bluuebunny/crossref_metadata_2025 huggingface dataset:
The Conformation of 2-Phenylpropionaldehyde and Alkyl 1-Phenylethyl Ketones as Evidenced by Ab Initio Calculations. Relevance of the CH/π and CH/O Interactions in Stereochemistry
Authors: Takahashi Osamu , Yasunaga Kenji , Gondoh Yoshinobu , Kohno Yuji , Saito Ko , Nishio Motohiro
Published: September 2002

Ab initio MO calculations were carried out for the conformation of 2-phenylpropionaldehyde 1 and related ketones CH3CH(C6H5)–CO–R (R = CH3  2, C2H5  3, i-C3H7  4, and t-C4H9  5) at the MP2/6-311G(d,p)//MP2/6-31G(d) level. The conformation whereby the alkyl group R is synclinal to the phenyl group (rotamer a, C6H5–C–CO–R torsion angle φ 64–93°) has been found to be the most stable. The second most favorable one has been shown to have R flanked by the benzylic methyl group and C6H5 (rotamer b: φ 282–297°). The difference in the enthalpy between a and b has been calculated to be 1.58, 2.16, 2.19, 2.08, and 4.89 kcal mol−1, respectively, for 1, 2, 3, 4, and 5. The C6H5/R antiperiplanar conformation (rotamer c) has been shown to be the least stable for 1 (φ 171°) and is not at an energy minimum for 2–5. In rotamers a and b, short interatomic distances have been shown between one of the alkyl hydrogens and the phenyl group. In rotamer a, a short distance has been calculated between one of the hydrogens of the benzylic methyl group and the carbonyl oxygen. The ab initio results are compatible with those obtained by NMR measurements. Contributions of the CH/π and CH/O interactions to the conformational equilibria have been invoked to accommodate the above results. Instability of rotamer c may be due to the unfavorable electrostatic interaction of the C=O dipole vs the quadrupole of the phenyl group. Conformational energies of methyl formate 6, N-methylformamide 7, and propionaldehyde 8 were also calculated to examine the effect of the CH/O interaction in carbonyl compounds. The results are consistent with the notion that the CH/O interaction is important in stabilizing the CH3/O eclipsed conformation.
Theoretical Study of Dimethyl Maleate and Its Complexes with Lewis Acids: Effect of the Interaction between Two Methoxycarbonyl Groups on Equilibrium Structures
Authors: Akakura Matsujiro , Koga Nobuaki
Published: September 2002

The five equilibrium structures of dimethyl maleate were theoretically determined using the RHF and B3LYP methods. In all of the structures, one of the O=C–O planes is nearly perpendicular to, and the other is coplanar with, the C–C=C–C plane. It is well known that maleic acid diester has peculiar reactivity compared with other conjugated esters, which can be ascribed to the characteristics of the conformations. Calculations of complexes of dimethyl maleate and Lewis acids were performed, and the binding energies for the complexes were analyzed by decomposing them into the deformation energy and the interaction energy. For a comparison, the conformational properties of methyl acrylate and its Lewis acid complexes were also investigated.
Synthesis, Structures, and Properties of Two Isomeric Naphthodithiophenes and Their Methyl, Methylthio, and 2-Thienyl Derivatives; Application to Conductive Charge-Transfer Complexes and Low-Bandgap Polymers
Authors: Takimiya Kazuo , Kato Ken-ichi , Aso Yoshio , Ogura Fumio , Otsubo Tetsuo
Published: September 2002

Two isomeric naphthodithiophenes (syn-NDT and anti-NDT), isoelectronic with pyrene, as well as their dimethyl, bis(methylthio), and di(2-thienyl) derivatives have been successfully synthesized as novel peri-fused heteroaromatics. Among them, the parent syn-NDT and the di(2-thienyl) derivative of anti-NDT were examined by X-ray crystallographic analyses, revealing that the molecular structures comprise fairly planar, but considerably strained skeletal rings, and their crystal structures are characterized by a herringbone arrangement of uniform stacking columns. The UV/vis spectra of these heteroaromatics show considerable red-shifts of the π–π* transitions as compared to that of pyrene, making them chromogens ranging from yellow to purple. Cyclic voltammetry indicates that they have much stronger electron donating abilities than pyrene. Consequently, all of them, except for the methyl derivatives, can form highly conductive molecular complexes with iodine and DDQ. In addition, the electrochemical oxidation of the parent naphthodithiophenes and the di(2-thienyl) derivatives leads to the formation of conductive polymers, which show low HOMO–LUMO bandgaps upon undoping. In particular, both polymers of syn-NDT and anti-NDT have very low bandgaps of ca. 0.8 eV (77 kJ mol−1).
Addition Reactions of Polyhalides to Ketene Silyl Acetals and Silyl Enol Ethers under Thermal or Photo-Irradiated Conditions without a Promoter
Authors: Mitani Michiharu , Sakata Hideo , Tabei Hisayuki
Published: September 2002

The reactions of ketene silyl acetals and silyl enol ethers in a CCl4 solution containing no promoter under ambient temperature, reflux, or photo-irradiation conditions afforded products via the addition of a trichloromethyl group to those silyl substrates. Polyhalides other than CCl4 were subjected to photoreactions in a hexane solution, resulting in the formation of carbonyl derivatives based on the addition of polyhalogenated alkyl groups.
Oxidative Dehydrogenation of Propane on Magnesium Vanadates in the Presence of Tetrachloromethane
Authors: Sugiyama Shigeru , Iizuka Yutaka , Konishi Yukinori , Hayashi Hiromu
Published: September 2002

The oxidative dehydrogenation of propane to propene on active catalysts such as magnesium vanadates (MgV2O6, Mg2V2O7, and Mg3V2O8) has been investigated in the presence and absence of tetrachloromethane (TCM) at 723 K. The introduction of a small amount of TCM into the feedstream did not influence the selectivity to propene while the conversion of propane was improved on those catalysts. The conversion was enhanced by approximately twice on Mg2V2O7 upon addition of TCM. It has been shown that the effects of TCM on lattice oxygen in those catalysts mainly control the enhancement. The formation of an excess amount of the chlorinated species on the surface of the catalysts resulted in a decrease of the conversion.
Density Functional Studies on Kinetic Reactivity of “Higher Order” Lipshutz Cuprate in Addition Reaction to Acetylene
Authors: Yamanaka Masahiro , Mori Seiji , Nakamura Eiichi
Published: September 2002

