bluuebunny/crossref_metadata_2025_split huggingface dataset:
Highly Selective Adsorption Resins. I. Preparation of Chitosan Derivatives Containing 2-Pyridylmethyl, 2-Thienylmethyl, and 3-(Methylthio)propyl Groups and Their Selective Adsorption of Precious Metals
Authors: Baba Yoshinari , Kawano Yoshinobu , Hirakawa Hiroyuki 
Published: June 2006

Abstract
Crosslinked N-(2-pyridylmethyl)chitosan, N-(2-thienylmethyl)chitosan, and N-[3-(methylthio)propyl]chitosan were newly synthesized. The amino group of the active adsorption site of chitosan was protected by Schiff’s base formation prior to being crosslinked by 2-(chloromethyl)oxirane. The final chitosan derivatives were obtained by reducing the imine moiety of the Schiff’s bases with sodium borohydride. The adsorption behavior of metal ions on the chitosan derivatives was examined from a solution containing hydrochloric acid using a batchwise method. These chitosan derivatives exhibited high selectivities and excellent loading capacities for gold(III), palladium(II), and platinum(IV) over base metals in hydrochloric acid. In order to elucidate the adsorption species of palladium(II) on the chitosan derivatives, the effect of the chloride ion concentration on the distribution ratio in the adsorption of palladium(II) was examined. The adsorption capacities of these chitosan derivatives for palladium(II) were found to be about 2.5—3 times greater than that of the cross-linked original chitosan. The desorption of palladium(II) was performed to an extent of 70% by a single batchwise treatment with aqueous thiourea solution.
Studies of the Hydrous Titanium Oxide Ion Exchanger. VII. Effects of pH at Precipitation on the Isotopic Exchange Rate of Na+ and Cs+ Ions between the Exchanger in the Relevant Ionic Form and Aqueous Solutions
Authors: Kasuga Fuminori , Yamazaki Hiromichi , Inoue Yasushi , Tochiyama Osamu 
Published: June 2006

Abstract
The isotopic exchange rate of Na+ and Cs+ between hydrous titanium(IV) oxide in the relevant ionic form and aqueous solutions was measured radiochemically. Four kinds of exchangers were precipitated at various pH’s: pH 4, 6, 8, and 10. The rate of each alkali metal ion was controlled by the diffusion of the ions in the exchanger particles at any pH of the surrounding solutions. At high pH of the solution, the diffusion of Cs+ in the exchangers precipitated at pH 4 and 6 was faster than that of Na+, but the difference of diffusion coefficients between two ions was negligible in the exchangers precipitated above pH 8. The diffusion coefficient in a particular exchanger decreased with increasing amount of ions taken up on the exchanger, owing to the increase of frequency of the electrostatic interaction between ions and dissociated ion-exchange sites. The difference of diffusion coefficients among exchangers was interpreted in terms of the difference in the microstructure of the exchanger matrix.
Spectroscopic Properties of One-Electron-Reduced Species of Dichloro(phthalocyaninato)antimony(V) Cation
Authors: Isago Hiroaki , Kagaya Yutaka 
Published: June 2006

Abstract
Electrochemical properties of the titled complex in dichloromethane (DCM) solutions have been investigated by cyclic and rotating-disk-electrode voltammetry. Two successive reversible one-electron reduction waves (E1/2 = −0.23 and −0.65 V vs. ferrocene/ferricinium+, respectively) and one irreversible oxidation wave (Epa = 1.32 V) have been observed. These were assigned as phthalocyaninate-ring-centered. Ring-reduced species of the titled complex was generated by both chemical and electrochemical reduction of the complex in DCM solutions and was characterized by electronic absorption (UV; 250—1100 nm), magnetic circular dichroism (MCD; 250—800 nm), and ESR spectroscopy. A quite sharp ESR signal was observed at g = 2.0041 (with a width of 0.5 mT) for the electrochemically-generated species, confirming the formation of monomer but not of dimer. The reduced species showed some prominent bands in its UV spectra, at 328 (B1; π → π*), 382 (LMCT), 553 (n → π*), 599 (π* → π*), and 1059 nm (Q; π → π*). The MCD spectra showed sharp bands at 328 and 599 nm as Faraday C-terms, indicating that the ground state of the reduced species is orbitally degenerated. Thus the phthalocyanine-ring is not significantly Jahn–Teller-distorted and is approximately D4h in symmetry even upon reduction.
Conglomeratic Solid Solutions in trans(N,t-N)-[Co(leucinato)(tren)]I2 and trans(N,t-N)-[Co(norleucinato or norvalinato)(tren)][ClO4]2 [t-N = tertiary amine nitrogen; tren = tris(2-aminoethyl)amine]
Authors: Yamanari Kazuaki , Fuyuhiro Akira 
Published: June 2006

