bluuebunny/crossref_metadata_2025 huggingface dataset:
The Synthesis of C-Methyl Branched-Chain Deoxy Sugar Nucleosides by the Deoxygenative Methylation of O-Tosylated Adenosines with Grignard Reagents
Authors: Kawana Masajiro , Takeuchi Kikuko , Ohba Takayo , Kuzuhara Hiroyoshi
Published: July 2006

The reaction of appropriately protected 2′-O-tosyladenosines with methylmagnesium bromide (or iodide) gave 9-(2-deoxy-3-C-methyl-β-d-threo-pentofuranosyl)adenine after deprotection. The same reaction on 3′-O-tosyladenosine derivatives afforded an epimeric pair of 2′-C-methyl-3′-deoxy sugar nucleosides. The modified structures of the sugar moieties were determined unambiguously.
Studies on Lignan Lactone Antitumor Agents. V. 1-O-(Aminoethyl) Ether of 4′-O-Demethyl-1-epipodophyllotoxin
Authors: Saito Hitoshi , Nishimura Yoshio , Kondo Shinichi , Komuro Keiko , Takeuchi Tomio
Published: July 2006

1-O-(2-Aminoethyl)-4′-O-demethyl-1-epipodophyllotoxin derivatives were synthesized by a stereoselective BF3-catalyzed coupling of 4′-O-benzyloxycarbonyl-1-epipodophyllotoxin with the corresponding 2-aminoethanol derivatives, and with ethylene glycol followed by reductive amination of its aldehyde. Some 1-O-(2-aminoethyl) ethers of 4′-O-demethyl-1-epipodophyllotoxin prolonged markedly survival periods in mice with leukemia L-1210.
Addition of Diphenyldiazomethane to Unsubstituted and Chloro-Substituted 1,4-Benzoquinones. Effects of Chloro Substituents on the Addition Modes
Authors: Oshima Takumi , Nagai Toshikazu
Published: July 2006

Unsubstituted 1,4-benzoquinone (1a) reacted with diphenyldiazomethane (DDM) at the C=C double bonds to give dihydroxy-3H-indazole (2a) and its benzhydryl ether (3a) together with benzodipyrazole derivative (4a). Similarly, reactions of 2-chloro- and 2,3-dichloro-1,4-benzoquinones (1b and 1c) with DDM yielded the corresponding dihydroxy-3H-indazoles (2b, 2b′, and 2c) and their benzhydryl ethers (3b, 3b′, and 3c) along with 5–13% benzophenone (6). On the other hand, reaction of 2,6-dichloro-1,4-benzoquinone (1e) with DDM gave bicyclic 5e and tricyclic diones (7e), together with benzophenone dimethyl acetal (9) in the presence of added methanol. In the same conditions, 2,3,5-trichloro-1,4-benzoquinone (1f) provided bicyclic dione (5f) and 9. Formation of 6 and 9 was interpreted as arising from the hydrolysis and methanolysis of the 1:1 betaine intermediates given by the addition of DDM to the quinonoid C=O double bonds. The C=O addition increased with increasing chlorine substituents.
Stereoselective Syntheses of 1,3,5-Trihydroxy-2,4-dimethylpentane Equivalents from Methyl α-Mannopyranosides
Authors: Tatsuta Kuniaki , Koguchi Yoshihito , Kase Motohiro
Published: July 2006

The optically active 1,3,5-trihydroxy-2,4-dimethylpentane equivalents: methyl 2,4-dideoxy-2,4-di-C-methyl-α-d-ido- and talopyranosides and their enantiomers, which should be suitable for the syntheses of propionate-derived natural products, were stereo- and regioselectively prepared from methyl α-d- and l-mannopyranosides through the reactions of the 3,4-anhydro-2-O-mesyl- and 3,4-anhydro-2-C-methylaltropyranoside derivatives with methylmagnesium bromide and methylmagnesium chloride.
Synthesis and Reactions of 2-Arylhydrazinotropones. I. Preparation of 2-(2-Arylhydrazino)tropones and the 4-Substituted Derivatives
Authors: Nozoe Tetsuo , Imafuku Kimiaki , Yin Bing-Zhu , Honda Masaaki , Goto Yasutomo , Hara Yasushi , Andoh Takayoshi , Yamamoto Hiroshi
Published: July 2006

A wide variety of 2-(2-arylhydrazino)tropones were prepared by the reactions of 2-tosyloxytropone with arylhydrazines. The dimeric compounds 6,6′-bis(arylhydrazono)-1,1′-bi(2,4-cycloheptadiene)-7,7′-diones, 2-anilinotropones, and 3-(2-arylhydrazino)tropones were isolated as minor products in some cases. Similarly, starting with 2-tosyloxytropones bearing an isopropyl, isopropenyl, (1-acetamidoethyl), and protected acetyl group at the 5-position, 4-substituted 2-(2-arylhydrazino)tropones were obtained as the major products by the abnormal substitution reaction. These 2-(2-arylhydrazino)tropones are expected to effectively serve as precursors for a convenient synthesis of 5-aryl-substituted tropolones via benzidine-type rearrangement. 1H NMR (200 or 500-MHz) parameters for these 4-substituted 2-(2-arylhydrazino)tropones are given for their unambiguous structural assignments.
Synthesis of C3 and C4 Paraffins from Synthesis Gas with Hybrid Catalyst
Authors: Fujimoto Kaoru , Saima Hitoshi , Tominaga Hiro-o
Published: July 2006

Hybrid catalysts composed of the physical mixture of methanol synthesis catalysts and Y-type zeolites gave C3 and C4 paraffins from synthesis gas at 2.1 MPa, with a selectivity higher than 70%. The product contained small methane and little aromatic hydrocarbons. The hydrid catalyst kept its activity and selectivity at almost constant level for 50 h. The yield of hydrocarbon was much higher than the level estimated from the thermodynamic equilibrium of methanol formation from synthesis gas. The yield of hydrocarbon increased monotonically with the increase in temperature while the carbon number distribution of the product shifted to lower side between 523 and 623 K. The production of hydrocarbon was accompanied by the nearly equal amount of CO2.
Solid-State 2H NMR Study of Discotic Benzenehexayl Hexaheptanoate. Conformational Transition of Alkyl Side Chains
Authors: Toriumi Hirokazu , Shimmura Toru , Watanabe Hiroshi , Saitô Hazime
Published: July 2006

