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41.
Huffman LM Casitas A Font M Canta M Costas M Ribas X Stahl SS 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(38):10643-10650
A well-defined macrocyclic aryl–Cu(III) complex (2) reacts readily with a variety of oxygen nucleophiles, including carboxylic acids, phenols and alcohols, under mild conditions to form the corresponding aryl esters, biaryl ethers and alkyl aryl ethers. The relationship between these reactions and catalytic C-O coupling methods is demonstrated by the reaction of the macrocyclic aryl–Br species with acetic acid and p-fluorophenol in the presence of 10 mol% Cu(I). An aryl-Cu(III)-Br species 2(Br) was observed as an intermediate in the catalytic reaction. Investigation of the stoichiometric C-O bond-forming reactions revealed nucleophile-dependent changes in the mechanism. The reaction of 2 with carboxylic acids revealed a positive correlation between the log(k(obs)) and the pK(a) of the nucleophile (less-acidic nucleophiles react more rapidly), whereas a negative correlation was observed with most phenols (more-acidic phenols react more rapidly). The latter trend resembles previous observations with nitrogen nucleophiles. With carboxylic acids and acidic phenols, UV-visible spectroscopic data support the formation of a ground-state adduct between 2 and the oxygen nucleophile. Collectively, kinetic and spectroscopic data support a unified mechanism for aryl-O coupling from the Cu(III) complex, consisting of nucleophile coordination to the Cu(III) center, deprotonation of the coordinated nucleophile, and C-O (or C-N) reductive elimination from Cu(III). 相似文献
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Hussain S Brotherhood PR Judd LW Davis AP 《Journal of the American Chemical Society》2011,133(6):1614-1617
Decalins bearing two axial -NHCONHAr substituents and an ester-linked alkyl side chain have been synthesized and studied as anion receptors and transporters. The design relates to steroid-based "cholapods" but is more compact and less intrinsically lipophilic. Transport rates depend on both NHAr and the alkyl side chain. High activities can be achieved; with optimal substitution, chloride-nitrate exchange across vesicle membranes is measurable at transporter/lipid ratios as low as 1:250,000. 相似文献
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45.
Jaume Casabó Andreu Solans Carmen Diaz Joan Ribas Alexandre Seguí Montserrat Corbella 《Transition Metal Chemistry》1985,10(4):128-130
Summary Mixed difluoro(diamine)(diamme)chromium(III) complexes have been synthesized with ethylenediamine (en), 1,3 propanediamine(tn) and 1,2-cyclohexanediamine(chxn):trans-[CrF2(aa)(bb)]Br (aa=en, bb=tn; aa=tn, bb= chxn) andcis-[CrF2(aa)(bb)]Br (aa=en, bb=chxn). The corresponding fluoroaqua(diamine) (diamine)chromium(III) complexes have been prepared by acid hydrolysis as perchlorate or iodide salts. All have been characterized by chemical analysis, electronic and i.r. spectra and conductivity measurements. 相似文献
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63-Cu and 75-As quadrupole resonance results have been obtained for the tetrameric triethylarsine copper(I) halides (Cl, Br and I). Unusual behaviours of the temperature dependence of the 63-Cu and 75-As quadrupole resonance lines have been observed simultaneously. Between 77 and 300 K, the chlorine derivative undergoes two structural phase changes at 93 and 173 K, while phase transformations occur at 152 and 86 K respectively for the bromine and iodine derivatives. 相似文献
49.
The solid phase thermal deaquation of trans[CrF(H2O)(aa′)2]K[Cr(CN)6]H2O and trans[CrF(H2O)(aa′)2]K[CrNO(CN)5]H2O (aa′=ethylenediamine or 1,3-diaminopropane) has been investigated by means of TG measurements. The kinetic parameters (activation energy, Ea, activation entropy, ΔS#, and frequency factor, k0) have been determined by comparison of the isothermal and non-isothermal studies for all the principal g(α) expressions. The values found for the activation energy are low (between 80 and 110 kJ mole?1, approximately) and permit the assignment of the deaquation-anation mechanism of the SN1 type, involving square-pyramid activated complex and elimination of water as Frenkel defects. 相似文献
50.
A straightforward derivation of the Dirac-Schwinger covariance condition is given within the framework of classical field
theory. The crucial role of the energy continuity equation in the derivation is pointed out. The origin of higher order derivatives
of delta function is traced to the presence of higher order derivatives of canonical coordinates and momenta in the energy
density functional. 相似文献