Abstract
Ternary solubility isotherms of trans(N,t-N)-[Co(leu)(tren)]I2, trans(N,t-N)-[Co(n-leu)(tren)][ClO4]2, and trans(N,t-N)-[Co(n-val)(tren)][ClO4]2 [t-N = tertiary amine nitrogen; leu = leucinate(1−), n-leu = norleucinate(1−), n–val = norvalinate(1−), and tren = tris(2-aminoethyl)amine] were determined at 25 °C. Each isotherm consists of two branches of the solubility curve and one eutectic point; the tie lines do not converge to any apex of the pure enantiomers, but diverge widely. These facts mean that the three complexes simultaneously form a conglomerate and a solid solution. X-Ray crystal analyses were carried out for crystals grown from the three racemic aqueous solutions. All of the crystals were isomorphous to each other in spite of having different amino acidates and counter ions. The crystal structures clearly demonstrated the coexistence of d-amino acidate and l-amino acidate at one site of the crystal lattice, that is, a solid solution. Furthermore, all of the crystals were partially optically active: d : l = 63 : 37 for leu complex (space group P32), d : l = 32 : 68 for n-leu one (P31), and d : l = 44 : 56% for n-val one (P31). Head-to-tail hydrogen bonding contacts, which form spiral chains along the c-axis, were commonly found for these complexes.
The Influence of Protecting Groups on the β-Sheet-Structure Stability of Protected Peptides
Authors: Oh-uchi Sho-kichi , Lee Jin-Shik , Narita Mitsuaki 
Published: June 2006

Abstract
The influence of protecting groups on the β-sheet-structure stability of protected peptides was studied in organic solvents. α-Amino groups, carboxyl groups, and side-chain functional groups of model peptides were protected by availably used protecting groups. The difference between the solubilities of model peptides was investigated by the solvent-titration method using infrared (IR) absorption spectra. The β-sheet-structure-stabilizing potentials (SPβ) of each protecting group showed similar behaviors, except for Npys, Mts, and Z2. The result exhibits that the &lt;SPβ&gt; values of the protected peptide are almost independent of the kinds of their protecting group.
Cycloreversion of 1-(1-Naphthyl)-5-phenylbicyclo[3.2.0]hept-6-ene to 1-(1-Naphthyl)-4-phenyl-1,3-cycloheptadiene by Triplet Sensitization and Direct Irradiation
Authors: Nakabayashi Kenichi , Arimura Junichi , Yasuda Masahide , Shima Kensuke , Takamuku Setsuo 
Published: June 2006

Abstract
The cycloreversion of 1-(1-naphthyl)-5-phenylbicyclo[3.2.0]hept-6-ene (1b) to 1-(1-naphthyl)-4-phenyl-1,3-cycloheptadiene (2b) upon benzophenone (BP) sensitization and direct irradiation has been investigated. The triplet sensitization of 1b in benzene gave 2b quantitatively up to a stationary state where the quantum yield was 0.96. The triplet state of 2b (λmax = 455 nm, τ = 4.6 μs) was formed by the pulse radiolysis of 1b in benzene. It has been found that cycloreversion proceeds by an adiabatic mechanism via a triplet state. The quantum yield for the formation of 2b by the irradiation of 1b at 313 nm was determined to be 0.17 in hexane. The fluorescence spectra of 1b and 2b indicated that diabatic cycloreversion occurred via a singlet state. The singlet and triplet energies of 1b, as well as those of 2b, were estimated to be 88, 60, 72, and 39 kcal mol−1, respectively. The effect of a substitution of the naphthalene chromophore on bicyclo[3.2.0]hept-6-ene was estimated.
Intramolecular “Through-Bond” and “Through-Space” Electron Transfer Pathways in Covalently Linked Porphyrin-Quinone Molecules
Authors: Higashida Suguru , Tsue Hirohito , Sugiura Ken-ichi , Kaneda Takahiro , Sakata Yoshiteru , Tanaka Yoshinori , Taniguchi Seiji , Okada Tadashi 
Published: June 2006

