Synthesis of new layered-type and new mixed-layered-type bismuth compounds

Four new compounds, PbBi₂TiTaO₈F, PbBi₂TiNbO₈F, Bi₅Ti₂WO₁₄F, and Bi₇Ti₅O₂₀F, were prepared and identified by X-ray diffraction analysis. Two of them are new members of a family called layered bismuth compounds. The other two are new members of a family called mixed-layered bismuth compounds. Thermal properties of the new compounds were studied. Moreover, the possibility of the existence of other new members belonging to the family called mixed-layered bismuth compounds is discussed.     

Epitaxial Growth of Sr x Ba1 − x Nb2O6 Thin Films Prepared from Sol-Gel Process

In this study, we prepared Sr _x Ba_{1 – x} Nb₂O₆ (x = 0.3, 0.5 and 0.7) thin film on 0.75 wt% La doped SrTiO₃ (100) and (110) single crystal substrates. A homogeneous coating solution was prepared with Sr and Ba acetates and Nb(OEt)₅ as raw materials, and acetic acid and diethlene glycol monomethyl ether as solvents. The substrates were coated with the solution by spin coating method. As-coated thin films were heated from 973 to 1273 K in air. The grains of the thin film on La doped SrTiO₃ (100) were pillar shaped and arranged in right angle to each other. On the other hand, the grains of these thin films on La doped SrTiO₃ were pillar shape and arranged in one direction. The crystallographic relationship of the thin film between Sr _x Ba_{1 – x} Nb₂O₆ and substrate that the 130 and 310 direction of the thin film on the substrate were oriented with c-axis in parallel to the substrate surface. On the other hand, (hk0) phase diffractions of Sr _x Ba_{1 – x} Nb₂O₆ thin film on the substrate (110) were investigated in the XRD theta-2theta measurement. It is expected that the Sr _x Ba_{1 – x} Nb₂O₆ (x = 0.3, 0.5 and 0.7) were highly oriented or epitaxial growing on La doped SrTiO₃ (110) single crystal substrate.     

Pyrimidines-19: Ring transformation of 5-nitrouracil into nitroresorcinols

The first intermolecular right transformation of a uracil derivative into the benzene system is reported. Treatment of 1,3-dimethyl-5-nitrouracil (1) with acetone in NaOMe/MeOH afforded 6-acetonyl-5,6-dihydro-1,3-dimethyl-5-nitrouracil (6) which was converted into 4-nitroresorcinol (5) upon treatment with NaOEt/EtOH at reflux. Reaction of1 with butanone gave two major products, 3-(5,6-dihydro-1,3-dimethyl-5-nitrouracil-6-yl)butanone (7) and the 1-(uracil-6-yl)butanone isomer (8). Prolonged treatment of7 with NaOEt/EtOH afforded 4-methyl-6-nitro-resorcinol (9) whereas8 was converted into 2-methyl-4-nitro-resorcinol (10). Treatment of1 with diethyl acetonedicar?ylate in NaOEt/EtOH afforded diethyl-2-(5,6-dihydro-1,3-dimethyl-5-nitrouracil-6-yl)-acetonedicar?ylate (2). Prolonged treatment of2 with NaOEt/EtOH at reflux afforded (5,6-dihydro-1,3-dimethyl-6-nitrouracil-6-yl)-acetate (3). Apparently,2 underwent a retroClaisen reaction to give3. Reaction of1 with ethyl acetoacetate in NaOEt/EtOH gave adduct isomers4 which underwent transformation reaction to give eventually 6-nitroresorcinol (5).     

Isolation and crystal structure of a water-soluble iridium hydride: a robust and highly active catalyst for acid-catalyzed transfer hydrogenations of carbonyl compounds in acidic media

This paper reports the isolation and structural determination of a water-soluble hydride complex [Cp*Ir(III)(bpy)H](+) (1, Cp* = eta(5)-C(5)Me(5), bpy = 2,2'-bipyridine) that serves as a robust and highly active catalyst for acid-catalyzed transfer hydrogenations of carbonyl compounds at pH 2.0-3.0 at 70 degrees C. The catalyst 1 was synthesized from the reaction of a precatalyst [Cp*Ir(III)(bpy)(OH(2))](2+) (2) with hydrogen donors HCOOX (X = H or Na) in H(2)O under controlled conditions (2.0 < pH < 6.0, 25 degrees C) which avoid protonation of the hydrido ligand of 1 below pH ca. 1.0 and deprotonation of the aqua ligand of 2 above pH ca. 6.0 (pK(a) value of 2 = 6.6). X-ray analysis shows that complex 1 adopts a distorted octahedral geometry with the Ir atom coordinated by one eta(5)-Cp*, one bidentate bpy, and one terminal hydrido ligand that occupies a bond position. The isolation of 1 allowed us to investigate the robust ability of 1 in acidic media and reducing ability of 1 in the reaction with carbonyl compounds under both stoichiometric and catalytic conditions. The rate of the acid-catalyzed transfer hydrogenation is drastically dependent on pH of the solution, reaction temperature, and concentration of HCOOH. The effect of pH on the rate of the transfer hydrogenation is rationalized by the pH-dependent formation of 1 and activation process of the carbonyl compounds by protons. High turnover frequencies of the acid-catalyzed transfer hydrogenations at pH 2.0-3.0 are ascribed not only to nucleophilicity of 1 toward the carbonyl groups activated by protons but also to a protonic character of the hydrido ligand of 1 that inhibits the protonation of the hydrido ligand.     

