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61.
R.R. Fraser N. Chuaqui-Offermanns K.N. Houk N.G. Rondan 《Journal of organometallic chemistry》1981,206(2):131-138
The N-isopropyl imine of lithioacetaldehyde, I, was found to exist as a 50 : 50 mixture of two isomers, as seen below 20°C by 1H and 13C NMR. Comparison of the population ratio and spectral characteristics of the isomers of this and related lithiated imines leads to the conclusion that they are rotamers all of which possess the syn configuration. This conclusion is supported by calculations of the barriers to interconversion. 相似文献
62.
A tolerance region is a map from the sample space of one statistical model to the event space of a second statistical model having the same parameter. This paper derives an optimum β-expectation tolerance region for the multivariate regression model. A measure of power is proposed and evaluated. 相似文献
63.
64.
An orange/brown ionic and polymeric Mo(V) ion (Mo to Na ratio 2.3:1), soluble in H2O to give stable solutions at pH~6, with UV visible spectrum λmax 318nm, ?(per Mo) 330OM?1 cm?1, has been prepared and partially characterised. Various properties are described, including the conversion to the well established Mo(V) aquo dimer, MO2O42+, on adjustment of [H+] to 0.17–0.50 M, I=0.50 M (H/LiClO4). First-order rate constants, kobs(25°C), determined by conventional spectrophotometry give a good fit to the empirical rate law, 相似文献
65.
66.
Simon M. Doughty J.Fraser Stoddart Howard M. Colquhoun Alexandra M.Z. Slawin David J. Williams 《Polyhedron》1985,4(4):567-575
The crystal structure of 2Li picrate.dibenzo-36-crown-12.2H2O was determined by X-ray diffraction methods. The 2:1 (metal:ligand) complex crystalli 相似文献
67.
Translational isomerization can be induced by changing the anions associated with a bistable rotaxane in which the tetracationic cyclophane (blue box), cyclobis(paraquat-p-phenylene), encircles a dumbbell component containing bispyrrolotetrathiafulvalene (green) and a dioxynaphthalene (red) recognition sites. The rotaxane was isolated as both its hexafluorophosphate and tris(tetrachlorobenzenediolato)phosphate(v) (TRISPHAT(-)) salts. Photophysical measurements and NMR spectroscopy carried out in acetone (CD(3)COCD(3)) and acetonitrile (CD(3)CN) solutions reveal that the much larger TRISPHAT(-) anion favors predominantly the encirclement of the green site by the blue box. 相似文献
68.
t-BuOK-induced deprotonation of omega-haloalkylnitriles generates remarkably stable potassiated nitriles. In situ deprotonation and alkylation of omega-chloroalkylnitriles with aldehyde electrophiles trigger sequential nucleophilic-electrophilic alkylations generating substituted tetrahydrofuranyl and tetrahydropyranyl nitriles. Redirecting the cyclization manifold with 5-iodopentanenitrile and a ketone causes a complementary electrophilic-nucleophilic cyclization to the corresponding carbonitrile. Collectively these cyclizations provide rapid assembly of five- and six-membered oxa- and carbocyclic nitriles demonstrating the utility of omega-halonitriles in domino alkylations. 相似文献
69.
2-Hydroxy-2'-alkylthio-1,1'-binaphthyl compounds are catalytic promoters of the 1,4-addition of AlMe(3) to linear aliphatic enones in THF at -40 to -48 degrees C in the presence of [Cu(MeCN)(4)]BF(4). At ligand loadings of 5-20 mol %, enantioselectivities of 80-93 % are realised for most substrates. To attain these values, the use of highly pure AlMe(3) is mandatory. The presence of methylalumoxane (MAO), derived by hydrolysis, leads to reduced enantioselectivity and a conjugate addition product. 相似文献
70.
Vincent KA Tilley GJ Quammie NC Streeter I Burgess BK Cheesman MR Armstrong FA 《Chemical communications (Cambridge, England)》2003,(20):2590-2591
Addition of an equivalent of a polyaminocarboxylate ligand (L) to a solution of a redox protein and the aqua Eu2+ ion results in the instantaneous in situ generation of a very powerful reductant Eu(II)-L that can rapidly drive an electron stoichiometrically onto a redox centre having an extremely negative reduction potential (lower than -1 V): this is exemplified by straightforward generation of the super-reduced state of the Fe-protein of nitrogenase. 相似文献