There is a frequently used organocuprate species that was introduced by Lipshutz and possesses a molecular structure written as CuLi2R2(CN). This species was previously called “higher order cuprate”, but is now considered to exist as an equilibrating mixture of various isomers of R2CuLi·LiCN and R(CN)CuLi·LiR, among which R2Cu−·Li2CN+ is known to be dominant in solution. The present studies on the kinetic reactivity of these species in the addition reaction to acetylene suggest that the minor species R(CN)CuLi·LiR may be more reactive than the major species, thereby making it equally possible that addition reaction products may arise through both the major and the minor reactive species. The reason for the high reactivity of the minor species has been ascribed to the anisotropic and multi-coordination capability of the cyanide ligand to metals; such capability is not available for a halide or alkyl anion ligand.
Iminomalonate as a Convenient Electrophilic Amination Reagent for Grignard Reagents
Authors: Niwa Yasuki , Takayama Kazuki , Shimizu Makoto
Published: September 2002

Diethyl 2-[N-(p-methoxyphenyl)imino]malonate underwent amination reactions with alkyl Grignard reagents to give N-aklylation products in good yields. The obtained N-alkylation products were readily converted into N-alkyl-p-anisidines by the oxidative removal of the malonate moiety. The p-methoxyphenyl group was subsequently deprotected to give primary amines.
A Novel Synthetic Route to Redox-Active Oligo(thio-1,4-phenylene) Derivatives via a Michael-Type Addition
Authors: Yamamoto Kimihisa , Higuchi Masayoshi , Nishiumi Toyohiko , Takai Hirokazu
Published: September 2002

N,N′-Diphenyl-1,4-benzoquinone diimine (PBI), which is the minimum redox-active unit of polyaniline, was reduced to N,N′-diphenyl-1,4-phenylenediamine (PDA) derivatives through Michael-type additions of some nucleophiles. The addition of thiophenol to PBI proceeded very rapidly. The polyaddition of PBI-endcapped monomers (P-2PBI, B-2PBI, and TB-2PBI) with thiobisbenzenethiol (TB) produced the novel thermostable oligo(thio-1,4-phenylene)s (OTP) having PDA units as a redox-active site (OTP-P-PDA, OTP-B-PDA, and OTP-PDA). This polymerization proceeded at room temperature without catalysts. OTP-P-PDA, one of the oligomers obtained, was found to have a moderate molecular weight (Mw 8400) and to possess good thermostability (Td10% 400 °C). The polymerization based on Michael-type additions was also confirmed by NMR measurements. The oligomers obtained behaved as good electro-responsive materials. The redox process was determined by the slope of the Nernst plot that involved two electrons and two protons per PDA unit.
Oxygenative Perfluoroalkylation of Olefinic Compounds Using Perfluoroalkyl Iodide in the Presence of Oxygen
Authors: Yoshida Masato , Ohkoshi Masanori , Muraoka Tsunehiro , Matsuyama Haruo , Iyoda Masahiko
Published: September 2002

Reactions of perfluoroalkyl iodides with styrene and its derivatives were investigated under radical conditions in the presence of oxygen. The photochemical reaction of styrene with CF3(CF2)5I in the presence of tributyltin hydride or tris(trimethylsilyl)silane under an oxygen atmosphere afforded the corresponding perfluoroalkylated alcohols in moderate yields together with CF3(CF2)5H. However, the photochemical reactions of styrene and its derivatives with CF3(CF2)nI (n = 3, 5) in the presence of hexabutylditin under oxygen produced the perfluoroalkylated alcohols in good yields. Furthermore, the reactions of styrenes with CF3(CF2)nI (n = 3, 5, 9) and Na2S2O4 in the presence of a base under air formed the same alcohols in good yields. The alcohols were found to provide a novel type of α-fluoroalkylated styrenes by acidic dehydration. Perfluoroalkylated α,β-unsaturated ketones were synthesized by oxygenative perfluoroalkylations of α-chlorostyrene and its derivatives using CF3(CF2)nI (n = 3, 5) under radical reaction conditions. The ketones were found to be good synthetic building blocks for perfluoroalkylated heterocycles, such as pyrazoles, dihydrodiazepines, pyrimidines, and isoxazoles.
Effect of Alkaline Earth Metal Ions on the Phosphodiester Hydrolysis of RNA
Authors: Yashiro Morio , Higuchi Maiko , Washizu Yusuke , Komiyama Makoto
Published: September 2002

Hydrolyses of di- and triribonucleotides assisted by alkaline earth metal ions were investigated at pH 7.3 and 50 °C. Mg2+ was the most effective for the phosphodiester hydrolysis, and the rate exibited first-order dependence on the concentration of Mg2+ in a range of 0.1–1.0 mol dm−3.
Calix[4]arenes Bearing Four Redox-Active π-Conjugated Pendant Groups for a Dimensionally Oriented Redox System
Authors: Saito Kaori , Hirao Toshikazu
Published: September 2002

A p-t-butylcalix[4]arene bearing four redox-active phenylenediamine pendant groups on the lower rim was synthesized and characterized spectroscopically and electrochemically. The interconversion of the oxidation states of the pendant groups was demonstrated both chemically and electrochemically.
Symmetric, Asymmetric Charge Transfer Process of Substituted Stilbene or Its Analogues and the One-Photon-/Two-Photons-Excited Emission
Authors: Wang Xiaomei , Zhou Yufang , Zhou Guangyong , Jiang Wanli , Jiang Minhua
Published: September 2002

