bluuebunny/crossref_metadata_2025 huggingface dataset:
Accelerating Effect of Donor Solvents on Racemization of the Tris(1,10-phenanthroline)iron(II) Cation
Authors: Fujiwara Terufumi , Okamoto Yoshiharu , Yamamoto Yuroku
Published: July 2006

Rates of racemization of the tris(1,10-phenanthroline)iron(II) cation, [Fe(phen)3]2+, have been measured at 7.5 °C to 17.5 °C in 1,2-dichloroethane, o-dichlorobenzene, nitrobenzene, and nitromethane, and in 1,2-dichloroethane solutions containing dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), methanol (MeOH), acetone (Ac), and acetonitrile (AN). In the four pure solvents, the observed racemization rates are markedly smaller than those calculated by the Van Meter and Neumann equation, which relates the racemization rate to the solvation energy of the phen ligands and viscous resistance. Addition of donor solvents to 1,2-dichloroethane solutions of the iron complex enhances the racemization rates. The degree of enhancement increases in the order AN<Ac<MeOH<DMF<DMSO and the activation energy decreases in the same order. This sequence lies in the order of increasing Gutmann donor number of the solvents, indicating a nucleophilic interaction of the solvents with the iron metal in the transition state. These obsevations may be interpreted in terms of Kepert’ s model for solvent-assisted racemization of tris-chelated complexes and the molecular structure of a solvate complex determined previously, and allow us to modify the Van Meter and Neumann equation.
A Novel Synthesis of 2-Acyl Cyclic Ethers and 3-Keto Cyclic Ethers Including Spiro Cyclic Ethers via Intramolecular Ring-Opening of α,β-Epoxy Sulfoxides with Hydroxyl Group
Authors: Satoh Tsuyoshi , Iwamoto Ken-ichi , Sugimoto Atsushi , Yamakawa Koji
Published: July 2006

The α,β-epoxy sulfoxides 1 and 2 bearing ω-oxyalkyl group were synthesized from ω-oxyalkyl carbonyl compounds and 1-chloroalkyl phenyl sulfoxide. The intramolecular ring opening of the oxirane ring of these α,β-epoxy sulfoxides, through an attack of the terminal hydroxyl group, gave 2-acyl cyclic ethers or 3-keto cyclic ethers, including spiro-type cyclic ethers. This procedure is applicable to the preparation of five- and sixmembered cyclic ethers.
Synthetic Studies of Amphotericin B. III. An Enantiospecific Synthesis of the C-1–C-19 Segment of the Amphotericin B Aglycon
Authors: Kinoshita Mitsuhiro , Taniguchi Masato , Morioka Masahiko , Takami Hitoshi , Mizusawa Yasuhiro
Published: July 2006

The title compound, (3S,4S,5S,9S,11R,12R,15R,17S)-4-[(t-butyldimethylsilyloxy)methyl]-1,3,5,9,11,12,15,17,19-nonahydroxy-3,5:11,12:15,17-tri-O-isopropylidene-19-O-(4-methoxybenzyl)-9-O-[(2-methoxyethoxy)methyl]-7-nonadecanone (1) was effectively synthesized through the coupling of (3S,5R,8R,9R,11S)-12-iodo-3,5:8,9-di-O-isopropylidene-1-O-(4-methoxybenzyl)-11-O-[(2-methoxyethoxy)methyl]-1,3,5,8,9,11-dodecanehexol (2) and (3S,4R,5S)-4-[(t-butyldimethylsilyloxy)methyl]-3,5-O-isopropylidene-1,1-bis(methylthio)-1-trimethylstannyl-6-heptene-3,5-diol (36). The C-13–C-19 segment 36 was enantiospecifically synthesized from 1,2:5,6-di-O-isopropylidene-α-d-thero-d-glycero-3-hexofuranosulose (7) via (2S,4R,5S)-5,6-epoxy-3-[(t-butyldimethylsilyloxy)methyl]-1-hexen-3-ol (6a) in 11.6% overall yield.
Barium Ferrate Monohydrate BaFeO4·H2O, a Useful Oxidant for the Oxidation of Organic Compounds under Aprotic Conditions
Authors: Firouzabadi Habib , Mohajer Daryoush , Entezari-Moghadam Mohsen
Published: July 2006

Preparation of barium ferrate monohydrate with a slight modification is described. It is shown that this reagent is capable of oxidizing different organic compounds and could be used as a versatile reagent in organic synthesis. Primary and secondary alcohols are converted to their carbonyl compounds, α-hydroxy ketones to their diketones, and hydroquinones to their quinones. Aromatic amines are converted to their azo compounds, benzylamine to benzaldehyde, phenylhydrazones and oximes to their carbonyl compounds. Thiols are also converted to their disulfides in high yields. This reagent seems to be a non-toxic and a non-pollutant compound.
The Reaction of N″-Cyanoguanidine with Formaldehyde. II. Bis(N″-carbamoylguanidino)methane or N,N′-Methylenebis[N′-(diaminomethylene)urea]
Authors: Shiba Ryuichi , Takahashi Miyuki , Ebisuno Toichi , Takimoto Michiaki
Published: July 2006

The condensation product in the reaction of N″-cyanoguanidine with paraformaldehyde under strongly acidic conditions was identified as N,N′-methylenebis[N′-(diaminomethylene)urea] by X-ray analysis. This structure agreed with that estimated from the 1H NMR data.
Preparation of Novel N-Vinyl-, N-(1-Butylvinyl)-, and N-(1-Methyl-1-pentenyl)iminotriphenylphosphoranes and Their Reactions with α,β-Unsaturated Ketones
Authors: Iino Yukio , Nitta Makoto
Published: July 2006

The novel N-vinyl-(2a) and a mixture of N-(1-butylvinyl)-(2b) and N-(1-methyl-1-pentenyl) iminotriphenylphosphoranes (2c) were prepared by the reaction of azidoethylene and 2-azido-1-hexene with triphenylphosphine, respectively. The thermal reaction of 2a, 2b, and 2c with α,β-unsaturated ketones undergoes an enamine-type alkylation and the subsequent aza-Wittig reaction to give pyridine derivatives in modest yields.
Ion-Exchange Rate of Chromate and Dichromate Ions on Bis(triethylamine)zirconium
Authors: Rawat J P , Chitra
Published: July 2006

