Let be the spectrum of in L2(ℝ), where q is an even almost-periodic complex-valued function with bounded primitive and derivative. It is known that , where is the spectrum of the unperturbed operator. Suppose that the asymptotic approximation to the first asymptotic correction
is given. We prove the formula that recovers the frequencies and the Fourier coefficients of q in terms of Δμn.
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A sequence consisting of palladium-catalyzed benzamide ortho-arylation/reaction with (CF3CO)2O was developed allowing a convenient one-pot synthesis of ortho-arylated benzonitriles and fluorenone derivatives. The outcome of this transformation is dependent on the amide N-alkyl substituent. Dehydration of ortho-arylated N-cyclohexyl-benzamides by (CF3CO)2O results in efficient production of benzonitriles. In contrast, o-arylated N-propylbenzamides are converted to fluorenone derivatives. 相似文献
Pd(II) allyl and Pd(0) olefin complexes containing the configurationally labile ligand 1,2-bis-[4,5-dihydro-3H-dibenzo[c-e]azepino]ethane were studied as models for intermediates in Pd-catalyzed allylic alkylations. According to NMR and DFT studies, the ligand prefers C(s) conformation in both eta3-1,3-diphenylpropenyl and eta3-cyclohexenyl Pd(II) complexes, whereas in Pd(0) olefin complexes it adopts different conformations in complexes derived from the two types of allyl systems in both solution and, as verified by X-ray crystallography, in the solid state. These results demonstrate that the Pd complex is capable of adapting its structure to the reacting substrate. The different structural preferences also provide an explanation for the behavior of 1,3-diphenyl-2-propenyl acetate and 2-cyclohexenyl acetate in Pd-catalyzed allylic alkylations using pseudo-C2 and pseudo-C(s) symmetric ligands. 相似文献
The formation of a pentanuclear palladium(II) complex with a phenanthridinonetriazine-based ligand system, which itself is formed by a metal-mediated rearrangement of a triazinephenanthridinium proligand, is described. 相似文献
Three new N(1),N(5),N(14)-tris(4- hydroxycinnamoyl)spermines were identified in hydromethanolic root extracts of Microdesmis keayana J. Léonard and Microdesmis puberula Hook f. The electrospray ionisation tandem mass spectrometry (ESI-MS/MS) technique with specific nuclear magnetic resonance analysis of hydrolysed products made it possible to identify N(1),N(5),N(14)-tris(p-coumaroyl)spermine, N(1)-feruloyl,N(5),N(14)-di(p-coumaroyl)spermine and N(1),N(5),N(14)-tris(feruloyl)spermine, named keayanines B, C and D, respectively. ESI-MS/MS analysis most effectively provided structural data although high-performance liquid chromatography/electrospray ionisation tandem mass spectrometry was also used to characterise four other compounds from Microdesmis puberula-keayanidines A, B, C and keayanine A-which had already been identified in M. keayana. This chemical data is the first to be published for M. puberula which is a commonly used plant in Central African traditional medicine. 相似文献
The anionic solution polymerization of buta‐1,3‐diene was modeled, considering the reactivity of the active sites to be different due to varying geometric configurations. With the first‐order Markov model, expressions for the fraction of active sites and dyad distribution were obtained. The rate constants were determined by fitting to the conversion and dyad experimental data using the nonlinear least squares method. The kinetic model shows that the microstructure and the dyads do not depend on initiator and butadiene concentration but only on rate constants. Without a modifier, the butadiene addition mechanism is entropic; with a modifier, the mechanism changes to entropic‐enthalpic.
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