A 2H NMR study of discotic benzenehexayl hexaheptanoate carrying perdeuterated alkyl side chains (BH7-d78) is reported. Solid-state 2H NMR measurements reveal that the conformational transition of the heptanoate chains takes place at 230 K from nearly static to mobile state. The chains above 230 K undergo flip-flop type reorientational motion, with the degree increasing upon heating. This temperature coincides with the solid-to-solid phase transition temperature, indicating that the phase transition takes place accompanied by the conformational melting of the flexible alkyl side chains. A spectrum measured in the discotic mesophase is also reported.
Conductance Study of Alkali Metal Chlorides and Ammonium Chloride in 1,2-Dimethoxyethane–Water Mixtures at 25 °C
Authors: Prabhu P V S S , Ramanamurti M V
Published: July 2006

Conductance data for alkali metal chlorides and ammonium chloride in 1,2-dimethoxyethane (DME)–water mixtures (14.00<dielectric constant<56.76) at 25 °C are reported in the concentration range 0.0001–0.06 mol·dm−3. The data have been analyzed by Fuoss (1978) conductance–concentration relation. Preferential solvation of cations by water does not show systematic trend depending on the cationic size. Walden product variations indicated the complex dependence of conductance of alkali metal cations on solvent sorting and structural effects. The energy (Es) values suggest that alkali metal cations and chloride ions in majority exist as contact pairs in these solutions.
Atomization Enthalpies of Aliphatic Compounds with Alternately Adjacent Carbonyl Groups and Nitrogen Atoms
Authors: Sakiyama Minoru , Kuriyama Nobuhiro , Imamura Akira , Murata Shigeo
Published: July 2006

Hückel MO calculations were made for the title compounds using Hess–Schaad heteroatom parameters. The bond-contribution values were determined for the total π-bonding energies of the acyclic compounds. No resonance stabilization is present for molecules with six-, eight-, and ten-membered rings composed of CO–N linkages. Graph-theoretical calculations gave a similar result. Atomization enthalpies were calculated from the available thermochemical data and analyzed within the framework of the Hess–Schaad theory. The destabilization energies of normal alkanamides and N,N-dimethylformamide are close to zero. Diacetamide is not destabilized, while N-butyldiacetamide and triacetamide showed small destabilization energies. Trimethyl isocyanurate is not significantly strained. The total strengths of the CO–N bonds are in this order: amide>(urea and diacetamide)>internal bond of acetylurea.
Roles of Kinetic and Potential Energies in Conjugation. I. A Study of Prototypes
Authors: Ichikawa Hiroshi , Ebisawa Yukiko , Sameshima Keiichiro
Published: July 2006

The analysis of the potential and kinetic energy changes between conjugative and nonconjugative structure in vinylamine and nitroethene led to the conclusion that there were two different types of conjugations: the conjugative stability caused by a decrease in the kinetic energy and that given by a decrease in the potential energy. Those two types could be termed conjugations of kinetic energy origin and potential energy origin respectively. The cojugative stability in vinylamine is produced by an excess decrease in the kinetic energy over the increase in the potential energy (kinetic energy origin), which was attributed to a release of the kinetic energy pressure of the lone pair of electrons on nitrogen. On the other hand, the conjugation of nitroethene causes an overwhelming decrease in the potential energy, especially in that belonging to the nitro group (potential energy origin).
The CO–H2 Reaction over ZrO2 to Form Isobutene Selectively
Authors: Maruya Ken-ichi , Maehashi Tatsuichi , Haraoka Takashi , Narui Shinichiro , Asakawa Yukihiko , Domen Kazunari , Onishi Takaharu
Published: July 2006

The CO–H2 reaction over ZrO2 was studied in detail. Methanol and isobutene were selectively formed at 473–523 and 623–673 K, respectively. The activation energies for C2, C3, and linear C4 hydrocarbon formation are 79, 84, and 96 kJ mol−1 (523–723 K), while that for branched-chain C4 hydrocarbons is about 210 kJ mol−1 (523–623 K). At 673 K the rate of C4 hydrocarbon formation is as follows: r=kPH2·Pco2, while those of C1, C2, and C3 are written by the functions having the maximum values regarding CO pressure. C4 hydrocarbons consist mostly of isobutene at the temperature. From these results it was concluded that isobutene is formed via different path from those of C1, C2, C3, and linear C4 hydrocarbons. The addition of high electronegative oxides such as SiO2 and Nb2O5 resulted in the decrease of isobutene and the increase of methane. The selective formation of isobutene proceeds over pure ZrO2 and ZrO2 modified with 3a Group and basic metal oxides. The nature of active site for isobutene formation was discussed.
Spectrophotometric Study of Complexation Equilibria between Lanthanoids(III) and 2-(5-Bromo-2-pyridylazo)-5-(N-propyl-3-sulfopropylamino)phenol
Authors: Ohyoshi Emiko
Published: July 2006

Complex formation (1:1) between lanthanoids(III) and 2-(5-bromo-2-pyridylazo)-5-(N-propyl-3-sulfopropylamino)phenol (5-Br-PAPS, HL) has been studied by spectrophotometry at 25 °C and at I=0.1 (NaNO3). The protonated complex MHL is found to exist in equilibrium with the normal complex ML at pH 5–6. The formation constants KML and KMHL are obtained by a graphical analysis. The KML values uniformly increase with increasing atomic number except for those in the Gd–Ho region where a distinct decrease is observed. However, there is little variation in the KMHL values with atomic number. A linear relation holds well between log KML values of 5-Br-PAPS and 4-(2-pyridylazo)resorcinol (PAR) complexes for the elements up to Eu(III), the intercept of which reflects the difference in the basicity of the oxygen atom ortho to the azo group between the two ligands. This is not the case for log KMHL of the two systems.
Dynamic NMR as a Nondestructive Method for the Determination of Rates of Dissociation. XII. Dissociation of the Olefin in trans-Dichloro(4-methyl-1-pentene)(4-substituted pyridine 1-oxide)platinum(II) Complexes
Authors: Toyota Shinji , Oki Michinori
Published: July 2006

