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991.
992.
XI Shang-Zhong 《结构化学》2001,20(4)
1 INTRODUCTIONAtrope alkaloids, which exist in eggplant plants, such as atrope and scopolamine, are used as a series of important drugs in medical science [1,2]. The typical character of atrope alkaloid is that these compounds contain the main skeleton of 8-azabicycle[3,2,1]octane , which results in the very complicated synthetic routine[3]. During our research for the reaction of 1,3,5,7-tetraphenyl-4- nitro-1,7-heptadione with low-valent titanium reagent, we easily synthesized the title … 相似文献
993.
994.
H. Schomerus 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(1):5-8
We investigate broken rational tori consisting of a chain of four (rather than two) periodic orbits. The normal form that
describes this configuration is identified and used to construct a uniform semiclassical approximation, which can be utilized
to improve trace formulae. An accuracy gain can be achieved even for the situation when two of the four orbits are ghosts.
This is illustrated for a model system, the kicked top.
Received 3 August 1999 相似文献
995.
We prove a large deviation principle for Minkowski sums of i.i.d. random compact sets in a Banach space, that is, the analog of Cramér theorem for random compact sets.
996.
2-苄硫基-5,7-二甲氧基-1,2,4-三唑并[1,5-a]嘧啶(Ⅲ)是磺草唑胺(metosulam)及1,2,4-三唑[1,5-a]嘧啶醚类超高效除草剂的重要中间体.由5-氨基-3-苄硫基-1,2,4-三唑(Ⅰ)为起始原料,经环合、氯代一步反应制得2-苄硫基-5,7-二氯-1,2,4-三唑并[1,5-a]嘧啶(Ⅱ).优化试验发现90℃、丙二酸与(Ⅰ)摩尔比为1.1:1、反应20h时收率达85%以上.(Ⅱ)与甲醇钠进行置换反应制得(Ⅲ),对反应温度和物料配比进行了优化试验,发现25℃、甲醇钠与(Ⅱ)的摩尔比为5:1时收率达到90%以上.中间体(Ⅱ)、(Ⅲ)的结构经^1H-NMR、MS、IR确证.该方法原料易得、操作简便,总收率较高. 相似文献
997.
Gnanamani Shanthi 《Tetrahedron letters》2008,49(50):7139-7142
An InCl3 catalyzed efficient synthesis of novel dispiro[cyclopent-3′-ene]bisoxindoles is accomplished via a one-pot reductive cyclization of isatylidene malononitriles using the Hantzsch ester. 相似文献
998.
Two new azo-perester compounds, di-tert-butyl-6,6′-azobis-(6-cyanoperoxyheptanoate) (6,6-di-tBu) and di-tert-amyl-6,6′-azobis-(6-cyanoperoxyheptanoate) (6,6-di-tAm), synthesized on the basis of 6,6′-azobis-(6-cyanoheptanoic acid) (ACHpA), were investigated for their use in the radical polymerization of styrene (S) and methyl methacrylate (MMA). Their characteristics are given, including chemical (IR spectra), thermal (DSC) and kinetic, i.e., thermal decomposition studied by volumetric and gas chromatographic methods. The rate constants and activation energies of the decomposition of both the azo and perester bonds were determined. The new azo-peresters were utilized to initiate the radical solution polymerizations of S and MMA at 60 °C. The kinetic parameters of the processes, i.e., polymerization rate and overall rate constant, were determined. Subsequently, the polymerization products were characterized by IR and DSC. It was found that the perester groups were present in the obtained polymers, and hence, the polymers are “active” for further polymerization. 相似文献
999.
本文采用了一例特定的Lyapunov函数,来研究带Markov调制的随机微分延迟方程的p阶指数稳定性,并对其几乎必然指数稳定性也进行了探讨. 相似文献
1000.
S. P. Gromov E. N. Ushakov A. I. Vedernikov L. G. Kuz’mina M. V. Alfimov 《Theoretical and Experimental Chemistry》2009,45(1):3-11
A universal approach to the molecular design of light-sensitive nanodimensional systems with specific characteristics was
developed on the basis of unsaturated and macrocyclic compounds. It was possible to construct various nanodimensional systems
within the scope of a single class of compound using a limited number of components. The use of photostructural transformations
to control complex formation and mechanical movements in molecular devices and machines is discussed.
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 45, No. 1, pp. 1–7, January-February, 2009. 相似文献