The luminescence behaviors of a series of symmetrically and asymmetrically substituted stilbene or its analogues on one-photon excitation (OPE) and two-photons excitation (TPE) have been investigated and compared. To understand the influence of intramolecular charge transfer upon the fluorescence properties, steady-state and time-resolved fluorescence spectra on one-photon-/two-photons-excitation, the solvent effect and the linear absorption spectra as well as the relative fluorescence quantum yields were examined. Based on the quantum chemical calculations of the charge density and the twisted intramolecular charge transfer (TICT) model, the luminescence properties have been interpreted. The results obtained have shown that the OPE and the TPE fluorescence behaviors are both strongly influenced by the intramolecular charge transfer process and by the planarity of effective fluorophore under the excited state. On the other hand, for a given dye, its luminescence behaviors on one-photon- and two-photons-excitation are very much alike, which means that the knowledge of two-photon fluorescence properties can be obtained by understanding the one-photon fluorescence behaviors.
Corrosion of Iron Coexisting with Molten Sodium Hydroxide and Sodium Peroxide
Authors: Ota Ken-ichiro , Mitsushima Shigenori , Hattori Naotaka , Kamiya Nobuyuki
Published: September 2002

Liquid sodium is used in new energy conversion systems such as fast breeder reactors and sodium-sulfur batteries. Liquid sodium forms high-temperature molten salts once it is exposed to air by reactions with oxygen or moisture. These molten salts might cause the severe corrosion of metals. In this study, the high-temperature corrosion of iron was studied in the presence of sodium salt using thermogravimetry in an air-simulated atmosphere. The corrosion reaction with coexisting NaOH obeyed a parabolic rate law. On the other hand, severe corrosion occurred with coexisting Na2O2. The corrosion reaction changed from a parabolic rate law to a linear rate law as the amount of melt increased, because the dissolution on the corrosion of the corrosion layer would increase with the amount of melt. Since the oxidation ability of Na2O2 is not as high as that of O2, dissolution of an oxide scale on iron would be the main reason for severe corrosion.
Formation of the Copper(II) Nitrosyl Cation, [CuNO]2+, in Strong Acids
Authors: Tsumori Nobuko , Xu Qiang
Published: September 2002

In strong acids, the reaction of Cu0, CuI or CuII compounds with atmospheric NO at room temperature results in the formation of the copper(II) nitrosyl cation, [CuNO]2+, during which the oxidation of Cu0 to CuII is accompanied by the formation of N2 and N2O, whereas the oxidation of CuI to CuII results in the formation of N2O without a significant amount of N2.
Design and Application of Ion-Channel Sensors Based on Biological and Artificial Receptors
Authors: Sugawara Masao , Hirano Ayumi , Bühlmann Philippe , Umezawa Yoshio
Published: September 2002

This paper reviews approaches to chemical sensing with receptor-modified electrodes that mimic the function of natural membranes containing biological and synthetic receptor channels. We highlight different types of ion-channel sensors, focusing on the working principle and the fundamental aspects, such as sensitivity and selectivity. It is demonstrated that biological receptors such as glutamate receptor ion channels and gramicidin, embedded in bilayer lipid membranes, have the potential as sensing elements for ion channel sensors with excellent sensitivity and selectivity. In addition, higher selectivities by improved receptor desigh, taking into account the particular advantages of interfacial analyte recognition at LB membranes and SAMs, are also shown with ion-channel sensors for antibodies, protamine, heparin, abasic DNA sites, and oligonucleotides.
Total Synthesis of Bioactive Marine Terpenoids
Authors: Miyaoka Hiroaki , Yamada Yasuji
Published: September 2002

This paper presents the total synthesis of bioactive marine terpenoids as conducted at this laboratory. The syntheses of marine sesquiterpenoid upial and marine diterpenoid sanadaol were conducted from D-mannitol via sequential Michael reaction and fragmentation reaction. The marine diterpenoid fuscol, its related compound, and phomactin D were obtained by sequential Michael reaction and oxidative cleavage of carbon–carbon double bond. The marine diterpenoid claenone was produced by sequential Michael reaction and retro-aldol reaction. Synthesis of the marine diterpenoid (+)-mayolide A involved the stereoselective introduction of a C2-unit and repeated Claisen rearrangement to construct the side chain as key steps. Synthesis of the marine diterpenoid (+)-halimedatrial involved stereoselective formation of the cyclopropane moiety and formation of the diformylcyclopentane moiety as crucial steps. The marine sesterterpenoid dysidiolide was synthesized by intramolecular Diels–Alder reaction as the key step to obtain the decalin moiety.
Carbon Materials and the Surface Modification in View of Electrochemical Li Insertion/Extraction
Authors: Takamura Tsutomu
Published: September 2002

Carbon is an old, and at the same time, a new material. Carbon plays the leading part in the practical design of Li-ion secondary batteries, the most advanced secondary batteries, where as the negative electrode material it takes Li into the internal structure during the charging. This guarantees the reliability and safety by preventing the dangerous deposition of Li metal. In responding to a strong demand of the high power capability, the author has developed several surface modification methods.

This article describes the surface modification methods I have developed, together with several new findings in relation to the behavior of Li in the interior and on the surface of carbon. The following items are described and analyzed: (1) electrochemical reaction rate in relation to the battery reaction could be enhanced by surface modification such as (a) a simple heating in vacuum, (b) mild oxidation, and (c) vacuum deposition of a metal film on the carbon surface with such metals as Ag, Au, Bi, Cu, In, Pb, Pd, Sn, and Zn together with the oxidized ones. The cause of the enhancement was studied on the basis of SEI (solid-electrolyte-interphase); (2) use of a single fiber electrode enabled us to find what really occurs on the electrode surface, to determine the most reliable values of the Li diffusion coefficient in carbon; and to prevent decomposition of propylene carbonate on graphite; (3) electrical contact was demonstrated as a key factor to reduce the initial charging irreversibility and to enhance the cycleability; (4) underpotential deposition of Li on the carbon surface was pointed out; and (5) free movement of Li in metal at an ambient temperature was confirmed by the use of a bipolar cell.