The rates of dissociation of the olefin in the title compounds were determined by the dynamic NMR technique by taking advantage of the line shape change due to the isopropyl-methyl protons. The rates of dissociation were independent of concentration in bromoform-d solutions. The free energy of activation was between 17.0 and 19.1 kcal mol−1 at 353 K for the compounds, of which line shapes were fully analyzed, depending upon the substituent in the pyridine ring and electron-withdrawing substituents giving low activation energy. The solvent effect was noticed on the dissociation rates: Aromatic hydrocarbons give higher rates of dissociation than halogenated hydrocarbons. Although solvents of strong affinity toward platinum(II) tend to decompose the complex, tetrahydrofuran-d8 was found to give definitely higher rates of dissociation of the olefin in trans-dichloro(4-methoxycarbonylpyridine 1-oxide)(3-methyl-1-butene)platinum(II) than bromoform-d, when it was used as a solvent. The mechanism of dissociation was discussed from the available data.
Friedel–Crafts Acetylations of Methoxy-4H-cyclopenta[def]phenanthrenes and the 4-Ketones
Authors: Minabe Masahiro , Yoshida Masaaki , Takabayashi Yutaka , Masuda Masatoshi
Published: July 2006

Acetylations of 2- and 3-methoxy-4H-cyclopenta[def]phenanthrene gave predominantly the 1- and 8-acetyl derivatives, respectively. The acetylation of the 1-methoxy compound afforded the 2-, 3-, 5-, 7-, and 8-yl ketones and the reaction of the 8-methoxy derivative yielded the 1- and 3-acetyl derivatives. Similar reactions of 1-, 2-, 3-, and 8-methoxy-4H-cyclopenta[def]phenanthren-4-one occurred mainly at the 2-, 1-, 8-, and 9-positions, respectively.
Surface States of Titania(Rutile and Anatase)-Supported Vanadium Oxide Catalysts as Prepared by a Column-Exchange Adsorption Method and Their Catalytic Features
Authors: Kera Yoshiya , Inoue Takashi , Matsukaze Yoshihiro
Published: July 2006

Monolayer or less monolayer vanadium oxide catalysts supported on TiO2(rutile and anatase), V2O5/R-and A-TiO2, were prepared by a “column-exchange adsorption” method such as passing an oxovanadium ion solution, the pH of which was adjusted at 2, 4, and 7, through a column packed with titania (TiO2) for impregnation. V2O5/R-TiO2 pretreated at 450 °C showed an ESR spectrum with an unresoluved hfs for V(IV) ions at 77 K without depending upon the pH upon impregnation. V2O5/A-TiO2 petreated at room temperature showed quite small ESR signals due to Ti(III) and V(IV) ions. These signals tended to be intensive with increasing pH upon impregnation. After a heat treatment at 400 °C a huge and quite broad spectrum, which was ascribed to some reduced vanadia species(V2O5−δ), appeared in addition to the spectra for the Ti(III) and V(IV) ions, while such a change was never found in V2O5/R-TiO2. Based on a theoretical treatment for the g-values, V(IV) ions on V2O5/R-TiO2 have been confirmed to be replaced just into Ti ion sites on rutile(almost D2h symmetry). With V2O5/A-TiO2, V(IV) ions were shown to be placed so as to be partially subject to an anatase surface field(almost D2d symmetry); that is, to be placed only near the vacant Ti ion site on anatase. From a comparison of the hf-coupling constant the vanadia species on rutile was clearly shown to interact more strongly with the surface than that on anatase. The 2-propanol decomposition rates over the catalysts were measured in the temperature range 270–350 °C as a test reaction. The activity of V2O5/R-TiO2 was generally higher than that of V2O5/A-TiO2. The lowest activation energy was obtained upon the impregnation at pH=2 for V2O5/R-TiO2 and at pH=7 for V2O5/A-TiO2. The best catalyst was not necessarily prepared through conditions with pH=4, which had been suggested as giving an effective monolayer-vanadia species.
A Behavior of Donnan Salt within Membrane
Authors: Yamauchi Akira , Date Masashi , Yamamoto Yukiko , Hirata Yutaka , Kimizuka Hideo
Published: July 2006

In an amphoteric ion exchange membrane-electrolyte system, three independent experiments were carried out, that is, the membrane potential, membrane conductance and concentration of ions within membrane were measured, respectively. The electrolytes adopted in the systems were NaCl, CaCl2, LaCl3. From the analysis of the results, the specific conductance attributed to Donnan salt within membrane was separated. As a result, it was pointed out that the dynamic state of Donnan salt is obviously different from that of salt in aqueous solution. Furthermore, the comparison between the ions constituting Donnan salt and the counterions which interact with the ion-exchange sites suggested us the existance of two different dynamic states on the ions within membrane.
Reactions of Coordination Compounds in the Solid State. II. The Interconversion of the Isomers of Dichloro(triethylenetetramine)cobalt(III) Chloride, [Co(trien)Cl2]Cl, upon Heating in the Solid State
Authors: Fujiwara Terufumi , Bailar John C
Published: July 2006

The three isomers of the ion [Co(trien)Cl2]+, where trien=triethylenetetramine, have been synthesized and their interconversion upon heating in the solid state has been studied. The trans isomer changes to the β-cis isomer, which in turn is converted to the α-cis isomer. The changes have been followed by proton NMR spectroscopy. The first change cannot be explained by a twist mechanism. Experiments with the trans monohydrate or hydrochloride in sealed tubes or in an atmosphere of HCl show that the presence of H2O accelerates the conversion of the trans isomer to the cis-β isomer, and the presence of HCl accelerates the conversion of cis-β to cis-α, suggesting that the former conversion takes place through an aquation, followed by anation and for the latter conversion nucleophilic attack of a chloride ion on the cis-β isomer is important.
Synthesis and Reactions of Selenoketones
Authors: Ishii Akihiko , Okazaki Renji , Inamoto Naoki
Published: July 2006