Kinetic studies of K2Cr2O7 and K2CrO4 have been performed on an inorganic anion exchanger, bis(triethylamine)zirconium in Cl− form. F values have been determined at four different temperatures 30, 40, 50, and 60 °C with ±1 °C variation and corresponding Bt values are evaluated and plotted as a function of temperature. The mechanism is found to be particle diffusion control. Various parameters viz. effective diffusion coefficient (Di), diffusion coefficient (Do), energy of activation (Ea), and entropy of activation (ΔS*) have been evaluated.
A Pulse Radiolysis Study of the Formation of Dimer Radical Cations of Aromatic Olefins
Authors: Chikai Yukio , Yamamoto Yukio , Hayashi Koichiro
Published: July 2006

The formation of dimer radical cations of several aromatic olefins has been studied by the pulse radiolysis technique. The aromatic olefins examined are 2-vinylnaphthalene (VN), 2-(1-propenyl)naphthalene (PN), 4-vinylbiphenyl (VBP), trans,trans-1,4-diphenyl-1,3-butadiene (1,4-DPB), and s-trans-2,3-diphenyl-1,3-butadiene (2,3-DPB). The formation of dimer radical cations were observed with all of them except 1,4-DPB, although it was very limited with VBP. Two types of dimer radical cations, bonded and associated ones, are formed with VN, whereas only the associated dimer radical cation is formed with PN. The influence of the aromatic substituents on the formation of the dimer radical cations is described.
Thermodynamic Studies on Order-Disorder Phase Transitions of p-Terphenyl and p-Terphenyl-d14
Authors: Saito Kazuya , Atake Tooru , Chihara Hideaki
Published: July 2006

The heat capacities of p-terphenyl and p-terphenyl-d14 were measured by adiabatic calorimetry between 3 and 300 K. The phase transition associated with a molecular conformation change was observed as a λ-shaped anomaly at (193.5±0.1) K and at (180.3±0.1) K. The enthalpies of transition are (304±20) J mol−1 and (288±20) J mol−1 and the entropies of transition are (1.63±0.10) J K−1 mol−1 and (1.63±0.10) J K−1 mol−1, respectively. The anisotropy of the intermolecular interaction is discussed and the anomalous portion of the heat capacities in the transition region was compared favorably with a two-dimensional Ising model.
Structure and Racemization of Optically Active mer-(3-Azapentane-1,5-diamine or 3-methyl-3-azapentane-1,5-diamine)(ethylenediamine-N-acetato)cobalt(III) Complexes
Authors: Kawaguchi Hiroshi , Fukaki Hironobu , Ama Tomoharu , Yasui Takaji , Okamoto Ken-ichi , Hidaka Jinsai
Published: July 2006

The crystal structure of (−)500CD-mer-[Co(edma)(dien)]Br2·2/3CH3OH·2/3H2O was determined by the X-ray diffraction method. The crystal is triclinic, space group P1, a=13.824(8), b=13.814(8), c=8.055(3) Å, α=101.18(6), β=101.17(6), γ=116.32(5)°, and Z=3. All of the crystallographically independent complex cations, in which the terdentate ligands coordinate meridionally, have a δ spiral configuration, and the asymmetric nitrogen donor atoms of the edma ligands take an S configuration. The racemization reactions due to the inversion at the secondary amine nitrogen atom of the edma ligand in (−)500CD-mer-[Co(edma)(dien)]2+ and (−)514CD-mer-[Co(edma)(mdien)]2+ were studied at 20–35 °C in the pH range of 6.10–7.24. The rate law for both complexes was described as R=k[OH−][complex]. The activation parameters at 30.0 °C were ΔH\eweq of 94.9 kJ mol−1 and ΔS\eweq of 126 J K−1 mol−1 for the dien complex and ΔH\eweq of 73.8 kJ mol−1 and ΔS\eweq of 62.0 J K−1 mol−1 for the mdien complex.
Total Synthesis of Elaiophylin (Azalomycin B)
Authors: Toshima Kazunobu , Tatsuta Kuniaki , Kinoshita Mitsuhiro
Published: July 2006

Antibiotic elaiophylin (1) has been first synthesized by a convergent route involving aldol coupling of (5R,6R,7R)-5-O-[2-deoxy-3,4-bis-O-(isopropyldimethylsilyl)-α-l-fucopyranosyl]-6-ethyl-7-O-(diethylisopropylsilyl)-5,7-dihydroxy-3-octanone (25f) and (7S,8S,15S,16S:3E,5E,11E,13E)-8,16-bis[(1R)-1-formylethyl]-7,15-dimethyl-1,9-dioxa-3,5,11,13-cyclohexadecatetraene-2,10-dione (3), followed by desilylation. The appropriately O-protected segment 25f and the macrocyclic dialdehyde 3 were synthesized from d-glucose and 2-deoxy-l-fucose.
Synthesis and Structure of 6,7-Dihydro-2,3-disubstituted 5H-2a-Thia(2a-SIV)-2,3,4a,7a-tetraazacyclopent[cd]indene-1,4(2H,3H)-dithione
Authors: Matsumura Noboru , Tomura Masaaki , Mori Osamu , Tsuchiya Yuko , Yoneda Shigeo , Toriumi Koshiro
Published: July 2006

Symmetrical tetraazapentalene derivatives 5 and 6 were synthesized by a convenient one-pot reaction using lithium thioureide/phenacyl chloride/alkyl (or allyl) isothiocyanate system. Unsymmetrical tetraazapentalene derivatives 8 were prepared by the reaction of various isothiocyanates with thiadiazolopyrimidine derivatives 7 which were derived from symmetrical tetraazapentalene derivatives. The structure of 5c was determined by a single crystal X-ray diffraction.
Intramolecular End-to-End Reactions of Photoactive Terminal Groups Linked by Poly(oxyethylene) Chains
Authors: Ashikaga Kazuo , Ito Shinzaburo , Yamamoto Masahide , Nishijima Yasunori
Published: July 2006