In the final remarks I offer a new term of “carbon alloys” based on the nano-technology, which will be an attractive material both in science and technology in the new century.
A New Method for Oxidation of Various Alcohols to the Corresponding Carbonyl Compounds by Using N-t-Butylbenzenesulfinimidoyl Chloride
Authors: Matsuo Jun-ichi , Iida Daisuke , Tatani Kazuya , Mukaiyama Teruaki
Published: September 2002

Various primary and secondary alcohols were smoothly oxidized to the corresponding aldehydes and ketones by using a new oxidizing agent, N-t-butylbenzenesulfinimidoyl chloride (4a), in the coexistence of DBU or zinc oxide. The present oxidation proceeded under mild conditions via five-membered intramolecular proton-transfer of an alkyl arenesulfinimidate intermediate.
Ion-Transfer Processes across Liquid/Liquid Interfaces Promoted by a Convective Flux.
Authors: Wilke Natalia , Iglesias Rodrigo Alejandro , Chesniuk Sergio Gustavo , Dassie Sergio Alberto , Baruzzi Ana María
Published: September 2002

Convective flux produced by stirring either the aqueous or the organic phase is proposed as a mechanistic tool to study the ion-transfer processes at ITIES. The dependence of the voltammetric response on the sweep rate and the rotation frequency was used to differentiate the simple transfer of TEA+ from the assisted transfer of K+ by DB18C6 at a water 1,2-dichloroethane interface.
Mass-Spectrometric Study on Ion-Molecule Reactions of CH5+, C2H5+, and C3H5+ with C9–C19 Alkylbenzenes in an Ion Trap
Authors: Tanaka Yuki , Tsuji Masaharu
Published: September 2002

Chemical ionization of alkylbenzenes (PhCxH2x  + 1 = M: x = 3–13) by the CH5+, C2H5+, and C3H5+ ions has been studied under a reactant-ion selective mode of an ion-trap type of GC/MS. The dominant product ions for short-chain reagents (x < 7) were [M + H]+, [PhH + H]+, and CxH2x  + 1+ ions, produced through proton-transfer to benzene ring. On the other hand, the dominant product ions for long-chain reagents (x ≥ 7) were CyH2y + 1+ (y < x) and PhCyH2y+ (y ≤ x) ions. The former ions are produced through the attack of the reactant ions on the alkyl chain and/or the benzene ring, while the latter ones are exclusively formed through the attack of the reactant ions on the alkyl chain. Major formation processes of CyH2y + 1+ and PhCyH2y+ ions in each reaction were discussed on the basis of observed distributions and calculated thermochemical data.
Structural Characterization of Neptunyl(VI) Trinitrato Complexes: M[NpO2(NO3)3] (M = NH4+ and K+)
Authors: Wang Junhu , Kitazawa Takafumi , Nakada Masami , Yamashita Toshiyuki , Takeda Masuo
Published: September 2002

237Np Mössbauer spectra of two neptunyl(VI) trinitrato complexes, M[NpO2(NO3)3] (M = NH4+  1 and K+  2) were measured at 4.5 K, 10 K and 30 K, respectively. The spectra show magnetic hyperfine splittings similar to the spectrum of Rb[NpO2(NO3)3] 3 already reported. Since the SQUID data of 1 indicate that 1 is paramagnetic from 2 K to room temperature, the magnetic hyperfine splittings are due to slow paramagnetic relaxation. The crystal structures of 1 and 2 were refined by the Rietveld analysis, and the mean Np–O bond distances of 1 and 2 have been obtained. Almost the same Np–O bond distances of 1, 2 and 3 exhibit about the same δ values. This is consistent with the linear relationship between the δ values and the mean Np–O bond distances established for the neptunyl(VI) compounds.
Synthesis and Magnetic Properties of MnIIIMnIIMnIII Trinuclear Complexes with Hydroxo Bridges. Comparison of Magnetic Properties between Hydroxo- and Alkoxo-Bridged Complexes by Density Functional Calculations
Authors: Hirotsu Masakazu , Aoyagi Mutsumi , Kojima Masaaki , Mori Wasuke , Yoshikawa Yuzo
Published: September 2002

A hydroxo-bridged MnIIIMnIIMnIII trinuclear complex, [Mn3(L1)2(2,6-dcba)2(OH)2] (1), where H2L1 is N′,N′-bis-(2-hydroxybenzyl)-N′,N′-dimethylethylenediamine and H2,6-dcba is 2,6-dichlorobenzoic acid, was synthesized by the reaction of Mn(ClO4)2·6H2O with H2L1, H2,6-dcba, and a base in acetonitrile. The structure of 1 was determined by X-ray crystallography: 1 crystallizes in the monoclinic space group P21/c with a = 9.616(4) Å, b = 12.537(4) Å, c = 23.099(4) Å, β = 94.73(2)°, V = 2775(1) Å3, and Z = 2. The central MnII and terminal MnIII ions are bridged by phenolato, carboxylato, and hydroxo ligands to form a linear MnIII–MnII–MnIII arrangement. The bridging structure between MnIII and MnII is similar to that of analogous alkoxo-bridged complexes, [Mn3(L)2(carboxylato)2(alkoxo)2], where L is L1 or its derivatives. Most of the alkoxo-bridged complexes [Mn3(L)2(carboxylato)2(alkoxo)2] exhibit a weak ferromagnetic interaction between MnIII and MnII, while the hydroxo-bridged complex 1 exhibits a weak antiferromagnetic interaction. A comparison of the magnetic properties between the hydroxo- and alkoxo-bridged complexes was performed by density functional calculations of MnIIIMnII dinuclear model complexes.
Solvent-Dependent Formation of Di- and Trinuclear Rhodium and Iridium Complexes Bridged by N, N′-Donor Ligands
Authors: Yu Xiao-Yan , Maekawa Masahiko , Morita Tomonori , Chang Ho-Chol , Kitagawa Susumu , Jin Guo-Xin
Published: September 2002