A new, convenient method for the synthesis of selenoketones has been reported. The reaction of dimagnesium salts of ketone hydrazones with diselenium dichloride affords an intermediate tentatively assigned as tetraselenides, which are converted into selenoketones by heating in the presence of tributylamine. A comparative study on the reactions of 1,1,3,3-tetramethyl-2-indanselone and the corresponding thioketone with Grignard and organolithium reagents have been carried out. Analysis of the reaction products has revealed that the heterophilic attack of the organometallic reagents is much more significant in the reaction with the selone than with the thione.
The Fries Rearrangement of 4H-Cyclopenta[def]phenanthrenyl Acetate
Authors: Minabe Masahiro , Yoshida Masaaki , Amimoto Tsukasa , Nagata Toshihiro , Kobori Masamichi
Published: July 2006

A Fries rearrangement of 4H-cyclopenta[def]phenanthren-1-yl acetate gave 2- and 7-acetyl derivatives. The reaction of isomeric 2-acetoxy compound afforded 1- and 7-acetyl derivatives. The acetyl group of the 3- and 8-acetoxy compounds rearranged into the 2- and 9-positions, respectively. In addition, 1-, 2-, 3-, 4-isopropyl compounds were derived from the corresponding acetyl derivatives.
Racemic Structure and Optical Resolution by Preferential Crystallization of (±)-Organic Ammonium Hydrogen Malates
Authors: Shiraiwa Tadashi , Sado Yujin , Inoue Mitsuo , Sakamoto Keiji , Miyazaki Hideya , Kurokawa Hidemoto
Published: July 2006

Gibbs energies of formation of racemate, binary melting point diagrams, and ternary solubility diagrams indicate that (±)-propylammonium ((±)-PA salt) and (±)-1,1,3,3-tetramethylbutylammonium ((±)-TMB salt) hydrogen malates are conglomerates at room temperature, whereas (±)-TMB salt forms a racemic compound at its melting point. Free energies of critical nucleation in supersaturated solutions were examined to resolve (±)-PA and -TMB salts efficiently by preferential crystallization. Successive preferential crystallization of (±)-PA salt in methanol at 10 °C and that of (±)-TMB salt in water give (+)- and (−)-PA and -TMB salts with about 90% optical purity. Optically pure (+)- and (−)-malic acids are obtained from purified (−)- and (+)-salts.
Nitrene-Transfer Reaction between Azide and Unsaturated Ether in the Presence of Pd(II) Catalyst
Authors: Migita Toshihiko , Hongoh Kazuya , Naka Hiroyuki , Nakaido Setsuko , Kosugi Masanori
Published: July 2006

Azidoformate reacted with allylic ethers to give 1-alkoxy-1-(alkoxycarbonylimino)alkane under catalysis by PdCl2(PhCN)2. The same imines were formed almost quantitatively by noncatalyzed reaction of the azide with the corresponding vinylic ethers. The rate of the catalyzed reaction was found to be first order each in the allylic ether and in the azide. Easiness of the imine formation from the allylic ethers depended on the nature of azide, decreasing in the order of N3SO2Me>N3CO2Me>N3Ph. Based on these results the most probable mechanism for the catalyzed reaction is proposed.
Crystal and Molecular Structure of (E)-1,1′-Bitetralinylidene
Authors: Ogawa Keiichiro , Suzuki Hiroshi , Futakami Motoko , Yoshimura Shin , Sakurai Tosio , Kobayashi Kimiko , Kira Akira
Published: July 2006

The crystal structure of the title compound was determined by X-ray diffraction. The crystals have monoclinic symmetry with a=13.481(5), b=8.285(5), c=l3.092(3) Å. β=96.24(3)°, and space group P21⁄n with Z=4. The final R-factor was 0.065 for 2191 independent reflections. The torsion angles of the C–Ph bonds are 47.4(4) and 44.4(4)°. The cyclohexene rings have approximate twist-boat conformations. The molecular structure in the crystal is compared with that in the solution phase, that of (E)-stilbenes, and the results of the molecular mechanics calculations. It is also discussed in relation to the molecular packing.
Syntheses and Properties of 2,2′-Binaphtho[1,8-de]-1,3-dithiinylidene and Its Selenium Analog, 2-(1,3-Dithiol-2-ylidene)naphtho[1,8-de]-1,3-dithiin, and 2-(4H-Thiopyran-4-ylidene)naphtho[1,8-de]-1,3-dithiin
Authors: Yui Koji , Aso Yoshio , Otsubo Tetsuo , Ogura Fumio
Published: July 2006

In order to discover new electron donors for conducting charge-transfer complexes, the four title compouds 1–4 composed of two heterocycles have been prepared via 1,8-dichalcogen-bridged naphthalene. The cyclic voltammetery indicates that symmetrical 1 and 2 are poor donors, but unsymmetrical 3 and 4 possess considerable donor abilities. The latter compounds are thus capable of forming some crystalline charge-transfer complexes with strong acceptors such as TCNQ, TCNQF4, and DDQ, which are, however, semi-conducting.
Synthesis, Reactions, Spectral (IR and Visible) and Magnetic Studies of Bimetallic Alkoxides Containing Co(μ-OR)3M(M=Nb or Ta) Bridging Units
Authors: Dubey Raj Kumar , Singh Anirudh , Mehrotra Ram Charan
Published: July 2006

Interactions of CoCl2 with K{M(OPri)6} in 1:2 molar ratio in PriOH and C6H6 result in products with the composition [Co{M(OPri)6}b42] (M=Nb or Ta) in quantitative yields. Interchange reactions of these isopropoxide derivatives with alcohols of varying steric bulk (e.g., MeOH, EtOH, PrnOH, BunOH, and ButOH, or AmtOH) yield derivatives of composition, [Co{M(OR)6}2] (R=Me, Et, Prn, and Bus); [Co{M(OPri)3(OBus)3}2]; [Co{M(OPri)5(OBut)}2] and [Co{M(OPri)2(OR)4}2] (R=But or Amt). All these novel compounds have been characterized by elemental analyses and molecular weight determinations as well as by infrared, visible spectral and magnetic studies.
An Improved Synthesis of Methyl 7-(2-Hydroxy-5-oxo-1-cyclopentenyl)heptanoate
Authors: Naora Hirokazu , Ohnuki Takashi , Nakamura Asao
Published: July 2006

