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21.
[reaction: see text] Vinylation of various azoles (pyrrole, indole, carbazole, and their derivatives) and phenothiazine with vinyl bromides catalyzed by palladium-phosphine complexes results in the respective N-vinylazoles in 30-99% yields. This reaction with cis- and trans-beta-bromostyrenes is stereospecific giving the respective products with full retention of configuration. 相似文献
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Mechanochemical reaction of cluster coordination polymers 1infinity[M3Q7Br4] (M = Mo, W; Q = S, Se) with solid K2C2O4 leads to cluster core excision with the formation of anionic complexes [M3Q7(C2O4)3]2-. Extraction of the reaction mixture with water followed by crystallization gives crystalline K2[M3Q7(C2O4)3].0.5KBr.nH2O (M = Mo, Q = S, n = 3 (1); M = Mo, Q = Se, n = 4 (2); M = W, Q = S, n = 5 (3)). Cs2[Mo3S7(C2O4)3].0.5CsCl.3.5H2O (4) and (Et4N)1.5H0.5K{[Mo3S7(C2O4)3]Br}.2H2O (5) were also prepared. Close Q...Br contacts result in the formation of ionic triples {[M3Q7(C2O4)3](2)Br}5- in 1-4 and the 1:1 adduct {[Mo3S7(C2O4)3]Br}3- in 5. Treatment of 1 or 2 with PPh(3) leads to chalcogen abstraction with the formation of [Mo3(mu3-Q)(mu2-Q)3(C2O4)3(H2O)3]2-, isolated as (Ph4P)2[Mo3(mu3-S)(mu2-S)3(C2O4)3(H2O)3].11H2O (6) and (Ph4P2[Mo3(mu3-Se)(mu2-Se)3(C2O4)3(H2O)3].8.5H2O.0.5C2H5OH (7). All compounds were characterized by X-ray structure analysis. IR, Raman, electronic, and 77Se NMR spectra are also reported. Thermal decomposition of 1-3 was studied by thermogravimetry. 相似文献
23.
Synthesis of 1-aryl-1H-indazoles via palladium-catalyzed intramolecular amination of aryl halides 总被引:1,自引:0,他引:1
Palladium-catalyzed cyclization of arylhydrazones of 2-bromoaldehydes and 2-bromoacetophenones to give 1-aryl-1H-indazoles has been studied in detail. The cyclization of arylhydrazone of 2-bromobenzaldehydes can be performed with good to high yields using Pd(dba)2 and chelating phosphines, of which the most effective are rac-BINAP, DPEphos, and dppf, in the presence of Cs2CO3 or K3PO4 as a base. Electron-rich, bulky ligands commonly employed for intermolecular amination such as PtBu3 and o-PhC6H4PtBu2 were shown to be ineffective for cyclization and to lead instead to extensive oligomerization and tarring. The method developed is applicable for preparation of a wide scope of indazoles bearing electron-donating or electron-withdrawing substituents, among them, unprotected carboxyl, as well as various indazole heteroanalogues. The cyclization of arylhydrazones of less reactive halides such as 2-chlorobenzaldehyde, as well as 2-bromoacetophenone and bromotetralone, has been achieved. The purity of the starting hydrazone has been shown to be a critical parameter, as various impurities inhibit the cyclization. 相似文献
24.
Artyom A. Astafiev Olga V. Repina Boris S. Tupertsev Alexey A. Nazarov Maria R. Gonchar Anna V. Vologzhanina Valentine G. Nenajdenko Andreii S. Kritchenkov Victor N. Khrustalev Victor N. Nadtochenko Alexander G. Tskhovrebov 《Molecules (Basel, Switzerland)》2021,26(6)
Arylazoimidazoles are important dyes which were intensively studied in the past. In contrast, triarylazoimidazoles (derivatives which carry aryl substituents at the imidazole core) received almost no attention in the scientific literature. Here, we report a new family of simple and easily accessible triarylazoimidazole-group 12 metal complexes, which feature highly efficient photo-luminescence emission (Φ up to 0.44). Novel compounds exhibit bright red emission in solution, which could be excited with a visible light. 相似文献
25.
We introduce a generalized criterion for the stability of Markovian queueing systems in terms of stochastic fluid limits.
We consider an example in which this criterion may be applied: a polling system with two stations and two heterogeneous servers.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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We present a continuous, bilinear formulation for the fixed charge network flow problem. This formulation is used to derive
an exact algorithm for the fixed charge network flow problem converging in a finite number of steps. Some preliminary computational
experiments are reported to show the performance of the algorithm. 相似文献
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Vladimir O. Abramov Anna V. Abramova Vadim M. Bayazitov Alexander V. Marnosov Sergey P. Kuleshov Artyom S. Gerasin 《Applied Acoustics》2016
A technique for treatment of perforation zones of horizontal oil wells for water cut reduction based on selective ultrasonic treatment was suggested. The technique involves online geophysical studies of horizontal wells, determination of treatment intervals based on these studies, selective ultrasonic treatment of the chosen interval and subsequent pump-out using a specially designed jet pump. The technology does not involve reduction of the flow in the well. The developed innovative technique of water cut reduction using selective ultrasonic treatment is studied within this article. Theoretical estimations and computer modeling revealed that the position of the downhole ultrasonic tool near the sidewall of the well leads to more homogeneous distribution of the induced acoustical field and wider penetration of the acoustical waves. The developed method was tested on a horizontal well in Western Siberia, which was characterized by high water cut. Based on geophysical studies only zones with low water and high oil production were treated, this lead to a decrease of the water cut by 20% and an increase of oil production by 91% after treatment of the test well. 相似文献
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This paper proposes a system optimal dynamic traffic assignment model that does not require the network to be empty at the
beginning or at the end of the planning horizon. The model assumes that link travel times depend on traffic densities and
uses a discretized planning horizon. The resulting formulation is a nonlinear program with binary variables and a time-expanded
network structure. Under a relatively mild condition, the nonlinear program has a feasible solution. When necessary, constraints
can be added to ensure that the solution satisfies the First-In-First-Out condition. Also included are approximation schemes
based on linear integer programs that can provide solutions arbitrarily close to that of the original nonlinear problem. 相似文献