The triplet-sensitized photochemical reaction using a series of poly(oxyethylene) chains with a pair of photoactive terminal groups, dibenz[b,f]azepine (DBA) chromophores (DBA–COCH2CH2(OCH2CH2)nOCH2CH2CO–DBA, n=0–10) was examined. The photoirradiation of bichromophoric compounds caused either intra- or intermolecular reactions. These reactions were kinetically analyzed by two different methods: the measurement of deactivation processes of the reaction intermediates (excited triplet state of DBA) by nanosecond laser photolysis and the quantitative analysis of the reaction products by GPC. The intramolecular deactivation rate constant, kintra, showed a remarkable chain-length dependence; the maximum kintra value appeared at n=5 and it was found to be 5.9×104 s−1. On the other hand, the intramolecular cyclization rate also depends on the chain length; the maximum quantum yield, φdintra, was given at n=7 (φdintra=0.51). The chain length for the maximum cyclization yield shifted slightly to the longer region than that for the maximum kintra value due to the restriction of the terminal structure (anti-configuration). The results obtained for this reaction system are compared with those obtained for the previously reported polymethylene system and the effect of chain flexibility on the intramolecular ring-closure reaction is discussed.
Synthesis and Structural Analysis of 5-Deoxy-3-O-methyl-5-C-[(R)- and (S)-phenylphosphinothioyl]-α- and β-d-xylopyranoses
Authors: Hanaya Tadashi , Shigetoh Nobuyuki , Yamamoto Hiroshi
Published: July 2006

Treatment of 5-deoxy-5-iodo-1,2-O-isopropylidene-3-O-methyl-α-d-xylofuranose with ethyl phenylphosphinothioate in the presence of NaH in DMF gave a 1:1 mixture of the 5-deoxy-5-C-[(R)- and (S)-(ethoxy)phenylphosphinothioyl] derivatives. Reduction of these d-xylofuranoses with sodium dihydrobis(2-methoxyethoxy)aluminate, followed by the acid hydrolysis, provided the title compounds, which are the first sugar analogues having a phosphinothioyl group in the hemiacetal ring. These compounds were converted into four, separable 1,2,4-tri-O-acetates, the structures and conformations of which were established by spectroscopy. The corresponding per-O-acetyl-5-deoxy-5-C-[(R)- and (S)-phenylphosphinyl] analogues were also prepared and their previously presented structures were revised. Complete 1H NMR (500-MHz) parameters of these two types of compounds are given for a comparative, structural study.
Promoter Effect of Platinum on Liquid-Phase Dehydrogenation of 2-Propanol by a Nickel Fine-Particle Catalyst
Authors: Noda Michio , Shinoda Sumio , Saito Yasukazu
Published: July 2006

A platinum-deposited nickel fine-particle catalyst was shown to be more active than a nickel-alone catalyst. A study of the temperature dependence of a rate constant revealed that platinum increased the frequency factor of the rate constant. An experiment regarding poisoning showed that the number of active sites was the same for the two catalysts. Thus the promoter effect was ascribed to an increase in the frequency factor per active site.
The Crystal Structure of 1,5-Dithioniabicyclo[3.3.0]octane Bis(trifluoromethanesulfonate). The First Structural Characterization of Dithionia Dication and Strong S···O Interactions between Cations and Anions
Authors: Iwasaki Fujiko , Toyoda Nobuhiko , Akaishi Ryouichi , Fujihara Hisashi , Furukawat Naomichi
Published: July 2006

The crystal structure of 1,5-dithioniabicyclo[3.3.0]octane bis(trifluoromethanesulfonate) has been determined by the X-ray method to elucidate the structure of a dithionia dication. Crystal data; C6S2H122+·2CF3SO3−, Fw=446.43, orthorhombic, Pccb, a=16.775(2), b=9.893(3), c=19.592(3) Å, V=3251(1) Å3, Z=8, Dx=1.825 Mg m−3. There are two independent dications, A and B, in the crystals, each of which has a crystallographic twofold axis. The mean S+–S+ distance is 2.124 Å. The conformation of the eight-membered ring is a distorted chair–chair form. Very strong interactions were observed between S+ of dications and O atoms of counter anions. The average distance of S+···O is 2.724 Å and colinear arrangements of O···S–S···O are formed with the central twofold axis. Other weak S···O interactions (2.903–3.153 Å) were also observed between dications and anions. The coordination around S is a roughly distorted octahedron with two C and two O atoms in a plane and apical S and O atoms.
Rotational Lattice Vibrations of Tetramethyl- and Tetramethyl-d12-pyrazine Crystals
Authors: Maehara Masayoshi , Hieida Toshikazu , Nibu Yoshinori , Shimada Hiroko , Shimada Ryoichi
Published: July 2006

The low-frequency Raman bands of the tetramethyl- and tetramethyl-d12-pyrazine crystals and their hydra ted crystals were studied at various temperatures between 4.2 and 298 K. The isotopic factors and the temperature effects on the frequencies of the Raman bands indicate that the low-frequency Raman bands observed in the crystal are to be ascribed to the rotational lattice vibrations. A smooth curve of the plot of the Raman frequency versus temperature suggests that no apparent temperature-induced phase transition takes place in the tetramethylpyrazine crystal. Classification of the rotational lattice vibrations into symmetry species was made based on the polarization behavior of the Raman bands. It was also observed that tetramethylpyrazine hydrates quite easily with a trace of moisture in the air.
A Conductance Study of 1:1 Complexes of 15-Crown-5, 16-Crown-5, and Benzo-15-crown-5 with Alkali Metal Ions in Nonaqueous Solvents
Authors: Takeda Yasuyuki , Katsuta Koji , Inoue Yoshihisa , Hakushi Tadao
Published: July 2006

Conductivities of alkali metal salts in the presence of 15-crown-5 (15C5), 16-crown-5 (16C5), and benzo-15-crown-5 (B15C5) were measured at 25 °C in acetonitrile, propylene carbonate, and methanol. Formation constants (KML+) of 1:1 complexes of 15C5 and 16C5 with alkali metal ions and conductance parameters (λ0 and å) of the Na+ complexes of 15C5, 16C5, and B15C5 were determined, λ0 and å being limiting ionic molar conductivity and distance of closest approach of ions, respectively. In general, selectivities of 15C5 and 16C5 for alkali metal ions show the size-fit correlation. In contrast to 15C5, 16C5 forms much the most stable complex with Na+ in every solvent. Generally, KML+-value sequences of a given crown ether complex for the solvents are the reverse of donor-number sequences of the solvents. Value of å increases with an increase in the cationic size (Na+→Na(15C5)+→Na(16C5)+→Na(B15C5)+). Mobility of the Na+–crown ether complex decreases with an increase in the size of the crown ether. From λ0 values and Walden products of these Na(crown ether)+ complexes and a tetrapropylammonium ion, it seems likely that Na(15C5)+ and Na(16C5)+ act as structure breakers in hydrogen-bonding solvents, whereas Na(B15C5)+ as a structure maker.
Stabilities and Transfer Activity Coefficients of Benzo-15-crown-5-Alkali Metal Ion Complexes in Various Solvents
Authors: Takeda Yasuyuki , Kumazawa Toshihiro
Published: July 2006

