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Murphy JA Commeureuc AG Snaddon TN McGuire TM Khan TA Hisler K Dewis ML Carling R 《Organic letters》2005,7(7):1427-1429
[reaction: see text] N-Methoxy-N-methylamides (Weinreb amides) are converted efficiently into ketones by reaction with alkylidenetriphenylphosphoranes and in situ hydrolysis of the product. 相似文献
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The heat capacities of potassium, rubidium, cesium, and thallium azides were determined from 5 to 350 K by adiabatic calorimetry. Although the alkali-metal azides studied in this work exhibited no thermal anomalies over the temperature range studied, thallium azide has a bifurcated anomaly with two maxima at (233.0±0.1) K and (242.04±0.02) K. The associated excess entropy was 0.90 calth K?1 mol?1. The thermal properties of the azides and the corresponding structurally similar hydrogen difluorides are nearly identical. Both have linear symmetrical anions. However, thallium azide shows a solid-solid phase transition not exhibited by thallium hydrogen difluoride. At 298.15 K the values of Cpo, So, and , respectively, are 18.38, 24.86, and 12.676 calth K?1 mol?1 for potassium azide; 19.09, 28.78, and 15.58 calth K?1 mol?1 for rubidium azide; 19.89, 32.11, and 18.17 calth K?1 mol?1 for cesium azide; and 19.26, 32.09, and 18.69 calth K?1 mol?1 for thallium azide. Heat capacities at constant volume for KN3 were deduced from infrared and Raman data. 相似文献
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Andrew Mitchinson Wesley P. Blackaby Sylvie Bourrain Robert W. Carling Richard T. Lewis 《Tetrahedron letters》2006,47(13):2257-2260
Novel syntheses of 2,3,8-trisubstituted pyrido[2,3-d]pyridazines and 2,3,5-trisubstituted pyrazino[2,3-d]pyridazines are described. Two complementary routes to pyrido[2,3-d]pyridazines were developed, the first of which began by constructing the pyridine ring, and the second of which started by constructing the pyridazine ring. Pyrazino[2,3-d]pyridazines were prepared in a route employing an aza-Wadsworth-Emmons cyclization as the key step. The resulting compounds were found to be high affinity ligands for the GABAA receptor benzodiazepine binding site. 相似文献
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The p-median model is used to locate P centers to serve a geographically distributed population. A cornerstone of such a model is the measure of distance between a service center and demand points, i.e. the location of the population (customers, pupils, patients, and so on). Evidence supports the current practice of using Euclidean distance. However, we find that the location of multiple hospitals in a rural region of Sweden with a non-symmetrically distributed population is quite sensitive to distance measure, and somewhat sensitive to spatial aggregation of demand points. 相似文献
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Murphy JA Mahesh M McPheators G Anand RV McGuire TM Carling R Kennedy AR 《Organic letters》2007,9(17):3233-3236
A new fragmentative rearrangement of nitrone derivatives to form 9-membered rings is reported. The fragmentations are triggered when nitrones are treated with triflic anhydride; a C-C bond antiperiplanar to the cleaving N-O bond is activated either by an oxygen lone pair or by an electron-rich aromatic ring. In the former case, further cyclization of the 9-membered intermediate leads to a rearranged condensed ring system, but when triggered by arenes, 9-membered ring amides are isolated. 相似文献
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