pyridyl)-2-thiophenecarbaldehyde Using HPLC
Authors: Nakajima Riichiro , Yamamoto Akifumi , Hara Tadashi
Published: July 2006

5-(4-Pyridyl)-2-thiophenecarbaldehyde has been prepared as a new fluorescent derivatization reagent and utilized for the determination of primary alkylamines. A definite detection limit was achieved for the amines by using a method based on the combination of precolumn derivatization and postcolumn hydrolysis–detection of the original fluorescent reagent regenerated from the derivatives. Approximately a 0.1 pmol (10 μl injection) (S/N=2) of detection limit was obtained. A dynamic linear range was over 5 orders of magnitude.
Deuterium Isotope Effects on Aromatic Carbon-13 Chemical Shifts. II. Dependence of One- and Two-bond Isotope Shifts on Electron Densities of Substituted Benzenes
Authors: Nakashima Yasuki , Nakane Hideki , Ban Sadanori , Takahashi Kensuke
Published: July 2006

One- and two-bond deuterium isotope effects (1Δ and 2Δ) on 13C chemical shifts of substituted benzenes are reported. The one-bond effects are correlated with the π-electron densities on the observed carbons, and the two-bond effects are correlated with the σ-electron densities on the observed carbons. There are no correlations between 1Δ and 2Δ. 1Δs reflect the direct change on going from a C–H bond to a C–D bond, but 2Δs reflect their indirect effect.
Preparation of Fluoroarenes in One-Pot Diazotization and Fluoro-Dediazoniation of Aminoarenes Using HF or HF-Base. The Functions of Bases in the HF Solution
Authors: Fukuhara Tsuyoshi , Sasaki Satoshi , Yoneda Norihiko , Suzuki Akira
Published: July 2006

In a one-pot diazotization of anilines followed by fluoro-dediazoniation in situ using HF or HF with bases (HF-Base) as a solvent, the diazotization stage has been found to play the most important part to yield fluoroarenes effectively. Diazotization of anilines was greatly influenced by the composition of the HF solution, and greatly enhanced by employing appropriate amounts of bases, such as pyridine. On the other hand, fluorodediazoniation of diazonium salts, once formed, took place very readily in HF or HF-Base to produce fluoroarenes in high yield, although such bases served to slow down the rate of decomposition of diazonium salts to some extent.
Structure-Activity Relationship of Escherichia coli Heat-Stable Enterotoxin: Role of Ala Residue at Position 14 in Toxin-Receptor Interaction
Authors: Yamasaki Shinji , Sato Takashi , Hidaka Yuji , Ozaki Hiroshi , Ito Hideaki , Hirayama Toshiya , Takeda Yoshifumi , Sugimura Takashi , Tai Akira , Shimonishi Yasutsugu
Published: July 2006

A heat-stable enterotoxin (STh) produced by a human strain of enterotoxigenic Escherichia coli consists of 19 amino residues including 6 half-cystine residues. Analogs of STh from positions 6 to 19 with replacements of the Ala residue at position 14 by other amino acid residues were synthesized by a solid-phase method and examined by biological and biochemical methods. This Ala residue was demonstrated to be very important for expression of the toxicity of STh and for interaction of the toxin with its receptor protein(s).
Absorption Spectra of the Cationic Radical Salt of 3,3′,5,5′-Tetramethylbenzidine in Acetonitrile
Authors: Awano Hiroshi , Ohigashi Hiroji
Published: July 2006

The absorption spectrum of 3,3′,5,5′-tetramethylbenzidine (TMB) perchlorate in acetonitrile strongly depends on both the temperature and concentration. Analyzing the absorption band around 660 nm, which corresponds to the charge transfer from TMB to (TMB)2+, the equilibrium constant and the enthalpy change of the charge-transfer complex formation at 25°C have been obtained as 1.9×104 mol−1 dm3 and −66.2 kJ mol−1, respectively.
Reactions of Arylazoxy Aryl Sulfones with α,β-Unsaturated Esters and Nitriles in the Presence of a Palladium(0) Catalyst
Authors: Kamigata Nobumasa , Satoh Mayumi , Fukushima Takamasa
Published: July 2006