Stability constants in acetonitrile and methanol of 1:1 benzo-15-crown-5 (B15C5)–alkali metal ion complexes and the solubility of B15C5 in acetonitrile, propylene carbonate, methanol, and water were determined at 25 °C by conductometry and spectrophotometry, respectively. In general, selectivity tendency of B15C5 for the alkali metal ions except for Li+ can be interpreted in terms of size-relationship. Stability sequences of the B15C5–alkali metal ion complex among the solvents, except for Rb+ and Cs+ complexes, are the reverse of solvation-ability sequences of the solvents to the corresponding alkali metal ion. By using the stability constants of the B15C5–alkali metal ion complexes, transfer activity coefficients (γ) of the B15C5 complexes were then calculated from γ values of B15C5 (obtained from solubilities of B15C5) and those of alkali metal ions. The γ value of the B15C5 complex from methanol to acetonitrile and propylene carbonate generally varies with a variety of alkali metal ions. From γ values of the B15C5 complexes, it is concluded that there exists a possible specific interaction between the alkali metal ion held in the B15C5 cavity and solvent molecules when the alkali metal ion is much smaller or larger than the B15C5 cavity.
Application of Hydrogen Ion Sensitive Field Effect Transistor to the Kinetic Study of Fast Reaction in Solution
Authors: Nakatsuka Thoru , Nakamura Michihiro , Sano Takayuki
Published: July 2006

The ion sensitive field effect transistor(ISFET) developed for pH measurement was incorporated with the stopped flow apparatus for direct detection of the fast change in the hydrogen ion concentration. By the experiments on the dehydration reaction of carbonic acid, it was proved that the pH sensor has a fast response time (<2 ms) beyond the resolution time of stopped flow apparatus, and the constructed apparatus can be satisfactorily applied to the fast reaction kinetics with the sensitivity for the pH change more than 0.01 pH unit.
57Fe-Moessbauer and 13C-CP-MAS NMR Spectroscopic Studies of the Reaction Products of Ruthenocene Derivatives with Lewis Acids
Authors: Watanabe Masanobu , Masuda Yuichi , Motoyama Izumi , Sano Hirotoshi
Published: July 2006

Adducts of ruthenocene with Lewis acids, such as HgCl2, SnCl4, and I2, are studied mainly by means of high resolution solid state 13C NMR spectroscopy and 57Fe-Moessbauer spectroscopy. The large low-field shifts found in the 13C-CP-MAS NMR spectroscopy suggest the presence of a direct chemical bond between the ruthenium and the Lewis acids. Ferrocenylruthenocene and biruthenocene give stable adducts with HgCl2 and I2. 57Fe-Moessbauer and 13C-CP-MAS NMR spectroscopic studies suggest the presence of a chemical bond, such as Ru–Hg, Ru–I, in the adducts.
Effects of Methyl Substituent on Solvent Extraction of Copper(II) with o-, m-, and p-Methylbenzoic Acids
Authors: Yamada Hiromichi , Horikawa Shiho , Fujii Yukio , Mizuta Masateru
Published: July 2006

The extraction of copper(II) with o-, m-, and p-methylbenzoic acids in 1-octanol was carried out at 25 °C and aqueous ionic strength of 0.1 mol dm−3 (NaClO4). In contrast to the extraction with benzoic acid, in which only the monomeric copper(II) benzoate is extracted, the dimeric copper(II) species is also responsible for the extraction of copper(II) with o- and m-methylbenzoic acids in 1-octanol together with the monomeric one. On the other hand, p-methylbenzoic acid has a poorer extracting capability than o- and m-methylbenzoic acids and only the monomeric copper(II) species is responsible for the extraction.
Raman Spectral Characteristics of Bis(terdentate)cobalt(III) Complexes with N and O Donor Atoms
Authors: Kawamoto Tatsuya , Yasui Takaji , Einaga Hisahiko , Hidaka Jinsai
Published: July 2006

The Raman spectra were measured for the bis and mixed type cobalt(III) complexes with ethylenediamine-N-acetate (edma) in an aqueous solution in the skeletal vibration region. The Raman bands could be classified into five vibration modes; a totally symmetric stretching vibration mode in the 510–650 cm−1 region, a stretching vibration mode excluding the totally symmetric one in the 410–540 cm−1 region, a skeletal breathing vibration mode in the 370–490 cm−1 region, a skeletal bending deformation mode in the 270–420 cm−1 region, and a chelate ring deformation mode in the 220–270 cm−1 region. Differences in the skeletal vibrations were observed between the fac and mer isomers for the chelate ring arrangement. Further, differences for the chelate ring arrangement between the Raman spectra of sym-fac and unsym-fac isomers were observed in the skeletal bending deformation mode. The cobalt(III) complexes with the terdentate ligands containing N-methyl group exhibited Raman bands shifted to a lower frequency than those of the corresponding cobalt(III) complexes containing no N-methyl group in the totally symmetric stretching vibration mode region.
Phase-Transfer-Catalyzed Azo Coupling Reactions in Two-Phase Systems
Authors: Hashida Yoji , Kubota Kazuhiro , Sekiguchi Shizen
Published: July 2006

The azo coupling reaction of p-methoxybenzenediazonium tetrafluoroborate with N,N-dimethylaniline has been investigated in a water-1,2-dichloroethane system. It has been found that, among the several additives examined, the phenolate ion, generated from picric acid or 2,4-dinitro-1-naphthol, acted as an effective phase-transfer catalyst. Further, the reaction of p-diethylaminobenzenediazonium tetrafluoroborate with dimedone, an active methylene compound, has also been investigated in the same two-phase system; a remarkable acceleration in the rate was observed in the presence of tetraalkyl onium salts, and even in their absence.
Studies on Chitin. 14. N-Acetylation Behavior of Chitosan with Acetyl Chloride and Acetic Anhydride in a Highly Swelled State
Authors: Kurita Keisuke , Chikaoka Satoyuki , Kamiya Mami , Koyama Yoshiyuki
Published: July 2006

