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31.
Hidetake Sakuraba Toshimori Nakai Yoshio Tanaka 《Journal of inclusion phenomena and macrocyclic chemistry》1984,2(3-4):829-839
Asymmetric halogenation and hydrohalogenation oftrans-cinnamic acid have been achieved in the microcrystals of cyclodextrin complexes. The bromination of the organic acid in the cavity of -cyclodextrin gave theerythro-dibromide in 40 % optical yield which was much larger than that from the resolution treatment of the racemic dibromide with -cyclodextrin and the absolute configuration was opposite in sign. The asymmetric induction in the gas-solid reaction was not due to optical resolution but to the reaction itself which was influenced by the chiral frame of cyclodextrin. The reaction shows the molecular size effect that the acid in the cavity of -cyclodextrin reacted with smaller hydrogen bromide but did not with larger bromine and chlorine. In contrast, the guest molecule in the wider cavity of -cyclodextrin reacted with bromine and chlorine as well as hydrogen bromide. The stereospecificities of the gas-solid halogenations of the acid in -cyclodextrin were similar to those of the both reactions in the solid state and in carbon tetrachloride solution without -cyclodextrin: bromination of the acid yieldederythro-2, 3-dibromo-3-phenylpropionic acid stereospecifically in 100 % in three different conditions, but chlorination gave an excess ofthreo-2, 3-dichloro-3-phenylpropionic acid to theerythro-isomer in 7287 % yields. 相似文献
32.
Yoshitane Imai Kakuhiro Kawaguchi Tomohiro Sato Michiya Fujiki Yoshio Matsubara 《Tetrahedron letters》2007,48(16):2927-2930
By using (1R,2R)-1,2-diphenylethylenediamine as a chiral molecule and 2-anthracenecarboxylic acid as a fluorescent molecule, we created a chiral supramolecular organic fluorophore having circularly polarized luminescence properties in the solid-state. 相似文献
33.
In order to examine 13C-SCS of substituted benzoic acids, chemical shifts of the acid form (I) and the dissociated form (II) have been obtained separately. Single substituent parameters, σ0 or σ+ are correlated with the shifts for the carboxyl (δco) or ipso carbons (δipso), respectively. Among the available five equations which are developed for the analysis with dual (or divided) substituent parameters (DSP), the Swain-Lupton equation (eqn 3) and the Taft-Swain-Lupton equation (eqn 4) give much better correlations, not only for δco and δipso but also for the results for ring carbons (C(2), C(5), C(6)), except for those attached to or neighboured by substituents. It is concluded that the SCS of aromatic compounds are best analyzed with substituent parameters derived from reactions or equilibria on the basis of linear free energy relationships. 相似文献
34.
Zhi C Bando Y Tang C Xie R Sekiguchi T Golberg D 《Journal of the American Chemical Society》2005,127(46):15996-15997
We report for the first time that boron nitride nanotubes (BNNTs) may be dissolved in organic solvents by wrapping them with a polymer. Transmission electron microscopy and cathodoluminescence studies indicate the strong pi-pi interactions between BNNTs and the polymer. A band gap ranging from 5.2 to 5.5 eV was documented for the BNNTs independent of their geometrical characteristics by using ultraviolet-visible absorption experiments on composite films and thin BNNT films prepared from solutions. 相似文献
35.
Yoshio Imai N. N. Maldar Masa-Aki Kakimoto 《Journal of polymer science. Part A, Polymer chemistry》1984,22(9):2189-2196
2,5-Bis(4-aminophenyl)-3,4-diphenylthiophene, a polyimide-forming monomer, was prepared in three steps starting from benzyl chloride and sulfur. Novel polyimides were synthesized from the diamine and pyromellitic dianhydride or 3,3′, 4,4′-benzophenonetetracarboxylic dianhydride (BTDA). Polymerization was carried out either by the usual two-step procedure that included ring-opening polyaddition giving polyamic acids, followed by cyclodehydration to polyimides, or by the direct one-pot procedure involving cyclodehydration in situ. The polyimide derived from the diamine and BTDA, especially that prepared by the one-pot procedure in m-cresol containing isoquinoline, is soluble in various organic solvents and gave a yellow, transparent, tough, and flexible film. Solubility of this polyimide varied by the preparative method and by the copolymerization with bis(4-aminophenyl) ether. All the polyimides are highly thermally stable and exhibited no appreciable decomposition up to 450°C in air and nitrogen atmospheres. 相似文献
36.
