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71.
Bulo RE Allaart F Ehlers AW de Kanter FJ Schakel M Lutz M Spek AL Lammertsma K 《Journal of the American Chemical Society》2006,128(37):12169-12173
anti-W(CO)(5)-complexed 9-methyl-9-phosphabicyclo[6.1.0]nonatriene represents a covalently interlocked molecular bevel gear. Correlated movement of the phosphorus atom and the eight-membered ring by way of a "walk" rearrangement makes gear slippage impossible. The gearing motion is transferred to the four-toothed W(CO)(5) propeller connected to the rotating phosphorus atom, enabling a gearing ratio of 2:1 according to B3LYP and Car-Parrinello Molecular Dynamics calculations. Methyl substitution of the eight-membered ring tempers the gearing process, with the PMeW(CO)(5) entity passing the substituted carbon atom only at temperatures above 50 degrees C. 相似文献
72.
Gelens E De Kanter FJ Schmitz RF Sliedregt LA Van Steen BJ Kruse CG Leurs R Groen MB Orru RV 《Molecular diversity》2006,10(1):17-22
Optimization of Radziszewski's four-component reaction employing a microwave-assisted protocol, led to a small library of
48 imidazoles with a success rate of 65% (conversion > 45%). All three diversity points of the four-component reaction were
varied. Aromatic and aliphatic inputs were successfully implemented and mono-, di-, tri- and tetrasubstituted imidazoles with
various substitution patterns were synthesized. Furthermore, unsymmetrical diketones could successfully be used which improved
the intrinsic diversity of the method significantly. If the unsymmetrical diketone 1,2-phenylpropanedione (R1 and R2) was used two regioisomers were formed. Depending on the type of amine (R4) and aldehyde (R3) applied, regioselectivity was modest to good. Based on these results, a reaction mechanism is proposed. 相似文献
73.
Paravidino M Bon RS Scheffelaar R Vugts DJ Znabet A Schmitz RF de Kanter FJ Lutz M Spek AL Groen MB Orru RV 《Organic letters》2006,8(23):5369-5372
[Structure: see text] In a search for new multicomponent strategies leading to valuable small heterocycles, a new highly diastereoselective four-component reaction (4CR) was found in which a phosphonate, nitriles, aldehydes, and isocyanoacetates combine to afford functionalized 3-isocyano-3,4-dihydro-2-pyridones. In this strategy, initially a 1-azadiene is generated, which is trapped in the same pot by an isocyanoacetate as the fourth component. Multicomponent reactions (MCRs) that lead to heterocycles containing isocyano substituents are unprecedented and offer many possibilities for further differentiation. 相似文献
74.
75.
Marek Kanter 《Acta Appl Math》1997,47(3):351-373
The notion of a continuously observed quantum process constrained at both its initial and final states is introduced. It is shown that under suitable regularity conditions, such a process fulfills a 'least action' principle, wherein action is identified with change of state transitions. 相似文献
76.
77.
Van Baelen G Kuijer S Rýček L Sergeyev S Janssen E de Kanter FJ Maes BU Ruijter E Orru RV 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(52):15039-15044
Compared with the widespread use of carbonylative Pd-catalyzed cross-coupling reactions, similar reactions involving isocyanide insertion are almost virgin territory. We investigated the intramolecular imidoylative cross-coupling of N-(2-bromoaryl)amidines, leading to 4-aminoquinazolines. After thorough optimization of the reaction with respect to palladium source and loading, ligand, base, temperature, and solvent, a small library of 4-aminoquinazolines was prepared to determine the scope of this method. Various substituents are tolerated on the amidine and the isocyanide, providing efficient access to a broad range of diversely substituted 4-aminoquinazolines of significant pharmaceutical interest. 相似文献
78.
79.
E.P. Kanter D. Kollewe K. Komaki I. Leuca G.M. Temmer W.M. Gibson 《Nuclear Physics A》1978,299(2):230-254
Using the crystal blocking technique, we have measured the emission distributions of protons near the 〈110〉 axis elastically scattered from a 7000 Å thick single nickel crystal, at 5.65 and 6.50 MeV. These distributions are fitted by an analytic multiple string calculation of the blocking process which yields the time-dependent compound-nucleus decay probability curve. Shape- and compound-elastic cross sections are simultaneously determined in a reaction-model-independent way, as is the mean compound nucleus lifetime. The resulting decay curves for the delayed component are consistent with a single exponential at both energies and show no indication of the presence of level-level correlations. Use of such data in testing recent statistical theories is discussed. 相似文献
80.
The information processing abilities of a multilayer neural network with a number of hidden units scaling as the input dimension are studied using statistical mechanics methods. The mapping from the input layer to the hidden units is performed by general symmetric Boolean functions, whereas the hidden layer is connected to the output by either discrete or continuous couplings. Introducing an overlap in the space of Boolean functions as order parameter, the storage capacity is found to scale with the logarithm of the number of implementable Boolean functions. The generalization behavior is smooth for continuous couplings and shows a discontinuous transition to perfect generalization for discrete ones. 相似文献