N-Acetylation on chitosan has been studied in a highly swelled state with acetyl chloride in comparison with that with acetic anhydride under various conditions to establish the general possibility and scope of the acylation reactions on chitosan and other polysaccharides. A highly swelled chitosan precipitate prepared by pouring a chitosan solution in aqueous acetic acid/methanol into pyridine is quite suitable for efficient modifications, and the reaction with either acylating reagent proceeded smoothly and reproducibly under mild conditions. Although acetic anhydride is generally more appropriate in protic solvens, acetyl chloride is effective and advantageous especially in pyridine containing only small amounts of protic solvents.
Solvation Structure of Copper(II) Ion in N,N-Dimethylformamide and N,N-Dimethylformamide–Acetonitrile Mixtures Determined by the X-Ray Diffraction Method
Authors: Ozutsumi Kazuhiko , Ishiguro Shin-ichi , Ohtaki Hitoshi
Published: July 2006

The solvation structure of copper(II) ion in N,N-dimethylformamide (DMF) and N,N-dimethylformamide–acetonitrile (AN) mixtures has been investigated by means of X-ray diffraction at 25 °C. The X-ray scattering data for the copper(II) perchlorate DMF solution were well-interpreted in terms of the presence of the axially elongated octahedral [Cu(dmf)6]2+ ion in DMF. Among the six DMF molecules, four of them are at the distance of 203(3) pm at the equatorial position and the other two are at 243(5) pm at the axial one. On the other hand, in copper(II) perchlorate DMF–AN solutions with the Cdmf⁄CCu mole ratios of 5.308 and 7.435, where Ci denotes the total concentrations of species i, the copper(II) ion is coordinated with four DMF molecules within the square-plane and with no solvent molecule along the axis of the plane. The equatorial Cu–O bond length is 200(1) pm and practically the same as that within the [Cu(dmf)6]2+ ion in DMF. In copper(II) nitrate DMF solutions (1.086 and 1.500 mol dm−3), a nitrate ion binds to copper(II) ion at the equatoral position and the distorted octahedral [CuNO3(dmf)5]+ complex is formed.
Alumina-Anchored Cobalt Porphine Catalysts for the Conversion of Quadricyclane to Norbornadiene
Authors: Miki Sadao , Asako Yoshinobu , Morimoto Masayoshi , Ohno Toshinobu , Yoshida Zen-ichi , Maruyama Toshiro , Fukuoka Masahiro , Takada Tomoaki
Published: July 2006

Methods are described for the preparation of cobalt(II) deuteroporphyrin and cobalt(II) tetrakis(p-sulfonatophenyl)porphine anchored on alumina beads coated with polyaminesulfone-A. Wavelength dispersive X-ray microanalysis showed that the cobalt(II) porphine distributes within the catalyst outer surface layer of ca. 100 μm depth. The catalysts are highly active for the cycloreversion of quadricyclane to norbornadiene. A detailed kinetics of the isomerization using an isothermal recycle reactor gave a rate expression of Langmuir–Hinshelwood type. The catalysts gradually lose their activity, which can be regenerated completely by heating the catalysts at 200 °C in vacuo.
The Crystal Structure of the Gold(III) Complex, Tribromo(dibenzyl sulfide)gold(III)
Authors: Takahashi Kazuhiro , Kato Katsuo
Published: July 2006

The crystal structure of tribromo(dibenzyl sulfide) gold(III) has been determined. The crystal belongs to the triclinic system, with a=7.002(1), b=7.949(1), c=17.244(2) Å, α=88.83(1), β=79.52(1), and γ=66.35(1)°, with the space group P\bar1 and with Z=2. The complex has a square-planar coordination geometry with 3BrlS donor atoms. The bond lengths of the three Au–Br coordinations are in the range of 2.41–2.43 Å.
Active and Selective Transports of Alkali Metal Ions through Hydrophobic Membrane
Authors: Hayashita Takashi , Tedo Kiyotaka , Yamabe Takeo , Igawa Manabu
Published: July 2006

The active and selective transport of alkali metal ions coupled with proton permeation, were observed through a dense hydrophobic membrane. The flux of alkali metal ions increased with the decrease in the degree of hydration. The behavior can be comprehended in terms of the asymmetrical permeabilities of ions through the hydrophobic membrane.
Inclusion Properties of Acyclic p-Substituted Phenol–Formaldehyde Oligomers
Authors: Sone Tyo , Ohba Yoshihiro , Yamazaki Hajime
Published: July 2006

Acyclic para-substituted phenol–formaldehyde oligomers (R=H, Me, n-Bu, t-Bu, and cyclohexyl; the number of phenol units=3–6) form host–guest complexes with various organic compounds. The inclusion property of the acyclic oligomers is greatly influenced by the p-substituents of phenol and the number of phenol units in the oligomers; for example, a) while the t-butyl tetramer is effective, the corresponding butyl tetramer has a poor ability for the complex formation, and b) the tetramers and pentamers are good hosts for organic compounds, forming 2:1 (host:guest) complexes in many cases.
Sequential Reactions of Michael Addition and Peterson Condensation of 1-Silylvinyl Ketones with Grignard Reagents: Study of Stereoselectivity
Authors: Tanaka Junji , Kobayashi Hiroshi , Kanemasa Shuji , Tsuge Otohiko
Published: July 2006

1-Silylvinyl ketones undergo smooth Michael addition with Grignard reagents generating magnesium enolates which are then trapped with benzaldehyde to give E- and Z-isomers of enones after Peterson condensation. (E)-Olefins become major products under a thermodynamic control when the condensation with benzaldehyde is carried out at room temperature in diethyl ether, while Z-isomers are more favored as kinetically controlled products at −78 °C in THF. Reaction mechanism is briefly discussed.
Voltammetric Characterization of α- and β-Dodecamolybdophosphates in Aqueous Organic Solutions
Authors: Himeno Sadayuki , Osakai Toshiyuki , Saito Atsuyoshi
Published: July 2006

The electrochemical properties of α- and β-dodecamolybdophosphates were characterized at the glassy carbon (GC) electrode. It was found that the β-isomer was only stable in neat organic solvents. When molybdophosphate was prepared in aqueous organic solutions, a mixture of α- and β-isomers formed.
A New Method for Determination of Disulfide Pairing in Peptides
Authors: Hidaka Yuji , Shimonishi Yasutsugu
Published: July 2006