Masanao Oya Keikichi Uno Yoshio Iwakura 《Journal of polymer science. Part A, Polymer chemistry》1972,10(2):613-623
Copolymerization of NCA's was undertaken in a heterogeneous system in acetonitrile, which is not a solvent of the polypeptides. The reactivity ratio was calculated by using the Lewis-Mayo equation. Further, the conversion rate in the copolymerization and the configuration of the copolymer produced were compared with those of the copolymerization in the homogeneous system in nitrobenzene, in which the copolypeptides are swollen. The rate of copolymerization in acetonitrile was between the rates of polymerization of the individual monomers. It has been reported that the configuration of the copolymer obtained in dimethylformamide, in which the copolypeptides are swollen, is of the block type. On the other hand, many polypeptides obtained in acetonitrile, which is not a solvent of the copolypeptides, had a random configuration near to an alternating configuration. 相似文献
37.
Mitsuru Ueda Akira Sato Yoshio Imai 《Journal of polymer science. Part A, Polymer chemistry》1979,17(3):783-787
Catalytic actions of various additives were studied in the polycondensation of di(4-nitrophenyl) isophthalate with bis(4-aminophenyl) ether in N-methyl-2-pyrrolidone, and 1-hydroxybenzotriazole (HOBt) was found to be a highly effective catalyst that yielded high-molecular-weight polyamide. In addition to the polycondensation of the 4-nitrophenyl ester, the polymerization of negatively substituted phenyl esters like di(2,4,5-trichlorophenyl) isophthalate was also accelerated by HOBt. For the HOBt-catalyzed aminolysis of esters a bifunctional concerted mechanism that involves an eight-membered transition state was proposed. 相似文献
38.
The relative stability of various organosulfur radicals is estimated by competitive elimination technique using tributyltin radical and acetophenone derivatives having two different sulfur substituents at α and α positions. 相似文献
39.
Staphylionosides A-K: megastigmane glucosides from the leaves of Staphylea bumalda DC 总被引:1,自引:0,他引:1
Chemical investigation of leaves of Staphylea bumalda DC., collected in the suburbs of Hiroshima City, afforded 11 new megastigmane glucosides, named staphylionosides A-K (3-13), along with two known megastigmane glucosides (1, 2). The relative structures were elucidated from spectroscopic evidence, and the absolute structures of the aglycones were determined by means of the combination of beta-D-glucosylation-induced shift-trends and the modified Mosher's method. 相似文献
40.
γ-Radiolysis of 5-fluorouracil and 5-fluorouridine derivatives having sulfur-containing substituents
Tokuyuki Kuroda Koji Hisamura Hiroshi Nishikawa Nobuhiro Nakamizo Yoshio Otsuji 《Journal of heterocyclic chemistry》1994,31(2):335-339
γ-Radiolysis reactions of eight 5-fluorouracil (5-FU) derivatives having sulfonyl group-containing substituents at the 1-position and five 5-fluorouridine (5-FUR) derivatives having thioureido group-containing substituents were studied under the conditions where hydrated electron (eaq?) and hydroxyl radical (HO·) become the principal reactive species. The 5-FU and 5-FUR derivatives were radiolyzed to give 5-FU and 5-FUR, respectively. The efficiency of the reactions depended upon the nature of reactive species and also upon the nature of substituents. The reactivity features of the γ-radiolysis reactions are discussed. 相似文献