共查询到20条相似文献,搜索用时 15 毫秒
1.
Muriel Funck 《Tetrahedron letters》2010,51(49):6399-6402
A series of resorcin[4]arene and pyrogallol[4]arene macrocycles have been synthesized efficiently within 5 min, affording crystalline products suitable for single crystal X-ray diffraction, utilising microwave irradiation in a ‘one-pot’ reaction whilst controlling the selective formation of the rccc cone stereoisomer. 相似文献
2.
3.
Possible rearrangement mechanisms of hydrogen-bond arrays formed at the lower rim of tetrahydroxycalix[4]arene and tetrahydroxythiacalix[4]arene were studied by means of density functional theory and the resolution identity approximation modification of M?ller-Plesset perturbation theory (RI-MP2). Influence of solvent to height of energy barriers was quantified by use of the conductorlike screening model (COSMO) of implicit solvent (chloroform). Generally, two types of mechanisms were investigated. The first is represented by a synchronous single-step jump of all four hydroxyl protons. Pathways of the second mechanism include the rotation of one or more hydroxyl groups around the CAr-O bond. Theoretical results, in agreement with recently published experimental data (Lang et al. J. Chem. Phys. 2005, 122, 044056), prefer a jump mechanism for the methylene-bridged calix[4]arene. Concerning the thiacalix[4]arene, results obtained by COSMO as well as RI-MP2 calculations show that the rotational mechanism is very competitive and it could even be more favorable. 相似文献
4.
Mayya Korochkina Alessandro Casnati Arturo Arduini Rocco Ungaro Vladimir Kataev Vladimir Alfonsov 《Tetrahedron》2005,61(23):5457-5463
Novel calix[4]arene derivatives functionalized with two or four isosteviol units at the upper rim and a new calix[6]arene having six isosteviol moieties at the lower rim have been synthesized. The structures of these compounds have been confirmed by NMR and mass spectrometry data. All 1H and 13C NMR chemical shifts of isosteviol were fully assigned by extensive NMR spectroscopic methods, and used to clarify the structures and conformations of isosteviol-calixarene conjugates. 相似文献
5.
Furer VL Borisoglebskaya EI Kovalenko VI 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(1-2):355-359
The experimental IR and Far IR spectra of the calix[4]arene, p-tert-butylcalix[4]arene, thialcalix[4]arene and p-tert-butylthiacalix[4]arene were examined at different temperatures and interpreted. The band frequencies and intensities in the IR spectra of the calix[4]arene and thialcalix[4]arene were calculated. The absorption curves of the four possible calix[4]arene conformations: cone, partial cone, 1,2- and 1,3-alternate were computed. The bands characteristic for each conformation are defined and assigned. The obtained spectra-structure correlation can be used for the characteristic of calixarenes conformation. 相似文献
6.
7.
The influence of the metallic cation of the base (Li+, Na+ or K+) was determined on the acid–base constants of p-t-butylthiacalix[4]arene (TC4), p-t-butylcalix[4]arene (CA4) and p-t-butylcalix[6]arene (CA6) in ethanol/water in an large interval of pH values by potentiometry and spectrophotometry. The pKa values determined by both methods correlate very well and these are characteristic for each macrocycle with influence of the cation of the base without a straight evidence of an effect by the size of the metallic cation. In the case of TC4, pKa1 and pKa2 were lower to Li+ and Na+ than with K+. For CA4, an effect of K+ on the pKa2 with respect to Li+ was observed. A very different behaviour was observed for CA6 with Li+ and K+ showing a lower pKa2 and a higher pKa3 than with Na+. These effects were interpreted on the basis of the interaction/complexation of each cation with each macrocycle. 相似文献
8.
The synthesis of calix[4]arene based dendrimers containing up to seven calix[4]arene moieties is described, including the X-ray crystal structure of a tris-calix[4]arene branching derivative. 相似文献
9.