Unambiguous Determination of the Absolute Configurations of Acetylene Alcohols by Combination of the Sonogashira Reaction and the CD Exciton Chirality Method – Exciton Coupling between Phenylacetylene and Benzoate Chromophores

The CD exciton chirality method was applied to various phenylacetylene alcohols to determine their absolute configurations; the long axis polarized –^* transition (_max=252nm) of the 4-methoxyphenylacetylene chromophore couples with the transition (_max=257nm) of the 4-methoxybenzoate group to generate intense exciton split CD Cotton effects, from the signs of which the absolute configurations of phenylacetylene alcohols were unambiguously determined. As an extension of the results, a new methodology for determining the absolute configurations of acetylene alcohols having the HCCCH(OH)-moiety by combination of the Sonogashira reaction and the CD exciton chirality method has been developed and applied. Since the –^* transition of acetylene triple bond is located below 180nm, it is difficult to observe ideal bisignate CD Cotton effects due to the exciton coupling between acetylene and benzoate chromophores. To observe the ideal exciton split Cotton effects necessary for the unambiguous determination of absolute configuration, the terminal acetylene group was converted, by the Sonogashira reaction, to the 4-methoxyphenylacetylene moiety, which exhibits an intense –^* absorption band polarized along the long axis of the chromophore at 252nm. As a partner of exciton coupling, 4-methoxybenzoate showing a –^* band at 257nm was introduced into the alcohol moiety, and the benzoates formed showed intense bisignate CD Cotton effects, from the signs of which the absolute configurations of original acetylene alcohols could be determined in an unambiguous manner.     

Model Construction for the A–B–C Ring System of Lysergic Acid via Vilsmeier–Haack‐Type Cyclization of 1H‐Indole‐4‐propanoic Acid Derivatives

Vilsmeier–Haack‐type cyclization of 1H‐indole‐4‐propanoic acid derivatives was examined as model construction for the A–B–C ring system of lysergic acid ( 1 ). Smooth cyclization from the 4 position of 1H‐indole to the 3 position was achieved by Vilsmeier–Haack reaction in the presence of K₂CO₃ in MeCN, and the best substrate was found to be the N,N‐dimethylcarboxamide 9 (Table 1). The modified method can be successfully applied to an α‐amino acid derivative protected with an N‐acetyl function, i.e., to 27 (Table 2); however, loss of optical purity was observed in the cyclization when a chiral substrate (S)‐ 27 was used (Scheme 5). On the other hand, the intramolecular Pummerer reaction of the corresponding sulfoxide 20 afforded an S‐containing tricyclic system 22 , which was formed by a cyclization to the 5 position (Scheme 3).     

Diarylurea-linked zinc porphyrin dimer as a dual-mode artificial receptor: supramolecular control of complexation-facilitated photoinduced electron transfer

A novel porphyrinic receptor 1 in which two zinc porphyrins are bridged by two diarylurea linkers was developed for recognition of a viologen derivative (hexyl viologen, HV). The electronic absorption spectra as well as the 1H NMR experiments revealed that the HV molecule was bound to the cleft in 1 mainly through carbonyl dipole-charge interactions to afford a 1:1 complex. From the steady-state fluorescence spectroscopic study, the photoinduced electron transfer (PET) from 1 to HV was extremely facilitated by the receptor-substrate complexation. The receptor 1 also formed a 1:1 complex with 1,4-diazabicyclo[2.2.2]octane (DABCO) through two Zn-N coordination interactions, and, using DABCO as an inhibitor, we suppressed the PET reaction via the substrate exchange.     

Production of endohedral 133Xe-fullerene by ion implantation

Ion implantation was applied to the production of endohedral ¹³³Xe-fullerene. Using an isotope separator, ¹³³Xe ions were implanted into a fullerene target of C₆₀ and C₇₀ produced by vacuum evaporation on a Ni backing. An HPLC analysis following dissolution of the fullerene targets in o-dichlorobenzene corroborated the formation of ¹³³Xe@C₆₀ and ¹³³Xe@C₇₀, showing a strong correlation between C₆₀/C₇₀ and ¹³³Xe. The observed tailing following ¹³³Xe peaks in the elution curves suggests a possibility of the isolation of endohedral ¹³³Xe-fullerene from empty fullerene.     

γ-Ray-induced polymerization of α-haloacrylic acids

The γ-ray induced polymerizations of α-chloroacrylic acid, mp 66°C, and α-bromo-acrylic acid, mp 72°C, were investigated in the temperature range from 35°C to 85°C. An analysis of polymerization kinetics was made, and results were similar to those reported in the literature for other vinyl monomers. On heating of the polymer obtained, elimination of hydrogen halide takes place, and intramolecular lactone formation is observed. The rate of lactone formation of poly(α-chloroacrylic acid) obtained in the solid-state polymerization was found to be higher than that in the liquid state, because a highly isotactic configuration of polymers, tends to be formed in the solid-state polymerization, and elimination of hydrogen chloride is facilitated with an isotactic 5₂ helix structure.