共查询到20条相似文献,搜索用时 11 毫秒
1.
Marco Martino 《Tetrahedron letters》2004,45(17):3387-3391
The first examples of doubly bridged calix[7]arenes 2a-h have been obtained by base-promoted O-alkylation of p-tert-butylcalix[7]arene 1 or 1,4-tetramethylene-bridged calix[7]arene 3a with a variety of bis-electrophiles including BrCH2Cl, oligoethylene glycol ditosylates, and 1,2-bis(bromomethyl)benzene. In the presence of Cs2CO3 as the base, in acetone, the syn-1,4:2,3-bis-bridged regioisomer was obtained in yields up to 76%. Assignment of bridging pattern was based on chemical shift of OH groups in conjunction with chemical correlations with known compounds. Stereochemical and conformational features were investigated with the aid of 2D and Dynamic NMR studies and MM3 calculations. 相似文献
2.
The article describes the synthesis and evaluation of the dichromate anion (Cr2O72−/HCr2O7−) extraction properties of p-tert-butylcalix[4]arene diamide derivatives (5-7) containing different binding sites. Among these compounds, 6 and 7 have been synthesized via aminolysis in a toluene-methanol solvent system with 3-aminomethylpyridine and 3,6-dioxa-1,8-diamino octane, respectively. On the other hand, compound 5 has been synthesized via an acid chloride method due to its inefficiency under aminolysis. The extraction properties of these diamides toward dichromate anions are studied by liquid-liquid extraction. The results show that p-tert-butylcalix[4]arene diamide derivative 7 exhibited a much higher affinity toward dichromate anions than that of 6 due to its special structure, while 5 was an ineffective ligand for these anions. 相似文献
3.
Francesco Troisi 《Tetrahedron letters》2005,46(46):8041-8045
The first examples of dioxamethylene bridged calix[8]arenes 2-6 have been obtained by Cs2CO3-promoted direct O-alkylation of p-tert-butylcalix[8]arene with BrCH2Cl. Assignment of the 1,2-, 1,2:3,4-, 1,2:3,4:6,7-, 1,4:2,3:5,6:7,8-, and 1,2:3,4:5,6:7,8-bridging pattern of 2-6, respectively, was mainly based on chemical shift of OH groups and chemical correlations. Dynamic 1H NMR studies and MM3 calculations indicated that in these compounds the dioxocine subunit adopts a boat-chair conformation. 相似文献
4.
Satish Balasaheb Nimse Van-Thao Ta Keum-Soo Song Van-Thuan Nguyen 《Tetrahedron letters》2009,50(52):7346-3755
We report the synthesis of a new water-soluble iminecalix[4]arene host 4c with a deep hydrophobic cavity. The negatively charged four carboxylate functions on the top of the cavity play a major role in the recognition of charged molecular species. The 1H NMR titration experiments revealed that host 4c binds with cationic (10-12) and neutral guests (6-9) in water with high binding constants in the order of 104-105 M−1. Cationic guest 9 showed highest binding constant of 2.81 × 105 M−1 with host 4c amongst all tested guests. Selectivity over anionic guests (13-17) is established by the presence of negative charges at the top of the deep hydrophobic cavity, as guests 15 and 17 were not recognized by host 4c. Neutral pyridine derivatives with hydrophobic chains at para positions showed high binding constants of 6.02 × 104-2.23 × 105 M−1. The data obtained for the recognition of the guests by host 4c revealed that the ionic as well as the hydrophobic-hydrophobic interactions are crucial in the molecular recognition in aqueous medium. 相似文献
5.
Satish Balasaheb NimseJunbae Kim Keum-Soo Song Junghoon Kim Jeong Tae LeeVan-Thuan Nguyen Van-Thao TaTaisun Kim 《Tetrahedron letters》2011,52(29):3751-3755
In this Letter, the role of the depth of the cavity in the recognition processes of the guests by the hosts has been investigated. The hosts 2, 3 interact with both the cationic function and the aromatic moiety in the guests 5, 6 but with a slight preference for the cationic functions. The host 4 selectively recognizes the trimethylammonium functions of the guests 5 and 6. However, the host 1 selectively recognizes the aromatic moiety of the ditopic trimethylammonium guests 5 and 6. The recognition and orientation of the guest in the cavity of the host are directly dependent on the depth of the hydrophobic cavity of the host. 相似文献
6.
