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21.
Kim SY Saxena A Kwak G Fujiki M Kawakami Y 《Chemical communications (Cambridge, England)》2004,(5):538-539
Cooperative amplification of the C-F...Si weak interaction between side chains and the main chain was found to afford rigid rodlike helical polysilanes with a preferential screw sense. 相似文献
22.
The ruthenium-catalysed double addition of trimethylsilyldiazomethane to alkynes developed by Dixneuf and co-workers was applied to the synthesis of 2-alkyl- or 2-aryl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1,4-bis(trimethylsilyl)-1,3-butadienes by use of alkynylboronates instead of alkynes. Di- and tetrasubstituted 1,3-butadienes were prepared from a 2-boryl-1,4-disilyl-1,3-butadiene, using the Suzuki-Miyaura coupling reaction, iodolysis of the alkenylsilane moieties with N-iodosuccinimide and hydrolysis of the carbon-silicon bonds with trifluoroacetic acid. The same compound was converted also to a bicyclic compound, a trisubstituted 1,3-butadiene and a dienone through the Diels-Alder reaction, oxidation of the alkenylboronate moiety and the Mukaiyama aldol reaction. 相似文献
23.
The ring conformation of 2-O-methyl-1,3,4,5-tetrakis-O-tert-butyldiphenylsilyl-myo-inositol was in a twist form both in solid state and in solution. This is the first observation of a stable twist conformer induced by the introduction of bulky silyl protecting groups. 相似文献
24.
Yasuhiro Takahashi Yusuke Ozaki Minoru Takase W. R. Krigbaum 《Journal of Polymer Science.Polymer Physics》1993,31(9):1135-1143
Redetermination of the crystal structure of poly(p-benzamide) was made by using newly collected intensity data. The molecular conformation is TCTC, where the internal rotation angles about the N? C bond of the amide group and about the virtual bond of N-phenyl-C are T (trans) and C (cis) conformations, respectively. Two molecular chains pass through a rectangular unit cell with dimension, a = 7.75 Å, b = 5.30 Å, c (fiber axis) = 12.87 Å, and the space group, P212121-D. The reflection observed at the spacing of 010 may be attributed to the reflection due to another crystal polymorph or the diffuse scattering due to disorder. © 1993 John Wiley & Sons, Inc. 相似文献
25.
A novel self-oscillating polymer was prepared by utilizing the Belousov-Zhabotinsky (BZ) reaction. In this study, a sulfonic acid group was newly introduced as a pH-control site into the copolymer of N-isopropylacrylamide, and the ruthenium complex was introduced as a catalyst site. By introducing the pH-control site, we succeed in causing the soluble-insoluble self-oscillation of the polymer solution under acid-free conditions in which only two BZ substrates, malonic acid and sodium bromate, were present as added agents. The self-oscillating behavior was remarkably influenced by the temperature and polymer concentration, which reflects the intermolecular aggregative capacity of the polymer chains in the reduced state to change the lower critical solution temperature. This achievement of self-oscillation of polymer chains under acid-free conditions may lead to their practical use as novel biomimetic materials under biological conditions. 相似文献
26.
Tsuchimoto T Kamiyama S Negoro R Shirakawa E Kawakami Y 《Chemical communications (Cambridge, England)》2003,(7):852-853
A palladium-indium triflate catalyst was found to be much more active for the dimerization of vinylarenes compared with generally used cationic palladium(II) catalysts. 相似文献
27.
Nishimura T Ohsawa S Maeda K Yashima E 《Chemical communications (Cambridge, England)》2004,(6):646-647
Novel [60]fullerene-based poly(phenylacetylene)s prepared by the copolymerization of achiral phenylacetylenes bearing a C(60) or crown ether pendant form a one-handed helix upon complexation with L- and D-alanine, yielding a helical array of the pendant fullerenes with a predominant screw-sense along the polymer backbone. 相似文献
28.
Hong-Ling Li Koichi Takahashi Yusuke Ujihira Mariko Ishiwatari Kurima Kobayashi Takahiko Iriyama Tokuzo Konishi 《Journal of Thermal Analysis and Calorimetry》1995,45(6):1359-1371
The Mössbauer spectra of Sm2Fe17Nx, prepared by the nitrogenation of Sm2Fe17 powders in an ammonia and hydrogen atmosphere, were observed at elevated temperatures to shed light on the thermal behavior of nitrogen in the compounds Sm2Fe17Nx. It was found that there were large differences in thermal behavior between the starting Sm2Fe17, crystalline Sm2Fe17Nx (x≈1.7) and amorphous Sm2Fe17Nx(x~7). The thermal decomposition behavior of Sm2Fe17N3.2, developed as one of the most promising hard magnetic materials, was found to be different under different atmospheres. 相似文献
29.
In an effort to develop an efficient synthetic method of highly diastereoselective (2′R)- and (2′S)-2′-deoxy[2′-2H]guanosines, chemoenzymatic conversion was investigated. The synthesis of (2′R > 98% de)-2′-deoxy[2′-2H]guanosine was achieved by biological transdeoxyribosylation using (2′R > 98% de)-2′-deoxy[2′-2H]uridine, 2,6-diaminopurine, and Enterobacter aerogenes AJ-11125, followed by treatment with adenosine deaminase. (2′S > 98% de)-2′-Deoxy[2′-2H]guanosine was synthesized from (2′S > 98% de)-2′-deoxy[2′-2H]uridine and 2,6-diaminopurine using thymidine phosphorylase and purine nucleoside phosphorylase instead of E. aerogenes AJ-11125. 相似文献
30.
Ohno H Takeoka Y Kadoh Y Miyamura K Tanaka T 《The Journal of organic chemistry》2004,69(13):4541-4544
Two novel palladium(0)-catalyzed cyclizations of allenenes are described. Treatment of allenenes such as N-(1-alkyl-2,3-butadienyl)-N-allylsulfonamide with an aryl halide and K(2)CO(3) in the presence of a catalytic amount of Pd(PPh(3))(4) in dioxane affords 2,3-cis-pyrrolidines in a stereoselective manner. In sharp contrast, cyclization of the same allenenes using catalytic Pd(2)(dba)(3) x CHCl(3) in the presence of allyl methyl carbonate in CH(3)CN leads to stereoselective formation of a 3-azabicyclo[3.1.0]hexane framework in moderate yields. 相似文献