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51.
Moon Jeon-Yeol Miura Takatsugu Imae Ichiro Park Dae-Won Kawakami Yusuke 《Silicon Chemistry》2002,1(2):139-143
Disiloxane-arylene polymers having phenylene, biphenylene, and fluorenylene groups as arylene units were synthesized by dehydrocoupling polymerization of corresponding bis(silane) derivatives with water. The reactivity of Si-H was not affected by the structure of aromatic groups in the reaction. The polymers containing biphenylene and fluorenylene units are amorphous and show higher glass transition temperatures than the polymer from 1,4-bis(dimethylsilyl)benzene. 相似文献
52.
53.
Direct Addition of Amides to Glycals Enabled by Solvation‐Insusceptible 2‐Haloazolium Salt Catalysis
Yuya Nakatsuji Yusuke Kobayashi Yoshiji Takemoto 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(40):14253-14257
The direct 2‐deoxyglycosylation of nucleophiles with glycals leads to biologically and pharmacologically important 2‐deoxysugar compounds. Although the direct addition of hydroxyl and sulfonamide groups have been well developed, the direct 2‐deoxyglycosylation of amide groups has not been reported to date. Herein, we show the first direct 2‐deoxyglycosylation of amide groups using a newly designed Brønsted acid catalyst under mild conditions. Through mechanistic investigations, we discovered that the amide group can inhibit acid catalysts, and the inhibition has made the 2‐deoxyglycosylation reaction difficult. Diffusion‐ordered two‐dimensional NMR spectroscopy analysis implied that the 2‐chloroazolium salt catalyst was less likely to form aggregates with amides in comparison to other acid catalysts. The chlorine atom and the extended π‐scaffold of the catalyst played a crucial role for this phenomenon. This relative insusceptibility to inhibition by amides is more responsible for the catalytic activity than the strength of the acidity. 相似文献
54.
Bo Huang Hirokazu Kobayashi Tomokazu Yamamoto Takaaki Toriyama Syo Matsumura Yoshihide Nishida Katsutoshi Sato Katsutoshi Nagaoka Masaaki Haneda Wei Xie Yusuke Nanba Michihisa Koyama Fenglong Wang Shogo Kawaguchi Yoshiki Kubota Hiroshi Kitagawa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(8):2252-2257
Ru is an important catalyst in many types of reactions. Specifically, Ru is well known as the best monometallic catalyst for oxidation of carbon monoxide (CO) and has been practically used in residential fuel cell systems. However, Ru is a minor metal, and the supply risk often causes violent fluctuations in the price of Ru. Performance‐improved and cost‐reduced solid‐solution alloy nanoparticles of the Cu‐Ru system for CO oxidation are now presented. Over the whole composition range, all of the CuxRu1?x nanoparticles exhibit significantly enhanced CO oxidation activities, even at 70 at % of inexpensive Cu, compared to Ru nanoparticles. Only 5 at % replacement of Ru with Cu provided much better CO oxidation activity, and the maximum activity was achieved by 20 at % replacement of Ru by Cu. The origin of the high catalytic performance was found as CO site change by Cu substitution, which was investigated using in situ Fourier transform infrared spectra and theoretical calculations. 相似文献
55.
Hiroki Kiyama Tsubasa Inokuma Yusuke Kuroda Yousuke Yamaoka Kiyosei Takasu Ken-ichi Yamada 《Tetrahedron letters》2019,60(2):175-177
A new catalytic method for separating enantiomers of racemic compounds is proposed. Catalytic asymmetric addition of racemic trans-2-substituted cyclohexanols to imines provided diastereomeric mixtures of aminals, and the subsequent separation of the enantiomers by silica-gel column chromatography and the hydrolysis of the aminals produced the alcohols in an optically active form. 相似文献
56.
Extremely Photostable Electron-Deficient Phthalocyanines that Generate High Levels of Singlet Oxygen
Prof. Dr. Taniyuki Furuyama Yusuke Miyaji Kazuya Maeda Prof. Dr. Hajime Maeda Prof. Dr. Masahito Segi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(7):1678-1682
A robust lead-mediated synthetic procedure for the generation of phthalocyanines substituted with electron-withdrawing groups has been developed. The free-base phthalocyanine and various metal complexes were prepared without discernible degradation of the peripheral electron-withdrawing substituents. Upon irradiation with red light, some of the thus-obtained metal complexes generated high levels of singlet oxygen. In particular, a palladium complex exhibited attractive photostability upon exposure to singlet oxygen as a bleaching agent. The photostability of such complexes that may manifest concomitantly to the generation of high levels of singlet oxygen was attributed to the presence of the electron-withdrawing groups, which results in energetically low-lying highest occupied molecular orbitals. 相似文献
57.
