排序方式: 共有75条查询结果,搜索用时 31 毫秒
21.
Saida Sultanic 《Journal of Mathematical Analysis and Applications》2006,324(1):639-649
In this paper we analyze sub-Bergman Hilbert spaces in the unit disk associated with finite Blaschke products. We also analyze their analogues in weighted Bergman spaces. 相似文献
22.
Schlemminger I Saida Y Groger H Maison W Durot N Sasai H Shibasaki M Martens aJ 《The Journal of organic chemistry》2000,65(16):4818-4825
The catalytic and enantioselective hydrophosphonylation of cyclic imines using cyclic phosphites is described for the first time. In contrast to the application of acyclic phosphites, significant improvements are presented arising from the concept of improved rigidity by utilization of cyclic phosphites in the lanthanoid BINOL complex catalyzed hydrophosphonylation of 3-thiazolines. Cyclic phosphites are shown to provide certain improvements within the catalytic cycle. Influence of parameters such as concentration of the catalyst and the phosphite on the catalysis is examined as well as the effects of the substituents on the starting material. The pharmacologically interesting thiazolidinyl phosphonates are synthesized in excellent optical purities of up to 99% ee and high chemical yields of up to 99%. The required amount of catalyst is reduced to 2.5 mol %. The highest efficiency of the reaction involving cyclic phosphites is achieved using the catalytic system "2.5 mol % (S)-YbPB/2.5 equiv phosphite/50 degrees C/48 h/THF-toluene (1:7)". On the basis of the results a refinement of the proposed catalytic cycle has been provided. For comparison cyclic phosphites were used in hydrophosphonylation with a chiral titanium catalyst. 相似文献
23.
Al-Subu Mohammad M. Jondi Waheed J. Dado Saida A. Hilal Hikmat S. 《Transition Metal Chemistry》2002,27(2):223-227
The kinetics of oxidation of 1-octene and heptanal by 18-crown-6-ether-solubilized KMnO4 in benzene and CH2Cl2 have been investigated. In benzene, the oxidation of 1-octene is first order with respect to the oxidant and zero order with respect to the substrate, whereas in CH2Cl2 the reaction is first order with respect to both substrate and oxidant. The reaction of heptanal followed different kinetics being first order with respect to both substrate and oxidant, regardless of whether benzene or CH2Cl2 was employed as the solvent. The values of activation energy E
a, standard enthalpy H
*, standard entropy change S
*, and standard free energy G
*, for the reaction, are reported. Mechanistic pathways for the studied reactions are also proposed. 相似文献
24.
Nalla Ram Reddy Ghanta Mahesh Reddy Battu Saida Reddy Padi Pratap Reddy 《Journal of heterocyclic chemistry》2005,42(5):751-754
A general synthetic approach to pyrazolo[4,3‐d]pyrimidines is reported. Aldehydes, arylideneanilines, carboxylic acids and orthoesters are used as one‐carbon units for bridging the two amino functions of 4‐amino‐1‐alkyl‐3‐propylpyrazole‐5‐carboxamides. 相似文献
25.
Feriel Necibi Saida Ben Salah Julien Roger Jean-Cyrille Hierso Taoufik Boubaker 《国际化学动力学杂志》2020,52(10):669-680
The kinetics of the reactions of 4-nitrobenzofurazane 1a , 4-nitrobenzothiadiazole 1b , and 4-nitrobenzoselenadiazole 1c with a series of 4-Y-substituted phenoxide anions 2a-e (Y = OMe, Me, H, Cl, and CN) in aqueous solution at 20°C were investigated photometrically. The derived second-order rate constants (k2) have been combined with the nucleophilicity parameters values of these series of anions 2a-e to determine the electrophilicity parameters E of electrophiles 1a-c according to the linear free-energy relationship (log k2)/s versus N. General reactivity of these electrophiles 1a-c is found to be fairly similar with E values ranging in −10.77 ± 0.61 < E < −7.53 ± 0.29. The comparison with structurally related neutral electron-deficient heteroaromatic and aromatic compounds revealed that 1a - c are more reactive than 1,3,5-trinitrobenzene, as benchmark aromatic electrophile used in nucleophilic addition or substitution processes. The rate constants for the reactions of 4-nitrobenzochalcogenadiazoles 1a-c with some other nucleophiles were measured and found to agree with those calculated from Mayr's equation. Finally, analysis of the rate data in terms of the Brønsted approach reveals that 1a-c exhibits especially low intrinsic reactivity in σ-adducts 3 forming reactions. 相似文献
26.
