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Ohne Zusammenfassung 相似文献
84.
Masayuki Morita Atsushi Kishimoto Nobuko Yoshimoto Minato Egashira 《Research on Chemical Intermediates》2006,32(5):523-532
The surface processes at carbon and platinum electrodes have been studied using the electrochemical quartz crystal microbalance
technique in organic electrolyte solutions for lithium ion batteries. The changes in resonance frequency were analyzed as
a function of the electrode potential, indicating that the process depended not only on the electrode material but also on
the cathode potential. In the solution containing LiBF4 as the electrolyte, the main product at the platinum surface was Li2CO3 and LiF, whereas formation of lithium alkylcarbonates was the primary process at the platinum and carbon electrodes in LiPF6 solution. 相似文献
85.
Minato Egashira Yuji Yamamoto Tsubasa Fukutake Nobuko Yoshimoto Masayuki Morita 《Journal of fluorine chemistry》2006,127(9):1261-1264
A new method for the preparation of substituted imidazolium tetrafluoroborate salt, some of which are known as versatile room temperature ionic liquids, is proposed. The new method based on N-methylation of imidazole provided tetrafluoroborate derivatives containing no counterions, with shorter time and lower cost than conventional ion-exchange method. 相似文献
86.
Heteroarene-substituted vinyl- and allyl-silanes were obtained in good yields by the cross-coupling reaction of either heteroaryl Grignard reagents with halovinyl- and haloallyl-silanes or, alternatively, silyl- and silylmethyl-substituted vinylmetallic reagents with heteroaryl halides in the presence of PdCl2(dppb) as a catalyst. 相似文献
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89.
Daishirou Minato 《Tetrahedron letters》2006,47(31):5485-5488
Copper ion-catalyzed regioselective introduction of active methylene groups into the γ-position of piperidine skeleton was exploited. In the case of using chiral ligand as an additive, this reaction proceeded with moderate enantioselectivities. This method was applied to the synthesis of (−)-cincholoiponic acid from N-methoxycarbonylpiperidine. 相似文献
90.
Machiguchi T Okamoto J Takachi J Hasegawa T Yamabe S Minato T 《Journal of the American Chemical Society》2003,125(47):14446-14448
This paper describes a new mechanistic feature for the Staudinger ketene-alkene cycloaddition reactions to give cyclobutanones. Low-temperature NMR (13C, 19F, and 1H) monitoring of a reaction between bis(trifluoromethyl)ketene (1) and ethyl vinyl ether (2) has shown that the Staudinger reaction proceeds to form initially and exclusively an alpha-methyleneoxetane (3) by [2 + 2](C=O) cycloaddition across the ketene C=O bond. The initial intermediate 3 undergoes ring cleavage to produce a 1,4-zwitterion (4), which is converted to the final [2 + 2](C=C)-type product, cyclobutanone (5). The key intermediate 3 has been isolated in its pure form and was found to be converted to the final products 5 on warming, via the 1,4-zwitterion 4. The alpha-methyleneoxetane 3 is so reactive that it reacts with methanol rapidly even at -80 degrees C via solvolysis to afford an adduct 7. The ion 4 derived from the pure isolated oxetane 3 was intercepted with acetone by a 1,4-dipolar cycloaddition to give a 1,3-dioxane 8. An open-chain alpha,beta-enone (6) has been also obtained from 3. We conclude that the (1 + 2) reaction proceeds in a new three-step mechanism; formation of an alpha-methyleneoxetane 3, a [2 + 2]-type cycloadduct across the C=O bond of ketene, followed by ring cleavage to give the zwitterion 4 and by recombination to form the final product, cyclobutanone 5. The zwitterion 4 is not equilibrating with reactants 1 and 2 but comes from the alpha-methyleneoxetane 3. Exclusive formation of another oxetane 12 has been observed in a reaction between diphenylketene (9) and methyl isopropenyl ether (11). The selectivity of initial formation of cyclobutanone or oxetane has been generalized with aid of frontier-orbital theory and ab initio calculations. 相似文献