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81.
82.
Tsukasa Akaishi Keizo Miyasaka Kinzo Ishikawa Hideki Shirakawa Sakuji Ikeda 《Journal of Polymer Science.Polymer Physics》1980,18(4):745-750
The fine structure of bulk trans-polyacetylene (PA) was investigated by x-ray diffraction. The degree of crystallinity 0.81, determined by Ruland's method, was significantly higher than the value for linear polyethylene. The disorder parameter k was 5, which is much larger than the value for polyethylene. These results led us to propose that PA crystals are more disordered than PE crystals owing to the higher rigidity of PA chains. Small-angle x-ray diffraction indicated that the crystal morphology is of the extended-chain type rather than lamellar. All results obtained in this work showed that the fine structure of PA bulk is such as to facilitate electrical conduction of bulk PA. 相似文献
83.
T. Yamabe K. Tanaka H. Terama-e K. Fukui A. Imamura H. Shirakawa S. Ikeda 《Solid State Communications》1979,29(4):329-333
The electronic structures of two possible forms of the so-called -skeletal polyacetylene (-polyacetylene) are investigated on the basis of the tight-binding LCAO-SCF-MO method under the CNDO/2 version. The analyses of the total energies per unit cell, the π bond orders and the interatomic interaction energies as to the both forms predict the -transoid backbone for the -polyacetylene. The examination of the patterns of particular molecular orbitals of the hypothetical -polymer with equal C-C bond lengths also supports the -transoid form. 相似文献
84.
Ichikawa S Minakawa N Shuto S Tanaka M Sasaki T Matsuda A 《Organic & biomolecular chemistry》2006,4(7):1284-1296
3'-beta-Carbamoylmethylcytidine (CAMC) and its derivatives were synthesized using an intramolecular Reformatsky-type reaction promoted by SmI2 as the key step. In vitro tumor cell growth inhibitory activity was evaluated and CAMC was found to exhibit potent cytotoxicity against various human tumor cell lines. From a structure-activity relationship study it was postulated that the cytotoxic mechanism of action of CAMC did not require phosphorylation at the 5'-hydroxyl group. This study provides a novel strategy for the development of a new type of antitumor nucleoside. 相似文献
85.
Shirakawa E Hironaka K Otsuka H Hayashi T 《Chemical communications (Cambridge, England)》2006,(37):3927-3929
The combination of hexamethyldisilane and a catalytic amount of [PdCl(eta3-C3H5)]2-PPh3 was found to be effective for the trimethylsilylation of alcohols, where both of the two trimethylsilyl groups of hexamethyldisilane were transferred to alcohols without coproduction of any stoichiometric amount of byproduct but H2. 相似文献
86.
Uchiyama M Ozawa H Takuma K Matsumoto Y Yonehara M Hiroya K Sakamoto T 《Organic letters》2006,8(24):5517-5520
We systematically investigated, for the first time, the relationship between regioselectivity and acid/base effects in the cyclization reactions between carboxylic acids and carbon-carbon triple bonds. We found novel acid- and base-promoted cyclizations to selectively give isocoumarin or pyran-2(2H)-one and phthalide or furan-2(5H)-one skeletons, respectively, and established a catalytic version of regioselective heterocyclic ring synthesis. Density functional theory calculations and application to a short route to thunberginol A were also described. [reaction: see text]. 相似文献
87.
[reaction: see text] The carboxylic acid catalyzed three-component aza-Friedel-Crafts reactions of aldehydes, primary amines, and indoles in water have been developed. The aza-Friedel-Crafts products could be easily transformed to various 3-substituted indoles including biologically active compounds. This system offers a novel efficient method for the synthesis of 3-substituted indoles. 相似文献
88.
Akira Shirakawa Kazumichi Nakagawa Noriaki Itoh 《Molecular Crystals and Liquid Crystals》2013,570(3-4):211-226
The optical absorption spectra of 1-, 2- and 9-dibenzo-cyclohexadienyl radical in anthracene crystals have been obtained and analyzed. It is shown that the absorption lines consist of vibrational progression and charge-transfer lines for 2- and 9-DBCR. Each line belonging to the former has the same polarization as the most intense 0–0 vibrational line and the latter show polarization character depending on the direction of charge transfer and the transition energy was found to have a coulombic dependence on the distance of charge transfer. It is pointed out that only charge transfer lines were observed for 1-DBCR. The splitting of lines were observed and ascribed either to the resonance transfer interaction between two neighboring molecules situated at an equal distance from the radical or to the site symmetry. It is suggested that the intensity of the charge-transfer lines are borrowed from the intra-radical transition. The result that the charge transfer lines are more intense than the intra-radical lines for 1-DBCR was discussed. 相似文献
89.
Takaaki Takatsuka Hideki Tomita Tetsu Sonoda Volker Sonnenschein Chika Sakamoto Hiroki Mita Takuma Noto Chikara Ito Shigetaka Maeda Tetsuo Iguchi Michiharu Wada Klaus Wendt Iain Moore 《Hyperfine Interactions》2013,216(1-3):41-46
93Nb(n, n′)93mNb reaction allows retrospective estimation of integrated fast neutron dose in nuclear reactor. We proposed isomer-selective trace analysis of 93mNb by Resonance Ionization Mass Spectrometry (RIMS) combined with a gas-jet atomic source and an injection locked Ti:Sapphire laser system operated at several kHz. Resonant ionization spectroscopy of Nb in gas-jet using Ti:Sapphire laser was demonstrated. 相似文献
90.
Tomohiro Umeno Atsushi Ueda Mitsunobu Doi Takuma Kato Makoto Oba Masakazu Tanaka 《Tetrahedron letters》2019,60(49):151301
The introduction of a five-membered ring α,α-disubstituted α-amino acid into l-Leu-based heptapeptides preferentially induced right-handed (P) helical structures. Using 5 ~ 20 mol% of a single helical foldamers-catalyst, enantioselective 1,4-addition reactions of dialkyl malonates to cycloalk-2-enones (5 ~ 7 rings) proceeded to give chiral 3-substituted cycloalkanones with 94 ~ 99% ee in moderate chemical yields, regardless of the ring size of substrates. 相似文献