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1.
2.
The pentafluorobenzenethiyl radical is an efficient hydrogen abstractor from an activated methylene or methine group and bis(pentafluorophenyl) disulfide is an efficient electron acceptor from the resulting radical intermediate. Thus benzyl-OTBS ether was easily converted into the corresponding pinacol, and 2-phenyl-1,3-dioxanes are converted into the monobenzoates of diols. 相似文献
3.
Ciguatoxin C-CTX-1 was isolated as a principal causative toxin of ciguatera seafood poisoning in the Caribbean Sea, and is structurally classified as a ladder-shaped polycyclic ether. In this Letter, we report the synthesis of the tricyclic LMN-ring system of C-CTX-1. SmI2-mediated reductive cyclization efficiently constructed the seven-membered M-ring with the axially oriented 1,3-dimethyl structure. 相似文献
4.
Hynd Remita Prem Felix Siril Israel-Martyr Mbomekalle Bineta Keita Louis Nadjo 《Journal of Solid State Electrochemistry》2006,10(7):506-511
Three Pt-based catalysts prepared in different radiolytic conditions and supported on graphite powder were packed into a carbon paste electrode configuration. They were compared to each other, to the commercial (Pt) deposited on activated carbon powder (Johnson Matthey) and to pure Vulcan XC-72 for their respective abilities toward the hydrogen evolution reaction (HER). The Tafel parameters were determined for all these electrodes. From the I–V curves and their quantitative treatment, the following order of activity emerged unambiguously and reads: (PtCO)2 (fcc structure) > (PtCO)1 (Chini cluster) > (Pt)neat > (Pt)JM (Johnson Matthey) ≫ (Vulcan XC-72). As expected, all the Pt-loaded electrodes were more efficient than Vulcan XC-72. The classification appears to be linked with the mean nanoparticle size, and for comparable sizes, with the surface morphology of the materials. The results and the stability of the electrodes suggest that the small particle sizes and the good dispersity on the carbon support were maintained during the HER. 相似文献
5.
The demetalation process of 10 multi-iron Wells-Dawson polyoxometalates is studied by cyclic voltammetry and controlled potential coulometry. Eight sandwich-type complexes (alphaalphaalphaalpha-Na(16)[(NaOH(2))(2)(Fe(III))(2)(X(2)W(15)O(56))(2)], alphaalphabetaalpha-Na(14)[(NaOH(2))(Fe(III)OH(2))(Fe(III))(2)(X(2)W(15)O(56))(2)], alphabetabetaalpha-Na(12)[(Fe(III)OH(2))(2)(Fe(III))(2)(X(2)W(15)O(56))(2)], and alphabetabetaalpha-Na(14)[(Mn(II)OH(2))(2)(Fe(III))(2)(X(2)W(15)O(56))(2)] (where X = P(V) or As(V))) and two monomeric complexes (alpha-Na(11)[(P(2)(Fe(III)Cl)(2)(Fe(III)OH(2))W(15)O(59))] and alpha-Na(11)[(As(2)(Fe(III)Cl)(2)Fe(III)OH(2))W(15)O(59))]) were selected for this study. All 10 complexes show Fe(III) waves which are well-separated from the redox activity of the W(VI) centers. At room temperature and under mild conditions, iron release from the complexes is observed upon reduction of the Fe(III) centers. This release is controlled by the ionic strength of the medium, the nature and concentration of the anions present in the supporting electrolyte, and by the pH of the solution. This behavior parallels those described for most siderophores which depend on the same parameters. 相似文献
6.
Y Nomoto H Takai T Hirata M Teranishi T Ohno K Kubo 《Chemical & pharmaceutical bulletin》1991,39(1):86-90
A series of 1-(6,7-dimethoxy-4-quinazolinyl)piperidines carrying various 5-membered heterocycles at the 4-position was synthesized and examined for cardiotonic activity in anesthesized dogs. The (4-oxo-2-thioxo-3-imidazolindinyl)amino derivatives showed the most potent inotropic activity. Marked loss of activity was observed in the 2,4-dihydro-3-thioxo-3H-1,2,4-triazolyl, the 2,4-dihydro-3-oxo-3H-pyrazolyl and the (2,3-dihydro-2-thioxo-3H-1,3,4-thiadiazol-5-yl)amino derivatives. The synthesis and structure-activity relationships are discussed. 相似文献
7.
Katsunori Teranishi 《Journal of inclusion phenomena and macrocyclic chemistry》2002,44(1-4):313-316
A useful technique to bifunctionalize the secondary hydroxyl faces of cyclodextrins is described. Regioselective2A,2D-disulfonylations ofcyclodextrins were achieved by reacting cyclodextrins with a combinationof a novel disulfonyl imidazole reagent and molecular sieves inN,N-dimethylformamide. The resulting disulfonates were convertedto 2A,3A,2D,3D-dimannoepoxy-cyclodextrins and3A,3D-diamino-3A,3D-dideoxy-(2AS,3AS),(2DS,3DS)-cyclodextrins, which contain twofunctional groups on the periphery of the molecules. 相似文献
8.
9.
Tadahiro Kato Motoyuki Tanaka Shin‐suke Takagi Keita Nakanishi Masahiro Hoshikawa 《Helvetica chimica acta》2004,87(1):197-214
The synthesis of kempa‐6,8‐dien‐3β‐ol ( 4a ), as a synthetic leading model of the natural product 4b , was carried out starting from intermediate 12 , the synthetic route of which has been developed previously (Scheme 1). The conversion of 12 to the model compound 4a involved the elaboration of three structure modifications by three processes, Tasks A, B, and C (see Scheme 2). Task A was achieved by epoxy‐ring opening of 41 with Me3SiCl (Scheme 9), and Task B being performed by oxidation at the 13‐position, followed by hydrogenation, and then epimerization (Schemes 4 and 5). The removal of the 2‐OH group from 12 (Task C) was achieved via 30b according to Scheme 6, whereby 30b was formed exclusively from 30a / 31a 1 : 1 (Scheme 7). In addition, some useful reactions from the synthetic viewpoint were developed during the course of the present experiments. 相似文献
10.
Fabrication of mesoporous ZnO nanosheets from precursor templates grown in aqueous solutions 总被引:1,自引:0,他引:1
Keita Kakiuchi Eiji Hosono Toshio Kimura Hiroaki Imai Shinobu Fujihara 《Journal of Sol-Gel Science and Technology》2006,39(1):63-72
Mesoporous ZnO nanosheets were successfully prepared by pyrolytic transformation of zinc carbonate hydroxide hydrate, Zn4CO3(OH)6·H2O. The nanosheets were initially formed as assemblies on glass substrates during chemical bath deposition (CBD) in aqueous
solutions of urea and zinc acetate dihydrate, zinc chloride, zinc nitrate hexahydrate, or zinc sulfate heptahydrate at 80°C.
It was key to induce heterogeneous nucleation of Zn4CO3(OH)6·H2O by promoting a gradual hydrolysis reaction of urea and controlling the degree of supersaturation of zinc hydroxide species.
Morphology of Zn4CO3(OH)6·H2O was largely influenced by the anions present in the CBD solutions. The Zn4CO3(OH)6·H2O nanosheets were transformed into wurtzite ZnO by heating at 300°C in air without losing the microstructural feature. 相似文献