Abstract
In order to understand electron transfer (ET) pathways through bonds and through space, a porphyrin-spacer-benzoquinone molecule, where the spacer is spiro[4.4]nonane and a phenyl group is inserted between the space of the redox pair, was prepared. On the basis of MM2 calculation, the edge-to-edge distances between the phenyl and the porphyrin or quinone rings are in the range of 2.5—4.2 Å. Therefore, it was expected that there are two possible intramolecular ET pathways in the compound, i.e., through bond and through space. The ET rates for charge separation process (kcs) were obtained on the basis of fluorescence lifetime. The kcs value of the above compound is almost identical with that of a reference compound in which no inserted phenyl ring is present. Therefore, it was concluded that the inserted π-system between the redox pair is not used as a stepping stone in ET pathways; in other words, ET in the present molecules takes place in a through-bond mechanism. To compete with fast ET with through-bond pathways in covalently linked donor–acceptor systems where the two ET pathways are possible, through-space ET may function under quite limited conditions.
Hydrocarbonylation of Enol Esters Catalyzed by a Palladium(II) Complex
Authors: Kudo Kiyoshi , Oida Yuji , Mitsuhashi Koichi , Mori Sadayuki , Komatsu Koichi , Sugita Nobuyuki 
Published: June 2006

Abstract
The palladium(II)-catalyzed carbonylation of various enol esters in the presence of methanol under pressurized carbon monoxide was investigated. As typical results, the carbonylation of isopropenyl acetate afforded a cyclocarbonylation product, 2-methoxy-2,5,5-trimethyl-1,3-dioxolan-4-one, in 46% yield under carbon monoxide of 150 atm at 100 °C, whereas vinyl acetate selectively gave an α-hydroesterification product, methyl 2-acetoxypropionate, in 56% yield under 250 atm at 100 °C. On the contrary, the reaction of 3,3-dimethyl-1-buten-2-yl acetate gave exclusively a β-hydroesterification product, methyl 3-acetoxy-4,4-dimethylpentanoate, in 64% yield. The yields of these products show a maximum as a function of the base/palladium ratio and of the carbon monoxide pressure. The effects of the reaction variables, such as the MeOH/substrate ratio, the structure of the base, the base/Pd ratio, the CO pressure, and the reaction temperature, were examined for optimizing the process. The mechanisms for the unique cyclocarbonylation and highly regioselective hydrocarbonylation of enol esters involving hydridopalladium(II) intermediate are discussed.
Chain Extension of Carbohydrates VI. Synthesis of the Two C-6 Epimers of the 6-Acetylamino-4,6-dideoxyheptopyranosiduronic Acid Present in Amipurimycin by Means of Stereocontrolled Ethynylation of Methyl 2,3-Di-O-benzyl-4-deoxy-α-d-xylo-hexodialdo-1,5-pyranoside
Authors: Czernecki Stanislas , Valery Jean-Marc , Wilkens Roland 
Published: June 2006

