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排序方式: 共有313条查询结果,搜索用时 609 毫秒
101.
Shunji Ito Shohei Yamazaki Shun Kudo Ryuta Sekiguchi Jun Kawakami Masayuki Takahashi Takashi Matsuhashi Kozo Toyota Noboru Morita 《Tetrahedron》2014
Three new 1,2-dihydro-1-oxabenz[a]azulen-2-one derivatives, 1a (R1=H, R2=Me), 1b (R1=H, R2=Ph), and 1c (R1=COOEt, R2=Me), have been synthesized by the reaction of 2-hydroxyazulene (2a) and its 1-ethoxycarbonyl derivative 2b with ethyl acetoacetate (3a) or ethyl benzoylacetate (3b) in the presence of aluminum chloride. To our knowledge, these are the first examples of this type of compound, although the yield of the products is low in some cases. Their electronic properties were studied in detail utilizing the analyses of 1,2-dihydro-1-oxabenz[a]azulen-2-one derivative 1a by the spectroscopic and voltammetric analyses. The analyses revealed that the fused α-pyrone system lowers both the HOMO and the LUMO energies, relative to those of parent azulene (10), but has much pronounced effect on the LUMO, consequently, leading to decrease in HOMO–LUMO gap, compared with those of 10. These results should be attracted to the development of amphoteric redox materials. Reactivity toward electrophilic reagents was also examined by bromination and Vilsmeier–Haack formylation reactions of 1a. To evaluate the scope of the reaction products we have examined Sonogashira cross-coupling reaction of the bromination products with trimethylsilylacetylene and conversion of the formylation product to dibromoolefin by the reaction with phosphorous ylide prepared with CBr4 and Ph3P. Effective extension of the π-electron system in the ethynyl products has been revealed by the spectroscopic analysis. These reaction products would be attracted to the application as a terminal group for electronic applications. 相似文献
102.
Yutaka Amao Akemi Tadokoro Miki Nakamura Naho Shuto Ayumi Kuroki 《Research on Chemical Intermediates》2014,40(9):3257-3265
Photovoltaic conversion has been achieved by use of chloroplasts (photosynthetic organs) from spinach adsorbed on a nanocrystalline TiO2 film on an indium tin oxide (ITO) glass electrode (chloroplast/TiO2 electrode). The shape of the absorption spectrum of the chloroplast/TiO2 electrode is almost the same that of a dispersion of the chloroplasts. Absorption maxima of the chloroplast/TiO2 electrode observed at 430, 475, and 670 nm were attributed to carotenoid and chlorophyll molecules, suggesting that chloroplasts have been adsorbed by the nanocrystalline TiO2 film on the ITO electrode. The photocurrent responses of chloroplast/TiO2 electrodes were measured by using a solution of 0.1 M tetrabutylammonium hexafluorophosphate in acetonitrile as redox electrolyte in the presence or absence of water and 100 mW cm?2 irradiation. The photocurrent of the chloroplast/TiO2 electrode was increased by adding water to the redox electrolyte. The photocurrent responses of chloroplast/TiO2 electrodes irradiated with monochromatic light (680 nm, the absorption band of photosystem II complexed with evolved oxygen) were measured by use of a solution of 0.1 M tetrabutylammonium hexafluorophosphate in acetonitrile as redox electrolyte in the presence or absence of water. A chloroplast/TiO2 electrode photocurrent was observed only when the redox electrolyte containing water was used, indicating that the oxygen evolved from water by photosystem II in chloroplasts adsorbed by a nanocrystalline TiO2 film on an ITO electrode irradiated at 680 nm is reduced to water by the catalytic activity of the platinum electrode. The maximum incident photon-to-current conversion efficiency (IPCE) was 0.8 % on irradiation at 670 nm. 相似文献
103.
In order to provide a general synthetic method for carbocyclic nucleosides, regioselectivities in Mitsunobu reaction of purine, pyrimidin-2-one and their substituted derivatives with a variety of alcohols were examined and found to depend upon both substituents of the bases and kind of the alcohols. 相似文献
104.
