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排序方式: 共有318条查询结果,搜索用时 15 毫秒
91.
Tetsu Tsubogo Yuichiro Kano Koki Ikemoto Yasuhiro Yamashita Shū Kobayashi 《Tetrahedron: Asymmetry》2010,21(9-10):1221-1225
The first catalytic asymmetric 1,4-addition reactions of azlactones with acrylic esters have been developed. A chiral coordinative calcium catalyst was found to be effective for these reactions, and the desired 1,4-adducts were obtained in good yields and enantioselectivities. The product was converted to the corresponding α-alkylated glutamic acid by acid hydrolysis. 相似文献
92.
[reaction: see text] A variety of selenoiminium salts were obtained by reacting the corresponding selenoamides with methyl triflate at room temperature for 30 s. All of the salts were stable under air. The structures of the selenoiminium salts were determined by X-ray molecular analysis. An aromatic selenoiminium salt reacted with BuLi (3 equiv) to give two types of ketones. In a reaction with LiAlH(4)/Te, the selenoiminium salts were converted to telluroamides. 相似文献
93.
Hashimoto Y Waki I Yoshinari K Shishika T Terui Y 《Rapid communications in mass spectrometry : RCM》2005,19(2):221-226
We report a new hybrid mass spectrometer, which is a combination of a quadrupole ion trap and an orthogonal time-of-flight (TOF) mass spectrometer. This new configuration consists of a collisional-damping chamber (CDC) inserted between an MSn-capable ion trap and a high-mass-accuracy orthogonal-TOF mass spectrometer. Because the CDC converted an ion packet into an energy-focused and quasi-continuous beam, a high mass resolution of over 10,000 and a high mass accuracy of better than 3 ppm were achieved. Moreover, the ratio of the maximum detectable m/z to the minimum detectable m/z, which is referred to here as the mass window, was improved to more than 10. 相似文献
94.
Hikaru Aramoto Motofumi Osaki Subaru Konishi Chiharu Ueda Yuichiro Kobayashi Yoshinori Takashima Akira Harada Hiroyasu Yamaguchi 《Chemical science》2020,11(17):4322
Stimuli-responsive hydrogels have attracted attention as soft actuators that act similarly to muscles. In this work, hydrogel actuators controlled by host–guest interactions have been developed. The introduction of a 1:1 inclusion complex into a hydrogel is a popular design for achieving a change in cross-linking density. To realize faster and larger deformation properties, the introduction of a 1:2 inclusion complex is effective because the alteration in cross-linking density in a hydrogel with 1:2 complexes is larger than that in a hydrogel with 1:1 complexes. A redox-responsive hydrogel actuator cross-linked with 1:2 inclusion complexes is designed, where γ-cyclodextrin (γCD) and viologens modified with an alkyl chain derivative (VC11) were employed as the host and guest units, respectively. γCD includes two VC11 molecules in its cavity. The obtained γCD–VC11 hydrogel cross-linked with the 1:2 complex showed faster and larger deformation behaviour than the αCD–VC11 and the βCD–VC11 hydrogels cross-linked with a 1:1 complex. The deformation ratio and response speed of the γCD–VC11 hydrogel, which forms a supramolecular cross-linking structure by stimuli, are 3 and 11 times larger, respectively, than those of our previous hydrogel consisting of a βCD/ferrocene 1:1 inclusion complex.A hydrogel actuator with a 1:2 host–guest complex controlled by redox stimuli has been developed to realize faster and larger deformation. 相似文献
95.
Takashi Ooi Yuichiro Kondo Keiji Maruoka 《Angewandte Chemie (International ed. in English)》1998,37(21):3039-3041
A reaction chamber is formed by a cage compound in which a dicarbonyl guest molecule is encapsulated by two bowl-shaped aluminum tris(2,6-diphenylphenoxide) molecules through Lewis acid–base interactions (structure of complex with 1,4-dimethylpiperazine-2,5-dione depicted). The carbonyl compound held inside the molecular capsule is effectively protected against the approach of external nucleophiles. On the other hand, the chamber is large enough to allow Diels–Alder cycloadditions to take place under mild conditions and with high selectivity. 相似文献
96.
97.
98.
Katsufumi Tanaka Yuichiro Tanabe Takatoshi Morina Ryuichi Akiyama 《Liquid crystals》2008,35(3):253-264
Solid cast films with polydomain textures were prepared on a glass substrate with transparent interdigitated electrodes from an isotropic aqueous solution of hydroxypropyl cellulose via its liquid crystalline phase under the sinusoidal electric field with small amplitude and frequency of 0.05 V µm-1 and 105 Hz, respectively. The process was monitored using microdielectrometry as well as polarised optical microscopy. The apparent dielectric constant εr' and loss factor εr' sensitively changed with time depending on the process conditions. On the other hand, the logarithmic relation between εr' and εr' showed a single curve, when they were normalised by an effective portion of the electrostatic energy density estimated using each solid-film thickness. The conversion to the solid film was estimated during the process based on the concentration dependences of εr' and εr'. Characteristic times were reported for the onset of the biphasic phase, fully developed cholesteric phase and termination of the process. 相似文献
99.
Masuyuki Sugiyama Hideki Hasegawa Yuichiro Hashimoto 《Rapid communications in mass spectrometry : RCM》2009,23(18):2917-2922
We have developed a new mass‐selective axial ejection method from a linear ion trap (LIT). In this method, a set consisting of a trap wire lens and an extraction wire lens positioned orthogonally to each other was placed between quadrupole rods. The trap wire lens confines the ions inside the trap, and the extraction wire axially extracts ions from the trap. Ions introduced into the LIT are trapped between the inlet lens and the trap wire lens. In addition to the wire lenses, a set of excitation lenses, which are aligned orthogonally to the trap wire lens, are inserted between rods. The ions are resonantly excited in the direction perpendicular to the trap wire lens by applying a supplemental alternating current (AC) to the excitation lenses. Excited ions with a large motion pass over the trap wire lens, while unexcited ions remain trapped inside. Ions that have passed over the trap wire lens are then extracted by the extraction wire lens. The characteristics of the mass‐selective ejection with a direct current (DC) extraction field were investigated by both simulation and experiment. A mass resolving power of m/Δm = 1300 was achieved at a scan rate of 500 Th/s. The dependence of the ejection efficiency on trap wire lens bias was measured, and an ejection efficiency of 20% at a scan rate of 500 Th/s was achieved by optimizing the DC bias on the trap wire lens. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
100.
Reduction of dichlorodiphenylstannane with lithium followed by treatment with methyl iodide gave methyltriphenylstannane, dimethyldiphenylstannane and 1,2‐dimethyldistannane. 1,2‐Dilithiodistannane and triphenylstannyllithium were intermediates of this reaction. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献