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51.
Takeuchi Hiroshi Watanabe Ryosuke Enmi Jun-ichiro Egawa Toru Konaka Shigehiro 《Structural chemistry》1998,9(1):33-38
The molecular structure and conformation of methyl acrylate have been determined by analyzing the 1H NMR spectrum with 13C satellites of the molecules dissolved in the liquid crystal ZLI 1132. In the structural analysis, direct coupling constants have been corrected for molecular vibrations and converted to those in the r
structure. The correlation between reorientational motion and internal rotation has been taken into account by using the mean external potential described in terms of bond interaction tensors. The potential for the internal rotation about the
bond has been represented as V() = (V
1/2) (1 – cos ) + (V
2/2)(1 – cos 2), where is zero for the s-cis configuration, and the determined values of V
1 and V
2 are 2.7(1) and 8.4(13) kJ mol–1, respectively. The relative abundance of the s-cis conformer, 76(1)%, agrees with a gas-phase value, 67(11)%, determined by electron diffraction within experimental errors. 相似文献
52.
Moriwaki H Harino H Hashimoto H Arakawa R Ohe T Yoshikura T 《Journal of chromatography. A》2003,995(1-2):239-243
We describe a novel method for the determination of two kinds of aromatic amine mutagens, 2-[2-(acetylamino)-4-[bis(2-methoxyethyl)-amino]-5-amino-7-bromo-4-chloro-2H-benzotriazole (PBTA-1) and 2-[2-(acetylamino)-4-[bis(2-cyanoethyl)-ethylamino]-5-amino-7-bromo-4-chloro-2H-benzotriazole (PBTA-2), in river water based on liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS-MS). A solid-phase extraction procedure was used for the extraction of PBTA-1 and PBTA-2 from river water. The procedure was rapid and the relative standard deviations were below 4%. The detection limits of PBTA-1 and PBTA-2 in river water using the proposed method were found to be 1 and 2 ng/l, respectively. The compounds were detected by this method in river water taken from two sites in the Yodo River system at the ng/l level. 相似文献
53.
Miki K Yokoi T Nishino F Kato Y Washitake Y Ohe K Uemura S 《The Journal of organic chemistry》2004,69(5):1557-1564
The reaction of alkenes with conjugated ene-yne-ketones, such as 1-benzoyl-2-ethynylcycloalkenes, with a catalytic amount of Cr(CO)(5)(THF) gave 5-phenyl-2-furylcyclopropane derivatives in good yields. The key intermediate of this cyclopropanation is a (2-furyl)carbene complex generated by a nucleophilic attack of carbonyl oxygen to an internal alkyne carbon in pi-alkyne complex or sigma-vinyl cationic complex. A wide range of late transition metal compounds, such as [RuCl(2)(CO)(3)](2), [RhCl(cod)](2), [Rh(OAc)(2)](2), PdCl(2), and PtCl(2), also catalyzes the cyclopropanation of alkenes with ene-yne-ketones effectively. When the reactions were carried out with dienes as a carbene acceptor, the more substituted or more electron-rich alkene moiety was selectively cyclopropanated with the (2-furyl)carbenoid intermediate. 相似文献
54.
The physical correlation between the fictive temperature dependence of the cooling rate of the melts and the temperature dependence of the equilibrium viscosity has been found by doing differential scanning calorimetric and viscometric measurements on a silicate melt, and by performing finite element simulations of the fiber drawing from that melt. This correlation is governed by a correlation factor Kc (in Pa K) which is constant and universal for silicate glasses. The factor Kc is obtained in the cooling rate range from 10(-2) to 10(6) K/s and is in good agreement with that theoretically predicted. The physical feature of the correlation is discussed in the paper. When the fictive temperature equals the actual temperature, a linear relation exists between the cooling rate and the Maxwell relaxation rate, the slope of which depends on the fragility of the glass melts. The Avramov equation is extended to describe the cooling rate dependence of the fictive temperature. The cooling rate equation contains only one adjusting parameter, i.e., the fragility parameter alpha. 相似文献
55.
Treatment of o-bromophenoxide anion with sodium salts of active methylene compounds in the presence of copper(I) bromide in dioxane afforded benzofuran-2-one derivatives. The phenoxide group of o- and p-bromophenol activates the coupling reaction. 相似文献
56.
[Reaction: see text] GaCl3 is found to be a superior catalyst for the skeletal rearrangement of alpha,alpha,alpha-trisubstituted aldehydes to ketones. The rearrangement can proceed smoothly in the presence of a catalytic amount of GaCl3, and even substrates having no heteroatoms alpha to the carbonyl group or without steric strains can be used. Double activation of a carbonyl group by two molecules of GaCl3 was supported on the basis of experimental data and a DFT study. 相似文献
57.
58.
Asymmetric Synthesis of 2H‐Azirines with a Tetrasubstituted Stereocenter by Enantioselective Ring Contraction of Isoxazoles
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Dr. Kazuhiro Okamoto Atsushi Nanya Akira Eguchi Prof. Dr. Kouichi Ohe 《Angewandte Chemie (International ed. in English)》2018,57(4):1039-1043
Highly strained 2H‐azirines with a tetrasubstituted stereocenter were synthesized by the enantioselective isomerization of isoxazoles with a chiral diene–rhodium catalyst system. The effect of ligands and the coordination behavior support the proposed catalytic cycle in which the coordination site is fixed in favor of efficient enantiodiscrimination by a bulky substituent of the ligand. In silico studies also support the existence of a rhodium–imido complex as a key intermediate for enantiodiscrimination. 相似文献
59.
Prof. Dr. Koji Miki Takeru Noda Prof. Dr. Masayuki Gon Prof. Dr. Kazuo Tanaka Prof. Dr. Yoshiki Chujo Prof. Dr. Yoshiyuki Mizuhata Prof. Dr. Norihiro Tokitoh Prof. Dr. Kouichi Ohe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(39):9211-9216
Carbon-based double helicates consisting of two anthracene-containing oligo(p-phenyleneethynylene) units and two flexible chiral 1,1′-binaphthyl units or two rigid chiral 9,9′-spirobifluorene units were developed. The curved oligo(p-phenyleneethynylene) fragments in the double helicates were successfully constructed by tin-mediated reductive aromatization. Helical oligo(p-phenyleneethynylene) double strands fixed by two rigid spirobifluorene units showed little structural change under photoirradiation, thereby emitting circularly polarized luminescence (CPL) in the visible region with a high quantum yield (ΦPL=0.93). In contrast, flexible binaphthyl units induced dynamic structural change of the oligo(p-phenyleneethynylene) luminophores under photoirradiation, leading to strong CPL (|glum|=1.1×10−2) in the near-infrared (NIR) region. UV/Vis, circular dichroism (CD), CPL and NMR spectroscopic analyses of the binaphthyl-hinged double helicate suggested excimer formation between two π-conjugated strands in the excited state. Theoretical calculations highlight the importance of the tightly interlocked excimer structure of the carbon-based double helicate in controlling the angle between the electric and magnetic transition dipole moments for strong NIR CPL generation. 相似文献
60.
The green and effective oxidation of alcohols to carboxylic acids with molecular oxygen via biocatalytic reaction 总被引:1,自引:0,他引:1
Jun-ichiro Hirano 《Tetrahedron letters》2008,49(7):1217-1219
A clean and effective alcohol oxidizing system using three enzymes has been developed. Regeneration of NAD+ by NADH oxidase with molecular oxygen enabled to oxidize alcohols to carboxylic acids in good yield under mild conditions (25 °C, 1 atm). 相似文献