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91.
A New Synthetic Route to Ubiquinones Ubiquinones 11 have been prepared employing a new strategy: as key step, the Diels-Alder reaction of 1,1,2-trichloroethene 3 with 2,5-bis[(trimethylsilyl)oxy]-3-methylfuran ( 2 ) has been used for the construction of the quinone part. After methanolysis of the [4 + 2] adducts 4a/4b , further reaction with cyclopentadiene and substitution of the Cl-atoms by MeO groups, the intermediate 7 is obtained. Diketone 7 can easily be alkylated with the desired polyprenyl side chain 9 (X = Br) using a strong base to yield, after a retro-Diels-Alder reaction, the corresponding ubiquinones 11 in high yields. 相似文献
92.
Gans und Goldschmidt Elektrizitäts-Ges. m. b. H. Berlin W. A. Roth J. Shukow A. Gerassimov Tödt Rossée v Morgenstern E. E. Weibel A. L. Thuras H. T. Stern F. Scheminzky R. Lorenz H. Klauer R. E. Hall L. H. Adams und O. Pfundt 《Fresenius' Journal of Analytical Chemistry》1928,75(3-4):120-123
Ohne Zusammenfassung 相似文献
93.
94.
Potassium-mirror reduction of tetracyanoethylene (TCNE) acceptor in tetrahydrofuran affords K(THF)2 TCNE salt (1) showing double TCNE/K chains assembled via unusual μ3-TCNE-bridging of potassium cations. These parallel ladder-type chains are further tethered by pairs of THF bridges between potassium centers and by intermolecular π-bonding in (TCNE)22? dimers, and this results in formation of quasi-2-D coordination networks. In the presence of crown-ether ligand, the same potassium-mirror reduction lead to formation of [K(18-crown-6)(THF)2]TCNE salt (2) in which monomeric tetracyanoethylene anion-radicals are positioned between bulky [K+(18-crown-6)(THF)2] counter-ions. In comparison, crystallization of tetracyanoethylene anion-radicals with K+(18-crown-6) counter-ions in dichloromethane affords K(18-crown-6)TCNE salt (3) consisting of 1-D chains with 1,2-(N,N’)-TCNE bindings of potassium cations (nested in the crown-ether cavities). Temperature-dependent magnetic susceptibility study revealed essentially isolated tetracyanoethylene anion-radicals (S = 1/2) in this 1-D coordination polymer. 相似文献
95.
Pierre Bonami Lorenz T. Biegler Andrew R. Conn Grard Cornujols Ignacio E. Grossmann Carl D. Laird Jon Lee Andrea Lodi Franois Margot Nicolas Sawaya Andreas Wchter 《Discrete Optimization》2008,5(2):186-204
This paper is motivated by the fact that mixed integer nonlinear programming is an important and difficult area for which there is a need for developing new methods and software for solving large-scale problems. Moreover, both fundamental building blocks, namely mixed integer linear programming and nonlinear programming, have seen considerable and steady progress in recent years. Wishing to exploit expertise in these areas as well as on previous work in mixed integer nonlinear programming, this work represents the first step in an ongoing and ambitious project within an open-source environment. COIN-OR is our chosen environment for the development of the optimization software. A class of hybrid algorithms, of which branch-and-bound and polyhedral outer approximation are the two extreme cases, are proposed and implemented. Computational results that demonstrate the effectiveness of this framework are reported. Both the library of mixed integer nonlinear problems that exhibit convex continuous relaxations, on which the experiments are carried out, and a version of the software used are publicly available. 相似文献
96.
Thomas Lorenz 《Set-Valued Analysis》2008,16(1):1-50
The mutational equations of Aubin extend ordinary differential equations to metric spaces (with compact balls). In first-order
geometric evolutions, however, the topological boundary need not be continuous in the sense of Painlevé–Kuratowski. So this
paper suggests a generalization of Aubin’s mutational equations that extends classical notions of dynamical systems and functional
analysis beyond the traditional border of vector spaces: Distribution-like solutions are introduced in a set just supplied
with a countable family of (possibly non-symmetric) distance functions. Moreover their existence is proved by means of Euler
approximations and a form of “weak” sequential compactness (although no continuous linear forms are available beyond topological
vector spaces). This general framework is applied to a first-order geometric example, i.e. compact subsets of ℝ
N
evolving according to the nonlocal properties of both the current set and its proximal normal cones. Here neither regularity
assumptions about the boundaries nor the inclusion principle are required. In particular, we specify sufficient conditions
for the uniqueness of these solutions.
相似文献
97.
98.
Göttig Walther Hempel C. Reinhardt R. Lorenz A. Ledebur C. G. Müller Osmond Abel und Forquignon 《Fresenius' Journal of Analytical Chemistry》1895,34(1):191-224
Ohne Zusammenfassung 相似文献
99.
N. v. Lorenz 《Fresenius' Journal of Analytical Chemistry》1893,32(1):64-67
Ohne ZusammenfassungMittheilung der K. K. landw. chemischen Versuchsstation in Wien. 相似文献
100.