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41.
Nagao M Asano K Umeda K Katayama H Ozawa F 《The Journal of organic chemistry》2005,70(25):10511-10514
[reaction: see text] Complex 1 bearing a diphosphinidenecyclobutene ligand (DPCB-OMe) catalyzes highly stereoselective hydrosilylation of diethynylarenes with HSiMe2Ph to afford (Z,Z)-bis(2-silylethenyl)arenes. Treatment of the hydrosilylation products with N-bromosuccinimide causes bromodesilylation in a stereospecific manner, giving (Z,Z)-bis(2-bromoethenyl)arenes in high geometrical purity (>98%). 相似文献
42.
Dianjie Ma Yasuaki Okamoto Takahiro Kumamaru Etsuro Iwamoto 《Analytica chimica acta》1999,390(1-3):201-206
Tungsten-coated non-pyrolytic graphite (NPG), pyrolytic graphite (PG) and pyrolytic L'vov platform graphite (PPG) tubes were prepared, and their analytical performances were compared. The coating process simply involved injecting 100 μl of a sodium tungstate solution (0.01 mol l−1) into each graphite tube, followed by heating according to a temperature programme similar to an atomisation cycle for the determination of gallium. This procedure for coating was repeated at least 12, 25, and 7 times towards NPG, PG, and PPG tubes, respectively. Among these tubes, the tungsten-coated PPG tube showed excellent performance for the determination of gallium. By combined use of a chemical modifier such as aluminium(III) or nickel(II) a detection limit (3σ) of 6 pg and sensitivity (1% absorption) of 3–4 pg were achieved. The practical potential of the proposed technique was demonstrated for the determination of gallium in several samples of alloys and fresh water. 相似文献
43.
The heat capacity of [Fe(2-pic)3]Cl2·C2H5OH Crystal (2-pic: 2-picolylamine) has been measured with an adiabatic calorimeter between 13 and 315 K. Two phase transitions centered at 114.04 and 122.21 K were observed. This finding accords with recent prediction of possible existence of two-step spin-conversion (H. Köppen et al., Chem. Phys. Lett., 91 (1982) 348). The total transition enthalpy and entropy amounted to ΔH = 6.14 kJ mol?1 and ΔS = 50.59 J K?1 mol?1. The transition entropy consists of the magnetic contribution (13.38 J K?1 mol?1), the orientational order-disorder phenomenon of the solvate ethanol molecule (8.97) and the change in the phonon system, in particular the change in stretching and deformation vibrations of the metal-ligand (28.24). 相似文献
44.
Takeshi Hanamoto Yuhko Iwamoto Kenji Yamada Ryoko Anno 《Journal of fluorine chemistry》2007,128(10):1126-1130
The 1,3-dipolar cycloaddition reaction of fluoro(trimethylsilyl)acetylene prepared in situ with an excess of diazomethane smoothly proceeded to give the corresponding 4-fluoro-5-trimethylsilyl-1H-pyrazole in 84% yield. The copper iodide-catalyzed N-arylation of the fluorinated pyrazole with a variety of aryl iodides afforded N-aryl-4-fluoropyrazoles as desilylation products in good to excellent yields. 相似文献
45.
Tanaka T Ogino H Iwamoto M 《Langmuir : the ACS journal of surfaces and colloids》2007,23(23):11417-11420
Azobenzene (Az) groups were planted on the pore wall of mesoporous silica MCM-41 (M41) by silylation of triethoxy[4-phenylazo(phenyl)]silane. The optimal surface density of Az groups was 0.9 group nm-2, and too much loading of Az induced the lowering of the efficiency of the trans-cis isomerization due to the congestion of the groups. The reversible change in the pore diameters upon UV-vis irradiation could not be confirmed by N2 adsorption at 77 K but was revealed to be ca. 1.0 nm by the shift of the UV-vis absorption band of p-N,N-dimethylaminobenzylidenemalononitrile introduced into the Az-modified pores. 相似文献
46.