Abstract
The two C-6 epimers of 6-acetylamino-4,6-dideoxy-heptopyranosiduronic acid present in amipurimycin were prepared by selective reactions from methyl 2,3-di-O-benzyl-4,6,7,8-tetradeoxy-α-l-ido-7-ynopyranoside (4) in which the ethynyl group was employed as a precursor of the carboxylic acid function. The masked amino group was introduced at C-6 by reaction of 4 with zinc azide in the presence of triphenylphosphine and diisopropyl azodicarboxylate. The resulting methyl 6-azido-2,3-di-O-benzyl-4,6,7,8-tetradeoxy-α-d-gluco-oct-7-ynopyranoside (5) was transformed into benzyl[6-(acetylamino)-2,3-di-O-benzyl-4,6-dideoxy-α-d-gluco-heptopyranosid]uronate (7) by two different sequences of reactions: (1) oxidative cleavage of the triple bond, benzylation, reduction of the azido group, N-acetylation or (2) reduction of the azido group, N-acetylation, oxidative cleavage of the triple bond and treatment with phenyldiazomethane. The second sequence of reactions was found to be more efficient (33% overall yield versus 13%). The configuration at C-6 was unambiguously confirmed by X-ray diffraction with a single crystal of 7. Final hydrogenolysis of benzyl groups afforded methyl 6-(acetylamino)-4,6-dideoxy-α-d-gluco-heptopyranosiduronic acid (9). A Mitsunobu reaction on acetylenic alcohol 4 followed by saponification afforded the C-6 epimer 11. The same sequences of reactions was applied to 11 and methyl 6-(acetylamino)-4,6-dideoxy-α-l-ido-heptopyranosiduronic acid (16) was obtained.
New Method for Derivatization of Squaric Acid to Highly Substituted Cyclobutenones: Lewis Acid-Catalyzed Reaction of Cyclobutene-1,2-dione Monoacetal and Its Vinylog with Unsaturated Organosilanes, and Subsequent Ring Transformation of the Adducts
Authors: Yamamoto Yoshihiko , Ohno Masatomi , Eguchi Shoji 
Published: June 2006

Abstract
Described herein is a novel method for regio-controlled synthesis of highly substituted cyclobutenones having an unsaturated substituent at 4-position, starting from commercially available squaric acid. Both cyclobutene-1,2-dione monoacetal (4,4-diethoxycyclobutenone) and its vinylog (2,4-diethoxycyclobutenone), which were easily obtained from diethyl squarate, reacted with allylsilanes in the presence of Et2O·BF3 to afford 4-allyl-4-ethoxycyclobutenones having various substituents at 2-position regioselectively. These products were efficiently transformed to highly substituted bicyclo[3.2.0]heptenones by refluxing in xylene. The synthetic utility of this process was demonstrated in the construction of tricyclic ring systems. Further extension of the Lewis acid-catalyzed reaction of the monoacetal using an allenylsilane, a silyl enol ether, and a silyl ketene acetal also afforded the corresponding 4-substituted products. In contrast to the above 4-allylated products, 4-propargylated and 4-acylmethylated products did not undergo an analogous ring transformation under the same conditions.
Synthesis of 3-Chloro-Δ3-cephem-4-carboxylate by Addition/Cyclization of Allenecarboxylate. Copper(II)-Promoted Aerobic Oxidation of Arenesulfinic Acids
Authors: Tanaka Hideo , Kikuchi Ryo , Torii Sigeru 
Published: June 2006

Abstract
The selective transformation of allenecarboxylate derived from penicillin into 3-chloro-Δ3-cephem-4-carboxylate was successfully achieved by an addition/cyclization reaction with chloride salts in aerobic media containing a copper(II) catalysts, in which copper(II)-catalyzed aerobic oxidation of in situ generated benzenesulfinate ion into less nucleophilic sulfonate ion prior to the nucleophilic addition of the former ion to the allenecarboxylate would completely eliminate the formation of undesired 3-phenylsulfonyl-Δ3-cephem-4-carboxylate. Under similar aerobic conditions, arenesulfinates salts and arenesulfinic acids were smoothly oxidized to the corresponding sulfonate salts and sulfonic acids, respectively.
Kinetics of Oxidation of Cyclic Alcohols by Quinolinium Dichromate
Authors: Nongkynrih Irona , Mahanti Mahendra K 
Published: June 2006

Abstract
When treated with quinolinium dichromate (QDC) in acid medium using dimethylformamide as the solvent, cyclic alcohols were converted to the corresponding cyclic ketones. Kinetic data have been presented. The order of reactivity was 8 &gt; 7 &gt; 5 &gt; 6. The reaction proceeds via a cyclic transition state, with the subsequent cleavage of the carbon–hydrogen bond (kH/kD = 5.8) in the rate determining step. The electrocyclic mechanism involved six electrons, and being a Hückel-type system (4n + 2), this was an allowed process.
Magnetic Properties of 1,3,5-Tris[bis(p-methoxyphenyl)amino]benzene Cation Radicals
Authors: Yoshizawa Kazunari , Hatanaka Masashi , Ago Hiroki , Tanaka Kazuyoshi , Yamabe Tokio 
Published: June 2006