Harald Gröger Yoshinobu Saida Shigeru Arai Jürgen Martens Hiroaki Sasai Masakatsu Shibasaki 《Tetrahedron letters》1996,37(52):9291-9292
The catalytic and enantioselective hydrophosphonylation of a cyclic imine, namely the 3-thiazoline 1, is described. We have discovered a highly efficient enantioselective de novo approach to the pharmaceutically interesting 4-thiazolidinylphosphonate 2 using either titanium or lanthanoid chiral catalysts, which gives excellent enantiomeric purities (up to 98 %ee) and high chemical yields. 相似文献
27.
Saida Azzouzi Rachid Jalal Malika El Messaoudi Luis R. Domingo M'hamed Esseffar M. José Aurell 《Journal of Physical Organic Chemistry》2007,20(4):245-254
A novel heterocyclic compound 3‐mesityl‐5‐methyl‐4,5,11,11a‐tetrahydro‐6H‐[1,2,4]oxadiazolo [5,4‐b][1,3,4]benzotriazépin‐6‐one 4 has been synthesised by a 1,3 dipolar cycloaddition (13DC) reaction of 1,3,4‐benzotriazepin‐5‐one 1 with mesitylnitrile oxide 3 . The reaction, beside its synthetic interest, has shown to be completely chemo‐ and regioselective. The structure of the compound was determined by X‐ray crystallography and analysed by spectral methods (NMR and mass spectrometry). The molecular mechanism for the reaction has been studied using quantum mechanical calculations at the B3LYP/6‐31G* theory level. Two mechanisms are possible for the formation of the cycloadduct 4 . The first one involves a 13DC reaction between 1 , as dipolarophile and 3 , as dipole. Analysis of the results indicates that it takes place along asynchronous concerted bond‐formation process with a very low polar character. The regioselectivity obtained from the calculations are in complete agreement with the unique formation of the cycloadduct 4 . The second mechanism is initiated by the nucleophilic attack of the N3 nitrogen of the tautomer form of 2 , to the C5 carbon of the nitrile oxide 3 to yield an amidoxime. However, the large energy involved in this addition prevents this mechanism. The large energy difference between the tautomers 1 and 2 , makes that only the C?N site of benzotriazepin‐5‐one 1 could act as a dipolarophile site. This fact makes the 13DC reaction to be chemoselective. The analysis of global electrophilicity of the reagents allows explaining the low polar character of these 13DC reactions. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
28.
Ichitsubo T Matsubara E Yamamoto T Chen HS Nishiyama N Saida J Anazawa K 《Physical review letters》2005,95(24):245501
By utilizing ultrasonic annealing at a temperature below (or near) the glass transition temperature Tg, we revealed a microstructural pattern of a partially crystallized Pd-based metallic glass with a high-resolution electron microscopy. On the basis of the observed microstructure, we inferred a plausible microstructural model of fragile metallic glasses composed of strongly bonded regions surrounded by weakly bonded regions (WBRs). The crystallization in WBRs at such a low temperature under the ultrasonic vibrations is caused by accumulation of atomic jumps associated with the beta relaxation being resonant with the ultrasonic strains. This microstructural model successfully illustrates a marked increase of elasticity after crystallization with a small density change and a correlation between the fragility of the liquid and the Poisson ratio of the solid. 相似文献
29.
Médout-Marère V Belarbi H Haouzi A Giuntini JC Douillard JM Zanchetta JV Vanderschueren J 《Journal of colloid and interface science》2000,223(1):61-73
This work shows that hydration of clays can be studied by means of a new interpretation of thermally stimulated depolarization currents technique. These measurements have been performed on four exchanged natural clays: Na-montmorillonite, Ca-montmorillonite, kaolinite, and illite. The results are analyzed using both the recently developed analysis of relaxation times distribution and the electronegativity equalization method. They provide evidence of the surface heterogeneity of clays. It is established that sites, identical from a crystallographic point of view, are different when the energy of the phenomenon is considered. The main interest of this work is to give for the first time a value of the hydration energy of cation onto clay surfaces. Copyright 2000 Academic Press. 相似文献
30.
Takeo Sasaki Takayuki Kondo Motoki Noro Kazuya Saida Hiroaki Yaguchi Yumiko Naka 《Journal of polymer science. Part A, Polymer chemistry》2012,50(8):1462-1468
Photoinduced depolymerization of poly(olefin sulfone)s mixed with a photobase generating compound was investigated. Irradiation of 254 nm UV light to films comprising of a mixture of a photobase generating compound and poly(olefin sulfone)s with volatile monomers caused photoinduced depolymerization and the irradiated part of the film vaporized. The effect of the poly(olefin sulfone) structure on the photoinduced depolymerization process was investigated. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献