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51.
Starting from (R)-camphordiamine, 13 new camphor-annulated imidazoline ligands are synthesized in good yields as two regioisomeric series. Yields of up to 94% and good enantioselectivities up to 67% are achieved for the copper(II)-catalyzed Henry reaction giving the product stereoselectively according to the regioisomer used. 相似文献
52.
Antonín Klásek Filip Křemen Hana Křemenová Antonín Lyčka Michal Rouchal 《Tetrahedron》2017,73(12):1583-1593
The reaction of tertiary α-chloroketones with ethanolamine has not been hitherto described in the literature. Herein, we describe the reaction of tertiary 3-chloroquinoline-2,4-diones with ethanolamine to give novel 3-(2-hydroxyethylamino)quinoline-2,4-diones. These compounds provide 3-(2-oxooxazolidin-3-yl)quinoline-2,4(1H,3H)-diones and new compounds with dimeric character after reaction with triphosgene. Molecular rearrangement proceeds during the reaction of 3-(2-hydroxyethylamino)quinoline-2,4-diones with isocyanic acid. Three types of reaction products arise: 2-(2-hydroxyethyl)imidazo[1,5-c]quinazoline-3,5-diones, 3-(2-hydroxyethyl)-3,3a-dihydro-2H-imidazo[4,5-]quinoline-4(5H)diones and primarily 5-hydroxy-1-(hydroxyethyl)-1′H-spiro[imidazolidine-5,3′-indole]-2,2′-diones. The reaction mechanism and product stereochemistry are discussed. The 1H, 13C and 15N NMR spectra of the prepared compounds were measured, and all resonances were assigned from appropriate two-dimensional experiments. 相似文献
53.
We propose a criterion giving a sufficient condition for quantum states of a harmonic oscillator not to be expressible as a convex mixture of Gaussian states. This nontrivial property is inherent to, e.g., a single-photon state and the criterion thus allows one to reveal a signature of the state even in quantum states with a positive Wigner function. The criterion relies on directly measurable photon number probabilities and enables detection of this manifestation of a single-photon state in quantum states produced by solid-state single-photon sources in a weak coupling regime. 相似文献
54.
Filip Bureš Oldřich Pytela Milan Kivala François Diederich 《Journal of Physical Organic Chemistry》2011,24(4):274-281
A representative data set has been gained by the measurement of the electronic absorption spectra of 12 systematically selected push–pull systems with an intramolecular charge‐transfer (CT) absorption and the general structure D–π–A (D = donor, A = acceptor) featuring electron‐withdrawing CN groups, electron‐donating N(CH3)2 groups, and various π‐conjugated backbones in 32 solvents with different polarities. The longest‐wavelength absorption maxima λmax and the corresponding wavenumbers $\tilde {v}_{{\rm max}} $ were evaluated from the UV/Vis spectra measured in 32 well‐selected solvents. The D–π–A push–pull systems were further characterized by quantum‐chemical quantities and simple structural parameters. Structure–solvatochromism relationships were evaluated by multidimensional statistic methods. Whereas solvent polarizability and solvent cavity size proved to be the most important factors affecting the position of λmax, the solvent polarity was less important. The most important characteristics of organic CT compounds are the energy of the LUMO, the permanent dipole moment, the COSMO (COnductor‐like Screening MOdel) area, the COSMO volume, the number, and ratio of N,N‐dimethylamino and cyano groups, and eventually the number of triple bonds (π‐linkers). A relation between the first‐order polarizability α, the longest‐wavelength absorption maxima λmax, and the structural features has also been found. The higher‐order polarizabilities β and γ are not related to the observed solvatochromism. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
55.
This article presents extensions of the Cramér-Wold theorem to measures that may have infinite mass near the origin. Corresponding
results for sequences of measures are presented together with examples showing that the assumptions imposed are sharp. The
extensions build on a number of results and methods concerned with injectivity properties of the Radon transform. Using a
few tools from distribution theory and Fourier analysis we show that the presented injectivity results for the Radon transform
lead to Cramér-Wold type results for measures. One purpose of this article is to contribute to making known to probabilists
interesting results for the Radon transform that have been developed essentially during the 1980s and 1990s. 相似文献
56.
Tomáš Řezníček Libor Dostál Aleš Růžička Jiří Kulhánek Filip Bureš Roman Jambor 《应用有机金属化学》2011,25(3):173-179
The phosphines L1PPh2 (1) and L2PPh2 (2) containing different Y,C,Y‐chelating ligands, L1 = 2,6‐(tBuOCH2)2C6H3? and L2 = 2,6‐(Me2NCH2)2C6H3?, were treated with PdCl2 and di‐µ‐chloro‐bis[2‐[(N,N‐dimethylamino)methyl]phenyl‐C,N]‐dipalladium(II) and yielded complexes trans‐{[2,6‐(tBuOCH2)2C6H3]PPh2}2PdCl2 (3), {[2,6‐(Me2NCH2)2C6H3]PPh2} PdCl2 (4), {[2,6‐(tBuOCH2)2C6H3]PPh2}Pd(Cl)[2‐(Me2NCH2)C6H4] (5) and {[2,6‐(Me2NCH2)2C6H3]PPh2}Pd(Cl)[2‐(Me2NCH2)C6H4] (6) as the result of different ability of starting phosphines 1 and 2 to complex PdCl2. Compounds 3–6 were characterized by 1H, 13C, 31P NMR spectroscopy and ESI‐MS. The molecular structures of 3,4 and 6 were also determined by X‐ray diffraction analysis. The catalytic activity of complexes 3–6 was evaluated in the Suzuki‐Miyaura cross‐coupling reaction. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
57.
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59.
Air-coupled ultrasound (ACU) provides a tool to evaluate wood samples of small or moderate thickness (<30 mm) thereby avoiding direct contact or liquid coupling. Results of through-transmission ACU measurements on wood veneer samples and related products are reported with respect to a wide variety of quality aspects. Fluctuations in the averaged received signal levels appear to be correlated to the presence of natural or machine-induced thickness and density variations, flaws and grain damage, errors produced by the manufacturing process, insufficient bonding on a substrate, etc. In addition it is seen that the variability of the signal levels enables to distinguish between quarter and crown areas. 相似文献