105.
Akemi Suzuki 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2006,82(3):93-103
Sialic acid is a family of acidic monosaccharides and consists of over 30 derivatives. Two major derivatives are N-acetylneuraminic acid (NeuAc) and N-glycolylneuraminic acid (NeuGc), and the hydroxylation of CMP-NeuAc is the rate limiting reaction for the production of NeuGc. The hydroxylation was carried out by a complex formed with hydroxylase, cytochrome b5, and NADH-cytochrome b5 reductase. Mouse hydroxylase was purified from the cytosolic fraction of the liver and its cDNA was cloned. Normal human tissues do not contain NeuGc. Human hydroxylase cDNA was also cloned and the sequence revealed that human hydroxylase has 92 bp deletion. The deletion is the cause of defective expression of NeuGc in human. Chimpanzee has intact hydroxylase gene and the 92 bp deletion occurred after the divergence of human ancestor from chimpanzee ancestor. Biochemical and molecular biological studies on the biosynthesis of NeuGc and biological functions of NeuGc are reviewed. 相似文献
106.
H. Bhang S. Ajimura K. Aoki A. Banu T. Fukuda O. Hashimoto J. I. Hwang S. Kameoka B. H. Kang E. H. Kim J. H. Kim M. Kim T. Maruta Y. Miura Y. Miyake T. Nagae M. Nakamura S. N. Nakamura H. Noumi S. Okada Y. Okayasu H. Outa H. Park P. K. Saha Y. Sato M. Sekimoto S. Shin T. Takahashi H. Tamura K. Tanida A. Toyota K. Tsukada T. Watanabe H. J. Yim 《The European Physical Journal A - Hadrons and Nuclei》2007,33(3):259-263
Recent exclusive coincidence measurements of non-mesonic weak decays (NMWD) reported for the ratio of the partial decay width
of neutron-induced-to-proton-induced NMWD, Γn/Γp , values of 0.45±0.11±0.03 and 0.51±0.13±0.04 for 5lam and 12
Λ
C , respectively. These observations agree well with the improved theoretical Γn/Γp ratios which are in the range of 0.3-0.7. It appears that the long-standing discrepancy between the experimental and theoretical
values of Γn/Γp has finally been solved. However, when compared to the results of intra-nuclear cascade (INC) calculations, the observed
numbers of both single nucleons and coincident nucleon pairs are strongly quenched. The quenching of the proton yield observed
previously has been interpreted as an increase of the Γn/Γp ratio. On the other hand, significant contributions from the two-nucleon-induced three-body process ΛNN → nNN are predicted. Indeed, the angular correlation of the emitted nucleon pairs in the NMWD of 12
Λ
C showed not only decay events in back-to-back kinematics, but also events with non-back-to-back kinematics. In this paper
we show that the difficulties to extract the correct Γn/Γp ratio from the proton spectra is related to the three-body weak-interaction process which strongly quenches the nucleon yields. 相似文献
107.
108.
The SAC (symmetry adapted cluster)/SAC-CI method is applied to calculations of the ground and excited states of free base tetrazaporphin (FBTAP). The electronic spectrum is reproduced in fairly good agreement with experiments, and unknown absorption bands in the energy region higher than 4 eV are predicted. The effect of meso-tetraaza-substitution on the excited states of porphin macrocycle explains why the compound is colored, as in the closely related compounds, phthalocyanines, used as pigments. 相似文献
109.
Reaction of 3-chloropyrazine 1 -oxide ( 1 ) with 1-hexyne ( 2a ) in the presence of tetrakis(triphenylphosphine)-palladium(O) and potassium acetate in DMF afforded 3-(1-hexynyl)pyrazine 1 -oxide ( 3a ) and 3-(2-butyl-1-octen-3-ynyl)pyrazine 1-oxide ( 4a ). The novel formation of 4a was elucidated to result from codimerization of 3a with 2a . The details of reaction are discussed on the basis of findings in palladium(O)-catalyzed reaction of other chloroheterocycles. 相似文献
110.