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11.
Terukazu Nishizaki Yoshihiko Takano Tomohiro Takenouchi Norio Kobayashi 《Journal of Physics and Chemistry of Solids》2008,69(12):3027-3030
We have performed scanning tunneling microscopy/spectroscopy (STM/STS) experiments on (1 1 1)-oriented epitaxial films of heavily boron-doped diamond (Tc∼5.4 K). We present that tunneling conductance spectra show temperature-dependent spatial variations. In the low-temperature region (T=0.47 K), the tunneling spectra do not show strong spatial dependence and a superconducting energy gap is observed independent of the surface morphology. In the high-temperature region (T=4.2 K), on the other hand, the tunneling conductance spectra show significant spatial dependence, indicating the inhomogeneous distribution of the superconducting property due to the distribution of boron atoms. 相似文献
12.
Reaction of 2-arylsulfonyloxytropones (IV) and active methylene compounds, diethyl malonate, ethyl acetoacetate, ethyl cyanoacetate, malononitrile or cyanoacetamide, in the presence of NaOEt give 8-hydroxy-2H-cyclohepta[b]furan-2-one derivatives (V) and/or 2-amino-8H-cyclohepta[b]furan-8-one derivatives (VII), in addition to azulene derivatives (1) or 2H-cyclohepta(b]furan-2-one derivatives (II), known to be obtained by the reaction of 2-chlorotropones or 2-methoxytropones with active methylene compounds. Relative yields of products are influenced markedly by conditions, e.g. base type or molar ratios. The formation of V and VII is characteristic of 2-arylsulfonyloxytropones, not being observed with 2-chlorotropones or 2-methoxytropones. A reaction course involving elimination of the arylsulfonyl group as arenesulfinate ion is presented. 相似文献
13.
Computational calculations of Becke's three-parameter hybrid method using the LYP correlation functional (B3LYP) have been performed on (B12H12)2− dodecaborane anions with different boron isotopic compositions. This was done in order to investigate isotopic dependence of vibrational spectral properties of B12 icosahedra, and for comparison of the optical vibrational properties of the icosahedral molecule with the characteristics of inter- or intra-icosahedral optical phonon vibrational modes in boron-rich crystals. 相似文献
14.
Sigmatropic Rearrangements of Hypervalent‐Iodine‐Tethered Intermediates for the Synthesis of Biaryls
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Mitsuki Hori Dr. Jing‐Dong Guo Tomoyuki Yanagi Dr. Keisuke Nogi Prof. Dr. Takahiro Sasamori Prof. Dr. Hideki Yorimitsu 《Angewandte Chemie (International ed. in English)》2018,57(17):4663-4667
Metal‐free dehydrogenative couplings of aryliodanes with phenols to afford 2‐hydroxy‐2′‐iodobiaryls have been developed. This reaction proceeds through ligand exchange on the hypervalent iodine atom followed by a [3,3] sigmatropic rearrangement and with complete regioselectivity. This coupling, in combination with in situ oxidation by mCPBA, enables the convenient conversion of iodoarenes into desirable biaryls. The obtained biaryls have convertible iodo and hydroxy groups in close proximity, and are thus synthetically useful, as exemplified by the controlled syntheses of π‐extended furans and a substituted [5]helicene. DFT calculations clearly revealed that the rearrangement is sigmatropic, with C?C bond formation and I?O bond cleavage proceeding in a concerted manner. Acetic acid, which was found to be the best solvent for this protocol, renders the iodine atom more cationic and thus accelerates the sigmatropic rearrangement. 相似文献
15.
Shinya Otsuka Dr. Keisuke Nogi Prof. Dr. Hideki Yorimitsu 《Angewandte Chemie (International ed. in English)》2018,57(22):6653-6657
Insertion of tert‐butyl isocyanide into the C(sp2)?S bonds of heteroaryl sulfides is catalyzed by a palladium diphosphine complex. Thioimidates generated through this reaction could be readily hydrolyzed under acidic conditions to yield the corresponding thioesters, which are of synthetic use. This insertion is useful because starting heteroaryl sulfides were readily prepared by either conventional ways or through sulfur‐specific extended Pummerer reactions. 相似文献
16.
Yun Hu Jinlong Zhang Madoka Minagawa Terukazu Ayusawa Masaya Matsuoka Hiromi Yamashita Masakazu Anpo 《Research on Chemical Intermediates》2003,29(2):125-135
In order to investigate the cause of the decline in the photocatalytic activity of TiO2 in the decomposition of NO in a flow reaction system, detailed TPD measurements of the photocatalysts were carried out after the photoreactions. It was found that the TPD peak assigned to the adsorbed NO species observed at around 524 K is directly associated with a decline in the photocatalytic activity. The TPD spectrum of the adsorbed NO species consisted of three different types of species. The -adsorbed species of NO, formed under UV irradiation on the active surface sites, was found to cause a remarkable decline in the photocatalytic activity of TiO2. It was also found that this decline could be recovered to its original activity by heat treatment with Ar and/or O2 at around 573 K. 相似文献
17.