Reactions of Rh and Ir hydrido complexes, [Rh(H)2(PPh3)2(solv)(EtOH)]ClO4 (solv = Me2CO, 1a; EtOH, 1b) and [Ir(H)2(PPh3)2(Me2CO)2]BF4 (2), with various N,N′-donor bridging ligands, such as pyrazine (pyz), 4,4′-trimethylenedipyridine (tmdp) and di(4-pyridyl) disulfide (dpds), in some solvents were examined, and their reaction products were characterized by X-ray crystal structure analysis, IR, 1H NMR and UV-vis spectra. Rh hydrido complexes, 1a or 1b, formed a dinuclear Rh complex, [Rh2(PPh3)2{(η6-C6H5)PPh2}2](ClO4)2·6CH2Cl2 (3·6CH2Cl2), in dichloromethane with a reductive elimination of hydrogen. The reactions of 1a or 1b with the pyz ligand in dichloromethane and tetrahydrofuran gave triangular Rh3 complexes, [Rh3(PPh3)6(pyz)3](ClO4)3·CH2Cl2 (5·CH2Cl2) and [Rh3(PPh3)6(pyz)3](ClO4)3·EtOH (5·EtOH), respectively, in contrast to the formation of a dinuclear Rh hydrido complex, [Rh2(H)4(PPh3)4(Me2CO)2(pyz)](ClO4)2·EtOH (4·EtOH), in acetone. The reactions of 1a or 1b with the tmdp ligand in dichloromethane and 3-methyl-2-butanone also afforded dinuclear Rh complexes, [Rh2(PPh3)4(tmdp)2](ClO4)2 (6) and [Rh2(PPh3)4(tmdp)2](ClO4)2·4MeCOCHMe2 (6·4MeCOCHMe2), respectively. On the other hand, Ir hydrido complex 2 reacted with pyz and dpds ligands in dichloromethane to afford dinuclear Ir complexes, [Ir2(H)4(PPh3)4(Me2CO)2(pyz)](BF4)2·3CH2Cl2 (7·3CH2Cl2) and [Ir2(H)4(PPh3)4(dpds)2](BF4)2·3CH2Cl2·H2O (8·3CH2Cl2·H2O), respectively, without any reductive elimination of hydrogen. Based on structural studies in solution and in the solid state, it was demonstrated that various Rh and Ir complexes were selectively produced depending on the choice of solvents and N,N′-donor bridging ligands.
Mössbauer and Infrared Studies of Reactions of Laser-Evaporated Iron Atoms with Methane
Authors: Yamada Yasuhiro , Katsumata Keiichi , Shimasaki Hideo , Ono Yuki , Yamaguchi Kayoko
Published: September 2002

The reaction of laser-evaporated iron atoms with methane gas was studied using a matrix-isolation technique, and the reaction products were observed by Mössbauer and infrared spectroscopy. The reaction produced CH3FeH in a CH4/Ar mixture, whereas Fe2H2(CH3)4 was also obtained in addition in a pure CH4 matrix. Molecular orbital calculations were performed in order to confirm the assignments.
Synthesis and Crystal Structure of {6-Amino-5-[6-amino-4-oxo-(1H)-pyrimidin-2-yl]thio-2-thioxo-pyrimidin-4-onato}[tris(2-aminoethyl)amine]cobalt(III) Perchlorate
Authors: Yamanari Kazuaki , Kida Makiko , Fuyuhiro Akira , Kaizaki Sumio
Published: September 2002

The novel tris(2-aminoethyl)aminecobalt(III) complex containing a dimerized ligand Hatuc-atuc (6-amino-5-[6-amino-4-oxo-(1H)-pyrimidin-2-yl]thio-2-thioxo-pyrimidin-4-onate(2-)) was prepared. The crystal structure revealed that Hatuc-atuc coordinates through the S/N donors and exhibits the intermolecular π–π stacking and the double N–H···O hydrogen bond interactions.
Effect of a Polymethylene Chain on the Intramolecular Hydrogen Bond between Adenine and Thymine
Authors: Itahara Toshio
Published: September 2002

The intramolecular hydrogen bond between the adenine and thymine rings of 9-[ω-(thymin-1-yl)alkyl]adenine was investigated in chloroform by means of NMR spectroscopy. The formation of the intramolecular hydrogen bond was dependent on the length of the polymethylene chains between adenine and thymine, and the thermodynamic parameters were estimated. The length of the polymethylene chains caused a marked difference in the physical properties of the compounds.
Protic Acid Catalyzed Stereoselective Glycosylation Using Glycosyl Fluorides
Authors: Jona Hideki , Mandai Hiroki , Chavasiri Warinthorn , Takeuchi Kazuya , Mukaiyama Teruaki
Published: September 2002

A catalytic and stereoselective glycosylation of various glycosyl acceptors, such as methyl glycosides, thioglycosides, or a disarmed glycosyl fluoride, with benzyl-protected armed glycosyl fluoride was successfully carried out by using various protic acids in the presence of MS 5A. In the cases when trifluoromethanesulfonic acid (TfOH) or perchloric acid (HClO4) was used in diethyl ether (Et2O), α-glycosides were obtained as major products, while β-stereoselectivity was observed when tetrakis(pentafluorophenyl)boric acid [HB(C6F5)4] was used in a mixed solvent of trifluoromethylbenzene (BTF)–pivalonitrile (tBuCN) = 5 : 1. Stereoselectivity of this glycosylation was controlled by the properties of counter anions of the catalyst as well as by those of solvents. Also, one-pot trisaccharide synthesis was performed by successive addition of NIS and third-sugar to afford Glcα or β1–6Glcβ1–6Glc and Glcα or β1–6GlcNβ1–6Glc in excellent yields.
Selective Oxidation of Phenols to Hydroxybenzaldehydes and Benzoquinones with Dioxygen Catalyzed by Polymer-Supported Copper
Authors: Takaki Ken , Shimasaki Yohei , Shishido Tetsuya , Takehira Katsuomi
Published: September 2002

Oxidation of 2,6-disubstituted 4-methylphenols with dioxygen by using a CuCl2-poly(4-methyl-4′-vinyl-2,2′-bipyridine) catalyst gave the corresponding 4-hydroxybenzaldehydes in high yields. The activity of the catalyst and the selectivity of the products significantly depended on the reaction conditions and the composition of the catalyst. When the molar ratio of the bipyridine unit of the polymer ligand to Cu was unity, i.e., N/Cu = 2, the best results were obtained. Moreover, the reaction is likely to be promoted by coordination of the products to the catalyst. Similarly, 2,3,6-trimethylphenol and related compounds were converted to p-benzoquinones selectively with a CuCl2-poly(4-vinylpyridine) catalyst. These polymer-supported catalysts were readily recovered and are reusable without noticeable decrease of their activity.
Structure Elucidation of 6-t-Butyl-6-phenylpentathiane Monoxides by X-ray Crystallography and DFT Calculations
Authors: Ishii Akihiko , Oshida Hideaki , Nakayama Juzo
Published: September 2002