A new method was developed for determination of disulfide pairings in peptides. This method consisted in the synthesis of peptides with deuteriocysteine residues at given positions and the analysis of deuteriocystine generated in the acid hydrolyzates of the synthetic peptides by fast atom bombardment mass spectrometry. The availability of this method was confirmed by its application for determining the positions of disulfide linkages in a heat-stable enterotoxin of enterotoxigenic Escherichia coli.
An Efficient Preparation and Reactions of [5,6′-Biguaiazulene]-3,3′(5H,6′H)-dione and 5-Isopropylidene-3,8-dimethyl-1(5H)-azulenone: Key Intermediates for the Autoxidation Products of Guaiazulene
Authors: Matsubara Yoshiharu , Matsui Shuichi , Takekuma Shin-ichi , Quo Yan Pin , Yamamoto Hiroshi , Nozoe Tetsuo
Published: July 2006

Oxidation of guaiazulene (1) with peracetic acid in hexane at 25 °C afforded as high as an 80% yield of the title biguaiazulenedione (12), which upon heating at 60 °C under nitrogen gave the title 1-azulenone (13) quantitatively. Oxidation of 12 and 13 was studied under various conditions, and these compounds were shown to be highly important key intermediates for a large number of the complex products obtained by autoxidation of 1.
Multi-Ionic Potential and Membrane Permeability Matrix. III. Diffusion and Concentration of Ions within Membrane Phase as a Controlling Factor to Ion Permselectivity
Authors: Kaibara Kozue , Inoue Hiroyoshi , Aritomi Toshio
Published: July 2006

Membrane concentrations of cations in the NaCl–CsCl and NaCl–CaCl2 systems with a highly selective cation-exchange membrane were measured under the extensive external electrolyte conditions. The modes of membrane/solution distribution and diffusion of cations, as a controlling factor to the membrane permselectivity, were correlated consistently with the electrochemical and cation flux data, as well as with the estimated membrane permselectivity parameters. The NaCl–CsCl uni-uni valent cation system was characterized well by the Na+/Cs+ concentration ratio of external solution, since the Na+/Cs+ concentration ratio in the membrane phase was related directly to the external ratio. Na+/Cs+ diffusion coefficient ratio varied from 0.5 to 3 with increasing external Na+/Cs+ concentration ratio from 1/100 to 100. While in the NaCl–CaCl2 uni-bi valent cation system, the high and constant membrane concentration of Ca2+ regulated the transport process. The Na+/Ca2+ diffusion coefficient ratio ranged from 0.5 to 500 with external Na+/Ca2+ ratio from 1/100 to 100. Analyses on the phenomenological coefficients, describing the inter-cationic correlations within the membrane phase, as a function of the external cation concentration ratio were also carried out.
Oxovanadium(V)-Induced Ring-Opening Oxygenation of Cyclic Ketones in Alcohol
Authors: Hirao Toshikazu , Mori Makoto , Ohshiro Yoshiki
Published: July 2006

Cyclic ketones underwent ring-opening oxygenation on treatment with VO(OEt)Cl2 in alcohol under oxygen to give the corresponding keto ester or diesters depending on the substituent at 2-position. This system was applicable to a catalytic reaction.
Synthesis and Reaction of a New Chiral Pyridoxamine Analogue; Some Doubt about the Stereochemical Process Tentatively Proposed for a Nonenzymatic Transamination Reaction
Authors: Ando Makoto , Kuzuhara Hiroyoshi
Published: July 2006

A pyridoxamine analogue-like chiral pyridinophane with two sulfonyl groups in the bridging chain, (S)-15-aminomethyl-14-hydroxy-2,8-dithia[9](2,5)pyridinophane S,S,S′,S′-tetraoxide ((S)-7), was prepared by oxidation of the sulfide precursor, (S)-2. The amino group was successfully transferred from (S)-7 to several 2-oxo carboxylic acids in methanol at room temperature in the presence of one-half equimolecular zinc(II) ion, giving (R)-amino acids in excess. The reaction rates of this nonenzymatic transamination using chiral (S)-7 were much smaller than those of the corresponding reaction using chiral (S)-2. The enantiomeric excess of the amino acids obtained through the reactions of (S)-7 was compared with those of (S)-2, showing that (S)-7 was more efficient than (S)-2 for the preparation of (R)-alanine, but was less than that of (S)-2 for the preparations of (R)-valine, (R)-leucine, and (R)-phenylalanine. These results aroused some doubt about the previous explanation of the stereochemical features of such nonenzymatic transamination reactions.
Alkylaion of Toluene with 2-Propanol over Titania–Silica–Alumina Catalysts
Authors: Rao K V C , Sabu K R , Nair C G R
Published: July 2006

The alkylating activity of titania supported on silica–alumina has been reported earlier (V. G. Kumar, T. S. Shoba, and K. V. C. Rao, Tetrahedron Lett., 26, 3281 (1985)). Further investigations to synthesize such a catalyst with optimum alkylation activity resulted in the coprecipitation of the catalyst from a solution of pH 4–the test reaction selected being the alkylation of toluene with 2-propanol in a fixed bed tubular reactor. The product mixtures at different reaction times are analyzed to have a view on the variation of yields of different alkylated products with reaction time. The alkylated products are o-cymene, p-cymene, and diisopropyltoluenes (DIT). The presence of titania exerts a synergistic effect upon the alkylating activity of silica–alumina. Also the catalytic activity is governed by the physical characteristics of the catalyst like surface area and porosity. The trend of para-rich isomer distribution observed in the product mixture is attributed to the steric factors. It has been observed that o-cymene is formed at a constant rate whereas p-cymene formation decreased with reaction time. Increased formation of diisopropyltoluenes are observed with the passing of reaction time. Alkylation studies in the temperature range 165–240 °C have been done to find the effect of reaction temperature on the product distribution. Thus a decrease in the ortho to para molar ratio with increase in reaction temperature and increased formation of diisopropyl toluenes at lower temperatures are observed. No considerable reduction in the alkylation activity has been noticed up to five regeneration cycles.
A Calorimetric Study on the β′ Phase in the System Tin–Antimony. Enthalpies of Mixing and Formation
Authors: Badawi Walid Ahmad
Published: July 2006

