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331.
332.
A Carbon Nanotube Confinement Strategy to Implement Homogeneous Asymmetric Catalysis in the Solid Phase
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Kazuki Hashimoto Dr. Naoya Kumagai Prof. Dr. Masakatsu Shibasaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(11):4262-4266
A readily recyclable asymmetric catalyst has been developed based on the self‐assembly of a homogeneous catalyst in a fibrous network of multiwalled carbon nanotubes (MWNTs). Dimerization of an amide‐based chiral ligand with a suitable spacer allows for the efficient formation of a heterogeneous catalyst by self‐assembly on addition of Er(OiPr)3. The self‐assembly proceeds in the MWNT fibrous network and small clusters of assembled catalyst are confined in the MWNTs, producing an easily handled solid‐phase catalyst. The resulting MWNT‐confined catalyst exhibits a good catalytic performance in a catalytic asymmetric Mannich‐type reaction, which can be conducted in a repeated batch system and in a continuous‐flow platform. 相似文献
333.
An anti-selective catalytic asymmetric nitroaldol reaction was implemented in a continuous-flow reaction platform for the synthesis of a key intermediate of a drug candidate. The requisite solid-phase catalyst was readily prepared by mixing an amide-based chiral ligand and inexpensive inorganic salts, NdCl3?6H2O and NaOtBu, without covalent bond linkages. The flow system was operated with 2-Me-THF as the eluent for ca. 400 h to provide a crude nitroaldol adduct in a highly stereoselective manner with no work-up procedure, reaching turnover number over 1600. Facile reduction of the nitro group of the product afforded a key intermediate of AZD7594, a therapeutic candidate for asthma and chronic obstructive pulmonary disease. 相似文献
334.
Akinobu Matsuzawa Dr. Christopher R. Opie Dr. Naoya Kumagai Prof. Dr. Masakatsu Shibasaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(1):68-71
An enantioselective total synthesis of thuggacin B, a natural product exhibiting antibiotic activity against Mycobacterium tuberculosis, is described. Asymmetric direct aldol reactions promoted by Cu and Zn catalysts play a pivotal role in constructing four stereogenic centers. The use of direct aldol reactions as the initial steps for the synthesis of two key fragments allowed the construction of the other stereogenic centers through chirality transfer. 相似文献
335.
A Photoelectrochemical Solar Cell Consisting of a Cadmium Sulfide Photoanode and a Ruthenium–2,2′‐Bipyridine Redox Shuttle in a Non‐aqueous Electrolyte
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Yosuke Kageshima Hiromu Kumagai Tsutomu Minegishi Prof. Jun Kubota Prof. Kazunari Domen 《Angewandte Chemie (International ed. in English)》2015,54(27):7877-7881
A photoelectrochemical (PEC) cell consisting of an n‐type CdS single‐crystal electrode and a Pt counter electrode with the ruthenium–2,2′‐bipyridine complex [Ru(bpy)3]2+/3+ as the redox shuttle in a non‐aqueous electrolyte was studied to obtain a higher open‐circuit voltage (VOC) than the onset voltage for water splitting. A VOC of 1.48 V and a short‐circuit current (ISC) of 3.88 mA cm?2 were obtained under irradiation by a 300 W Xe lamp with 420–800 nm visible light. This relatively high voltage was presumably due to the difference between the Fermi level of photo‐irradiated n‐type CdS and the redox potential of the Ru complex at the Pt electrode. The smooth redox reaction of the Ru complex with one‐electron transfer was thought to have contributed to the high VOC and ISC. The obtained VOC was more than the onset voltage of water electrolysis for hydrogen and oxygen generation, suggesting prospects for application in water electrolysis. 相似文献
336.
Shinya Honda Takahito Kumagai Kazuya Tomihashi Yoshihiro Narita 《Journal of sound and vibration》2013
The present paper extends the layerwise optimization (LO) procedure to the maximization problem of the fundamental frequencies of sandwich plates with fibrous composites and low stiffness core layers. Frequencies are calculated by the Ritz method based on a refined zigzag theory (RZT). Polynomial functions which satisfy at least geometrical boundary conditions with boundary indexes are employed as displacement functions, and they enable satisfying arbitrary sets of boundary conditions for rectangular plates. Results of the experimental modal analysis validate the accuracy of the present calculations, and a comparison with results of the classical laminated theory (CLPT) and the first order share deformation theory (FSDT) supports the effectiveness of the present method. Optimized results are compared with other typical sets of lay-up configurations and this shows the LO method as suitable means to the optimization problem for sandwich plates. 相似文献
337.
