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排序方式: 共有166条查询结果,搜索用时 15 毫秒
81.
Catherine BlancJérôme Hannedouche Francine Agbossou-Niedercorn 《Tetrahedron letters》2003,44(34):6469-6473
Chiral aminophosphine-oxazoline ligands derived from two different amino acids (tetrahydroisoquinoline carboxylic acid and proline) have been synthesized and examined as chiral auxiliaries in asymmetric allylic alkylation of three substrates. Stereoisomers 1a and 2a are providing the highest enantioselectivities (up to 94% ee) in the allylation of diphenylpropenyl acetate. 相似文献
82.
83.
Hélène Lebel Chehla Ladjel Francine Bélanger-Gariépy Frank Schaper 《Journal of organometallic chemistry》2008,693(16):2645-2648
Solid state structural studies were performed with (Ph3P)2IrCl(CO)(O2) and the O-O length redetermined to be 1.47(1) Å in contrast to results reported earlier. 相似文献
84.
85.
Hassane?Assaaoudi Ian?S.?ButlerEmail author Janusz?Kozinski Francine?Bélanger-Gariépy 《Journal of chemical crystallography》2005,35(10):809-820
Colourless crystals of a new, dicationic, hydropyrophosphate dihydrate salt, KHMgP2O7⋅ 2H2O, are formed, when a mixture of aqueous equimolar solutions of MgCl2⋅4H2O and K4P2O7, at pH 2.12, are left to stand at ambient temperature for 4 days. The new pyrophosphate salt has been characterized by single-crystal
X-ray diffraction, IR and Raman spectra, and DSC-TG thermal analysis. The structure consists of alternating layers of [HP2O7]3− groups and MgO6 octahedra, joined by K+ ions and bridging hydrogen bonds. The [P2O7]4− anions exhibit a bent eclipsed conformation. The absence of coincidences for the majority of the IR and Raman bands is in
accord with the centrosymmetric structure of the material. The 31P chemical shift tensor components have been determined from the solid-state MAS NMR spectra. The structural changes occurring
during thermal decomposition have been examined by TG-DSC, X-ray powder diffraction (XRD) and IR spectroscopy. When the new
pyrophosphate salt is heated gradually, it first becomes amorphous and then condenses to chain metaphosphates. 相似文献
86.
Tim Allman Francine Bélanger-Gariépy André L. Beauchamp 《Journal of chemical crystallography》1990,20(2):149-155
The title compound belongs to the monoclinic space groupP21/c,a=20.29(1),b=12.644(8),c=18.25(1), Å,=95.76(5)°. The unit cell contains two dimeric [Hg(CF3CO2)2PPh3]2 molecules in which each Hg atom forms strong primary bonds to a PPh3 molecule and an oxygen of a monodentate trifluoroacetate ligand. These two Hg atoms are bridged by two extra trifluoroacetate ligands, one providing a single oxygen to a Hg-O-Hg bridge, the other including both carboxylate oxygens in a Hg-O-C-O-Hg bridging moiety. This unusual type of bridging makes the two halves of the molecule symmetry independent, leading to distinct signals at 31.5 and 29.9 ppm for the phosphines in the31P CP-MAS NMR spectrum of the solid complex. 相似文献
87.
Wei-Passanese EX Han J Lin W Li T Laden F Qureshi AA 《Photochemistry and photobiology》2012,88(2):483-489
Residence in high ultraviolet (UV) locations is associated with increased risk for incident nonmelanoma skin cancer (NMSC). However, the effect of geographic location on multiple NMSC development has not been well studied. We evaluated the association between state of residence at birth, age 15 and 30 and risk of multiple NMSCs among 80275 women and men. After adjusting for age, gender, hair color, number of sunburns, tanning ability, family history of melanoma and nevus count, the cumulative relative risks (RRs) of developing ≥1 NMSC for those consistently residing in medium- and high-UV index states were 1.20 (95% CI 1.14-1.27) and 1.42 (95% CI 1.32-1.53) respectively. We found that compared to individuals with one lifetime NMSC, the multivariate cumulative RRs of developing ≥2 NMSCs for those who stayed in medium- and high-UV index states at all three timepoints were 1.09 (95% CI 1.00-1.19) and 1.15 (95% CI 1.02-1.30) respectively. These results cannot account for migration during the interval period and seasonal changes in residence; further, as BCC is the predominant NMSC, the results may be BCC-driven. In conclusion, we found that consistent residence in medium- or high-UVR locations was significantly associated an incremental risk of ≥2 NMSCs later in life. 相似文献
88.
89.
Neculai Catalin Lungu François Delattre Francine Cazier Pirouz Shirali 《Journal of fluorine chemistry》2005,126(3):385-388
The synthesis of a new fluorescent sensor incorporating a fluorinated indolizine unit bound to 6-amino-β-cyclodextrin by two different synthetic ways is described. Its sensing ability toward adamantanol has been demonstrated. 相似文献
90.
Mateus Santos Melo Roneval Félix de Santana Cinthia Meireles Batista M. S. Pinheiro R. L. C. Albuquerque Jr. Francine Ferreira Padilha Álvaro Silva Lima Paula Santos Nunes L. P. Costa A. A. S. Araújo Juliana Cordeiro Cardoso 《Journal of Thermal Analysis and Calorimetry》2013,111(3):2097-2102
The purpose of this study was to evaluate the physical–chemical properties of starch (SF), mangaba (MF), and mangaba/starch-based films (MSF), using differential thermal analysis, thermogravimetry/derivative thermogravimetry, infrared spectroscopy, mechanical profile, and scanning electron microscopy. The films were prepared by casting process using sucrose and propyleneglycol as plasticizers. The thermal profiles of MF and MSF were similar and showed increased thermal stability. The mechanical properties of MF and MSF presented decreases of tensile strength and elastic modulus when compared with SF. The MSF showed the best thermal and mechanical characteristics. 相似文献