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91.
Masakazu Iwamoto Shin-Ichiro Nakamura Hideto Kusano Shuichi Kagawa 《Journal of inclusion phenomena and macrocyclic chemistry》1986,4(1):99-103
The adsorption and/or decomposition pathway of Fe2(CO)9 or Fe3(CO)12 on hydrated or dehydrated NaY zeolites has been studied by an ESR technique. The adsorption resulted in the formation of three paramagnetic species withg
iso=2.0450, 2.0378, and 2.0016, which were attributable to Fe3(CO)11
–, Fe2(CO)8
–, and Fe(CO)4
– anion radicals, respectively. These radicals have been suggested as intermediates in the formation of HFe3(CO)11
– on the hydrated NaY zeolite and Fe3(CO)12 on the dehydrated NaY zeolite. 相似文献
92.
A new model of surface diffusion in reversed-phase liquid chromatography (RPLC) was derived by assuming a correlation between surface and molecular diffusion. Analysis of surface diffusion data under different conditions of sample compounds, mobile and stationary phases, and temperature in RPLC systems validates this assumption and shows that surface diffusion should be regarded as a molecular diffusion restricted by the adsorptive interactions between the adsorbate molecule and the stationary phase surface. A surface-restricted molecular diffusion model was proposed as a first approximation for the mechanism of surface diffusion. The model is formulated according to the absolute rate theory. The activation energy of surface diffusion (Es) was quantitatively interpreted assuming that Es consists of the contributions of two processes, a hole-making and a jumping one. The former contribution is nearly equal to the activation energy of molecular diffusion and is correlated with the evaporative energy of the mobile phase solvent. The latter contribution is a fraction of the isosteric heat of adsorption. An appropriate explanation based on this new model of surface diffusion is provided for two contradictory results related to the relationship between retention equilibrium and surface diffusion in RPLC and to the surface diffusion coefficient for weakly retained sample compounds. 相似文献
93.
Hideto NakagawaYoshio Okimoto Satoshi SakaguchiYasutaka Ishii 《Tetrahedron letters》2003,44(1):103-106
Enol and vinyl esters were successfully synthesized by the use of an iridium complex as a catalyst. The reaction of carboxylic acids with terminal alkynes in the presence of catalytic amounts of [Ir(cod)Cl]2 and Na2CO3 gave the corresponding 1-alkenyl esters. The addition of carboxylic acids to alkynes principally took place in the Markovnikov fashion. In addition, by the use of an Ir complex combined with NaOAc various vinyl esters were prepared through the transvinylation between carboxylic acids and vinyl acetate. 相似文献
94.
Ueda M Miyabe H Teramachi M Miyata O Naito T 《The Journal of organic chemistry》2005,70(17):6653-6660
The intermolecular radical addition to chiral nitrones 2, 4, 5, and 16 was studied. The isopropyl radical addition to Oppolzer's camphorsultam derivative 2 of glyoxylic nitrone proceeded with excellent diastereoselectivity to give the desired isopropylated product 3a accompanied by the diisopropylated product 3b. A high degree of stereocontrol in the reaction of cyclic nitrone 4 was achieved. The ethyl radical addition to nitrone 4 with triethylborane afforded the desired ethylated product 9a accompanied by the diethylated product 10a and the ethylated nitrone 11a. To evaluate the utility of cyclic nitrone 4, several alkyl radicals were employed in the addition reaction, which afforded the alkylated products 9b-d with excellent diastereoselectivities. In the presence of Mg(ClO(4))(2), the ethyl radical addition to BIGN 16 afforded selectively syn isomers. In contrast, the alkyl radical addition to 16 took place even in the absence of Lewis acid to give anti isomers. 相似文献
95.