Víctor García-López Jovana V. Milić Michal Zalibera Dmytro Neshchadin Martin Kuss-Petermann Laurent Ruhlmann Julia Nomrowski Nils Trapp Corinne Boudon Georg Gescheidt Oliver S. Wenger François Diederich 《Tetrahedron》2018,74(39):5615-5626
A light-actuated resorcin[4]arene cavitand equipped with two quinone (Q) and two opposite Ru(II)-based photosensitizing walls was synthesized and investigated. The cavitand is capable of switching from an open to a contracted conformation upon reduction of the two Q to the corresponding SQ radical anions by intramolecular photoinduced electron transfer in the presence of a sacrificial donor. The molecular switch was investigated by cyclic and rotating disc voltammetry, UV–Vis–NIR spectroelectrochemistry, transient absorption, NMR, and EPR spectroscopy. This study provides the basis for the development of future light-activated switches and molecular actuating nanodevices. 相似文献
10.
11.
12.
硫杂杯[4]二醛基衍生物(1)在水合肼中肼解,合成了新化合物硫杂杯[4]二醛腙基衍生物(2);1和2在弱酸的催化下反应合成了新的具有对称结构的苄连氮双硫杂杯[4]芳烃(3);2和3的结构经1H NMR,IR,ESI-MS和元素分析表征. 相似文献
13.
14.
We first make use of aminolysis of calix[4]arene esters to synthesize calix[4]arene amides. When the two ethyl esters of the calix[4]arene esters are aminolysized, the 1, 3-amide derivative is formed selectively. The crystal structures of the calix-[4]arene with two butyl amide (3b) and four butyl amide moieties (4b) were determined. The intermolecular hydrogen bonds make 4b form two-dimensional net work insolid state. The 1H NMR spectra prove that 3b is of a pinched cone conformation, while 4b and tetraheptylamide-calix[4]arene (6b) take fast interconversion between two C2v isomers in solution and appear an apparent cone conformation at room temperature. As decreasing temperature, the interconversion rate decreases gradually and, finally, the interconversion process is frozen at Tc = -10℃, which makes both conformations of 4b and 6b the pinched cone structures. The hydrogen bond improves the interconversion barrier, and the large different values of the potential barrier between 6b and 4b (or 6b) may 相似文献
15.
16.
Preferential crystallization from a mixture of C-methylresorcin[4]arene (RsC1) and calix[6]arene (Calix6) in the presence of different bases has been investigated. In the presence of pyridine, a boat conformer of RsC1 crystallizes, whereas in the presence of triethylamine, Calix6 crystallizes in a symmetrically distorted conformation. The packing arrangements of the macrocycles show discrete solvent pockets for calixarenes and channels for resorcinarenes. 相似文献
17.
18.
New convenient method for synthesis of p-chlorinated calix[4]arenes is reported. The sulfuryl chloride was used for chlorination of unsubstituted at the lower rim calix[4]arenes. The products of this reaction were very suitable for further O-alkylation. 相似文献
19.
Selectively functionalized resorcinarenes were obtained by weak-base-promoted O-alkylation of C-undecylresorcin[4]arene 1. Tetrasubstituted derivatives with C(4)-1,3,5,7, C(2v)-1,2,5,6, C(s)-1,2,4,7, and C(i)-1,2,4,6 pattern were obtained in workable yields by using K(2)CO(3) as the base in acetone at reflux. The good regioselectivity with respect to the statistical distribution was explained in terms of preferential formation of H-bonded monoanions. Heptaaroylated resorcin[4]arenes were also easily obtained by reaction of 1 with aroyl chlorides in pyridine. 相似文献
20.
In the acid-catalyzed synthesis of ethyl pyrogallarene, a novel hexamer, ethyl pyrogall arene, is obtained as a readily isolable minor product. Pyrogallarene can be isolated from the reaction mixture in three different ways yielding the hexamer in different forms and stabilities. Crystallization from DMSO and then recrystallization from acetone gives a stable crystalline solid, recrystallization directly from acetone yields an unstable white powder, while direct recrystallization from THF gives a stable white powder. Both pyrogallarene and pyrogallarene crystallize readily with DMSO filling the voids in the crystal lattice. Co-crystallization studies of the hexamer isolated by recrystallization from acetone resulted in a novel directly hydrogen-bonded capsule formed by two pyrogallarenes and an included TMA cation, while the DMSO/acetone isolated product yielded the intact hexamer with clathrate-type TMA inclusion. 相似文献