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71.
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This study presents the first example of continuous-flow reaction conditions for biomimetic reductive amination of fluorinated carbonyl compounds using silica-adsorbed DBU as catalyst for on-column process. This new on-column process features operationally convenient conditions, higher chemical yields and purity of products as compared with traditional in-flask reactions. Furthermore the removal of base-catalyst is not an issue in this process at all, as the catalyst (DBU) remains on the column in the “reaction zone”, the feature which makes the overall process substantially more efficient and inexpensive, in particular, for large-scale synthesis of the target α-perfluoroalkyl amines. 相似文献
73.
The presented results convincingly demonstrate that self-disproportionation of enantiomers via sublimation is substantially more complex phenomenon then was previously believed. We demonstrate that the racemic form of isopropyl 3,3,3-trifluoro-2-hydroxypropanoate (1) sublimed faster regardless of the starting enantiomeric composition of the enantiomerically enriched mixtures studied in the range from 20.8, 36.8, 58.7 to 79.4% ee. This preferential sublimation of the racemic form allowed for, the most possibly simple, preparation of optically pure samples of compound 1. In this work we also suggest some general experimental procedures, which may be easily used to facilitate the interpretation of the data collected in different laboratories. 相似文献
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75.
Ab initio molecular orbital theory and density functional theory calculations have been carried out on the reactions of the trifluoromethyl radical with the hydroxyl and the hydrogen radicals. These reactions are key reactions that underlie a new fire extinguishing mechanism of non-bromine-containing halon replacements. The activation energies calculated by the MP2 and QCISD methods are in good agreement with the experimental values. The B3LYP, as well as MP2 and QCISD, give good results for the calculations of the heats of reactions. The GAUSSIAN-1 and GAUSSIAN-2 theory calculations present the most acxcurate results on both the activation energies and the heats of reactions. The effects of the scaling factors on the activation energies and the heats of reactions are also evaluated. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 277–289, 1998 相似文献
76.
Tsuneyuki Sato Kazuo Kimura Taizo Sugioka Toshikazu Misaki Takayuki Otsu 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(5):1017-1032
Some electron-accepting compounds such as maleimide (MIm), maleic anhydride (MAn), and tetracyanoquinodimethane were found to show pronounced accelerating effects on vinyl polymerization initiated with metal chelates. The polymerization of methyl methacrylate (MMA) initiated with bis(ethyl acetoacetato)-copper(II) (Cu(eacac)2) and MIm was studied kinetically in benzene. The overall activation energy of the polymerization was calculated to be 11.5 kcal/mol. This value was much lower than that (17.6 kcal/mol) for the polymerization of MMA with Cu(eacac)2 alone. The polymerization rate (Rp) was expressed as Rp =k[MIm]1/2 [Cu(eacac)2]1/2 [MMA] The first-order dependence of Rp on the monomer concentration indicated that the monomer had no participation in the initiation step, in contrast with polymerization in the absence of MIm (where a monomer concentration dependence of 1.4th order was observed). Electronic spectroscopic study revealed that a complex between MIm and Cu(eacac)2 had been formed. The ligand radical, an acetylcarboethoxymethyl radical, was trapped by 2-methyl-2-nitrosopropane in the reactions of Cu(eacac)2 with MIm and with MAn in benzene. From these results the mechanism of the initiation of polymerization is discussed. 相似文献
77.
Katsuhiko Kishi Taizo Ishimaru Masayoshi Ozono Ikuyoshi Tomita Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2000,38(1):35-42
A new thermal latent hydrosilylation catalyst on the basis of H2PtCl6 and polystyrene derivatives having propargyl moieties is described. The polystyrene derivatives having various propargyl moieties were obtained by the reaction of propargyl alcohols with poly(p‐chloromethylstyrene) or its copolymer with styrene. The polymer‐supported platinum catalysts were prepared by aging H2PtCl6 with these polymers in tetrahydrofuran at 30 °C for 12 h. In the presence of the polymers, the hydrosilylation activity of H2PtCl6 was found to be controlled thermally in the model reaction of trimethylsilane and triethylvinylsilane. Effective control of the crosslinking reaction of silicone resin was also achieved by using these latent catalyst systems. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 35–42, 2000 相似文献
78.
K Sakakibara LA Joyce T Mori T Fujisawa SH Shabbir JP Hill EV Anslyn K Ariga 《Angewandte Chemie (International ed. in English)》2012,51(38):9643-9646
Push a host: Mechanical compression was applied to a host monolayer at an interface, which facilitated an indicator displacement assay. The fluorescence resonance energy transfer (FRET) between the host and indicator was switched on by this compression. Addition of D-glucose caused the indicator to be displaced, effectively quenching the FRET process. 相似文献
79.
Jiro Hokkyo Taizo Suzuki Kazunobu Chiba Kenichi Sato Yuichi Arisaka Toshikazu Sasaki Yoshihito Ebine 《Journal of magnetism and magnetic materials》1993,120(1-3):281-285
This paper describes technology for a Co-Ni evaporated tape, a metal evaporated, or ME tape fabricated by a vacuum evaporation method, focusing on magnetic properties, microstructure, recording characteristics and noise prosperties. The high reproduced signal output, low noise and high resolution of ME tape obtained by using a ring head are attributed to oblique anisotropy and a particle-like structure. A breakthrough in improving the durability of ME tape has been achieved by technological improvements in tribology. 相似文献
80.