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101.
Dr. Yoshihiro Sohtome Bongki Shin Natsuko Horitsugi Prof. Dr. Keiichi Noguchi Prof. Dr. Kazuo Nagasawa 《化学:亚洲杂志》2011,6(9):2463-2470
Herein, we present details of our conformationally flexible, 1,3‐diamine‐tethered guanidine/bisthiourea organocatalysts for chemo‐, regio‐, and enantioselective 1,4‐type Friedel–Crafts reactions of phenols. These organocatalysts show a unique stereo‐discrimination governed by the differential activation entropy (ΔΔS≠), rather than by the differential activation enthalpy (ΔΔH≠). Extensive kinetic analyses using Eyring plots for a series of guanidine/bisthiourea organocatalysts revealed the key structural motif in the catalysts associated with a large magnitude of differential activation entropy (ΔΔS≠). A plausible guanidine–thiourea cooperative mechanism for the enantioselective Friedel–Crafts reaction is proposed. 相似文献
102.
103.
Masazumi Ishiguro Kensuke Harada Keiichi Tanaka Takehiko Tanaka 《Journal of Molecular Spectroscopy》1996,180(2)
Rotational transitions of fluoroacetylene in the ν1(CH stretch) vibrational state have been observed by the laser–microwave double resonance technique using a color center laser as a radiation source in the 3 μm region. The rotational constant and centrifugal distortion constant in the ν1state were determined to be 9684.310(16) MHz and 2.68(62) kHz, respectively, where the uncertainties given in parentheses correspond to 2.5 standard deviations. 相似文献
104.
The extraction behavior of mono-, poly-, anal bis-(benzothiacrown ether)s is studied for alkali, alkaline-earth, heavy, and transition metal ions in the presence of picrate. These ethers show high selectivity for silver ion. Silver extractions from binary and quaternary mixtures of silver with heavy or transition metal ions were successful, except for mixtures with mercury(II) ion. Silver was extracted from a copper ore with ca. 80% recovery. 相似文献
105.
106.
Shosuke Mochizuki 《Journal of luminescence》1996,70(1-6):60-68
We have developed a simple measurement method for measuring the optical spectra of free microcrystals, by combining the time-resolved and space-resolved spectroscopies with the gas evaporation method. The structure of the obtained spectra and their time- and space-dependencies indicate well the quantum-confinement effects of carriers and excitons in free semiconductors microcrystals. 相似文献
107.
B 2-groups are special (torsion-free) abelian Butler groups. The interest in this class of groups comes from representation theory. A particular functor, also called Butler functor, connects algebraic properties of the category of free abelian groups with (a few) distinguished subgroups with these Butler groups. This helps to understand Butler groups and caused lots of activities on Butler groups. Butler groups were originally defined for finite rank, however a homological connection discovered by Bican and Salce opened the investigation of Butler groups of infinite rank. Despite the fact that classifications of Butler groups are possible under restriction even for infinite rank (see a forthcoming paper by Files and Göbel [Mathematische Zeitschrift]), general structure theorems are impossible. This is supported by the following very special case of the Main Theorem of this paper, showing that any ring with a free additive group is an endomorphism ring of a Butler group. The result implies the existence of large indecomposable or of large superdecomposable Butler groups as well as the existence of counter-examples for Kaplansky’s test problems. 相似文献
108.
Kayoko Tahara Emi Makii Shiro Iijima Yoshihiro Abe Masataka Mochizuki 《Analytical sciences》2008,24(7):935-938
The electrochemical oxidation of (+/-)-alpha-tocopherol on a porous graphite electrode was performed in the presence of methanol, and successive separation and detection of the products were performed by an on-line liquid chromatography/mass spectrometry system. Three products were identified, one of which was determined to be alpha-tocopheryl quinone, because its m/z was 469 [M+Na](+). The other two products showed identical mass and UV spectra, and were suspected to be diastereomers of 9-methoxy-alpha-tocopheron, because their molecular weights were m/z 483 [M+Na](+), and also because it is known that the chemical oxidation of alpha-tocopherol by benzoyl peroxide or N-bromosuccinimide in the presence of methanol should provide 9-methoxy-alpha-tocopheron. To confirm that these two compounds were diastereomers, a circular dichroism detector was used. The signs of both peaks detected by the circular dichroism detector at 230 nm were opposite. In addition to observations of identical mass and ultraviolet spectra, these results indicated that the two products were diastereomers of 9-methoxy-alpha-tocopheron, whose stereochemistry is different at the newly generated chiral center of the 9-position. The on-line use of a circular dichroism detector with an electrochemical cell/liquid chromatography system may expand the utility of the system to study the metabolism of a chiral drug. 相似文献
109.
N-Alkyl-N(1-hydroperoxyalkyl)nitrosamines were synthesized from N,N-dialkylnitrosamines by lithiation with lithium diisopropylamide, followed by oxygenation with oxygen in good yields. 相似文献
110.