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Reaction of the isodicyclopentadienide anion and its dehydro congener with Fe(II) leads to a stereochemically homogeneous ferrocene derivative in each instance. Through chemical correlation and X-ray analysis, above-plane complexation is established for both halves within the two sandwich compounds. 相似文献
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Letf(x,y) be a function of the vector variablesx R
n andy R
m. The grouped (variable) coordinate minimization (GCM) method for minimizingf consists of alternating exact minimizations in either of the two vector variables, while holding the other fixed at the most recent value. This scheme is known to be locally,q-linearly convergent, and is most useful in certain types of statistical and pattern recognition problems where the necessary coordinate minimizers are available explicitly. In some important cases, the exact minimizer in one of the vector variables is not explicitly available, so that an iterative technique such as Newton's method must be employed. The main result proved here shows that a single iteration of Newton's method solves the coordinate minimization problem sufficiently well to preserve the overall rate of convergence of the GCM sequence.The authors are indebted to Professor R. A. Tapia for his help in improving this paper. 相似文献
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By use of appropriate reactions and sequence of steps, 2,5-dimethoxybenzaldehyde can be converted either to 4-(bromo or iodo)-2,5-dimethoxybenzonitrile or 2-(bromo or iodo)-3,6-dimethoxybenzonitrile. 相似文献
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An absolute displacement-sensing system based on channeled spectrum processing capable of simultaneous interrogation of fiber Bragg gratings and fiber-optic interferometric sensors is presented in which the role of the optical spectrometer is performed by a scanning Fabry-Perot filter. We demonstrate a resolution of +/-50 nm with an estimated dynamic range of 1 part in 10(5). 相似文献
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The unparalleled substituent-dependent regulation of the course of cycloaddition reactions between isodicyclopentadienes and tropones is described. 相似文献
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Krzysztof E. Krakowiak Garren E. Maas Jerald S. Bradshaw Jon K. Hathaway Reed M. Izatt 《Journal of heterocyclic chemistry》1995,32(1):179-181
4,10-Diaza-15-crown-5, 4,10-diaza-18-crown-6, 4,13-diaza-21-crown-7, and 4,16-diaza-24-crown-8 were prepared by an improved method from the appropriate oligothylene glycol diiodides and diamines. The thermodynamic values of log K, ΔH and ΔS for the interaction of 4,10-diaza-18-crown-6 with Pb2+ and Ag+ were determined by a calorimetric titration method and compared with thermodynamic values for interactions of 4,13-diaza-18-crown-6 with the same cations. The thermodynamic values were found to be different for the two diaza-crown ligands. 4,10-Diaza-18-crown-6 and its 4,13-diaza-crown analog formed precipitates when treated with Co2+, Cd2+, Cu2+, and Ni2+ so that no thermodynamic data are reported for these interactions. 相似文献
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