Calix[4]arene derivatives bearing anionic carboxylato groups at the upper rim (p-carboxylatocalix[4]arenes) are able to ‘grab’ paraquat dicationic guest through an induced-fit mechanism, which originates from the conformational mobility of calixarene skeleton. 相似文献
7.
Regioselective distal dialkylation of p-tert-butylthiacalix[4]arene with alcohols was performed under the Mitsunobu protocol using the DEAD/TPP system. The method provides a versatile tool for obtaining 1,3-diethers with different functional groups in the alkyl chains. 相似文献
8.
A convenient procedure for direct introduction of one formyl group into p-tert-butylcalix[4]arenes through ipso substitution is described. 相似文献
9.
A novel bicyclic calix[4]arene (4) molecular receptor has been synthesized, and its sensory abilities toward noxious aromatic nitroamines evaluated in apolar media. Molecular host–guest interactions examined through fluorescence and 1H NMR spectroscopies showed the formation of 1:1 type endo-inclusion complexes with all the nitroaniline guests. The potential of 4 as a chemical sensor is established. 相似文献
10.
Functionalized thiacalix- and calix[4]arene-based Ag ionophores: synthesis and comparative NMR study
Thiacalix[4]arene ionophores comprised of cyclic or linear O,S,N ligating and/or π-coordinate groups on the lower rim were synthesized and their Ag+ binding was studied by 1H NMR methods in comparison with the respective known and novel calix[4]arene counterparts. Calix[4](O,S,N)crowns were found stronger binders than the π-coordinate molecules and thiacalixarene ionophores were generally superior to calixarenes. This study helped to develop silver ion-selective electrodes working in the subnanomolar region. 相似文献
11.
A novel calix[4]arene based molecular probe for metal ions has been designed, synthesized and evaluated. Studies on its binding with different metal ions reveal a noticeable naked eye color change, bathochromic shift in absorption spectrum and remarkable enhancement in fluorescence emission in the presence of Cu2+ only. The role of calix[4]arene scaffold for selective recognition of Cu2+ has been demonstrated by repeat evaluation and analysis of an appropriate reference molecule. A rational explanation for fluorescence enhancement in 3 on interaction with copper has been suggested. 相似文献
12.
Herbert Meier 《中国化学快报》2012,23(5):509-511
The first synthesis of pillar[7]arene is reported with two methods.Method A:the FeCl3-catalyzed condensation reaction of 1,4- dimethoxybenzene(1) with paraformaldehyde in CHCl3 gave dimethoxypillar[7]arene(3).Method B:the p-toluenesulfonic acid catalyzed condensation reaction of 2,5-bis(benzyloxymethyl)-1,4-dimethoxybenzene(2) in CH2Cl2 gave compound 3.Demethylation of 3 with BBr3 gave pillar[7]arene(4).The pillar[7]arene might be a perspective macrocyclic host in host-guest chemistry. 相似文献
13.
The first examples of singly bridged calix[7]arenes 2–4 have been obtained by base-promoted direct O-alkylation of p-tert-butylcalix[7]arene with a variety of bis-electrophiles including BrCH2Cl, oligoethylene glycol ditosylates, and 1,4-bis(bromomethyl)benzene. 1,2-Bridging was favored with ‘short bite’ spanning elements, while the 1,4-isomer predominated with the others (yields up to 72% in the presence of Cs2CO3). Assignment of bridging pattern was mainly based on chemical shift of OH groups, in some cases confirmed by 2D NMR experiments. A hampered conformational mobility, depending on the position and nature of the bridge, was observed for compounds 2–4. 相似文献
14.
p-tert-Butylcalix[8]arene bonded capillaries for open-tubular capillary electrochromatography were prepared with γ-glycidoxypropyltrimethoxysilane as a bridge. The bonded capillary displayed low and steady electroosmotic flow (EOF) values over the pH range from 4 to 9. Detection limits for direct spectrophotometric detection at 277 nm for benzenediols (at a signal to noise ratio of 2) were 0.96 mg l−1 for the unbonded capillary and 1.48 mg l−1 for the bonded capillary, showing that the bonded layer did not show significant absorbance and hence decreased sensitivity. The bonded capillaries showed good separation selectivity for o-, m- and p-benzenediols, α- and β-naphthols, and α- and β-naphthylamines. This selectivity was attributed to significant interactions between the analytes and the bonded p-tert-butylcalix[8]arene, which contributed to the electrochromatographic separation mechanism. The bonded capillaries gave high stability and reproducibility. 相似文献
15.