Kanazawa H Okada A Igarashi E Higaki M Miyabe T Sano T Nishimura R 《Journal of chromatography. A》2004,1031(1-2):213-218
This study demonstrated the analysis of midazolam and its metabolites by liquid chromatography-mass spectrometry (LC-MS) with a sonic spray ionization (SSI) interface. The analytical column was a YMC-Pak Pro C18 (50 mm x 2.0 mm i.d.) using 10 mM ammonium acetate (pH 4.8)-methanol (1:1) at a flow rate of 0.2 ml min(-1). The drift voltage was 100 V. The sampling aperture was heated at 110 degrees C and the shield temperature was 230 degrees C. The lower limits for the detection of midazolam and 1'-hydroxymidazolam were 26.3 and 112.76 pg injected, respectively. The calibration curves for midazolam and 1'-hydroxymidazolam were linear in the range of 0.1-5 microg ml(-1). Within-day relative standard deviations was less than 7%. The method was applied to the determination of midazolam in monkey plasma, and the analysis of midazolam and its metabolites in an in vitro study with recombinant cytochrome P450 (CYP) 3A4. This method is sufficiently sensitive and useful to elucidate the kinetics of midazolam metabolite formation. We also investigated the effect of propofol on the metabolism of midazolam using recombinant CYP3A4. Propofol competitively inhibited the metabolism of midazolam to 1'-hydroxymidazolam by CYP3A4. 相似文献
96.
Prof. Yuki Arakawa Yuko Ishida Prof. Hideto Tsuji 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(17):3767-3775
The twist–bend nematic (NTB) phase with a heliconical nanostructure of the local director generating symmetry breaking by achiral bent-shaped molecules is a hot topic of current liquid-crystal science. As opposed to the most common methylene-linked dimers, this study demonstrates chalcogen ether- and/or thioether-linked 6-(4-cyanophenyl)-2-naphthyl-based liquid-crystal dimers with symmetric and asymmetric π-conjugated mesogenic-arm structures that exhibit the NTB phase. Although the symmetric bis(ether)-linked dimer exhibits only the conventional nematic (N) phase, the asymmetric bis(ether)-linked dimer can form the NTB phase. All thioether-linked dimers form the NTB phase, wherein the dimers with asymmetric arms vitrify in the NTB phase on cooling to room temperature. The phase transitions are discussed in terms of the chalcogen linkage combination, mesogenic-arm symmetry, and spacer length. It is revealed that thioether-linked dimers based on asymmetric π-conjugated mesogenic arms with terminal cyano groups are highly beneficial for the realization of materials that form a wide range of NTB phases and glassy NTB states at room temperature. 相似文献
97.
Masaki Oba Yoichiro Maruyama Katsuaki Akaoka Masabumi Miyabe Ikuo Wakaida 《Applied Physics A: Materials Science & Processing》2010,101(3):545-549
Emission characteristics of gadolinium (Gd) oxide are studied, using ns and fs laser pulses for ablation in double-pulse laser
induced breakdown spectroscopy (LIBS). In the current conditions of pulse energy and signal detection timing, emission intensity
enhancement in the reheating mode is 25-fold, but little effect can be observed in a pre-pulse mode. It is shown that the
optimum focus position of the ablation pulse is about 5 mm apart from the sample surface in the reheating mode. Although little
emission can be observed in the single-pulse configuration with fs ablation pulses, the intense emission can be observed in
the reheating mode in the double-pulse configuration. 相似文献
98.
Kobayashi H Tokuda D Ichimaru J Ikegami T Miyabe K Tanaka N 《Journal of chromatography. A》2006,1109(1):2-9
The contribution of molecular diffusion to peak broadening was studied in a reversed-phase HPLC system, consisting of a monolithic silica C18 column and methanol-water mobile phase. Study on the band broadening effect of holding a solute in a column or elution at very low linear velocity of mobile phase allowed facile determination of the contribution of the molecular diffusion term. Less obstruction against molecular diffusion, or the faster axial band dispersion in a monolithic silica column than in a particle-packed column, was found both in mobile phase and in stationary phase. 相似文献
99.
Sawada T Nishiyama Y Tabuchi W Ishikawa M Tsutsumi E Kuwahara Y Shosenji H 《Organic letters》2006,8(10):1995-1997
[reaction: see text] Tetramethoxy[2.1.2.1]metacyclophane ([2.1.2.1]MCP) was prepared by the pinacol coupling reaction of diphenylmethane dialdehyde. The treatment of [2.1.2.1]MCP with trimethylsilyl chloride and sodium iodide yielded two unexpected calixarene derivatives, cone (hemisphere) and 1,2-alternate types, instead of octahydroxy[2.1.2.1]MCP. The X-ray structure of the cone-type derivative and its inclusion property with acetonitrile were also discussed. 相似文献
100.