Tomoyuki Yanagi Dr. Keisuke Nogi Prof. Dr. Hideki Yorimitsu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(4):783-787
An unprecedented S−N variant of the benzidine rearrangement for construction of biaryls has been developed. Aryl sulfoxides underwent dehydrogenative coupling with anilines by successive treatment with trifluoromethanesulfonic anhydride and trifluoromethanesulfonic acid to provide the corresponding 2-amino-2′-sulfanyl- and/or 4-amino-4′-sulfanylbiphenyls. Mechanistic studies indicate that the C−C-bond-forming sigmatropic rearrangement proceeds intramolecularly from dicationic S−N-tethered species. 相似文献
18.
Thi Thi Nge Masaya Nogi Hiroyuki Yano Junji Sugiyama 《Cellulose (London, England)》2010,17(2):349-363
A family of polysaccharide based scaffold materials, bacterial cellulose/chitosan (BC/CTS) porous scaffolds with various weight
ratios (from 20/80 to 60/40 w/w%) were prepared by freezing (−30 and −80 °C) and lyophilization of a mixture of microfibrillated
BC suspension and chitosan solution. The microfibrillated BC (MFC) was subjected to 2,2,6,6-tetramethylpyperidine-1-oxyl radical
(TEMPO)-mediated oxidation to introduce surface carboxyl groups before mixing. The integration of MFC within chitosan matrix
was performed by 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC)-mediated cross-linking. The covalent amide
bond formation was determined by ATR-FTIR. Because of this covalent coupling, the scaffolds retain their original shapes during
autoclave sterilization. The composite scaffolds are three-dimensional open pore microstructure with pore size ranging from
120 to 280 μm. The freezing temperature and mean pore size take less effect on scaffold mechanical properties. The compressive
modulus and strength increased with increase in MFC content. The results show that the scaffolds of higher MFC content contribute
to overall better mechanical properties. 相似文献
19.
Koichi Okamoto Dr. Keisuke Nogi Prof. Dr. Jun Shimokawa Prof. Dr. Hideki Yorimitsu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(25):5615-5618
Selective C−F arylation of polyfluorophenols with aryl sulfoxides has been accomplished by means of a sigmatropic dearomatization/defluorination sequence. This sequence consists of three processes: 1) interrupted Pummerer reaction to form S−O-tethered sulfonium salt; 2) C−C-forming [3,3] sigmatropic rearrangement with dearomatization; and 3) Zn-mediated defluorinative rearomatization. The present biaryl construction provides a facile access to polyfluorinated biaryls that is difficult to synthesize by other methods. The synthetic utility of the strategy is clearly demonstrated by the synthesis of a fluorinated analogue of Maxipost, a potassium channel modulator. 相似文献
20.
Pérez-Moreno J Asselberghs I Song K Clays K Zhao Y Nakanishi H Okada S Nogi K Kim OK Je J Mátrai J De Maeyer M Kuzyk MG 《The Journal of chemical physics》2007,126(7):074705
The authors study the combination of two independent strategies that enhance the hyperpolarizability of ionic organic chromophores. The first molecular-level strategy is the extension of the conjugation path in the active chromophore. The second supramolecular-level strategy is the bottom-up nanoengineering of an inclusion complex of the chromophore in an amylose helix by self-assembly. The authors study a series of five (dimethylamino)stilbazolium-type chromophores with increasing conjugation length between the (dimethylamino)phenyl donor ring and the pyridinium acceptor ring in conjunction with four amylose helices of differing molecular weights. The first hyperpolarizabilities of the self-assembled inclusion complexes, as determined with frequency-resolved femtosecond hyper-Rayleigh scattering at 800 and 1300 nm, are compared with experimental values for the free chromophores in solution and with theoretical values. While the experimental values for the hyperpolarizability in solution are lower than the theoretically predicted values, an enhancement upon inclusion is observed, with the longest chromophore in the best amylose helix showing an enhancement by one order of magnitude. Molecular modeling of the inclusion of the chromophore suggests that the coplanarity of the two rings is more important than all-trans configuration in the conjugation path. The fundamental limit analysis indicates that the inclusion inside the amylose helix results in an optimal excited-level energy spacing that is responsible for breaching the apparent limit. 相似文献