Methyl 7-(2-hydroxy-5-oxo-1-cyclopentenyl)heptanoate, which is a valuable synthon for prostanoids, was prepared in a good yield from dibenzyl malonate via three steps.
Rotational Isomerism in Fluorene Derivatives. XV. Conformational Equilibria of 2-Substituted and 2,7-Disubstituted 9-(2′-Dimethylaminophenyl)fluorene Derivatives and the Effects of Acid on Them
Authors: Nishida Akiko , Takeshita Makoto , Kawano Nobuaki , Fujisaki Shizuo , Kajigaeshi Shoji
Published: July 2006

Several 9-(2′-dimethylaminophenyl)-9-fluorenols (2) and 9-(2′-dimethylaminophenyl)fluorenes (3), which had electron-attracting or electron-releasing groups at 2- or 2,7-positions of the fluorene ring, were synthesized. The conformational equilibria (anti\ightleftarrowssyn) of 2 and 3 in CDCl3 lay near to their syn sides. However, the equilibria of 2 in DMSO-d6 inclined to the anti side. By the addition of trifluoroacetic acid to the solution of 3 in CDCl3, anti-3 salts were formed and stabilized by the N–H···π interaction between the dimethylammonio group and the fluorene ring. In this case, the intensities of the N–H···π interaction were affected by the magnitudes of the π-electron density of the fluorene ring.
Molecular and Electronic Structures of Thieno[3,4-b]thiophene-2-carboxylic Acid and Acetic Thieno[3,4-b]thiophene-2-carboxylic Anhydride. An AM1, MNDO, and CNDO/S Study
Authors: Buemi Giuseppe
Published: July 2006

AM1 and MNDO methods have been used for optimizing the molecular geometry of all the possible conformations of thieno[3,4-b]thiophene-2-carboxylic acid (1), of its methyl ester (2) and of acetic thieno[3,4-b]thiophene-2-carboxylic anhydride (3). Both methods give comparable results for the thieno[3,4-b]thiophene framework but rather different bond angles for the substituent group of 3. In any case, an equilibrium between two (1,2) or more (3) conformations is conceivable. Although the most stable conformations are predicted to be planar, the rotation of the substituent group implies only low energy increase (rotation barriers are calculated to be about 2 kcal mol−1) which allows wide oscillations. The π→π* electronic transitions do not differ appreciably from those of the parent thieno[3,4-b]thiophene molecule and are better accounted for by the conformations having remarkable rotation around the C7–C9 bond.
Photocycloadditions of Cyclodienes to Hexafluorobenzene
Authors: Šket Boris , Zupancic Nataša , Zupan Marko
Published: July 2006

The stereochemistry of photocycloaddition reactions of various cyclodienes to hexafluorobenzene in cyclohexane solution depends on the structure of the cyclodiene and [2+2]cycloadducts are mainly observed. Photoreaction of 1,5-cyclooctadiene with hexafluorobenzene gives nearly equal amounts of syn and anti[2+2]adducts, which are further transformed to tetracyclic systems, contrary to this, the stereochemistry observed by reactions with 1,4-cyclohexadiene depends on the molar ratio of cyclodiene–hexafluorobenzene and 30–54% of syn addition is observed, the syn adduct, however, being further transformed to 2,3,4,5,6,7-hexafluoropentacyclo[6.4.0.02,7.03,11.06,10]dodec-4-ene. Syn selectivity of [2+2]cycloaddition was enhanced when bicyclic dienes were used and it is interesting that in the case of norbornadiene and benzonorbornadiene only exo attack was observed, and no anti attack occurred in the case of benzonorbornene. The quantum yields of [2+2]photocycloaddition reactions depend on the structure of the cyclodiene and the concentrations of hexafluorobenzene and cyclodiene. The quantum yields for norbornadiene and 1,4-cyclohexadiene are nearly the same, while it is two times higher in a photoreaction with 1,5-cyclooctadiene, when equal amounts of hexafluorobenzene and 1,5-cyclooctadiene were irradiated in cyclohexane at λ=253.7 nm.
An Investigation into the Mechanism of Acid-Catalyzed Hydrolysis of N-Benzylbenzohydroxamic Acid
Authors: Ghosh Kallol K , Tandon Shiv G
Published: July 2006

The catalytic effects of hydrochloric, perchloric, and sulfuric acids on the hydrolysis of N-benzylbenzohydroxamic acid (BBHA) have been examined in 10% (v/v) dioxane–water at 55 °C. Plots of the pseudo-first-order rate constants kψ against [H+] show maxima which arise from extensive protonation of the substrate. Analyses of the kinetic data by Bunnett and Bunnett–Olsen criteria, solvent deuterium isotope effects, salt effects and entropies of activation are consistent with a bimolecular mechanism.
A Synthesis of (+)-Cyclaradine, Carbocyclic Analogue of 9-β-d-Arabinofuranosyladenine
Authors: Tadano Kin-ichi , Kimura Hiroshi , Ogawa Seiichiro
Published: July 2006

The title compound, a promising antiviral carbocyclic nucleoside analogue, was synthesized enantiospecifically. The present synthesis involves a coupling reaction of 5-amino-4,6-dichloropyrimidine and (1R,2R,3R,4R)-2,3-dihydroxy-4-(hydroxymethyl)cyclopentanamine which was in turn prepared from d-xylose.
Effects of Some Variables on the Point of Zero Charge of TiO2–ZrO2 Double Oxides
Authors: Karmakar Basudeb , Ganguli Dibyendu
Published: July 2006

Effects of variables such as acid/base reaction temperature, presence of impurities, method of oxide powder preparation, and calcination temperature on the point of zero charge (p.z.c) were investigated for TiO2–ZrO2 (79.41–20.59, wt.%) mixed oxides. The visually determined p.z.c. values were also compared with those arrived at by a computational method to obtain an estimate of the error of determination.
Fe(III)-Catalyzed Aromatic Hydroxylation with H2O2 in the Presence of a Variety of Electron-Transfer Agents
Authors: Tamagaki Seizo , Sasaki Masaaki , Tagaki Waichiro
Published: July 2006

