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21.
A variety of 1-(-alkylphenyl)- and 1-(-'-dialkylphenyl)- pyrrolidines and -piperidines were prepared by the gas phase alumina mediated condensation of tetrahydrofuran (THF), tetrahydropyran (THP) or the corresponding diols with primary aromatic amines in fair to high yield. This methodology can also be used for the synthesis of 1-phenylhexahydroazepine from aniline. A mechanistic interpretation of the catalytic action of alumina is presented. 相似文献
22.
G. Tamai H. Yoshida H. Imai T. Takashina K. Kotoo T. Fuwa Y. Tsuchioka H. Matsuura G. Kajiyama 《Chromatographia》1985,20(11):671-676
Summary New quinidine metabolites, including 10,11-dihydrodiol quinidine N-oxide, 10,11-dihydrodiol quinidine and their glucuronides, were found in human urine. A quinidine monitoring HPLC method including these metabolites, is proposed by the direct injection of body fluid samples onto the precolumn for deproteinization followed by reverse phase separation in the analytical column with a column switching technique. The recovery of spiked quinidine and its metabolites in plasma was quantitative (98–102%) with good reproducibility (C.V.: 1.6–4.0%). Several clinical samples such as whole blood and urine were analyzed by the present method. 相似文献
23.
为了应对新冠病毒肺炎(COVID-19)蔓延和响应教育部"停课不停教,停课不停学"的号召,作者从"两问题三误区"入手分析了现有在线教学存在的问题,并对比了不同直播平台的优缺点,提出了在线教学的具体教学建议。以基于"超星直播+学习通"的在线教学为例进行了教学示范指导。 相似文献
24.
Four new stationary phases for HPLC were prepared by modifying silica gel with a trifrnctional aminoalkyl silane. A conjugated π-electron system was linked to the amino group either directly or with a carboxylic anhydride as a spacer in between. Characterization and dynamic measurements of the new stationary phases were performed by solid state NMR spectroscopy. The results of the 29si and 13C CP/MAS techniques were compared with the recently developed 1H MAS-only technique. Despite strong homonuclear dipole-dipole interactions it was possible to obtain well resolved 1H MAS spectra of those stationaru phases with a high degree of crosslinking. Limited mobility of the aromatic ligand fragments is common for all examined stationaryu phases. The chromatographic properties of the new phases were tested by their ability tio sepatate a mixture of eight PAHS. It could be shown that the π-π interaction mechanism is responsible for the separation of the eight PAHs, because the elution order of the PAHs did not changem despite the use of both a nonpolar mobile phase (n-heptane) and a polar mobile phase (methanol/ water mixture). 相似文献
25.
Densities of boldine + alcohol binary mixtures were measured over the whole accessible range of boldine compositions at temperatures from 283.15 to 333.15 K using an Anton-Paar digital vibrating glass tube densimeter. The binary systems studied include, as a solvent, seven normal alcohols from n-C1 to n-C6, n-C8, and isopropanol. The density of these systems has been found an increasing function of the boldine composition. A new methodology based on density data of solutions of solid solutes with normal alcohols is described in order to determine solid molar volume of pure solutes. This methodology was validated with pure solid naphthalene molar volumes data at 298.15 K, with an average uncertainty of 6%. 相似文献
26.
27.
Rémy Lartia 《Tetrahedron letters》2004,45(31):5949-5952
We report here a novel, simple reagent enabling the chemical incorporation of a thiophosphate or a phosphate group at the 5′-end of oligonucleotides using very mild basic deprotection conditions. This method can be useful in the case of alkali sensitive modified oligonucleotides. This reagent also gives access to the preparation of bifunctional oligonucleotides with either a thiophosphate group at the 5′-end and a phosphate at the 3′-end, or two thiophosphate groups at both the 5′- and the 3′-ends, or a 5′-thiophosphate group and a 3′-amino-containing linker. 相似文献
28.
Ichimin Shirotani Yousuke Shimaya Chihiro Sekine 《Journal of solid state chemistry》2003,174(1):32-34
New filled skutterudites with heavy lanthanide, LnFe4P12 (Ln=Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) have systematically been prepared for the first time by the high-pressure technique. The relationship between lattice constants and atomic numbers of lanthanide (including Y) is established for LnFe4P12. Electrical and magnetic properties of several new filled skutterudites with heavy lanthanide have been studied at low temperatures; YFe4P12 shows a superconducting transition at around 7 K, and DyFe4P12 behaves as a ferromagnet below 10 K. Electrical and magnetic anomalies in DyFe4P12 and YFe4P12 are mainly discussed. 相似文献
29.
M. E. Rogers T. E. Glass S. J. Mecham D. Rodrigues G. L. Wilkes J. E. McGrath 《Journal of polymer science. Part A, Polymer chemistry》1994,32(14):2663-2675
New strategies for the synthesis of perfectly alternating segmented polyimide-polydimethyl siloxane copolymers were developed by utilizing a transimidization method. Imide oligomers endcapped with 2-aminopyrimidine were reacted with aminopropyl terminated (dimethyl siloxane) oligomers to afford perfectly alternating segmented imide siloxane copolymers. The polymerization was conducted in solvents such as chlorobenzene and chlorofrom. High molecular weight, fully imidized perfectly alternating segmented imide siloxane copolymers were obtained within 2 h at temperatures of 60-110°C. The mechanism of the reaction was further elucidated via model compounds and NMR characterization. The block copolymers exhibited two Tgs due to the microphase separation of the polyimide and polysiloxane phases. The Tg of the polyimide phase was a function of the length of the polyimide block. However, partial phase mixing was also evident from the DSC results on the imide siloxane copolymers prepared with low molecular weight polyimide segments. Thermooxidative stability and tensile properties of the perfectly alternating segmented imide siloxane copolymers were found to be principally dependent on the amount of poly (dimethyl siloxane) incorporated in the copolymer and did not correlate with the poly (dimethyl siloxane) or polyimide block lengths. The stress-strain behavior of both solvent cast films or molded films is also reported. © 1994 John Wiley & Sons, Inc. 相似文献
30.
New Oxides with the “Butterfly-Motive”: Rb6[Fe2O5] and K6[Fe2O5] Rb6[Fe2O5] and K6[Fe2O5] were obtained for the first time by annealing intimate mixtures of “Rb6CdO4” with CdO (molar ratio 1 : 1.1) and KO0.48 with CdO (molar ratio 5.9 : 1) respectively in closed Fe-cylinders. Determination and refinement of the crystalstructure confirms the space group C2/m (four-circle-diffractometer data). Rb6[Fe2O5]: Ag Kα , 720 out of 1220 Io(hkl), R = 9.68%, Rw = 6.09%; a = 718.9pm, b = 1183.1 pm, c = 695.4pm, β = 95.05°, Z = 2; K6[Fe2O5]: MoKα , 1214 Out of 12141o(hkl), R = 3.20070, Rw = 2.48%, a = 691.21 pm, b = 1142.78pm, c = 665.50pm, β = 93.82°, Z = 2. The binuclear unit [O2FeOFeO2]6? already known to be planar with oxoferrates(II) now was observed to be angular here and closely related to Na6[Be2O5]. 相似文献