6-t-Butyl-6-phenylpentathiane was oxidized with trifluoroperacetic acid (CF3CO3H) or dimethyldioxirane (DMD) at -20 °C. Oxidation with CF3CO3H yielded pentathiane 3-oxide as the main product, whereas that of DMD gave 1- and 3-oxides. The structures of 1- and 3-oxides were finally determined by X-ray crystallographic analysis. DFT calculations of the NMR chemical shifts were performed on the chair and twist forms of the pentathiane and sixteen isomers of the monoxides with the GIAO method at the B3LYP/6-31G* level. The calculated chemical shifts were verified to be in practical agreement with the experimental data of the pentathiane and the isolated 1- and 3-oxides.
Copper(II) Reagent-Promoted Degradation of N, N′-dialkyldiazenedicarboxamides
Authors: Yamaguchi Jun-ichi , Murayama Yukihito , Suyama Takayuki
Published: September 2002

Degradation of N,N′-dialkyldiazenedicarboxamides with a copper(II) reagent, which was prepared from lithium 4-nitrophenoxide and copper(II) bromide in tetrahydrofuran, proceeded via formation of isocyanate to produce the corresponding 4-nitrophenyl N-alkylcarbamate with the evolution of nitrogen. Further, it was also found that 4-nitrophenyl N-alkylcarbamate reacted with primary or secondary amines to give the corresponding multisubstituted urea. Based on the above results, we developed a new method for the one-pot preparation of multisubstituted ureas from N,N′-dialkyldiazenedicarboxamides.
Controlled Specific Ligand Substitution and Chiroptical Properties of Ruthenium Bis(bipyridine) Nitrosoarene Complexes
Authors: Hesek Dusan , Hembury Guy A , Drew Michael G B , Inoue Yoshihisa
Published: September 2002

Reaction of rac-cis-Ru(Cl)2(bpy)2 with N,N-diethyl-4-nitrosoaniline (2) yields the compound rac-cis-[Ru(Cl)-(bpy)2(2)]Cl in 90–95% yield. Irradiation at 420 nm results in the novel specific substitution of the equatorial chloride ligand for MeCN, leaving the nitrosoarene ligand unaffected. X-ray analysis shows that the nitrosoarene ligand does not participate in an intramolecular π–π interaction with a bipyridine; molecular modelling confirms the relative instability of such a conformation. High thermal stability allows the Δ and Λ enantiomers to be separated and the circular dichroism spectra to be obtained; the anisotropy, or g, factors that are subsequently derived are found to be unexpectedly large.
Efficient Method for the Preparation of Aromatic Bromides and Iodides by Ferrocenium Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate-Catalyzed Halogenation with Bromine and Iodine Monochloride
Authors: Kitagawa Hideo , Shibata Tsuyoshi , Matsuo Jun-ichi , Mukaiyama Teruaki
Published: September 2002

Direct iodination and bromination of various aromatic compounds with 1.1–2.0 molar amounts of iodine monochloride (ICl) and 1.1–3.0 molar amounts of bromine proceeded smoothly to afford the corresponding aromatic iodides and bromides, respectively, in good to excellent yields by using 0.05 molar amount of ferrocenium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, Cp2FeB[3,5-(CF3)2C6H3]4 (1), in the presence of ZnO. Iodination of toluene in the coexistence of 0.5 molar amount of DDQ also proceeded to give iodotoluenes in high yield.
Preparation of Deoxygenated Derivatives of Neoanisatin, a Neurotoxic Sesquiterpenoid Having a β -Lactone
Authors: Obitsu Kazuyoshi , Maki Shojiro , Hirano Takashi , Niwa Haruki
Published: September 2002

Seven deoxygenated neoanisatin derivatives were prepared from anisatin and neoanisatin by utilizing methoxalyl ester/tributylstannane (n-Bu3SnH) deoxygenation procedure coupled with a novel dehydration reaction of neoanisatin.
Over 98% Optical Yield Achieved by a Heterogeneous Catalysis. Substrate Design and Analysis of Enantio-Differentiating Factors of Tartaric Acid-Modified Raney Nickel Hydrogenation
Authors: Sugimura Takashi , Nakagawa Satoshi , Tai Akira
Published: September 2002

Tartaric acid-modified Raney nickel (TA-MRNi) is a chiral heterogeneous catalyst for the hydrogenation of prochiral ketones. An optical yield (OY) of 86% with methyl acetoacetate (1) as a substrate was improved to 94–96% by employing β-keto esters having a proper bulkiness at the γ -position. The γ -bulkiness effect contributes to a high intrinsic enantio-differentiating ability (factor-i) of the TA-MRNi catalysis. Through the study, we found the best substrate, γ -cyclopropyl-β-keto ester, the hydrogenation of which resulted in 98.6% OY. This further improvement in the OY was ascribed to a smaller contribution of non-enantio-differentiating hydrogenation (N-site catalysis) due to the substrate-specific activation of the enantio-differentiating hydrogenation by the chiral modifier. The OY of the hydrogenation of 1 was analyzed by comparing with well-behaved β-keto esters, and the contribution of the factor-i and the N-site to the OY value was evaluated to deduce the origin of the enantiodifferentiation.
A Unified Con/Dis Approach to Assigning Stereogenic Axis Configuration
Authors: Mandal Dipak K
Published: September 2002

A new and unifying approach based on a directional relationship between two arcs joining two ligands at either end of the stereogenic axis is presented for assigning stereogenic axis configuration, which is specified as Con (when both arcs are clockwise or counterclockwise) or Dis (when one arc is clockwise and the other counterclockwise). Con and Dis correspond, respectively, to the descriptors axial R and axial S for a chiral axis, and to E and Z for an achiral alkene axis.
A Novel and Efficient Method for the Synthesis of Tetrahydropyranyl Ethers Catalyzed by Sc(OTf)3
Authors: Watahiki Tsutomu , Kikumoto Hisashi , Matsuzaki Masaya , Suzuki Takeshi , Oriyama Takeshi
Published: September 2002