The reactions of arylazoxy aryl sulfones (1) with α,β-unsaturated esters and nitriles in the presence of a palladium(0) catalyst were found to give aryl-substituted esters and nitriles in good yield.
Synthesis and Heteroannulation of 3,4-Dibenzoyl-1-phenyl-2a,5-diazabenz[cd]azulene
Authors: Abe Noritaka , Ueno Tamae
Published: July 2006

3,4-Dibenzoyl-1-phenyl-2a,5-diazabenz[cd]azulene (2b) was synthesized by cycloaddition of 8-amino3-phenyl-1-azaazulene with dibenzoylacetylene. Heteroannulation to 2b has been achieved by reactions with hydrazine and phosphorus pentasulfide.
Crystal and Electronic Structures of Radical Salts of 2,7-Bis(methylthio)-1,6-dithiapyrene (MTDTPY) and 2,7-Bis(methylseleno)-1,6-dithiapyrene (MSDTPY)
Authors: Kawamoto Atsushi , Tanaka Jiro , Oda Akio , Mizumura Hideshi , Murata Ichiro , Nakasuji Kazuhiro
Published: July 2006

Radical salts of 2,7-bis(methylthio)-1,6-dithiapyrene (MTDTPY) with PF6− and 2,7-bis(methylseleno)-1,6-dithiapyrene (MSDTPY) with AsF6− and [Au(CN)2]− were prepared using an electrochemical method. The crystal structures of these salts were determined with an X-ray method. MTDTPY–(PF6)0.67 (triclinic P\bar1) and MSDTPY–(AsF6)0.67 (triclinic P\bar1) form uniform segregated stacks of MTDTPY and MSDTPY molecules with interplanar distances of 3.40 and 3.59 Å, respectively. Short S–S contacts of 3.46–3.56 Å for MTDTPY–(PF6)0.67 and 3.54–3.61 Å for MSDTPY–(AsF6)0.67 were observed between the columns. The chains of disordered PF6− and AsF6− were found to be parallel to the stack axis. Analysis of the disorder showed a stoichiometric ratio of the DTPY derivatives and counter anions at 1:0.67; the formal charge of MTDTPY and MSDTPY was estimated at +0.67. MSDTPY–Au(CN)2 (monoclinic P2/c) forms a segregated stack of MSDTPY molecules with an interplanar distance of 3.40 Å. The optical reflection spectra of these crystals were measured with polarized light both parallel and perpendicular to the stack axis. In spite of the short intercolumnar S–S contacts, the spectra of MTDTPY–(PF6)0.67 and MSDTPY–(AsF6)0.67 showed a strong one-dimensional character. The optical conductivity spectra (σ(ω)) and the real part of the dielectric constant (ε′(ω)) along the stack axis were obtained by means of Kramers–Kronig transformation. Both the conductivity spectra and the dielectric constant substantially differ from the simple Drude model. These results were analyzed with a one-dimensional electron-localization model in a disordered system with the following optical parameters: ωp=14000 cm−1; τi=2.2×10−15s (τi−1=2400 cm−1) and εcore=3.0 for MTDTPY-(PF6)0.67 and ωp=10000 cm−1; τi=2.2×10−15 (τi−1=2400 cm−1) and εcore=3.5 for MSDTPY–(AsF6)0.67. From the spectra of MSDTPY–Au(CN)2, the on-site Coulomb repulsion U was estimated at 6000 cm−1.
Solvent Effect on Reaction Mechanism and Kinetics of Triplet Ion Pairs between Chloranil and Acenaphthene
Authors: Kobashi Harumichi , Okabe Shunichi , Ohsugi Youichi , Shizuka Haruo
Published: July 2006