Electron-transfer agents such as N,N,N′,N′-tetramethylphenylenediamine (TMPD), ferrocenes, and phenothiazines have been found to mediate the hydroxylation of benzene with H2O2 in the presence of Fe3+. Of these, TMPD catalyst is the most effective to provide phenol in 80% or better yield based on added H2O2 under the optimized conditions. A general mechanism, involving the rate-determining reduction of Fe3+ to Fe2+ with such mediators, is suggested.
Novel Effects of K-Addition to Ru/SiO2 on Conversion of Cyclohexane
Authors: Lin Zheng-Zhong , Enomoto Toshiyuki , Okuhara Toshio , Misono Makoto
Published: July 2006

The effects of the addition of alkalis to a Ru/SiO2 catalyst upon the conversion (hydrogenolysis and dehydrogenation) of cyclohexane, hydrogenolysis of butane, and hydrogenations of benzene and CO were studied. The addition of K or Cs slightly enhanced the catalytic activity for the hydrogenolysis of cyclohexane, whereas dehydrogenation to benzene was markedly suppressed. This result is contrary to the effect of the addition of Cu or Au to group-VIII metals, as reported in the literature. Changes in the activities became less significant as the atomic number of the added alkali decreased. From a systematic examination by varying the alkali content, it was revealed that dehydrogenation and CO hydrogenation were very sensitively suppressed by an electronic effect imposed by the alkalis, whereas changes in the activities of hydrogenolysis and benzene hydrogenation were not great.
Solvent Extraction of Indium with 3-Hydroxy-2-methyl-1-phenyl-4-pyridone
Authors: Ishii Hajime , Numao Shinji , Odashima Tsugikatsu
Published: July 2006

Extraction behavior of indium has been investigated with 3-hydroxy-2-methyl-1-phenyl-4-pyridone (HMPP) at 25±0.1 °C and an ionic strength of 0.2. The values of the proton-dissociation constants, pKa1 and pKa2, of HMPP were determined spectrophotometrically to be 3.02 and 9.56. The value of the partition coefficient, logKD, of HMPP between 1,2-dichloroethane and water was determined to be 1.35. Indium(III) was extracted into 1,2-dichloroethane by forming a 1 : 3 (metal : ligand) complex with HMPP. The extraction constant, Kex, the overall formation constant, β3, and the distribution constant, KDC, of the indium(III)–HMPP complex were determined, their values being as follows: logKex=2.16, logβ3=32.63, and logKDC=2.26.
Nonstabilized Azomethine Ylides Generated by Decarboxylative Condensation of α-Amino Acids. Structural Variation, Reactivity, and Stereoselectivity
Authors: Kanemasa Shuji , Sakamoto Kazushige , Tsuge Otohiko
Published: July 2006

A variety of aldehydes, containing enolizable aldehydes other than acetaldehyde can be used in the generation method of nonstabilized azomethine ylides by decarboxylative condensation of α-amino acids. Reactivity of the nonstabilized ylides was examined in intermolecular and intramolecular cycloadditions with olefins; stereoselectivity of the intramolecular cycloaddition using nonstabilized ylides was compared with that of ester-stabilized ylides.
Photolysis of Alcohols and Alkanones in Acetone Solutions. Photochemical [2+2]Cycloaddition Reaction between Acetone and Aliphatic Enols
Authors: Shimizu Nobujiro , Miyahara Toru , Mishima Masaaki , Tsuno Yuho
Published: July 2006

Transient enols including those of acetaldehyde, acetone, cyclopentanone, 3-pentanone, 2,4-dimethyl-3-pentanone, 2-butanone, and 2-methyl-3-pentanone were trapped photochemically with acetone via a [2+2]cycloaddition and isolated as corresponding 3-oxetanols in reasonable yields in the photolysis of six different secondary alcohols and two alkanones, 3-octanone and hexanal, in acetone solutions. The trapping experiments indicated the photodehydrogenation of unsymmetrical alcohols, 2-butanol and 2-methyl-3-pentanol, in acetone to be highly regioselective in preference for the formation of the less alkylated enol.
One-Pot Synthesis of Tetrahydrofuran Derivatives from Allylic Alcohols and Vinyl Ethers by Means of Palladium(II) Acetate
Authors: Fugami Keigo , Oshima Koichiro , Utimoto Kiitiro
Published: July 2006

Reaction of allylic alcohol with vinyl ether in the presence of Pd(OAc)2 afforded furan derivatives in good yield. Pd(OAc)2 was essential for the reaction. PdCl2 complex did not afford cyclized product but gave acetal exclusively. Three components were combined at once to produce 4-(3-butenyl)-2-butoxy-4-methyltetrahydrofuran upon treatment of a mixture of 2-methyl-2-propen-1-ol, butyl vinyl ether, and allyl bromide. The reaction could successfully be extended to the synthesis of nitrogen containing heterocycles by use of N-tosyl allylic amines in place of allylic alcohols.
Synthesis of Hydroxy Ketones by Chemoselective Alkylation of Keto Aldehydes with Dialkylzincs Catalyzed by Amino Alcohol, Diamine, or Dilithium Salt of Piperazine
Authors: Soai Kenso , Watanabe Masami , Koyano Masashi
Published: July 2006

Hydroxy ketones were obtained in high yields by the chemoselective alkylation of formyl group of keto aldehydes with dialkylzincs in the presence of such catalysts as 2-dimethylaminoethanol, N,N,N′,N′-tetramethylethylenediamine, or dilithium salt of piperazine.
Electronic Control of Stereoselectivity in the Metal Hydride Reductions of a Series of Substituted 3,4-Dihydro-1,4-ethanonaphthalen-2(1H)-ones
Authors: Okada Keiji , Tomita Seiji , Oda Masaji
Published: July 2006