K Kawasaki T Tsuji K Hirase M Miyano Y Imoto M Iwamoto 《Chemical & pharmaceutical bulletin》1991,39(3):584-589
N-Terminal tripeptide analogs of fibrin alpha-chain were synthesized and their inhibitory effect on fibrinogen/thrombin clotting was examined. A new water-soluble active ester, 3-pyridinium ester, was used for the synthesis. Among the synthetic peptides, H-Gly-Pro-Arg-hexamethyleneimine exhibited the highest inhibitory effect on fibrinogen-thrombin clotting. 相似文献
47.
S Yokohama T Miwa S Aibara H Fujiwara H Matsumoto K Nakayama T Iwamoto M Mori R Moroi W Tsukada 《Chemical & pharmaceutical bulletin》1992,40(9):2391-2398
A series of 6-alkyl- or 6-(cycloalkylalkyl)-[1,3,4]thiadiazolo[3,2- a]-1,2,3-triazolo[4,5-d]pyrimidin-9(3H)-ones 1b--o was synthesized from the corresponding 1,3,4-thiadiazol-5-amines 3b--o and the antiallergic activities of the products were evaluated. Among the compounds 6-(2-cyclohexylethyl)- [1,3,4]thiadiazolo[3,2-a]-1,2,3-triazolo[4,5-d]pyrimidin-9(3H)-one 1h, whose X-ray crystallographic stereostructure is shown, was found to be a promising new antiallergic agent, which has low toxicity and dual activity as a leukotriene D4 receptor antagonist and as an orally active mast cell stabilizer. 相似文献
48.
Hidetaka Yuge Toschitake Iwamoto 《Journal of inclusion phenomena and macrocyclic chemistry》1992,14(3-4):217-235
The crystal structures of the four title clathrate compounds Cd(NH3)2Cd(CN)4 · 2C6H6,I, Cd(NH3)2Cd(CN)4 · 2C6H5NH2,II, Cd(NH2CH2CH2NH2)Cd(CN)4 · 2 C6H5NH2,III, and Cd(C6H5NH2)2Cd(CN)4 · 0.5C6H5NH2,IV, have been analyzed by single crystal X-ray diffraction methods. CompoundI crystallizes in the monoclinic space groupC2/c,a = 12.063(2),b = 12.174(2),c = 14.621(1) Å,β = 90.976(9)°,Z = 4,R = 0.042 for 2388 reflections;II: monoclinic C2/c,a = 12.1951(9),b = 12.078(1),c = 14.6921(7) Å,β = 93.436(5)°,Z = 4,R = 0.039 for 2374 reflections;III: monoclinicCc,a = 11.027(1),b = 12.0767(9),c = 15.837(1) Å,β = 92.059(9)°,Z = 4,R = 0.041 for 2883 reflections; andIV: monoclinicP21/n,a = 15.169(2),b = 16.019(2),c = 8.866(1) Å,β = 95.73(1)°,Z = 4,R = 0.052 for 3612 reflections. The three-dimensionalcatena-[diamminecadmium(II) tetra-μ-cyanocadmate(II)] hosts ofI andII are substantially isostructural to that of the already known Hofmann-Td-type Cd(NH3)2Hg(CN)4 · 2C6H6. The three-dimensional en-Td-typecatena-[catena-μ-ethylenediaminecadmium(II) tetra-μ-cyanocadmate(II)] host ofIII, reinforced by the catena-μ-en linking between the octahedral Cd atoms, accommodates the aniline as the guest with a monoclinic distortion from the tetragonal symmetry of the previously reported en-Td-type benzene clathrate. InIV dual behavior of aniline, one as the unidentate ligand in the three-dimensional host and the other as the guest in the cage-like cavity, has been demonstrated. 相似文献
49.
Kazutoshi Ando 《Discrete Mathematics》2006,306(24):3181-3188
A pair (X,τ) of a finite set X and a closure operator τ:2X→2X is called a closure space. The class of closure spaces includes matroids as well as antimatroids. Associated with a closure space (X,τ), the extreme point operator ex:2X→2X is defined as ex(A)={p|p∈A,p∉τ(A-{p})}. We give characterizations of extreme point operators of closure spaces, matroids and antimatroids, respectively. 相似文献
50.