Reaction of alcohols with dihydropyran in the presence of a catalytic amount of Sc(OTf)3 provides efficiently the corresponding tetrahydropyranyl ethers. After the reaction, the catalyst can be recovered quantitatively from the aqueous media and reused without loss of the activity.
Interpenetrating Polymer Networks Based on Hydrogenated Castor Oil–Isophorone Diisocyanate and Poly(butyl methacrylate)
Authors: Athawale Vilas D , Pillay Priti S
Published: September 2002

Hydrogenated castor oil was reacted with isophorone diisocyanate under different stoichiometric NCO/OH ratios to obtain polyurethanes. These polyurethanes were subsequently interpenetrated with butyl methacrylate monomer using ethylene glycol dimethacrylate as a crosslinker by radical polymerization using benzoyl peroxide as an initiator. Polyurethane/poly(butyl methacrylate) interpenetrating polymer networks (PU/PBMA IPNs) were obtained as tough films by casting in a glass mould. All IPNs were characterized for their resistance to thermal behavior, swelling (%), and mechanical properties. The morphology of the IPNs was studied by scanning electron microscopy. Enhanced mechanical properties were obtained with an increase in the NCO/OH ratios in addition to the regular trend obtained by increasing the polyurethane component in the blend.
Formation of Glyoxal by Oxidative Dehydrogenation of Ethylene Glycol
Authors: Ai Mamoru
Published: September 2002

Iron(III) phosphates doped with a very small amount of molybdenum(VI) were found to be effective as catalysts for a vapor-phase oxidative dehydrogenation of ethylene glycol to glyoxal. The effects of the molybdenum(VI) content and of the reaction variables on the conversion of ethylene glycol and selectivity to glyoxal were studied. The optimum Mo/Fe atomic ratio was in the range from 0.002 to 0.01. The highest selectivity to glyoxal was obtained in the temperature range of 290 to 310 °C. The rate of ethylene glycol consumption increased almost in proportion to the oxygen concentration, while the selectivity to glyoxal increased only slightly as the oxygen concentration was increased. The selectivity to glyoxal increased markedly as the concentration of water was increased. It reached 37 and 32 mol% at ethylene glycol conversions of 60 and 80%, respectively. The one-pass yield of glyoxal reached 26.5 mol%.
The Influence of Salt-Linkages on the Adhesion and Hardness Variance of Hydrogels
Authors: Tamagawa Hirohisa , Nogata Fumio , Umemoto Susumu , Okui Norimasa , Popovic Suzana , Taya Minoru
Published: September 2002

Adhesion between anionic and cationic gels was observed. This adhesion force varied according to the pH and the ionic strength of solutions bathing the gels. A quite strong adhesion was observed in neutral and the ionic-strength solutions. The cause of this phenomenon was suggested to be due to electrostatic interaction between the anionic and cationic fixed groups on the respective gel surfaces, that is, the formation of salt-linkages between the dissociated –COOH and –NH2 groups, –COO-···+H3N–. They were also found in an amphoteric gel body, thus suggesting a great influence on the degree of hardness. Salt-linkages serve as crosslinkings in amphoteric gel in addition to the permanently formed chemical crosslinkings of N,N-methylenediacrylamide. The degree of amphoteric gel hardness can be controlled reversibly by their formation and disruption. Since a reversible hardness change was also observed in real human muscle, the use of salt-linkages is a new principle used to design practical artificial gel muscles.
Optical Molecular Thermometer Based on the Fluorescence of Fullerene Dispersed in Poly(methyl methacrylate) Film
Authors: Amao Yutaka , Okura Ichiro
Published: September 2002

A new optical molecular thermometer based on the fluorescence intensities of the fullerene C60 dispersed in poly(methyl methacrylate) (PMMA) film was developed. The fluorescence intensity of the C60 film decreased with increasing the temperature in the range from 260 to 373 K. The Arrhenius plot of ln[(I(T)/I(Tref))] versus 1/T for the C60 film exhibits considerable linearity supported by the correlation factor, r2, estimated to be 0.989 by the least squares method (Tref = 260 K). The E/R value of the C60 film is estimated to be 22.3 K. These results indicate that the C60 film provides a linear temperature response in the range 260 to 373 K.
Nanoscale Molecular Containers
Authors: Rudkevich Dmitry M
Published: September 2002

Over the last few years, there has been a breakthrough in the design and synthesis of nanoscale molecular containers—cavitands, (hemi)carcerands, and capsules. These nanocavities are designed for selective binding, separation and sensing of smaller molecules and ions, molecular transport and delivery, stabilization of reactive intermediates, and catalysis through encapsulation. They also mimic the hydrophobic pockets of enzymes. The field has grown since the first hollow calixarenes of Collet, Cram, and Gutsche, which were able to trap a single solvent or gas molecule, in the early 1980s, to investigations of giant cavities of 15–20 Å inner dimensions and 1500 Å3 internal volume. This reflects current trends in molecular recognition which are rapidly moving towards nanotechnology and microfabrication on the one hand and molecular biology on the other. Recently prepared nanocavities are ready to be employed for encapsulation of drugs and their active transport/delivery through cell membranes. Cavity-containing informationally rich polymers, sensing materials and polymer-supported microreactors are also in sight. These and many other applications can only be possible if general approaches towards construction of nanoscale molecular containers are developed and if the key rules governing their inclusion complexes are understood at the level of their organic chemistry.
Preparation and Kinetic Stabilization of Highly Strained Paracyclophanes
Authors: Tsuji Takashi , Ohkita Masakazu , Kawai Hidetoshi
Published: September 2002

