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排序方式: 共有179条查询结果,搜索用时 15 毫秒
111.
112.
Murahashi SI Komiya N Oda Y Kuwabara T Naota T 《The Journal of organic chemistry》2000,65(26):9186-9193
The ruthenium-catalyzed oxidation of alkanes with tert-butyl hydroperoxide and peracetic acid gives the corresponding ketones and alcohols highly efficiently at room temperature. The former catalytic system, RuCl(2)(PPh(3))(3)-t-BuOOH, is preferable to the oxidation of alkylated arenes to give aryl ketones. The latter system, Ru/C-CH(3)CO(3)H, is suitable especially for the synthesis of ketones and alcohols from alkanes. The ruthenium-catalyzed oxidation of cyclohexane with CH(3)CO(3)H in trifluoroacetic acid/CH(2)Cl(2) at room temperature gave cyclohexyl trifluoroacetate and cyclohexanone with 90% conversion and 90% selectivity (85:15). The mechanistic study indicates that these catalytic oxidations of hydrocarbons involve oxo-ruthenium species as key intermediates. 相似文献
113.
M. Yamamoto T. Abe J. Kuwabara K. Komura K. Ueno Y. Takizawa 《Journal of Radioanalytical and Nuclear Chemistry》1994,178(1):81-90
The concentrations of210Po and210Pb were determined in about 30 species of marine organisms collected mainly from the north-easterm region of Japan to know the levels and distributions of these radionuclides and to estimate their intake levels from marine foods.210Po and210Pb showed a wide range of concentration in species: 0.6–26 and 0.04–0.54 Bq/kg (wet wt) in fishes, 0.5–220 and 0.2–43 Bq/kg (wet wt) in molluscs, echinoderms and chordatas, and 2.8–4.3 and 0.4–1.3 Bq/kg (wet wt) in algae, respectively. Higher accumulation of210Po relative to210Pb was found in all of the samples analyzed. The intake levels of210Po and210Pb by marine foods consumption were roughly estimated to be 0.48–0.69 and 0.022–0.042 Bq/d per person, respectively, on the basis of the statistical data on the consumption of seafood and/or production rates of marine foods. 相似文献
114.
Tanaka Y Kuwabara R Na YH Kurokawa T Gong JP Osada Y 《The journal of physical chemistry. B》2005,109(23):11559-11562
The fracture energy G of double network (DN) gels, consisting of poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) as the first network and poly(acrylamide) (PAAm) as the second network, was measured by the tearing test as a function of the crack velocity V. The following results were obtained: (i) The fracture energy G ranges from 10(2) to approximately 10(3) J/m2, which is 100-1000 times larger than that of normal PAAm gels (10(0) J/m2) or PAMPS gels (10(-1) J/m2) with similar polymer concentrations to the DN gels. (ii) G shows weak dependence on the crack velocity V. (iii) G at a given value of V increases with decreasing of cross-linking density of the 2nd network. The measured values of G were compared with three theories that describe different mechanisms enhancing the fracture energy of soft polymeric systems. A mechanism relating to a heterogeneous structure of the DN gel is convincing for the remarkable large values of G. 相似文献
115.
The ruthenium(III) complex bearing benzo[h]quinoline as a cyclometalated ligand was synthesized and characterized by ESI-MS, elemental analysis, cyclic voltammetry and crystallography. The complex serves as an efficient catalyst for the aerobic oxidative dehydrogenation of benzylamines to the corresponding benzonitriles under mild conditions. 相似文献
116.
Abstract Two cyclic viologen derivatives were prepared in order to investigate their photochromic properties in a thin polymer film. The absorption peaks of photoreduced cyclic viologen units were shifted to the red side by the inclusion of indole or 1,4-dimethoxybenzene, although those of photoreduced acyclic analogues were not shifted in the presence of the guests. 相似文献
117.
Ryo Tanaka Yuina Kuwabara Yuushou Nakayama Takeshi Shiono 《Molecules (Basel, Switzerland)》2022,27(24)
Diene comonomers bearing boronic acid masked with 1,8-diaminonaphthalene (dan) were applied to copolymerization with isoprene or butadiene using neodymium borohydride complex as a catalyst. The comonomers were tolerant to excess modified methylaluminoxane (MMAO) and thus were applicable to the polymerization system using MMAO. On the other hand, the corresponding pinacol borate was highly reactive toward MMAO, and no incorporation into the obtained polymer was observed. A 13C NMR microstructural analysis of the hydrogenated copolymer revealed that all of the comonomers were located at the chain end. Further functionalization using the boron moiety at the polymer chain end was also investigated. 相似文献
118.
Diversity of the Structures in a Distannene Complex and its Reduction to Generate a Six‐Membered Ti2Sn4 Ring Complex 下载免费PDF全文
Takuya Kuwabara Dr. Jing Dong Guo Prof. Dr. Shigeru Nagase Prof. Dr. Masaichi Saito 《Angewandte Chemie (International ed. in English)》2014,53(2):434-438
In contrast to olefin complexes, their congeners of heavier elements display various coordination modes, and their complexes may be present as bis(metallylene) complexes, with side‐on coordination, as metallacyclopropanes, or as π complexes. In the course of our studies on the reactivity of dilithiostannoles towards transition‐metal reagents, three‐membered TiSn2 and six‐membered Ti2Sn4 ring complexes were obtained. According to its geometric parameters, NMR analysis, and theoretical calculations, the TiSn2 complex cannot be categorized into any of these previously described bonding modes. Therefore, a novel resonance structure has been proposed for a complex that has a delocalized σ‐orbital over the TiSn2 ring to understand its electronic structure. The mechanism for the formation of the Ti2Sn4 ring complex and its EPR spectrum are also discussed. 相似文献
119.
Curved Oligophenylenes as Donors in Shape‐Persistent Donor–Acceptor Macrocycles with Solvatofluorochromic Properties 下载免费PDF全文
Dr. Takuya Kuwabara Jun Orii Prof. Dr. Yasutomo Segawa Prof. Dr. Kenichiro Itami 《Angewandte Chemie (International ed. in English)》2015,54(33):9646-9649
Many optoelectronic organic materials are based on donor–acceptor (D–A) systems with heteroatom‐containing electron donors. Herein, we introduce a new molecular design for all‐carbon curved oligoparaphenylenes as donors, which results in the generation of unique shape‐persistent D–A macrocycles. Two types of acceptor‐inserted cycloparaphenylenes were synthesized. These macrocycles display positive solvatofluorochromic properties owing to their D–A characteristics, which were confirmed by theoretical and electrochemical studies. 相似文献
120.