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71.
A. San Feliciano A.F. Barrero M. Medarde J.M. Miguel del Corral A. Aramburu A. Perales J. Fayos 《Tetrahedron letters》1985,26(19):2369-2372
A sesquiterpene lactone was isolated from the hexane extract of . Its constitution and stereochemistry were determined by spectroscopic techniques, principally two-dimensional NMR correlations (COSY, HCCORR, RELAY) and with the interpretation of certain chemical transformations. The results were confirmed by X-ray diffraction and the name asteriscane is proposed for the new natural skeleton. 相似文献
72.
We present the first systematic study of the Pd‐catalyzed asymmetric methoxycarbonylation of styrene in the presence of chiral ferrocenyl phosphine ligands. The reaction conditions were optimized, and a screening of different catalyst precursors was performed. A number of 1,1′‐bis(phosphino)ferrocenes of the Mandyphos, Josiphos, Walphos, and Taniaphos types were tested in combination with [PdCl2(NCPh)2], in the presence of TsOH as the acid source. These systems afforded high enantioselectivities, although the regioselectivity of the reaction was found to be in favor of the (undesired) linear ester. The catalytic system made with the Josiphos ligand 1 gave rise to an enantiomeric excess (ee) of 86%. 相似文献
73.
Aurora Gonzalez-Portal F. Bermejo-Martinez C. Baluja-Santos 《Microchemical Journal》1982,27(3):357-364
The absorption spectra in the infrared and vis-uv regions of mucic acid were established. The analytical behavior of mucic acid as a potential chromogenic reagent for the spectrophotometric determination of trace materials was studied. Interactions with iron(III), copper(II), cobalt(II) and (III), nickel(II), vanadium(IV), and uranyl(II) in basic medium were observed. 相似文献
74.
75.
We build Gaussian wave packets for the linear Schrödinger equation and its finite difference space semi-discretization and illustrate the lack of uniform dispersive properties of the numerical solutions as established in Ignat and Zuazua (2009) [6]. It is by now well known that bigrid algorithms provide filtering mechanisms allowing to recover the uniformity of the dispersive properties as the mesh size goes to zero. We analyze and illustrate numerically how these high frequency wave packets split and propagate under these bigrid filtering mechanisms, depending on how the fine grid/coarse grid filtering is implemented. 相似文献
76.
Alfonso Oliva Aurora Molinari Jean Angulo Ricardo Schrebler Humberto Gómez Ricardo Córdova 《合成通讯》2013,43(23):4353-4360
The electrooxidation of 1-phenyl-3-methyl-4-butyldithiocarboxylate-5-pyrazolone 1 has been studied in ethanol/water solution, using a glassy carbon electrode surface. The electrochemical and spectroscopic data are in agreement with a bis-ketenedithioacetal disulphide compound 2 as the only product of the reaction. 相似文献
77.
Transforming Computed Energy Landscapes into Experimental Realities: The Role of Structural Rugosity
Dr. Riccardo Montis Prof. Roger J. Davey Sarah E. Wright Dr. Grahame R. Woollam Dr. Aurora J. Cruz-Cabeza 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(46):20537-20540
We exploit the possible link between structural surface roughness and difficulty of crystallisation. Polymorphs with smooth surfaces may nucleate and crystallise more readily than polymorphs with rough surfaces. The concept is applied to crystal structure prediction landscapes and reveals a promising complementary way of ranking putative crystal structures. 相似文献
78.
79.
Olivier Jacquet Nicolas D. Clément Zoraida Freixa Aurora Ruiz Carmen Claver Piet W.N.M. van Leeuwen 《Tetrahedron: Asymmetry》2011,22(14-15):1490-1498
The use of C2-symmetric enantiopure nitrogen ligands in the asymmetric catalytic α-fluorination of β-ketoesters is described. SPANamine 1 in the presence of nickel salts gives up to 63% ee in the fluorination of tert-butyl 2-oxocyclopentanecarboxylate with N-fluorosuccinimide (NFSI). The same enantioselectivity is obtained when SPANamine 1 is used as an organocatalyst, although the reaction is much slower. 相似文献
80.
Miguel Rubio Rebeca Hernández Aurora Nogales Anna Roig Daniel López 《European Polymer Journal》2011,47(1):52-60
Isotactic polystyrene (i-PS) was employed as a matrix to disperse a metallo-organic polymer of [Fe(II) (4-octadecyl-1,2,4-triazole)3(ClO4)2] in order to obtain novel functional materials exhibiting thermal spin-crossover transition. A detailed investigation of the structure of the metallo-organic polymer and metallo-organic polymer/iPS blends has been carried out by DSC, WAXD and SAXS techniques as a function of temperature and metallo-organic polymer/iPS proportion.The results obtained confirm on the one hand that a structural transition associated with a change in the magnetic susceptibility of the metallo-organic polymer is preserved in the presence of i-PS. This transition was found to be associated to both, an inter-conversion of lamellar structures into hexagonal structures and to an increase of inter-sheet distances within the lamellar structures in metallo-organic polymer films prepared by casting from toluene solutions. On the other hand, an increase of the degree of crystallinity of the iPS is observed in the presence of the metallo-organic polymer which suggests some nucleating effect of the metallo-organic polymer in the crystallization of isotactic polystyrene. 相似文献