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991.
Sanjib Gogoi 《Tetrahedron letters》2009,50(19):2252-1652
The first enantioselective synthesis of biologically active 6-amino-5-cyanodihydropyrano[2,3-c]pyrazoles has been achieved through a cinchona alkaloid-catalyzed tandem Michael addition and Thorpe-Ziegler type reaction between 2-pyrazolin-5-ones and benzylidenemalononitriles. The reaction may also be carried out in a three-component or a four-component fashion via the in situ formation of these two components from simple and readily available starting materials. The desired products were obtained in excellent yields with mediocre to excellent enantioselectivities (up to >99% ee). 相似文献
992.
A synthesis of racemic thalidomide ( 1 ) was described and the important formal [3+3] cycloaddition strategy was a keystep. The total yield of thalidomide ( 1 ) was 18% in five steps from known 3 . 相似文献
993.
Our main results in the chemistry of 1,3-calix[4]-bis-crowns taken from recent literature are reported. 相似文献
994.
Yu. M. Volovenko V. V. Ivanov A. O. Pushechnikov 《Chemistry of Heterocyclic Compounds》2002,38(2):213-218
Bromination of 1-oxo(imino, amino)benzo[4,5]imidazo[1,2-a]pyridines gave the corresponding 2-bromo derivatives. Acylation using the Vilsmeier complex in acetic anhydride gave the N-formyl and N-acetyl derivatives. The reaction of the amine with the Vilsmeier complex, acetyl acetone, ethyl acetoacetate, and 2,5-dimethoxytetrahydrofuran occurs at the amino group. 相似文献
995.
S. V. Shishkina S. M. Desenko K. G. Nazarenko O. V. Shishkin 《Journal of Structural Chemistry》2005,46(1):191-194
X-ray diffraction investigation showed that protonation of 4H-benzo-[1,4]-oxazin-3-ylidene-cyclohexylamine occurs at the exocyclic nitrogen atom. In crystal, the cation has a structure with a distinct exocyclic C=N bond. 相似文献
996.
The intramolecular 1,3-dipolar cycloaddition of unsaturated nitrones derived from methyl α-d-glucopyranoside with 2-furaldehyde has been studied. This cycloaddition was found to afford three 9-oxa-1-azabicyclo[4.2.1]nonane diastereomers in a 3:1:1 ratio [with the principal isomer possessing a (3S,4R,5S,6S,8S) configuration, determined by NMR spectroscopy]. The effects of different Lewis acid catalysts (MgCl2, ZnCl2 and BF3·OEt2) on yields and diastereomeric ratios have been examined in detail. The best result (90% yield) was achieved when MgCl2 was present (in toluene, 120 °C bath temperature, 12 h). The stereoselectivity of the 1,3-dipolar cycloaddition was not significantly altered under the conditions investigated. 相似文献
997.
Viktor Csokai Diem Lan Ha Mai Olívia Varga Klára Tóth Miklós Kubinyi Alajos Grün 《Tetrahedron》2008,64(6):1058-1063
Novel fluorogenic 1,3-alt thiacalix[4](N-phenylazacrown-5)ether ionophore has been synthesized by conjugation of the N-phenyl group with borondipyrromethene (BODIPY) fluorophore moiety. The ionophore exhibits pronounced off-on type fluorescent responses to some transition metal ions, in particular to Cu2+. In a PVC membrane electrode, distinct Ag+ selectivity was observed in potentiometric transduction. 相似文献
998.
Ekaterina A. Shilova Valery P. Perevalov Corinne Moustrou 《Tetrahedron letters》2008,49(21):3453-3457
The novel photochromic [2]rotaxane based on chromene molecule introduced into a crown-containing macrocyclic receptor was synthesized. The photochemical properties of rotaxane could be modified by the complexation of the crown ether moiety. 相似文献
999.
Xiaoling Huang Yebang Tan Yuexia Wang Hui Yang Jie Cao Yuju Che 《Journal of polymer science. Part A, Polymer chemistry》2008,46(18):5999-6008
The novel copolymers of acrylamide (AM) with complex pseudorotaxane monomer (BAMACB) of butyl ammonium methacrylate (BAMA) and cucurbit[6]uril (CB[6]) were prepared via free‐radical polymerization in aqueous solution. The copolymers containing pseudorotaxane (PAM/BAMACB) were characterized by 1H‐NMR, FTIR, elemental analysis, TGA, and DSC. The glass transition temperature (Tg) of the copolymer PAM/BAMACB are higher than that of the copolymer of acrylamide and butyl ammonium methacrylate (PAM/BAMA) because of the enhanced rigidity and the bulky steric hindrance of BAMACB side chain in PAM/BAMACB. The molecular weights of copolymer PAM/BAMACB were obtained via static light scattering. The hydrodynamic radii of coils or aggregates were investigated by dynamic light scattering. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5999–6008, 2008 相似文献
1000.
D. V. Dar’in S. G. Ryazanov S. I. Selivanov P. S. Lobanov A. A. Potekhin 《Chemistry of Heterocyclic Compounds》2008,44(4):461-465
The cyclocondensation of α-acylacetamidines with esters of 2-fluoro-5-nitrobenzoic and 4-chloro-2-methyl-5-pyrimidinecarboxylic
acids leads to condensed azines. The reaction proceeds chemoselectively such that the α-carbon atom of the amidine replaces
the halogen atom in the aromatic ring, while the amino group reacts with the ester group.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 589–594, April, 2008. 相似文献