In this Account we describe the preparation, structures, and properties of the most highly strained paracyclophanes known to date, i.e. [4]- and [1.1]paracyclophanes and their derivatives. The preparation of these cyclophanes has been accomplished through the photochemical valence isomerization of corresponding 1,4-bridged Dewar benzene derivatives. These strained paracyclophanes are prone to polymerize and are not stable enough to isolate: [4]paracyclophane is rapidly consumed even below -100 °C in fluid solution, though it remains intact indefinitely in a frozen organic glass at 77 K, while [1.1]paracyclophane is stable only below -20 °C in solution. By introducing substituents which sterically hinder access to the bridgehead carbon atoms by other reagents, however, one can remarkably stabilize these species kinetically so as to allow the measurement of 1H NMR spectrum of the former and the isolation of the latter as crystals. The 1H NMR spectrum of the [4]paracyclophane strongly support, in conjunction with theoretical calculations, the sustenance of considerable aromaticity despite the extreme bending of its benzene ring. [4]Paracyclophane is so strained that it is thermodynamically less stable than the corresponding Dewar isomer and the thermal conversion of the benzene form to the Dewar form is observed for the first time. A fully unsaturated derivative of [4]paracyclophane is also generated and confirmed to prefer the structure of 1,2,3,4-tetradehydro[4]paracyclophane rather than that of π-bond isomer, bicyclo[4.2.2]deca-1,3,5,7,9-pentaene. The stabilized [1.1]paracyclophane is found to undergo efficient photochemical transformation into a benzene p,p′-dimer structure, from which the former is thermally regenerated upon mild heating. Structural characteristic features of the [1.1]paracyclophane and the benzene p,p′-dimer are revealed by X-ray crystallography. Limits for experimentally accessible strained paracyclophane are also discussed.
Dimerization Effect on the Physical Properties in New One-Dimensional Organic Conductors: (ChTM-TTP)2AuBr2, (ChTM-TTP)2GaCl4, and (ChTM-TTP)ReO4
Authors: Kawamoto Tadashi , Ashizawa Minoru , Mori Takehiko , Yamaura Jun-Ichi , Kato Reizo , Misaki Yohji , Tanaka Kazuyoshi
Published: September 2002

Crystal structure analyses, measurements of transport and magnetic properties, and low-temperature X-ray studies of new organic conductors: (ChTM-TTP)2AuBr2, (ChTM-TTP)2GaCl4, and (ChTM-TTP)ReO4, where ChTM-TTP is 2-[4,5-(1,2-cyclohexylenedithio)-1,3-dithiol-2-ylidene]-5-[4,5-bis (methylthio)-1,3-dithiol-2-ylidene]-1,3,4,6-tetrathiapentalene, have been carried out. In these compounds, the donors form quasi-one-dimensional columns with dimerization induced by the steric hindrance of the 1,2-cyclohexylene unit. The crystal structures and the energy band structures of both AuBr2- and GaCl4- salts are similar to those of the Bechgaard salts. The electrical resistivity and the thermoelectric power show metallic behavior above 100 K for the AuBr2- salt and above 150 K for the GaCl4- salt. The results of the ESR spin susceptibility, the static magnetic susceptibility, and the low-temperature X-ray studies indicate that the ground states of both salts are antiferromagnetic insulators. The Néel temperatures are about 38 K for the AuBr2- salt and about 32 K for the GaCl4- salt. These salts are the first materials showing an antiferromagnetic state among the TTP series conductors. In (ChTM-TTP)2X (X = Au(CN)2, AuBr2, and GaCl4), the strength of the dimerization is related to the charge localization temperature. For the ReO4- salt, the donor to anion ratio is 1 : 1 in spite of the tetrahedral anion being similar to the GaCl4- anion. Although the interstack interactions are not small, the degree of charge transfer of the donor molecule is +1; thus this salt has an energy gap at the Fermi level, in agreement with the semiconducting transport behavior.
Formation of Palladium Nanoclusters on Y-Zeolite via a Sonochemical Process and Conventional Methods
Authors: Okitsu Kenji , Yue Akihiko , Tanabe Shuji , Matsumoto Hiroshige
Published: September 2002

The preparation of Pd clusters was investigated by the sonochemical reduction of [Pd(NH3)4]2+ complexes on Y-zeolite in an aqueous solution at 20 °C. Through measurements of the UV–vis and X-ray photoelectron spectra, [Pd(NH3)4]2+ was found to be reduced by radicals formed from 2-propanol sonolysis to yield zero-valent Pd. It was confirmed that the binding energy of the Pd 3d core level on the Y-zeolite was shifted to a higher value in comparison with that of Pd bulk metal. The formation of Pd metal, however, could not be observed by TEM and EXAFS measurements, implying the formation of ultrafine Pd clusters. On the other hand, the results of XPS analyses for several standard Pd clusters of ca. 1nm prepared by the conventional thermal treatment indicated that the peak values of the Pd core level increased with decreasing particle size. The maximum difference in binding energy between these samples was 0.6 eV at the Pd 3d5/2 core level. This phenomenon was suggested to be attributed to a quantum size effect corresponding to a splitting of the band structure. In comparison with standard samples, the size of sonochemically formed Pd clusters was roughly estimated to be less than 1 nm and composed of several dozen Pd atoms.
Electric Field Effects on Electron Transfer between H+ and Carbon-Based Electrode Surfaces: A DFT and Anderson–Newns Hamiltonian Analysis Study
Authors: Ohwaki Tsukuru , Murai Takahiko , Yamashita Koichi
Published: September 2002

To investigate the nature of the characteristic properties (especially the wide potential window and the low background current) of boron-doped diamond electrodes, we discuss electric field effects on the electron transfer process between the diamond surface and a proton based on density functional theory (DFT) and Anderson–Newns Hamiltonian analysis. All of the necessary data for this analysis were obtained by a “finite-field DFT method” at the level of B3LYP/6-31G and natural bond orbital analysis (NBO). The diamond and graphite electrode surfaces were modeled by corresponding clusters. We investigated the differences in the electric-field response of the density of states (DOS) peak of the proton 1s orbital and the number of electrons on the proton for the cases of a diamond cluster and a graphite cluster. These differences are attributable to the differences in the overlap between the proton 1s orbital and the surface orbitals. We discuss the relationship between this electric-field effect on the DOS peak, critical points of the Q-curve and two characteristic properties of diamond electrodes, that is, low background currents and wide potential windows.