Abstract
In order to pursue the possibility of charge-transfer organic ferromagnets, magnetic properties of the monocationic ClO4- and BF4-salts of a triaminobenzene derivative, 1,3,5-tris[bis(p-methoxyphenyl)amino]benzene (TBMAB), were characterized by means of ESR and a Faraday-type magnetic balance. MNDO-PM3 calculations predicted 1,3,5-tris(diphenylamino)benzene (TDAB) dication and trication to be ground-state triplet and quartet, respectively. Thus these triaminobenzenes fulfill the necessary precondition for the appearance of intermolecular ferromagnetic coupling based on so-called McConnell’s second model. Negative Weiss constants (−1 to 0 K) and low spin concentrations (7—8 %) were observed for TBMAB–ClO4 and TBMAB–BF4, although, according to this rule, intermolecular ferromagnetic coupling is expected to occur for these systems.
Relationships between the Molecular Structures and Stabilities of Functional Dyes with a Phenothiazine Skeleton
Authors: Fujii Isao , Hirayama Noriaki , Aoyama Norihito , Miike Akira 
Published: June 2006

Abstract
10-N-Methylcarbamoyl-3,7-bis(dimethylamino)-10H-phenothiazine (MCDP) is one of the functional dyes which are applied clinically as diagnostics. MCDP spontaneously decomposes to methylene blue while increasing the undesirable background of diagnosis. Understanding the mechanisms of spontaneous decomposition is essential for the molecular design of better functional dyes. X-Ray analyses of two derivatives of MCDP, 10-N-methylthiocarbamoyl-3,7-bis(dimethylamino)-10H-phenothiazine and 10-N-benzylthiocarbamoyl-3,7-bis(dimethylamino)-10H-phenothiazine, have been undertaken. Based on the three-dimensional structures the structure-property relationships between them were analysed.
Characteristics of Alkali-Exchanged Y Zeolites, Montmorillonite, and Al-Pillared Montmorillonite, Studied by Physical and Chemical Methods
Authors: Hannus István , Pálinkó István , Tasi Gyula , Béres Attila , Kiricsi Imre 
Published: June 2006

Abstract
Microporous catalytic materials with various surface acidities have been prepared and characterized with instrumental methods as well as chemical reactions. The catalysts were LiY, NaY, KY, CsY, RbY, Na-montmorillonite (Na-mor), and Al-pillared montmorillonite (Al-PILC). Structural characterization involved atomic absorption and X-ray fluorescence spectroscopies, X-ray diffractometry, infrared spectroscopy in the region of framework vibrations, and thermogravimetric and BET measurements. Infrared spectroscopy of adsorbed pyridine and the acid-catalyzed isomerization of cyclopropane was used for testing surface acidity. The instrumental methods suggested a decreasing acidity order with increasing cationic radii, while the chemical reaction showed that the acidity decreased in the Al-PILC &gt; LiY &gt; NaY &gt; CsY &gt; KY ≈ RbY sequence. On the first two catalysts oligomerization followed isomerization, and the activity of isomerization decreased in the above order.
Liquid Crystalline Properties of 4-Alkoxyphenyl 4-Thiocyanatophenyl Terephthalates
Authors: Okamoto Hiroaki , Hayashi Mitsuaki , Takenaka Shunsuke 
Published: June 2006

Abstract
This paper describes the preparation and thermal properties of a homologous series of 4-alkoxyphenyl 4-thiocyanatophenyl terephthalates. The homologous series shows nematic and smectic A phases commencing from the pentyloxy homolog. The smectic A phase is immiscible with the smectic A phase of polar liquid crystals having a terminal cyano group. Interestingly, the smectic B phase is also formed from the hexyloxy homolog, while the compound has a polar group at the terminal position.
Toward Direct Synthesis of Organonitrogen Compounds from Dinitrogen: The Chemistry of Diazoalkane Complexes Derived from Dinitrogen Complexes
Authors: Hidai Masanobu , Ishii Youichi 
Published: June 2006

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

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