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991.
992.
Ahmad Shaabani Heshmatollah Sepahvand Ayoob Bazgir Hamid Reza Khavasi 《Tetrahedron》2018,74(49):7058-7067
The reactivity and chemo-, regio- and diastreo-selectivity of tosylmethyl isocyanides (TosMIC) are investigated in Van Leusen type [3 + 2] cycloaddition reactions with the various activate cyclic ketones and double CC bonds in the synthesis of spirooxazolines, spiropyrrolines and chromeno[3,4-c]pyrrols in good to excellent yields under catalyst-free conditions without any activation at ambient temperature. 相似文献
993.
Ahmad Shaabani Abbas Rahmati Elham Farhangi Ali Hossein Rezayan 《Monatshefte für Chemie / Chemical Monthly》2007,138(6):615-618
Summary. A novel class of 3,4-dihydrobenzimidazo[2,1-b]quinazolin-1(2H)-ones was synthesized in very short reaction times with good yields in the presence of 3-butyl-1-methyl imidazolium bromide
as a room temperature ionic liquid at 120°C. The ionic liquid can be recycled for subsequent reactions without any loss of
efficiency. 相似文献
994.
Ammonium chloride as a very inexpensive and readily available reagent, and efficiently catalyzes one-pot, three component, Biginelli condensation reactions of aldehydes, 1,3-dicarbonyl compounds and urea or thiourea under solvent-free conditions to afford the corresponding 3,4-dihydropyrimidin-2-(1H)-ones in high yields at 100°C. 相似文献
995.
This contribution presents an experimental approach to improve analytical performance of electromembrane extraction (EME) procedure, which is based on the scrutiny of current pattern under different extraction conditions such as using different organic solvents as supported liquid membrane, electrical potentials, pH values of donor and acceptor phases, variable extraction times, temperatures, stirring rates, different hollow fiber lengths and the addition of salts or organic solvents to the sample matrix. In this study, four basic drugs with different polarities were extracted under different conditions with the corresponding electrical current patterns compared against extraction recoveries. The extraction process was demonstrated in terms of EME-HPLC analyses of selected basic drugs. Comparing the obtained extraction recoveries with the electrical current patterns, most cases exhibited minimum recovery and repeatability at the highest investigated magnitude of electrical current. . It was further found that identical current patterns are associated with repeated extraction efficiencies. In other words, the pattern should be repeated for a successful extraction. The results showed completely different electrical currents under different extraction conditions, so that all variable parameters have contributions into the electrical current pattern. Finally, the current patterns of extractions from wastewater, plasma and urine samples were demonstrated. The results indicated an increase in the electrical current when extracting from complex matrices; this was seen to decrease the extraction efficiency. 相似文献
996.
Hossein Azari 《PAMM》2007,7(1):2040003-2040004
The aim of this paper is to study the parabolic inverse problem of determination of the leading coefficient in the heat equation with an extra condition at the terminal. After introducing a new variable, we reformulate the problem as a nonclassical parabolic equation along with the initial and boundary conditions. The finite difference methods, backward Euler and Crank–Nicolson schemes are studied. The results of a numerical example are presented, which demonstrate the efficiency and rapid convergence of the methods. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
997.
《Colloids and surfaces. A, Physicochemical and engineering aspects》2000,161(3):489-498
Colloidal amphiphilic particles were prepared with hydrophilic polyacrylamide cores encapsulated by hydrophobic poly(butyl methacrylate) shells. The hydrophobic shell possessed a porous structure, which made the hydrophilic core accessible to the outside liquid. The amphiphilicity of the particles was characterized by their water and diesel oil absorbabilities. The effect of the polymerization conditions on the structure and thickness of the hydrophobic layer was investigated in some detail. Such amphiphilic particles can be dispersed in both water and hydrophobic liquids, and the dispersions have a long life in water and a more moderate one in oil. 相似文献
998.
《Tetrahedron: Asymmetry》2000,11(16):3375-3393
Lipase Amano PS catalysed acylation of (±)-2-hydroxymethyl-2,3-dihydrobenzofurans using vinyl acetate as the acyl donor in n-hexane gave (−)-(R)-2-acetoxymethyl-2,3-dihydrobenzofurans and (+)-(S)-2-hydroxymethyl-2,3-dihydrobenzofurans in high enantiomeric excess. (−)-(R)-Acetate 18j is converted to (−)-(R)-MEM-protected arthrographol 22. 相似文献
999.
1000.