A comparative study on decay dynamics of triplet ion pairs has been performed for the chloranil (CA) and acenaphthene (ACN) system in both the nonpolar solvent benzene (BZ) and the moderately polar 1,2-dichloroethane (DCE) by means of nanosecond laser photolysis. Triplet chloranil (3CA) is quenched by ACN to yield the (1:1)triplet ion pair (IP1), 3(CA\ewdot, ACN\underset.+), in BZ, while the (1:2) ion pair (IP2), 3(CA\ewdot, ACN2\underset.+), in DCE as well as IP1 in the concentration range less than 1 M (1 M=1 mol dm−3) of ACN. Temperature dependence of the transient spectra indicates that IP2 is energetically lower than IP1 in DCE. In BZ, IP1 decays through both back electron transfer (back ET) to the ground state of the donor-acceptor pair and intra-ion-pair proton transfer (PT) leading to formation of the chloranil semiquinone radical (CAH·). In DCE, both IP1 and IP2 disappear through the back ET and ionic dissociation (ID) to free anion and cation radicals, while no PT is observed. The efficiency of ID is greater in IP2(0.70) than in IP1(0.33). From temperature dependence on decay profiles, Arrhenius parameters are obtained for each decay process of the ion pairs. The PT process in BZ requires a considerably high activation energy (30 kJ mol−1), while the ID process in DCE proceeds with practically no activation energy for both IP1 and IP2. The activation barrier for the back ET of IP1 in BZ is obtained to be 13 kJ mol−1 which is significantly greater than that (∼0 KJ Jmol−1) in DCE. This solvent effect may be attributed to the difference in the ion pair states: i.e., a contact type in BZ and solvent-separated type in DCE.
Intra- and Intermolecular Electron-Transfer Reaction of Viologen-Linked Copper(II) Schiff Base Complexes
Authors: Tsukahara Keiichi , Yoshida Youko , Kasuga Kuninobu
Published: July 2006

The copper(II) Schiff base complexes linked to viologen via number 3 and 4 of methylene groups were synthesized and characterized. The complexes are the binuclear type, the second Cu(II) of which binds with two iodide ions to the phenolate edge of N,N′-bis(salicylidene)ethylenediaminatocopper(II). A pulse radiolytic study in acetonitrile showed that the intramolecular electron transfer from the viologen radical to the Cu(II)O2I2 site occurred along with an intermolecular electron transfer between the viologen radical and the Cu(II)O2I2 site of the other complexes existing in excess; also, the number of the methylene groups (3 and 4) little affected the intra- and intermolecular electron-transfer rate. A trinuclear copper(II) Schiff base complex linked to viologen via number 5 of methylene groups was also synthesized and characterized.
Sesquiterpenes from the Rhizomes of Ligularia dentata Hara
Authors: Naya Keizo , Okayama Tohru , Fujiwara Masaaki , Nakata Makoto , Ohtsuka Tsutomu , Kurio Seiko
Published: July 2006

From the rhizomes of Ligularia dentata Hara two new compounds, a phenolic norsesquiterpene ligudentatol (2), and a eudesmanoid ligucyperonol (6), have been isolated in addition to the known caryophillene (1) and additional three phenolic norsesquiterpenes (3, 4, and 5). The structures and stereochemistries of 2 and 6 have been established by a combination of spectroscopic and chemical methods, and by correlation with known ligujapone (4) and (+)-α-cyperone (11), respectively.
2-(Trifluoroacetyloxy)pyridine as a Mild Trifluoroacetylating Reagent of Amines and Alcohols
Authors: Keumi Takashi , Shimada Masakazu , Morita Toshio , Kitajima Hidehiko
Published: July 2006

A new trifluoroacetylating reagent, 2-(trifluoroacetyloxy)pyridine (TFAP), was prepared by the reaction of 2-pyridinol and trifluoroacetic anhydride. TFAP has been found to be effective in the trifluoroacetylation of aliphatic and aromatic amines and alcohols including phenol under mild conditions. The reaction of p-nitrophenol with TFAP in ether gave the hydrogen-bonded complex between the phenol and 2-pyridone. This reagent has also been shown to be useful for the intramolecular dehydration of aldehyde oximes and amides to give nitriles in high yields.
High-Pressure Cycloaddition of Tropones to Ethoxyethene. An Occurrence of [4+2] and [8+2] Cycloadditions
Authors: Mori Akira , Li Zhi-Hong , Takeshita Hitoshi
Published: July 2006