The anti/syn stereoselectivity in the metal hydride reductions of a series of substituted 3,4-dihydro-1,4-ethanonaphthalen-2(1H)-ones was studied. The observed steroselectivity sequence was found to be parallel with the homoconjugation sequence except for the case of 5,8-dimethoxy-substituted derivative: the portion of anti attack increases as the benzene ring becomes electron-rich. The results were rationalized by Cieplak’s transition state model or by the nonclassical carboncation model. A special coordinated transition state was considered to explain the results for 5,8-dimethoxy-substituted compound.
ESR Studies on Chain Transfer Reactions: Rate Constants for the Reactions of Model Radicals of Polystyrene Growing Chain Ends with Tetrahalomethanes and Thiophenols
Authors: Kuwae Yoko , Kamachi Mikiharu
Published: July 2006

The absolute rate constants for reactions of the model radicals of the growing chain ends of styrene and methacrylonitrile with tetrahalomethanes and thiophenols were determined by spin-trapping methods using ESR spectroscopy. The model radicals were produced by the photodecomposition of 1,1′-diphenylazoethane and 2,2′-azobisisobutyronitrile. In the case of the styrene model radical, the rate constants for the halogen abstraction reaction from CBr4, CBrCl3, and CCl4 were 1.1×107, 2.0×106, and 1.1×105 M−1s−1, respectively, and increased with increasing electron affinity of tetrahalomethanes. The rate constants for the hydrogen abstraction reaction from thiophenols were of the order 106 M−1s−1, independent of the electron-donating and -accepting properties of the para substituents. In the case of the methacrylonitrile model radical, the rate constants for the halogen abstraction reaction from CBr4 and CBrCl3 were 1.1×105 and 4.5×103 M−1s−1, respectively. The rate constants for the hydrogen abstraction reaction from thiophenols with –CH3, –H, and –Cl substituent in the para position were 4.5×104, 2.7×104, and 1.7×104 M−1s−1, respectively. The rate constants decreased with increasing the electron-withdrawing power of the substituent.
Gel Filtration Chromatographic Study of Micellar Growth of Polyethylene Glycol Dodecyl Ethers
Authors: Funasaki Noriaki , Hada Sakae , Neya Saburo
Published: July 2006

The aggregation properties of polyethylene glycol dodecyl ethers (C12En; n=4, 5, and 8) are investigated with frontal gel (Sephadex G-200 and Sephacryl S-500) filtration chromatography (GFC) at 25 °C. At the trailing boundary of derivative GFC patterns for C12E5, unusual two peaks of micelles appear together with a peak of monomer. These micellar peaks are assigned to two types of micelle, viz., large (Rh=30 nm) and small (Rh=5 nm) micelles. As the C12E5 concentration is increased, the peak height for the large micelle increases more rapidly than that for the small micelle. Analysis of the centroid elution volume data by asymptotic theory reveals that the large micelle is the hexamer of the small micelle. This conclusion is supported by computer simulations of the GFC patterns, based on plate theory. In the derivative pattern of the trailing boundary for C12E8, the micellar peak becomes sharper and shifts to larger elution volume side, with increasing concentration. This pattern is well simulated with the assumption of linear concentration dependence of the micellar elution volume. Micelle size of C12E8 appears to remain constant. For C12E4, which is hydrophobically adsorbed on the gels, huge micelles coexist with a small amount of large micelles (Rh=33 nm).
Adsolubilization Behavior of Dyes Caused by Mixed Surfactant Bilayers Formed on Alumina
Authors: Esumi Kunio , Sakamoto Yuichi , Nagahama Tetsuya , Meguro Kenjiro
Published: July 2006

The adsolubilization of dyes (yellow OB and azobenzene) was performed on mixed bilayers consisting of anionic and nonionic surfactants formed on α-alumina. The adsolubilization capacity of the two dyes increased with the increase in the concentration of the dyes solubilized in the supernatant. The mixed bilayer consisting of anionic hydrocarbon (lithium dodecyl sulfate) and nonionic hydrocarbon surfactants (polyoxyethylene nonylphenyl ether) showed a greater adsolubilization capacity than that consisting of anionic fluorocarbon (lithium perfluorooctanesulfonate) and nonionic hydrocarbon surfactants. Further, the adsolubilization capacity of the dyes was affected by the oxyethylene chain length of the nonionic hydrocarbon surfactant in the mixed bilayer.
Studies on the Electrochemical Behavior of Thiadiazole Derivatives. Electroreduction of 2-Benzoylamino-5-[cyanoarylhydrazonomethyl]-1,3,4-thiadiazoles
Authors: Fahmy H M , Abdel Azzem M , Abdul Wahab M , Abdel Fattah N , Aboutabl M A
Published: July 2006

The electrochemical behavior of some 1,3,4-thiadiazole derivatives substituted at C5 (carbon number five in thiadiazole ring) with a hydrazono group has been studied at a dropping mercury electrode (DME) in different pH values. Controlled potential electrolysis (CPE) in alkaline medium, cyclic voltammetry (CV), ultraviolet spectra (UV) and pKa studies confirmed the proposed mechanism.
Transition Sequences of Oscillatory States of a Model Chemical System Showing Chaotic Oscillations
Authors: Morita Makoto , Iwamoto Kazutoshi , Sen\={o} Manabu
Published: July 2006

The transition sequence from a complex oscillation or a combined complex oscillation to a chaotic oscillation of a three-variable model system of chemical reactions were studied through analyses of the bifurcation diagrams. Period-doubling sequences, discontinuous transitions between two different oscillation states, and intermittency-type pseudo-periodic oscillations were observed. A pseudo-periodic oscillation appears when a combined complex oscillation changes to a new oscillatory state under some transition conditions. By changing the conditions, the discontinuous transition becomes to occur, leading the hysteresis behavior of transition.
A Highly Sensitive Fiber-Optic Immunosensor Using a Metal-Complex Compound as a Chemiluminescent Catalyst
Authors: Hara Tadashi , Tsukagoshi Kazuhiko , Arai Akihiro , Imashiro Yuji
Published: July 2006

