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141.
142.
2-pyridones from cyanoacetamides and enecarbonyl compounds: application to the synthesis of nothapodytine B 总被引:1,自引:0,他引:1
Carles L Narkunan K Penlou S Rousset L Bouchu D Ciufolini MA 《The Journal of organic chemistry》2002,67(12):4304-4308
The condensation of an enone or enal with cyanoacetamide derivatives and t-BuOK furnishes either 3-cyano-2-pyridones or 3-unsubstituted-2-pyridones, depending on whether the reaction is carried out in the presence or in the absence of O(2). In the first case, in situ oxidation of Michael-type intermediates takes place; in the second case, the products result from "decyanidative aromatization" of such intermediates. A one-step synthesis of 3-alkyl-2-pyridones has been devised on the basis of decyanative union of an enone/enal and a 2-alkylcyanoacetamide. The new reaction forms the centerpiece of an unusually concise synthesis of nothapodytine B (mappicine ketone). 相似文献
143.
144.
In the quantum rotor model with random exchange interactions having a nonzero mean, three phases, a (i) phase (Bose) glass, (ii) superfluid, and (iii) Mott insulator, meet at a bicritical point. We demonstrate that proximity to the bicritical point and the coupling between the energy landscape and the dissipative degrees of freedom of the phase glass lead to a metallic state at T = 0. Consequently, the phase glass is unique in that it represents a concrete example of a metallic state that is mediated by disorder, even in 2D. We propose that the experimentally observed metallic phase which intervenes between the insulator and the superconductor in a wide range of thin films is in actuality a phase glass. 相似文献
145.
We report quantitative measurements of both wave number selection and defect motion in nonequilibrium hexagonal patterns. A novel optical technique ("thermal laser writing") is used to imprint initial patterns with selected characteristics in a Bénard-Marangoni convection experiment. Initial patterns of ideal hexagons are imposed to determine the band of stable pattern wave numbers while initial patterns containing an isolated penta-hepta defect are imprinted to study defect propagation directions and velocities. The experimental results are compared to recent theoretical predictions. 相似文献
146.
Kraft P Bajgrowicz JA Denis C Fráter G 《Angewandte Chemie (International ed. in English)》2000,39(17):2963
The cover picture shows, on the lip of Oncidium tigrinum La Llave et Lex., the superposition of beta-ionone and a tailor-made bicyclo[6.4.0]dodecene. The structural similarity of the two molecules accounts for their close odors. beta-Ionone is present in the scent of the depicted tropical orchid at the unusually high level of 14.5 %. An overview of the olfactory spectrum is shown in the background. More on scents and their molecules can be found in the review of P. Kraft et al. on p. 2980 ff. 相似文献
147.
We briefly report on new results concerning a perturbation expansion structure within the framework of an analytic version of perturbative quantum chromodynamics (pQCD). This approach combines the RG symmetry with the Källén–Lehmann analyticity in the Q2 variable. The procedure of analytization matches this analyticity with the RG invariance by adding to the analytized invariant coupling
some nonperturbative contributions containing no adjustable parameters. In turn, the new perturbative expansion (the APT expansion) for an observable represents asymptotic expansion over a nonpower set of specific functions
rather than in powers of
. We analyze this set and show that it obeys different properties in various ranges of the Q2 variable. In the UV, it is close to the power set
used in the pQCD calculation. However, generally, this set is of a more complicated nature. In the low Q2 region the behavior of
is oscillating. Here, the APT expansion has a feature of asymptotic expansion à la Erdélyi. The issue of the consistency of an analytization procedure with the RG structure of observables is also discussed. 相似文献
148.
Title compounds have been prepared from carbonyl compounds by formal removal of hydroxyl and sulfenyl or hydroxyl and selenyl moieties from the corresponding functionalized β-hydroxysulfides or β-hydroxyselenides. 相似文献
149.
150.