Calorimetric studies on the behavior of the enthalpy of formation at 573 K in the system tin–antimony have been carried out at the compositions 44, 50, 57 at-% Sb using a presently constructed calorimeter. The enthalpy of mixing at 943 K has been determined in the whole range of composition. The relation of the behavior of mixing to that of formation is found as predicted earlier. The enthalpy of formation displays a pronounced temperature dependence above 623 K. The thermodynamic properties of the alloy SnSb at the three compositions exclude a transformation from β to β′ phase around 600 K. Also estimated entropy terms indicate the absence of such a transformation. Earlier reported additional β phase in the system Sn–Sb seemed therefore not to be present.
On the Intrinsic Difference between Topological Aromaticity and So-Called Quasi-Aromaticity
Authors: Ichikawa Hiroshi , Aihara Jun-ichi , Daehne Siegfried
Published: July 2006

In an attempt to understand the intrinsic difference between topological aromaticity and so-called quasiaromaticity, the authors examined the potential energy and the kinetic energy of electrons in 6-π-acyclic polymethine-like molecules (5–7), benzene (8), and hexatriene (9) as a reference structure. Protonation interrupts π conjugation; the energetic difference from the non-protonated structure depends on the conjugative stabilization energy. Such a difference from the reference system corresponds to extra stabilization. Analysis of this difference showed that benzene increases the kinetic energy by interrupting its conjugation more than hexatriene while polymethine-like molecules increase the potential energy by doing so. This indicates that extra stabilizaion in benzene is produced by lowering the kinetic energy of electrons. In marked contrast with this that in polymethine-like molecules is due to lowering the potential energy. Analogous results were obtained in the ten-π-electron systems (10–13). The authors discussed the inappropriateness of the term “quasi-aromatic” for polymethinic resonance stabilization.
A Modified Vapor Saturation Method for Preparing Aqueous Solutions of Solid Aromatic Hydrocarbons
Authors: Sanemasa Isao , Ishibashi Kazunari , Kumamaru Masaya , Deguchi Toshio
Published: July 2006

An excess quantity of a solid hydrocarbon is dispersed in water, and then air is bubbled through the aqueous phase to produce the solute vapor. The vapor is introduced into a separate water phase and circulated in a closed system. Aqueous solutions saturated with some solid aromatic hydrocarbons can be prepared in a relatively short time without any need to remove solute microcrystals. It can be confirmed whether the solubility obeys Henry’s law. The present method provides us with rough enthalpy of sublimation of a solute if its solubility follows Henry’s law. Biphenyl, naphthalene, phenanthrene, and anthracene were examined as solutes.
Implications of Unusual Population Ratios in Rotational Isomers of 9-(4-Substituted Benzyl)-8,13-dichloro-1,4-dimethyltriptycenes and 4-Substituted 9-Benzyl-8,13-dichloro-1-methyltriptycenes: CH3···π Hydrogen Bond
Authors: Nakai Yasufumi , Inoue Katsuya , Yamamoto Gaku , Oki Michinori
Published: July 2006

Population ratios of rotational isomers in substituted 9-benzyl-8,13-dichloro-1-methyltriptycenes were examined by equilibration in solution. The sc isomers increase in their populations as the electron density on the 9-benzyl group increases and the acidity of the 1-methyl group increases. The sc/ap ratios were larger than 2, the statistical value, in all the compounds examined, except the 4-nitrobenzyl compound. By contrast, MM2 calculations show that the sc isomers are less stable than the ap by ca. 1 kcal mol−1. This discrepancy together with the substitutent effects on populations of the rotamers are attributed to the presence of CH3···π interactions in the sc forms that stabilize the system mainly by charge-transfer interactions but are not included in the MM2 calculations.
Catalytic Intermolecular Hydrogen Transfer with Photogenerated Hydride Transient CoH[PPh(OEt)2]3
Authors: Onishi Masayoshi , Matsuda Masahiko , Takaki Isato , Hiraki Katsuma , Oishi Shigero
Published: July 2006

Pyrex-filtered photoirradiation of a thermally inert complex CoH[PPh(OEt)2]4 generated a coordinatively unsaturated active hydride species “CoH[PPh(OEt)2]3” (CoHP3), which catalyzed hydrogen transfer from secondary alcohols to carbonyl compounds, such as ketones. Study of initial reaction-rate dependence of the hydrogen transfer on complex and substrate concentrations indicated that the reaction was initiated by coordination of the carbonyl compounds to the photogenerated CoHP3 species, and these coordination was confirmed by the decay analysis of the transient CoHP3 absorbance observed after laser flash photolysis. In addition, the rate-determining step of the hydrogen-transfer reaction was associated with the hydride transfer to the carbonyl carbon, at the stage of the transformation of hydrido (ketone or aldehyde) cobalt into alkoxo intermediate. Second-order coordination-rate constants k′ of aldehydes and ketones to CoHP3 ranged from 105 to 108 M−1 s−1. The constants k′ of aldehydes were considerably larger than those of ketones, where substantial steric repulsion by the bulky substituents introduced in place of the aldehyde hydrogen, was presumed to hinder the CoHP3 approach to the carbonyl group.
A New and Convenient Synthesis of 1α,25-Dihydroxyvitamin D2 and Its 24R-Epimer
Authors: Tsuji Masahiro , Yokoyama Shinji , Tachibana Yoji
Published: July 2006

1α, 25-Dihydroxyvitamin D2 (1a) was synthesized by irradiation and subsequent thermal isomerization of (22E)-5,7,22-ergostatriene-1α,3β,25-triol (16a). The triol 16a was obtained via 22-oxo-5α,8α-(4-phenyl-3,5-dioxo-1,2,4-triazolidine-1,2-diyl)-23,24-dinor-6-cholene-1α,3β-diyl diacetate (12) starting from (22E)-5,7,22-ergostatriene-1α,3β-diyl diacetate (10), a precursor of 1α-hydroxyvitamin D2. Introduction of the new side chain with the desired stereochemistry was carried out selectively by the reductive elimination of the β-hydroxy sulfone derived from the C-22 aldehyde (12) and an optically active sulfone, prepared via (S)-2,3-dimethyl-1,3-butanediol from methyl (S)-3-hydroxy-2-methylpropionate. Similarly a C-24 epimer of 1a was synthesized.
A Synthesis of Unsymmetric Porphyrin Dimers
Authors: Maruyama Kazuhiro , Nagata Toshi , Ono Noboru , Osuka Atsuhiro
Published: July 2006

