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61.
The carbon-fluorine bond of a trifluoromethyl group attached to a π system can be activated by metallic magnesium in the system TMSCl-THF or DMF providing a variety of difluorinated compounds via a selective CF bond cleavage. Thus, trifluoromethyl ketones, α,β-unsaturated ketones, esters, imines, and aromatics can be transformed into the corresponding difluoroenol silyl ethers, enamines, and difluoro(trimethylsilyl)methyl aromatics in good to excellent yields, respectively. This protocol enabled us to synthesize β,β-difluoroamino acids, difluoroheterocycles, and functionalized difluoroacetates. 相似文献
62.
A mononuclear five-coordinate molybdenum(IV) monosulfide complex, (Et4N)2[MoS(L)2] (L = cyclohexene-1,2-dithiolate) (1), was obtained and characterized by IR, UV-vis spectroscopic methods, and X-ray crystallography. 1 was oxidized by an equivalent ferrocenium cation to give the corresponding mononuclear molybdenum(V) complex, (Et4N)[MoS(L)2] (2), which was stable for a few minutes under a lower concentration than 0.3 mM and then further dimerized to (Et4N)2[Mo(L)2]2(mu-S)2 (3). 相似文献
63.
We have shown the Lennard-Jones (LJ) phase diagram for a slit-shaped nanopore by molecular simulations and thermodynamically
predicted the results with no adjustable parameter. With this success, LJ phase diagrams are predictable. In this study, the
freezing of an LJ CH4 capillary condensate under a tensile condition in a nonstructural carbon nanopore with a cylindrical geometry was examined
using molecular dynamics (MD) simulation. We employ a unit cell in contact with a bulk vapor phase, which is useful for the
determination of the bulk vapor pressure in equilibrium with the molecules in a pore. The MD simulation results show liquid-solid
(amorphous) phase transitions with a variation in the bulk vapor pressure. The frozen particles are arranged in concentric
circular regions along the wall similar to those reported by Maddox and Gubbins. The freezing points are determined from the
variations in density, enthalpy, arrangement, and structural functions. The obtained liquid-solid coexistence points are found
to exhibit a significant dependence of the freezing point on the equilibrium bulk vapor pressure, forming an extraordinarily
skewed curve on the p-T diagram, in contrast to the bulk phase coexistence that is represented by an almost vertical line.
The origin of the significant dependence is considered to be the Laplace effect on the capillary condensate similar to the
case with a slit-shaped pore. A simple model, which the authors earlier presented for slit-shaped nanopores, successfully
predicted the p-T relation of the freezing point for cylindrical nanopores as well. 相似文献
64.
Matsuoka T Tokumori D Kotsuki H Ishida M Matsushita M Kimura S Itoh T Checcucci G 《Photochemistry and photobiology》2000,72(5):709-713
In the ciliated protozoan Blepharisma, step-up photophobic response is believed to be mediated by a novel type of photosensory pigment known as "blepharismins" (BL) that are contained in the pigment granules located just beneath the plasma membrane. We examined the ultrastructure of the pigment granules by freeze-fracture and thin-section electron microscopy and proposed a schematic diagram showing the granules' three-dimensional inner membranous structure. Some of the BL are suggested to be associated with 200 kDa membrane protein. High-pressure liquid chromatography analysis of pigment species associated with 200 kDa protein obtained from blue forms of Blepharisma (oxyblepharisma) revealed that the 200 kDa protein was associated with five types of oxyblepharismin. The fluorescence intensity was increased when the pigments were dissociated from the 200 kDa protein. The result supports the hypothesis that the pigment-200 kDa complex is able to transduce light energy into signals mediating the photobehavior of Blepharisma. 相似文献
65.
We estimated the energy barriers of proton transfers in the systems of (CF3SO3/H/SO3CF3)− and (CF3SO3/H/H2O/SO3CF3)− as models of a water-swollen Nafion membrane by an ab initio density functional quantum calculation method with consideration of the hydration effect. As a result, the proton transfer between the SO sites, which is accompanied by one water molecule, was found to be one of the proton-transfer mechanisms in the water-swollen Nafion membrane; that is, the surface diffusion mechanism was found to be important for the proton transfer in that membrane. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1905–1914, 2004 相似文献
66.