A highly sensitive fiber-optic immunosensor using an antibody-immobilized optical fiber was developed and introduced into a chemiluminescence complex catalyst immunoassay (CLCCIA) which had been reported by the authors in a previous paper. After optimization of the experimental conditions, human serum albumin as model protein was determined by both competitive immunoassay and sandwich immunoassay, using the fiber-optic immunosensor. Human serum albumin could be determined in the concentration range 1×10−4–1×10−1 g dm−3 with a lower limit of 400 pg by competitive immunoassay while in the concentration range 1×10−5–1×10−1 g dm−3 with a lower limit of 40 pg by sandwich immunoassay. The new fiber-optic immunosensor developed by the authors can be characterized as follows: 1) Highly sensitive for the determination of a small amount of protein, 2) applicable to a wide concentration range of protein sample, 3) feasible with a microvolume of sample, 4) suitable for automated operation, and 5) excellent regarding safety, cost, and treatment.
Spectral Studies on the Cooperative Binding Mechanism of Evans Blue to Poly(N-vinyl-2-pyrrolidone)
Authors: Maruthamuthu Meenakshi , Subramanian E
Published: July 2006

The binding of Evans Blue (EB) to poly(N-vinyl-2-pyrrolidone) (PVP) was studied at two pH’s 7.2 and 11.2 spectrophotometrically by absorbance change method. At pH 7.2, the absorption spectrum of EB changed unusually on adding PVP and this indicated the formation of two types of spectroscopically distinguishable PVP–EB complexes. At very low [PVP], a weak complex was formed which got converted into a strong complex at high [PVP]. Positive cooperativity was found to be operative in this conversion and in the strong complex at higher [PVP]. Scatchard, Hill, and Schwarz methods were employed to analyze this cooperativity and to determine the binding parameters. The analysis revealed: (i) the binding constants for the weak and strong complexes were of the order of 104 and 105 dm3 mol−1 respectively; (ii) positive cooperativity at higher [PVP] was due to the interaction of neighboring binding sites on different polymer chains. At pH 11.2, only one type of complex was formed with higher affinity. But the binding behavior remained the same as at pH 7.2.
The Catalytic Degradation Reaction of Polypropylene with Silica–Alumina
Authors: Ishihara Yumiko , Nanbu Hidesaburo , Iwata Chiemi , Ikemura Tadashi , Takesue Tomoyuki
Published: July 2006

A detailed analysis was carried out on the catalytic degradation of polypropylene with silica–alumina, using a glass tube reactor (25φ×150 mm) at 180 to 300 °C and a N2 flow rate of 120 ml min−1 over a period of 5 to 120 minutes. The ratio of C/S was from 0.1 to 6.0. The molecular weight of PP decreased slightly at about 160 °C by cationic degradation, but the decrease started at about 200 °C by radical degradation (without catalyst). The main chain of PP was remarkable weakened by the catalytic degradation with silica–alumina. Analysis of degradation products by 13C NMR, FD-MS and variation in chain scission number clearly indicated the catalytic degradation of PP to occur in two stages. The first stage at low temperature is initiated by the addition of a proton released from the catalyst to weak links in the main chain. The second stage at high temperature occurs by attack a low-molecular-weight carbonium ion of the saturated degraded oligomer. These ions are closely involved in the production of irregular structural oligomers and their redegradation.
Mixed-Valence States in TCNQ Salts of 1′,1'″-Dibutyl-, 1′,1'″-Dipentylbiferrocene and Their Mixed Crystals
Authors: Nakashima Satoru , Sano Hirotoshi
Published: July 2006

Mixed-valence states in TCNQ salts of 1′,1'″-dibutyl-, 1′,1'″-dipentylbiferrocene and their mixed crystals were investigated by Mössbauer spectroscopy. It was found that a valence delocalization of the mixed crystals was affected by the host lattice.
Behavior of the Enthalpies of Dissolution and Formation in the System Silver–Indium
Authors: Badawi Walid Ahmad , M. Oun Ahmed
Published: July 2006

The enthalpy of dissolution in the system Ag–In has been measured at 1100 K in the whole range of composition. The behavior of the enthalpy of dissolution points out the existence of the compound Ag3In in the liquid state. The enthalpy of formation in the range of the γ phase has also been determined at 623 and 773 K. The enthalpy of formation is negative. The partial molar enthalpy of formation of silver is negative but increase with the increase of the composition, and that of indium is negative and decreases with increasing composition. The enthalpy of formation depends insignificantly on the temperature. A pronounced temperature dependence of the enthalpy of formation seemed not to be a general property of all metallic alloys as reported earlier.
Infrared and Raman Studies of the [VO(O2)2F]2− Ion
Authors: Nour E M , El-Sayed A B , Sadeek S A
Published: July 2006

The IR and Raman spectra of Cs2 [VO(O2)2F] are recorded. The spectra are interpreted on the basis of Cs symmetry of the [VO(O2)2F]2− ion. The ν(V=O), νs(O–O), and νas(O–O) are assigned at 950, 890, and 875 cm−1, respectively. The calculated values of the force constants fV=O, fO–O, fV–O, fV–O′, and fV–F are 670, 298, 262, 273, and 248 N m−1, respectively. The band assignments and the force constant values are discussed in view of the bonding and structure of the [VO(O2)2F]2− ion.
Perkin–Markovnikov Type Reaction Initiated with Electrogenerated Superoxide Ion
Authors: Ojima Fumihiro , Osa Tetsuo
Published: July 2006

The cyclic condensation of active methylene compounds such as diethyl malonate, dimethyl malonate, ethyl acetoacetate, or acetylacetone and dibromoalkanes such as 1,2-dibromoethane, 1,3-dibromopropane, 1,4-dibromobutane, 1,5-dibromopentane, 1,6-dibromohexane, 1,3-dibromobutane, or 1,4-dibromopentane with electrogenerated superoxide ion was studied electrochemically in N,N-dimethylformamide (DMF) using cyclic voltammetry (CV) and controlled potential macro-electrolysis. The CV shows that electrogenerated superoxide ion reacts with both active methylene compounds and dibromoalkanes in the dissolved oxygen medium. Controlled potential macro-electrolysis of the above components generally yielded cycloalkanes as the main products. In comparison, the chemical method using sodium ethoxide was also carried out. Two reaction mechanisms via the proton abstraction of active methylene compounds with electrogenerated superoxide ion and via the nucleophilic attack of the superoxide ion on dibromoalkanes are presented.