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31.
Enantioenriched synthesis of cyclopropenes with a quaternary stereocenter, versatile building blocks
Uehara M Suematsu H Yasutomi Y Katsuki T 《Journal of the American Chemical Society》2011,133(2):170-171
Ir(salen) complexes were found to catalyze enantioselective cyclopropenation efficiently. Cyclopropenation can be carried out using either a donor/acceptor- or an acceptor/acceptor-substituted diazo compound such as α-aryl-α-diazoacetates, α-phenyl-α-diazophosphonate, 2,2,2-trifluoro-1-phenyl-1-diazoethane, and α-cyano-α-diazoacetamide as carbenoid precursors. The reactions provide highly enantioenriched cyclopropenes (84-98% ee) with a functionalized quaternary carbon as versatile building blocks. 相似文献
32.
Miyauchi M Li Y Yanai S Yotsugi K 《Chemical communications (Cambridge, England)》2011,47(30):8596-8598
A tungsten trioxide (WO(3)) coated aluminium (Al) substrate exhibits a reversible color change without light irradiation or an electric power supply. The sample turns blue upon exposure to an aqueous acid solution, but exposure to oxygen restores the original light yellow color. This color change is due to the galvanic redox reaction between WO(3) and Al. 相似文献
33.
Katsuki S. Akiyama H. Yamada T. Eguchi N. Maeda S. Sato K.N. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1993,21(6):755-759
Preacceleration of a projectile is important for reducing the erosion of the bore surface in a railgun. Gas guns, electrothermal guns, and other railguns are commonly used to preaccelerate the projectile. A new method, called the plasma initiation separated from the projectile (PISP) method is proposed, and its effectiveness is confirmed experimentally. A thin copper wire is placed near the edge of the railgun, and it explodes and forms a plasma that has a fast flow velocity due to the Lorentz force. This fast flowing plasma collides with the projectile, which obtains an initial velocity mainly by the momentum transfer. Since the current increases while only the plasma is accelerated, the driving force of the projectile just after the collision of the plasma with the projectile is large. The PISP method works as an inductive energy storage circuit with an opening switch 相似文献
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A new formulation of the environment potential approach (EPA) is developed within the Hartree-Fock-Slater framework. As the results of illustrative applications to C5 cluster which is the smallest unit of diamond lattice, EPA is shown to annul efficiently the fictitious-surface effects which are inevitably brought into a finite-size-cluster model. 相似文献
38.
A method of an electronic structure calculation of cluster is suggested. It consists of an “effective” potential with an electron to close the torn valence bonds which appear inevitably in a finite-size-cluster model. The method is applied to the C5 cluster representing the diamond lattice and is shown to be effective to nullify the pseudo-surface effects. 相似文献
39.
Zhang M Yudasaka M Miyauchi Y Maruyama S Iijima S 《The journal of physical chemistry. B》2006,110(18):8935-8940
Through fluorescence-spectrum measurements, we investigated the effects of light-assisted oxidation with H2O2 (LAOx) on single-wall carbon nanotubes (SWNTs) that were individually dispersed in an aqueous solution of surfactant. The intensities of the fluorescence spectra were decreased remarkably by the LAOx when the light's wavelength was 400-500 nm and a little when 600-700 nm. The spectrum intensity did not recover even when the pH was restored to an original value of 6.5. The spectra changed little when the LAOx wavelength was 500-600 nm or the light was not irradiated. In addition, the effect of LAOx on SWNTs was related to the diameters of SWNTs. We inferred that these phenomena reflected that H2O2 was dissociated by absorbing the fluorescence light emitted from optically excited SWNTs, which, in turn, accelerated the burning out of SWNTs. 相似文献
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