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排序方式: 共有197条查询结果,搜索用时 78 毫秒
191.
A novel one-pot azide-alkyne/ketenimine-nitrone cycloaddition sequence that is induced by copper(I) and allows the transformation of sulfonyl azides, alkynes, and nitrones to highly substituted imidazolidin-4-ones is described. The corresponding heterogeneous version utilizing Cu(I)-modified zeolites as recyclable heterogeneous catalysts shows marginally improved yield and diastereoselectivity. 相似文献
192.
A simple and efficient route for the synthesis of 5-substituted 1H-tetrazoles catalyzed by CoY zeolite is reported. The salient features of this atom-economical, cost-effective, and high-yield cobalt-catalyzed protocol are aerobic conditions, lower reaction time, and milder reaction conditions without additives. Other advantages include experimental ease of manipulation, safer alternative to hazardous, corrosive, and polluting conventional Lewis acid catalysts, recovery, and reusability with consistent catalytic activity. The results are rationalized by proposing a suitable mechanism. 相似文献
193.
Abstract Polyaniline, poly(o-methoxyaniline)and poly(N-phenylaniline) were synthesized chemically under different polymerization conditions by peroxodisulphate oxidation in HCl and in a mixture of HCl and CH3CN. The polymer prepared at 0°C, monomer-oxidant ratio 1:1.15 and a strong acidic medium, has the least bandgap and maximum electrical conductivity. The electrical conductivity depends on degree of oxidation and protonation. The bulky substituents increase the torsion angle and hence disorder causes the decrease in the electrical conductivity of polymer. 相似文献
194.
Per-6-amino-beta-cyclodextrin as an efficient supramolecular ligand and host for Cu(I)-catalyzed N-arylation of imidazole with aryl bromides 总被引:2,自引:0,他引:2
Per-6-amino-beta-cyclodextrin (per-6-ABCD), acting simultaneously as a supramolecular ligand for CuI and host for aryl bromides, catalyzes N-arylation of imidazole with aryl bromides under mild conditions. This simple method proceeds with excellent yield for the coupling of imidazole with various substituted aryl bromides demonstrating good tolerance of other functionalities. 相似文献
195.
Eichhöfer A Wood PT Viswanath RN Mole RA 《Chemical communications (Cambridge, England)》2008,(13):1596-1598
The synthesis, molecular structures, and magnetic and optical properties of [Mn(32)Se(14)(SePh)(36)(PnPr(3))(4)] and [Na(benzene-15-crown-5)(C(4)H(8)O)(2)](2)[Mn(8)Se(SePh)(16)] have been investigated which are the first examples of manganese chalcogenide cluster complexes, despite known manganese oxo compounds, which comprise more than four manganese atoms. 相似文献
196.
Billye Cheek Mieczyslaw Dabkowski Amr El Nagdi Louis R. Hunt T. P. LaFaveJr Ke Liu Duncan L. MacFarlane Viswanath Ramakrishna 《Acta Appl Math》2012,118(1):107-123
In this work, we consider design questions for an active optical lattice filter, which is being manufactured at the University
of Texas at Dallas, and which has proven to be useful in the signal processing task of RF channelization. The filter can be
described by a linear, discrete time state space model. The controlling agents, the gains, are embedded in the matrices intervening
in this state space model. Consequently, techniques from linear feedback control theory do not apply. We concentrate on the
question of finding real valued gains so that the A matrix of the state space model has a prescribed characteristic polynomial. We find that three of the coefficients can be
arbitrarily picked, but that the remaining are constrained by these and the other system parameters. Our techniques use methods
from constructive algebraic geometry. 相似文献
197.