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排序方式: 共有267条查询结果,搜索用时 296 毫秒
91.
Shotaro Takano Ryosuke Shiomi Yoshihiko Morimoto Dr. Takuya Kochi Prof. Dr. Fumitoshi Kakiuchi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(29):11852-11855
We report a hydroaminative cyclization of enynes using phosphine-quinolinolato rhodium catalysts. The hydroaminative cyclization of 2-vinylphenylacetylene derivatives with secondary amines gives 2-aminoindenes in good yields. The reaction is considered to proceed through carbon–carbon bond formation on a catalytically generated aminocarbene ligand. 相似文献
92.
Yasutake K Kakiuchi H Ohmi H Inagaki K Oshikane Y Nakano M 《J Phys Condens Matter》2011,23(39):394205
To grow epitaxial Si films with atomic- and electronic-level perfection, a high-temperature chemical vapor deposition (CVD) process (>1000 °C) has been generally employed. To reduce the growth temperature below 600?°C but keeping a high deposition rate, other energy sources than thermal heating are required. Atmospheric pressure plasma CVD (AP-PCVD) is considered to be suitable for fabricating high-quality films at high deposition rates due both to the high radical density and to the low ion bombardment against the film surface, because the collision frequency among ions and neutral atoms is high. The present study focuses on the low-temperature growth of epitaxial Si, and experimentally demonstrates that AP-PCVD is capable of growing epitaxial Si films with high perfection applicable for semiconductor devices. It is found that the pre-growth cleaning of the Si surface by H(2) AP plasma is effective to grow high-purity Si films, and that the exposure of a film-growing surface to AP plasma during growth is important to form particle-free and defect-free Si films. From the experimental results and the first-principles molecular dynamics simulations of surface atomic reactions, it can be mentioned that both H atoms in the AP plasma and high-density He atoms having thermal kinetic energy contribute to the reduction of growth temperature by supplying considerable energy to the surface. 相似文献
93.
Ueda M Kondoh E Ito Y Shono H Kakiuchi M Ichii Y Kimura T Miyoshi T Naito T Miyata O 《Organic & biomolecular chemistry》2011,9(7):2062-2064
Direct generation of a benzyl radical by C-H bond activation of toluenes and the addition reaction of the resulting radical to an electron deficient olefin were developed. The reaction of dimethyl fumarate with toluene in the presence of Et(3)B as a radical initiator at reflux afforded 2-benzylsuccinic acid dimethyl ester in good yield. 相似文献
94.
Torigoe H Rahman SM Takuma H Sato N Imanishi T Obika S Sasaki K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(9):2742-2751
Due to the instability of pyrimidine motif triplex DNA at physiological pH, triplex stabilization at physiological pH is crucial in improving its potential in various triplex-formation-based strategies in vivo, such as gene expression regulation, genomic DNA mapping, and gene-targeted mutagenesis. To this end, we investigated the thermodynamic and kinetic effects of our previously reported chemical modification, 2'-O,4'-C-aminomethylene-bridged nucleic acid (2',4'-BNA(NC)) modification of triplex-forming oligonucleotide (TFO), on triplex formation at physiological pH. The thermodynamic analyses indicated that the 2',4'-BNA(NC) modification of TFO increased the binding constant of the triplex formation at physiological pH by more than 10-fold. The number and position of the 2',4'-BNA(NC) modification in TFO did not significantly affect the magnitude of the increase in the binding constant. The consideration of the observed thermodynamic parameters suggested that the increased rigidity and the increased degree of hydration of the 2',4'-BNA(NC)-modified TFO in the free state relative to the unmodified TFO may enable the significant increase in the binding constant. Kinetic data demonstrated that the observed increase in the binding constant by the 2',4'-BNA(NC) modification resulted mainly from the considerable decrease in the dissociation rate constant. The TFO stability in human serum showed that the 2',4'-BNA(NC) modification significantly increased the nuclease resistance of TFO. Our results support the idea that the 2',4'-BNA(NC) modification of TFO could be a key chemical modification to achieve higher binding affinity and higher nuclease resistance in the triplex formation under physiological conditions, and may lead to progress in various triplex-formation-based strategies in vivo. 相似文献
95.
We study the radius and energies of oxygen isotopes towards the neutron drip-line. The abrupt increase of the radius at 23O is investigated with two different approaches; the m-scheme cluster-orbital shell model (COSM) and a simplified model approach with the core plus one and two valence neutrons. We investigate properties of the oxygen isotopes by changing the radius of the 16O-core in the m-scheme COSM approach and obtain the result that the broad structure of 16O is favored in the 23O and 24O. In the simplified model approach, we estimate the magnitude of the change of the size of 22O in 23O and 24O. 相似文献
96.
Kondo F Okada S Miyachi A Kurita M Tsuji K Harada K 《Analytical and bioanalytical chemistry》2012,403(7):1783-1791
The reaction of some physiologically active peptides with bacterial strain B-9 has been investigated. Bradykinin, β-endorphin, and [Leu(5)]enkephalin were quickly degraded, with half-lives of <5 min. Somatostatin, substance P, and angiotensin I were degraded relatively smoothly, with half-lives of 10 min to 1 h, whereas oxytocin and insulin were slowly degraded, with half-lives of 1 and 4 days, respectively. Vasopressin was barely degraded, with a half-life of >7 days. Linearized vasopressin, prepared by the reductive cleavage of the disulfide bond followed by alkylation with iodoacetamide, was degraded significantly faster than intact vasopressin, with a half-life of 2.5 h. A loop formed by disulfide bond formation was regarded as one of the degradation-resistant factors. Hydrolysis of the peptides in this study took place through cleavage of various peptide bonds, and the strain B-9 may bear similarities to the neutral endopeptidase in terms of its broad selectivity. 相似文献
97.
98.
Shigeyoshi Watanabe Masashi Nishioka Kiyomi Okamoto Mitsuru Awano 《Physics letters. A》1979,74(6):441-442
The resistive superconducting transition of vanadium films is studied experimentally. The behavior of the resistance is well explained by fluctuation theory. In parallel magnetic fields the pair-breaking parameter increases with the increase of the strength of the magnetic field. 相似文献
99.
Morimoto T Fuji K Tsutsumi K Kakiuchi K 《Journal of the American Chemical Society》2002,124(15):3806-3807
The reaction of enynes with aldehydes in the presence of a catalytic amount of [RhCl(cod)](2)/dppp results in the Pauson-Khand-type reaction without the use of gaseous carbon monoxide to give bicyclic cyclopentenones in high yields (14 examples). Aldehydes serve as a source of carbon monoxide, and their carbonyl moiety is transferred to enynes, resulting in the formation of the carbonylated products. This reaction represents the first example of a CO-transfer carbonylation. 相似文献
100.
A new synthetic method for γ-acetoxy-α,β-unsaturated esters by the acetoxylation of β,γ-unsaturated esters catalyzed by PdCl2 in the presence of KOAc and pentyl nitrite in acetic acid is presented. The reaction takes place at γ-position of the esters regioselectively with double bond migration to α,β-position. The E configuration of the double bond was confirmed by NMR analysis. Preliminary investigation to synthesize pyrenophorin and pyrenophorol using this reaction is described. 相似文献