A new synthetic method of porphyrins via bis(hydroxymethyl)dipyrromethanes is described. This new method can be utilized for preparation of several unsymmetric porphyrin dimers.
Adsorption of Poly(methyl methacrylate) on Silica Surfaces Having Various Silanol Densities
Authors: Kobayashi Kazutoshi , Araki Kazuo , Imamura Yoshio
Published: July 2006

The adsorption of poly(methyl methacrylate) (PMMA) on silica surfaces having various silanol densities was studied by ESR and IR spectroscopies. Three silica samples, Nipsil HD, Aerosil 300, and Aerosil R812, which have 8, 2.2, and 0.54 nm−2 silanol densities, respectively, were used as the adsorbents. The amount of adsorption, A, the surface coverage, θ, and the fraction of train segments in the polymer, p, were determined. The values of the segment fractions anchoring through the hydrogen bond in all train segments of the adsorbed polymer, fHB, were also estimated. When PMMA adsorbed on Nipsil HD, the polymer adsorbed predominantly by the formation of hydrogen bonds; on the other hand, when PMMA adsorbed on Aerosil 300, the polymer adsorbed through the hydrogen bond in the part of 30–40%. When PMMA adsorbed onto Nipsil HD, the value of pESR obtained by the ESR method was almost the same as the pIR obtained by the IR method. When PMMA adsorbed onto Aerosil 300, the value of pESR was 0.47, twice the value of pIR(0.24).
The Conformational Interconversion of 1,3-Diamine Chelate: Tetracyano(1,3-propanediamine)ferrate(III)
Authors: Kuroda Yoshitaka , Goto Masafumi , Sakai Tomoya
Published: July 2006

The activation parameters for the chair-to-chair interconversion of the six-membered chelate ring of [FeIII(CN)4(1,3-propanediamine)]− have been determined from a line-shape analysis of the 1H NMR spectra of the paramagnetic complex by taking advantage of the large differences in the chemical shift: ΔH≠=32.2±4.6 kJ mol−1, ΔS≠=31.2±28.6 J mol−1 K−1, and ΔG298≠=22.9±3.9 kJ mol−1. The ΔH≠ and ΔS≠ values are larger by 7.5 kJ mol−1 and 31 J mol−1 K−1 than those of the corresponding 1,2-ethanediamine chelate, [FeIII(CN)4(1,2-ethanediamine)]−, respectively. The kinetic data supported the transition state with a half-boat conformation.
Polar and Dipolar Substituent Effects and Transition State in the Reaction between Substituted Anilines and Nitrosobenzene. An Evaluation of Ortho and Electrostatic Effects
Authors: C. Schmitt Carla , A. Moritz Carlos , G. Pizzolatti Moacir , A. Yunes Rosendo
Published: July 2006

The rate constants of the hydronium catalyzed attack of substituted anilines on nitrosobenzene, to give azobenzene, exhibit a large dependence on the substituent constant σ− (ρ−=−1.92). The relatively high value of ρ− compared to that obtained from the equilibrium of protonation of anilines (ρ−=−2.77) and the solvent effect on the rate constants support the idea that the transition state involves a large amount of nitrogen–nitrogen bond formation and therefore a strong charge development on the nitrogen and oxygen of the amino and nitroso groups, respectively. A good correlation between basicity and nucleophilic reactivity is obtained by the Brönsted equation (β=0.65, r=0.988) for the para and meta dipolar substituents. Aminobenzoates show a significantly higher reactivity than that calculated from the Brönsted line and this is attributed to an electrostatic participation of the carboxylato group. Nevertheless, this effect is somewhat compensated by repulsion between the carboxylato and the negatively charged oxygen of the nitroso group.
Polyazamacrocycles. V. Structure of Isomeric 3,5,7,7,10,12,14,14-Octamethyl-1,4,8,11-tetraazacyclotetradecanes
Authors: Bembi Ramesh , M. Sondhi Sham , K. Singh Ashok , K. Jhanji Amrit , G. Roy Tapashi , Lown J William , Ball R G
Published: July 2006

Reduction of 3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene (Me8[14]diene) with sodium borohydride yields three diastereomeric Me8[14]anes. These diastereomers can be separated through fractional crystallization from xylene. The structure of these isomers has been established on the bseis of their NMR spectra. The structure of one isomer has been confirmed by X-ray crystallography.
Systematic Enumerations of Highly Symmetric Cage-Shaped Molecules by Unit Subduced Cycle Indices
Authors: Fujita Shinsaku
Published: July 2006

Cage-shaped hydrocarbons are enumerated, starting from the tetrahedron skeleton (Td symmetry). This enumeration stems from an edge strategy in which six edges of the skeleton are substituted by m methylene and n ethylene units. This is accomplished by a new method based on unit subduced cycle indices. This is a versatile methodology for counting cage-shaped hydrocarbons that have a given subsymmetry and an index term, xmyn, the latter of which corresponds to the molecular formula C4+m+2nH4+2m+4n.
1H and 79Br NMR in 1,4-Didecyl-1,4-diazoniabicyclo[2.2.2]octane Dibromide and Diiodide
Authors: Nakayama Hirokazu , Eguchi Taro , Nakamura Nobuo , Chihara Hideaki , Nogami Takashi , Imamura Kengo , Shirota Yasuhiko
Published: July 2006

Temperature dependence of 1H NMR spin-lattice relaxation time was measured in solid 1,4-didecyl-1,4-diazoniabicyclo[2.2.2]octane dibromide and diiodide (C10–DABCO–C10–Br2 and C10–DABCO–C10–I2). 79Br NMR spin-lattice relaxation time and chemical shift measurements in the high-temperature phase were also performed in C10–DABCO–C10–Br2. It was found that the cation rotates isotropically, while the anion diffuses at a correlation time of ca. 10−8 s in the high-temperature phase of C10–DABCO–C10–Br2. The activation energies for these modes are 30 and 34 kJ mol−1, respectively. Methyl reorientation is activated in the low-temperature phase (Ea=11.8 kJ mol−1 in C10–DABCO–C10–Br2 and Ea=12.0 kJ mol−1 in C10–DABCO–C10–I2). Near the phasetransition temperature some motion of decyl chain is observed (Ea=57 kJ mol−1 in C10–DABCO–C10–Br2 and Ea=35.5 kJ mol−1 in C10–DABCO–C10–I2).