Ikeda Y Nakamura T Yorimitsu H Oshima K 《Journal of the American Chemical Society》2002,124(23):6514-6515
A cobalt complex, CoCl2[1,6-bis(diphenylphosphino)hexane], catalyzes an alkylation reaction of styrenes in the presence of Me3SiCH2MgCl in ether to yield beta-alkylstyrenes. A variety of alkyl halides including alkyl chlorides can be employed as an alkyl source. A radical mechanism is strongly suggested for this alkylation reaction. 相似文献
67.
Wada A Ogo S Nagatomo S Kitagawa T Watanabe Y Jitsukawa K Masuda H 《Inorganic chemistry》2002,41(4):616-618
The first isolation and spectroscopic characterization of the mononuclear hydroperoxo-iron(III) complex [Fe(H(2)bppa)(OOH)](2+) (2) and the stoichiometric oxidation of substrates by the mononuclear iron-oxo intermediate generated by its decomposition have been described. The purple species 2 obtained from reaction of [Fe(H(2)bppa)(HCOO)](ClO(4))(2) with H(2)O(2) in acetone at -50 degrees C gave characteristic UV-vis (lambda(max) = 568 nm, epsilon = 1200 M(-1) cm(-1)), ESR (g = 7.54, 5.78, and 4.25, S = (5)/(2)), and ESI mass spectra (m/z 288.5 corresponding to the ion, [Fe(bppa)(OOH)](2+)), which revealed that 2 is a high-spin mononuclear iron(III) complex with a hydroperoxide in an end-on fashion. The resonance Raman spectrum of 2 in d(6)-acetone revealed two intense bands at 621 and 830 cm(-1), which shifted to 599 and 813 cm(-1), respectively, when reacted with (18)O-labeled H(2)O(2). Reactions of the isolated (bppa)Fe(III)-OOH (2) with various substrates (single turnover oxidations) exhibited that the iron-oxo intermediate generated by decomposition of 2 is a nucleophilic species formulated as [(H(2)bppa)Fe(III)-O*]. 相似文献
68.
We consider a binary classification problem for a test sequence to determine from which source the sequence is generated. The system classifies the test sequence based on empirically observed (training) sequences obtained from unknown sources and . We analyze the asymptotic fundamental limits of statistical classification for sources with multiple subclasses. We investigate the first- and second-order maximum error exponents under the constraint that the type-I error probability for all pairs of distributions decays exponentially fast and the type-II error probability is upper bounded by a small constant. In this paper, we first give a classifier which achieves the asymptotically maximum error exponent in the class of deterministic classifiers for sources with multiple subclasses, and then provide a characterization of the first-order error exponent. We next provide a characterization of the second-order error exponent in the case where only has multiple subclasses but does not. We generalize our results to classification in the case that and are a stationary and memoryless source and a mixed memoryless source with general mixture, respectively. 相似文献
69.
A simple protocol that uses [OsIII(OH)(H2O)(L ‐N4Me2)](PF6)2 ( 1 ; L ‐N4Me2=N,N′‐dimethyl‐2,11‐diaza[3.3](2,6)pyridinophane) as a catalyst and H2O2 as a terminal oxidant for efficient cis‐1,2‐dihydroxylation of alkenes is presented. Unfunctionalized (or aliphatic) alkenes and alkenes/styrenes containing electron‐withdrawing groups are selectively oxidized to the corresponding vicinal diols in good to excellent yields (46–99 %). In the catalytic reactions, the stoichiometry of alkene:H2O2 is 1:1, and thus the oxidant efficiency is very high. For the dihydroxylation of cyclohexene, the catalytic amount of 1 can be reduced to 0.01 mol % to achieve a very high turnover number of 5500. The active oxidant is identified as the OsV(O)(OH) species ( 2 ), which is formed via the hydroperoxide adduct, an OsIII(OOH) species. The active oxidant 2 is successfully isolated and crystallographically characterized. 相似文献
70.
Atsushi Tarui Shoji Kondo Kazuyuki Sato Masaaki Omote Hideki Minami Yoshihisa Miwa Akira Ando 《Tetrahedron》2013,69(5):1559-1565
A highly diastereoselective cross-coupling reaction of an α-bromo-α-fluoro-β-lactam with a wide range of aryl Grignard reagents was catalyzed by Ni/bis(oxazoline) in yields of up to 98%. The product was obtained diastereoselectively as an anti-isomer. This is the first successful α-arylation of an α-fluoro-β-lactam to produce diverse α-aryl-α-fluoro-β-lactams. 相似文献