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排序方式: 共有442条查询结果,搜索用时 9 毫秒
1.
Akito Kakuuchi 《Tetrahedron》2004,60(6):1293-1299
The 1,4-conjugated addition of alkenylzirconocene chloride complexes to α,β-enones, α,β-enoic acid esters, and α,β-enoic acid amides can be efficiently achieved by the use of [RhCl(cod)]2 catalyst. A high diastereoselectivity (95% yield, 90% de) was obtained through the reaction of α,β-enoic acid amide derived from Oppolzer's sultam and 2-butenoyl chloride, while the use of Evans' chiral oxazolidinone as a chiral auxiliary in place of Oppolzer's sultam gave a poor diastereoselectivity (98% yield, 26% de). 相似文献
2.
Takafumi Adachi Ichimin Shirotani Junichi Hayashi Osamu Shimomura 《Physics letters. A》1998,250(4-6):389-393
Lanthanide monophosphides LnP (Ln = La, Ce, Pr, Nd, Sm, Gd, Tb, Tm and Yb) with a NaCl-type structure have systematically been prepared at high temperatures. Using synchrotron radiation, X-ray diffractions of LnP have been studied up to 61 GPa at room temperature. The NaCl---CsCl transition for CeP is found at around 25 GPa. First-order phase transitions of LnP (Ln = La, Pr and Nd) with the crystallographic change occur at around 24, 26 and 30 GPa, respectively. The structure of the high pressure phases of these phosphides is a body center tetragonal structure (Ln: 0, 0, 0; P: 1/2, 1/2, 1/2; space group P4/mmm), which can be seen as the distorted CsCl-type structure. The Pr---P distance in the high pressure form of PrP is 2.789 Å. This almost agrees with the sum of covalent radii of Pr and P. The Pr---P bond has the covalent character at very high pressures. Similar results are also obtained for LaP and NdP. The pressure-induced phase transitions of SmP, GdP, TbP, TmP and YbP occur at around 35, 40, 38, 53 and 51 GPa, respectively. The structure of the high pressure phase is unknown. The phase transitions of LnP with many f-electrons are not due to the mechanism of the ordinary NaCl---CsCl transition. The transition pressures of LnP increase with decreasing the lattice constants in the NaCl-type structure, which decrease with increasing atomic number of the lanthanide atoms. 相似文献
3.
Ichikawa K Shimomura N Yamada M Ohkubo N 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(14):3235-3241
In vitro biomimetic mineralization by means of nanotechnology allows the formation of calcium carbonate polymorphs at low temperatures (<25 degrees C) under a CO(2) atmosphere of 500-1500 ppm. A two-dimensional zinc-ion ordered array (zinc array), which acts as an active-site mimic of carbonic anhydrase, has been prepared by immersing the self-organized monolayer of 3-(2-imidazolin-1-y)propyltriethosilane on mica (ImSi substrate) into aqueous zinc solution. The zinc array mounted on the ImSi substrate catalyzed the conversion from CO(2) to HCO(3) (-), and accelerated the formation of calcium carbonate. In situ X-ray diffraction data of the formed calcium carbonate on the poly(L-aspartate)-coated chitin substrate (pAsp substrate), with calcium ion-recognition sites, demonstrated that the interaction between the zinc array and pAsp substrates formed both vaterite and calcite at low temperature (15 degrees C) and mainly vaterite at 25 degrees C; this interaction also controlled the morphology of calcium carbonate formed on pAsp substrate. 相似文献
4.
Akihiko Sugie Hiromi Shimomura Junki Katsube Hisao Yamamoto 《Tetrahedron letters》1979,20(28):2607-2610
A stable PGI2 analog (methanoprostacyclin ) was synthesized starting from 5-norbornene-2,3-dicarboxylic anhydride. 相似文献
5.
Synthesis and inversion barriers of undeca- and dodeca-substituted saddle shaped porphyrin complexes
Synthesis and barriers to inversion of a series of highly saddle shaped complexes are reported. The ΔG≠ has decreased by 8 kJ mol−1 at 243 K when the meso phenyl groups are replaced by bulkier 2,6-dichlorophenyl groups, and by 17 kJ mol−1 when one of the peripheral ethyl groups is removed. 相似文献
6.
7.
K. Nagamine Y. Miyake P. Birrer K. Shimomura M. Iwasaki T. Kuga J. Marangos 《Hyperfine Interactions》1994,87(1):1083-1089
A concept, a construction and an account of commissioning experiments up to May 1993 are given for the recently completed ultra-slow positive muon facility at the pulsed muon facility of UT-MSL/KEK. The intense and ultra-slow
+ beam with an extremely small phase-space volume to be produced in this facility will open new muon sciences includingSR studies on material surfaces. 相似文献
8.
K. Nagamine Y. Miyake P. Birrer K. Shimomura M. Iwasaki K. Nishiyama P. Strasser T. Kuga J. Marangos 《Hyperfine Interactions》1993,80(1-4):1287-1295
A concept, a design, a construction and an account of commissioning experiments are given for the recently completed ultra-slow muon facility at the pulsed muon facility of UT-MSL/KEK. The intense (more than 103/s) slow + beam with an extremely narrow phase-space volume (0.2 eV×(3 cm)2) to be produced in this facility will open a new muon science including surface physics and chemistry and fundamental atomic physics.Post-doctoral fellow of Swiss National Science Foundation. 相似文献
9.
Akito Nomura 《manuscripta mathematica》1993,79(1):379-390
LetL/k be a finite Galois extension with Galois groupG, and
a group extension. We study the existence of the Galois extensionM/L/k such that the canonical projection Gal(M/k)→Gal(L/k) coincides with the given homomorphismj:E→G and thatM/L is unramified. 相似文献
10.
S. Kulprecha T. Nihira C. Shimomura K. Yamada N. Nilubol T. Yoshida H. Taguchi 《Tetrahedron》1984,40(15):2843-2846
The microbiological transformation of lithocholic acid (3α-hydroxy-5β-cholanic acid) into 3α, 15β-dihydroxy-5β-cholanic acid by Cunninghamella sp. is Investigated. The structure has been determined on the basis of two-dimensional 1H-NMR. 相似文献