Several water-soluble calix[4]arenes were synthesized via radical addition reaction between thiols and alkenes under UV lamp irradiation (λ= 365 nm) in good yields. The structures of these compounds synthesized herein were fully confirmed by 1H NMR, ESI-MS and elemental analysis. 相似文献
16.
A series of new calix[4]arene(amido)mono-crown compounds have been synthesized through aminolysis of calix[4]arene esters and intramolecular cyclization of the intermediates. The title compounds were converted into their nitro and azo substituted derivatives to provide novel photoresponsive molecular receptors for transition metal ions. Single crystal X-ray analysis of calix[4]arene(ethyleneamido)mono-crown (2a) revealed that the compound is present in a cone conformation with an amido loop that caps the lower rim of calix[4]arene cavity to result in stacking along axis a and axis c to provide supramolecular aggregates in the solid state. Evaluation of synthesized macrocycles in the solution phase for recognition of transition metal cations (Cr3+, Fe2+, Co2+, Ni2+, Cu2+, Ag+, Cd2+, Pb2+, Hg+, Hg2+, Pd2+, and Pt2+) by UV-visible spectroscopy revealed that p-tert-butyl-calix[4]arene mono-(amidocrown) 1c selectively shows a blue shift at 38 nm on interaction with Hg+ ions. 相似文献
17.
Cone, partial cone and 1,3-alternate conformers of tetrathiacalix[4]arene tetraethylacetate were synthesized and subjected to aminolysis with alkyl amines [CH3(CH2)nNH2; n=2, 3, 5] to yield mono-, di-, tri- or tetrasubstituted p-tert-butyltetrathiacalix[4]arene amides which were characterized by detailed analysis of their NMR spectral and single crystal X-ray crystallography. It has been observed that while the 1,3-alternate and cone conformers of the tetrathiacalix[4]arene tetraethylacetate gave corresponding tetrathiacalix[4]arene tetraamides under different experimental conditions, the corresponding partial cone conformer undergoes a cascade of regioselective reactions with the same amines. Variable temperature 1H NMR experiments allowed the determination of relative stability of different conformers within the temperature range of 298-333 K. The synthesized derivatives were evaluated as molecular extractants for cations and anions and were determined to facilitate extraction of oxyanions (CrO42− and Cr2O72−) from aqueous to the organic phase. The studies have a significance in the design of tetrathiacalix[n]arene based molecular receptors for innovative applications. 相似文献
18.
Bisazocalix[4]arenes [N,N′-bis(5-azo-25,26,27-tribenzoyloxy-28-hydroxycalix[4]arene)benzene (1), N,N′-bis(5-azo-25,26,27-tribenzoyloxy-28-hydroxycalix[4]arene)biphenyl (2) and N,N′-bis(5-azo-25,26,27-tribenzoyloxy-28-hydroxycalix[4]arene)-2,2′-dinitro biphenyl (3)] have been synthesized from 25,26,27-tribenzoyloxy-28-hydroxycalix[4]arene by diazocoupling with the corresponding aromatic diamines (p-phenylenediamine, 4,4′-diamino biphenyl and 4,4′-diamino-2,2′-dinitrobiphenyl). Extraction studies of bisazocalix[4]arenes 1, 2, and 3 show no difference in their extraction behavior and selectivity, whereas azocalix[4]arenes are a poor extractant for heavy metal cations. The absorption spectra of the prepared bisazocalix[4]arenes are discussed, both the effect of varying pH and solvent upon the absorption ability of bisazocalix[4]arenes. 相似文献
19.
The inclusion of tetramethylammonium and ditopic trimethylammonium cations by the water-soluble pentasulfonatocalix[5]arene 1 has been studied at neutral pH by 1H NMR and compared with the homologous tetrasulfonatocalix[4]arene 2. Unlike host 2, host 1 selectively binds the ditopic trimethylammonium ions by three different non-covalent interactions. Remarkably the flexible host 1 exhibits both more efficiency and selectivity in the complexation of ditopic methylammonium ions with respect to similar more preorganised calix[4]arene receptors. 相似文献
20.
Piyali Sarkar Samares Maiti Krishnendu Ghosh Sumita Sengupta Ray J. Butcher Chhanda Mukhopadhyay 《Tetrahedron letters》2014
A new efficient protocol for the synthesis of 3,5-dinitrothiophene scaffolds was developed by using simple p-tert-butylcalix[8]arene in aqueous medium. Biological activities of some representative compounds were also studied to inhibit the cell growth on selective anticancer cell lines. 相似文献