Dr. Esmail Doustkhah Prof. Dr. Jianjian Lin Prof. Dr. Sadegh Rostamnia Prof. Dr. Christophe Len Prof. Dr. Rafael Luque Prof. Dr. Xiliang Luo Prof. Dr. Yoshio Bando Prof. Dr. Kevin C.-W. Wu Dr. Jeonghun Kim Prof. Dr. Yusuke Yamauchi Dr. Yusuke Ide 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(7):1614-1635
Sulfonic acid based mesostructures (SAMs) have been developed in recent years and have important catalytic applications. The primary applications of these materials are in various organic synthesis reactions, such as multicomponent reactions, carbon–carbon bond couplings, protection reactions, and Fries and Beckman rearrangements. This review aims to provide an overview of the recent developments in the field of SAMs with a particular emphasis on the reaction scope and advantages of heterogeneous solid acid catalysts. 相似文献
58.
Honda S Akiba T Kato YS Sawada Y Sekijima M Ishimura M Ooishi A Watanabe H Odahara T Harata K 《Journal of the American Chemical Society》2008,130(46):15327-15331
What is the smallest protein? This is actually not such a simple question to answer, because there is no established consensus among scientists as to the definition of a protein. We describe here a designed molecule consisting of only 10 amino acids. Despite its small size, its essential characteristics, revealed by its crystal structure, solution structure, thermal stability, free energy surface, and folding pathway network, are consistent with the properties of natural proteins. The existence of this kind of molecule deepens our understanding of proteins and impels us to define an "ideal protein" without inquiring whether the molecule actually occurs in nature. 相似文献
59.
Prof. Akiharu Satake Yuki Suzuki Motonobu Sugimoto Dr. Yusuke Kuramochi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(3):669-684
Bis(imidazolylporphyrinatozinc) molecules linked through a 1,3-butadiynylene moiety respond to the solvents they are dissolved in to afford exclusively extended (E) or stacked (S) supramolecular polymers. This system is expected to be a solvation/desolvation indicator. However, the principles underlying the solvent-dependent formation of the two types of polymers and the mechanism of the transformation between them are unclear. The formation of the polymers is considered to depend on the two types of complementary coordination bonds that can be formed and the π–π interactions between the porphyrins. In this study, the contributions and solvent dependence of both the coordination bonds and the π–π interactions have been investigated. The results clearly indicate that the coordination bonds are weakly or little solvent-dependent, and that the π–π interactions function effectively only in the inner porphyrins of the S-polymer and are strongly solvent-dependent. Thermodynamic analysis revealed that the formation of the E- or S-polymer in solution is determined by the total energies and the type of solvent used. The transformation of the E- to S-polymer was investigated by gel permeation chromatography. The kinetics of the transformation were also determined. The role of the terminal imidazolylporphyrinatozinc moieties was also investigated: The results indicate that the transformation from the E- to S-polymer occurs by an exchange mechanism between the polymers, induced by attack of terminal free imidazolyl groups on a polymer to zinc porphyrins on other polymers. 相似文献
60.
Yusuke Arai Tetsuji Yano Shuichi Shibata 《Journal of Sol-Gel Science and Technology》2004,32(1-3):189-194
Microspheres of refractive index of nD > 2.0 have been investigated. The organic-inorganic hybrid microspheres of nD = 1.72 were prepared by the vibrating orifice technique using titanium-tetra-n-butoxide (TTBu) and diphenyldimethoxysilane (DPhDMS). For lasing demonstration, Eu3+-doped microspheres were prepared using europium (III) thenoyltrifluoroacetonate [Eu(TTFA)3] as the dopant. The particles have good spherical shape, smooth surface and high optical transparency. The diameters of the particles could be controlled to within 0.1 m. Subsequent heating of the microspheres at 550°C under oxygen atmosphere resulted in an increase in the refractive index up to nD = 2.6 with retention of the spherical shape. Resonant emission was confirmed from Eu3 +-doped microspheres after heating at 400–550°C, by pumping with the 514.5 nm line of a CW- Ar+laser. 相似文献