We consider quantum counterparts of testing problems for which the optimal tests are the χ2, t-, and F-tests. These quantum counterparts are formulated as quantum hypothesis testing problems concerning Gaussian state families, and they contain nuisance parameters, which have group symmetry. The quantum Hunt-Stein theorem removes some of these nuisance parameters, but other difficulties remain. In order to remove them, we combine the quantum Hunt-Stein theorem and other reduction methods to establish a general reduction theorem that reduces a complicated quantum hypothesis testing problem to a fundamental quantum hypothesis testing problem. Using these methods, we derive quantum counterparts of the χ2, t-, and F-tests as optimal tests in the respective settings. 相似文献
338.
Masanori Kumagai Kikuko Karube Tomoaki Sato Naganori Ohisa Toshio Amano Ryoei Kikuchi Nobuaki Ogawa 《Analytical sciences》2002,18(10):1145-1150
Using a portable near infrared (NIR) spectrometer, we discriminated flours for making Japanese noodles (Soba), not only relying on a statistical and mathematical approach, but also on a chemical interpretation of the NIR spectra. In original NIR spectra, the particle-size difference, which results in an undesired systematic variation, was extracted and interpreted as the first-principal component factor by a principal-component analysis. The discrimination of flour materials cannot be satisfied by this factor. However, after a standardized treatment for the original spectra, the particle-size effects were eliminated; alternatively, differences in the chemical contents were extracted as principal-component factors. Using these factors, flour material discrimination was achieved much better. This study suggests a novel idea of utilizing the wavelength contribution ratio spectra for interpreting the factors extracted from the principal-component analysis for the NIR spectra. This report also describes the relationship between the NIR spectra and the chemical-analysis data. 相似文献
339.
Y Furukawa S TakadaK Kumagai T KawashimaE Takayama-Muromachi N KobayashiT Fukase K ChibaT Goto 《Journal of Physics and Chemistry of Solids》2002,63(12):2315-2318
We have carried out 99/101Ru and 63/65Cu nuclear magnetic resonance experiments in order to investigate magnetic and electronic properties of the magnetic superconductor RuSr2RECu2O8 (RE=Gd, Eu and Y). The two kinds of 99/101Ru signals were observed in the magnetically ordered state for each system, suggesting a charge segregation of Ru5+ (S=3/2) and Ru4+ (S=1) ions in the RuO2 layers. The internal field at the Cu sites is revealed to be of the order of kilo Oe, indicating weak magnetic interactions between the CuO2 and RuO2 planes. The temperature dependence of nuclear spin-lattice relaxation time T1 of 63Cu in RE=Y shows a ‘spin gap’ like behavior, suggesting the system is under-doped. 相似文献
340.
A. Zhang Y. Wei M. Kumagai Y. Koma 《Journal of Radioanalytical and Nuclear Chemistry》2006,269(1):119-128
Summary The Minor Actinides Recovery from HLW by Extraction Chromatography (MAREC) process was used mainly for the separation of minor
actinides (MAs) and some specific fission products (FPs) from highly active liquid waste (HLW) by the composite CMPO/SiO2-P of the macroporous silica based polymeric octyl(phenyl)-N,N-diisobutylcarbamoylmethylphoshine oxide (CMPO) and others.
In this study a cascade of chromatographic separation was performed on a 3.0M HNO3 solution containing 5.0 . 10-3M of 13 elements, at 323 K. The cascade consisted of three columns the first and second ones were packed with CMPO/SiO2-P and the third with SiO2-P particles. The first column was employed to prepare various eluents containing saturated CMPO. The second column was used
for separation into groups. The CMPO of CMPO/SiO2-P was recovered from the effluent by the third column and a CMPO-free effluent containing minor actinides was obtained. The
elements contained in the simulated HLW of 3.0M HNO3 were separated into (1) a non-adsorption group (Sr, Cs, and Ru etc.), (2) a MA-hRE (heavy rare earth)-Mo-Zr group, and (3) a lRE (light rare earth) group by eluting with 3.0M HNO3, 0.05M DTPA (diethylenetriaminepentaacetic acid) (pH 2.0) and HNO3 (pH 3.5), respectively. The resultant MA-hRE-Mo-Zr mixture containing minor actinides was then separated into the groups (1) Pd-Ru, (2) MA-hRE, and (3) Mo-Zr by utilizing 3.0M HNO3, distilled water, and 0.05M DTPA (pH 2.0) as eluents. More than 92% of CMPO in the MA-hRE containing effluent was adsorbed by SiO2-P particles. The effectivity and technical feasibility of MAREC process were demonstrated. 相似文献