Although thermal cycloaddition of tropone to ethoxyethene under ordinary pressure conditions is synthetically impractical, the reaction was greatly improved under 10000 bar to give six products with 95% conversion (1 bar=105 Pa): the major products obtained in 66% yield were 9α- and 9β-ethoxybicyclo[3.2.2]nona-3,6-dien-2-ones, Diels–Alder adducts, which were accompanied by other two 8-ethoxy derivatives and two [8+2] cycloadducts. 2-Methoxy- and 2-chlorotropones similarly gave better results under high-pressure conditions. The 13CNMR spectra of these Diels–Alder adducts provided useful information regarding structure elucidations.
Synthetic Photochemistry LV. Characterization of the Lumiketone- Type Photoproducts, Bicyclo[3.2.0]hept-3-en-2-ones, from 2,6-Cycloheptadien-1-ones
Authors: Mori Akira , Kubota Tadahiko , Ikeda Yukari , Takeshita Hitoshi
Published: July 2006

Unlike the parent 2,6-cycloheptadien-1-one, the UV-light irradiation of polysubstituted 2,6-cycloheptadien-1-ones gave bicyclo[3.2.0]hept-3-en-2-ones, lumiketone-like products, which subsequently photoisomerized to bicyclo[2.2.1]hept-2-en-7-ones. The reaction of cycloheptadienones to lumiketones was proven to proceed via a triplet excited state from both sensitization and quenching experiments.
Synthesis and Characterization of Co(III) Complexes with 1,4,7,10-Tetraazacyclotetradecane, -pentadecane, and -hexadecane
Authors: Tsuchimoto Masanobu , Kita Masakazu , Nonoyama Matsuo , Fujita Junnosuke
Published: July 2006

New cobalt(III)-1,4,7,10-tetraazacyclotetradecane (N47), -pentadecane (N48), and -hexadecane (N49) complexes, trans-[CoCl2(N4x)]+ (x=7 (two isomers), 8 (two isomers), 9 (one isomer)), trans-[Co(NO2)2(N4x)]+ (x=7, 8, 9, one isomer), cis-[Co(NO2)2(N47)]+ (one isomer), and [Co(en)(N4x)]3+ (x=7, 8, one isomer) were synthesized and characterized. For analogous 1,4,7,10-tetraazacycloundecane (N46) complexes, two isomers for each of cis-[Co(NO2)2(N46)]+ and [Co(en)(N46)]3+ were also obtained and were found to isomerize to each other in acetonitrile. The ligand field parameters of nitrogen Δ(N) and chlorine Δ(Cl) estimated from the observed ligand field bands of trans-[CoCl2(N4x)]+ show a correlation between them; with an increase in ring size of N4x, the Δ(N) value decreases, while the Δ(Cl) value increases. The reduction potentials for each series of the dichloro, dinitro, and en complexes become less negative with an increase in ring size of N4x.
Preparation of Graphite Single-Crystal from an Iron Solution by a Temperature-Gradient Method
Authors: Sumiyoshi Yoshihiro , Ushio Masumi , Suzuki Sadao
Published: July 2006

A graphite single-crystal with maximum dimensions of 30 mm in diameter and 0.24 mm thick was prepared from an iron solution by a temperature-gradient method. A flux of 300–500 g of electrolytical iron, 10 g of graphite powder and silicon powder of 0–5 g for the flux weight were charged in a graphite crucible. Large and thickened graphite single-crystal films of good quality were prepared at 2100°C by repeating 4 times the heating and cooling processes. The cell parameters of the graphite single-crystal film were ao=2.463±0.003 and co=6.708±0.001 Å. The optimum amount of silicon additive was 1 wt% for the flux weight. In order to increase the thickness along the c-axis of graphite single-crystal films, the number of heating and cooling processes should be increased.