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21.
The synthesis of (RS)-(E)-nuciferal has been realized by two ways, starting from 2-(p-tolyl)-propanal, by Wittig's reactions. 相似文献
22.
Iron-catalyzed homo-coupling of simple and functionalized arylmagnesium reagents is described. The reaction is highly chemoselective (CN, COOEt and NO(2) groups are tolerated). The procedure was used to perform intramolecular couplings. This cyclization reaction is the key step of the total synthesis of the N-methylcrinasiadine. 相似文献
23.
We consider the problem of the existence of convergent series solutions for partial differential operators of the form
. We give first conditions for P such that the linear equation Pu=f has an analytic solution, then we solve nonlinear equations of the form Pu=F(x,u). For applications we treat also cases with parameters and give a proof of a theorem of S. Kaplan [5]. In the last section we consider a case where small denominators occur. 相似文献
24.
The first organically templated tin(IV) phosphate has been isolated and its structure solved from powder X-ray diffraction data; it exhibits a one-dimensional inorganic network built up from chains of trimers of tin(IV) octahedra on which phosphate tetrahedral groups are grafted interacting with water molecules and organic moieties. 相似文献
25.
Philippe Andrianary Gérard Jenner Alain Kiennemann 《Journal of organometallic chemistry》1983,252(2):209-220
The CO/H2 homologation of methanol to acetaldehyde and subsequently to its dimethyl acetal in the presence of cobalt acetate promoted by iodine was examined under various conditions. Temperature and pressure were found as critical parameters. High pressures (140 MPa) and low temperatures (160–170°C) give optimal yields and selectivity to acetaldehyde. According to pressure, temperature, contact time, gas ratio and ligand/catalyst ratio, the reaction is oriented towards acetaldehyde, its dimethyl acetal or methyl acetate. 相似文献
26.
Gérard G. Emch 《Communications in Mathematical Physics》1976,49(3):191-215
The classical concept ofK-flow is generalized to cover situations encountered in non-equilibrium quantum statistical mechanics. The ergodic properties of generalizedK-flows are discussed. Several non-isomorphic examples are constructed, which differ already in the type (II1, III, and III1) of the factor on which they are defined. In particular, generalized factorK-flows with dynamical entropy either zero (singularK-flows) or infinite (special non-abelianK-flows) are constructed.On leave of absence from the Depts. of Mathematics and Physics, The University of Rochester, Rochester, N. Y. 14627, USA 相似文献
27.
Danuta Piskorska Janusz Sokolowski Marlin Friesen Gérard Descotes 《Journal of carbohydrate chemistry》2013,32(8):1015-1025
AbstractThe synthesis and structure of N-D-pentopyranosylamines derived from the amines tiyptamine tyramine and the pentoses D-xylose, D-arabinose and D-lyxose are presented. NMR spectroscopy and mass spectrometry were used to verify the proposed α,β-D-pentopyranosylamine structures. 相似文献
28.
We present a short review of the experimental observations and mechanisms related to the generation of quasipatterns and superlattices by the Faraday instability with two-frequency forcing. We show how two-frequency forcing makes possible triad interactions that generate hexagonal patterns, twelvefold quasipatterns or superlattices that consist of two hexagonal patterns rotated by an angle α relative to each other. We then consider which patterns could be observed when α does not belong to the set of prescribed values that give rise to periodic superlattices. Using the Swift–Hohenberg equation as a model, we find that quasipattern solutions exist for nearly all values of α. However, these quasipatterns have not been observed in experiments with the Faraday instability for . We discuss possible reasons and mention a simpler framework that could give some hint about this problem. 相似文献
29.
A highly effective, convenient, and reproducible industrial process for palladium‐catalyzed carbon–nitrogen cross coupling has been developed and applied on a large scale. Thus various functionalized N‐arylhydrazones have been easily prepared and well characterized by conventional spectroscopic methods. 相似文献
30.
We investigate the motion of electrically charged test particles in spacetimes with closed timelike curves, a subset of the black hole or wormhole Reissner–Nordström-NUT spacetimes without periodic identification of time. We show that, while in the wormhole case there are closed worldlines inside a potential well, the wordlines of initially distant charged observers moving under the action of the Lorentz force can never close or self-intersect. This means that for these observers causality is preserved, which is an instance of our weak chronology protection criterion. 相似文献