Chlorination of Calix[4]arene Derivatives

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.     

Synthesis of Calix[4]resorcinarene Amide Derivatives

Three different synthetic routes were developed to introduce carbamoyloxy functional groups at the upper periphery of two calix[4]resorcinarenes. By treating activated esters 2a-b with excess corresponding amine such as 3-(dimethylamino)propylamine 3, ct-phenethylamine 4 and triethylenetetramine 5, six amide derivatives 6a-8b were obtained in high yield (Route 1). The pyridine-linked amide derivatives 9a-b were prepared by using acid chloride intermediate (Route 2).The amide derivatives 10a-b were obtained in moderate yields by direct alkylation of phenolic hydroxyl groups of la-b with N,N-dipropylchloroacetoamide in the presence of K2CO3/KI in acetone (Route 3).     

Calix[4]arene-based ditopic receptor for dicarboxylates

Shape-selective recognition for the dicarboxylates in DMSO can be attained by a new calix[4]arene-based receptor 1 having two urea groups. Biologically active chorismate selectively bound in 1 over its dehydrated derivative. Molecular mechanics calculations gave a plausible explanation for the selective binding.     

杯[4]芳烃衍生物的合成和构象研究

以对取代酚亚甲基桥三聚体和２，６－二溴甲基对取代酚为原料，在ＴｉＣｌ４催化下环化得到６种新的含不同取代基［Ｃｌ，Ｂｒ，ＣＨ３，Ｃ（ＣＨ３）３］的杯［４］芳烃衍生物，核磁共振谱研究表明：它们在溶液中的优势构象为锥形构象。     

Analysis of Calix[4]arenes Using Nonaqueous Capillary Electrophoresis

In nonaqueous capillary electrophoresis (NACE), an organic solvent is used in place of an aqueous medium as the background solution to improve the solubility and selectivity for hydrophobic analytes. In this study, we employed NACE with UV detection for the analysis of eight calix[4]arenes. We examined the influence of several parameters—the buffer composition, the nonaqueous solvent‘s composition and proportion, and the concentration of the electrolyte of the nonaqueous buffer—on the efficiency of the electrophoretic separation. The separation was achieved through the analyte's different effective mobility via different degrees of deprotonation on the phenolic OH groups of the calix[4]arene. This deprotonation can further affect the analyte's ability to form a complex with the metal ion. The optimized background electrolyte (BGE), comprising a mixture of N‐methylformamide/acetonitrile (30:70, v/v) and 100 mM AcOH/20 mM NH₄OAc, provided rapid (<11 min) separation of the calix[4]arenes with good resolution. The relative standard deviations of the migration times for the eight analytes were all less than 1%. Within the calibration concentration range, the coefficients of determination (R²) were all greater than 0.9914. Thus, the present study demonstrated NACE can provide adequate separation for the analysis of calix[4]arenes.     

Synthesis of Flavin–Calix[4]arene Conjugate Derivatives

The synthesis of two new flavin substituted calix[4]arene derivatives, 9 and 10 , is described. The first flavin substituted calix[4]arene derivative 9 was synthesized by the reaction of 3‐methylalloxazine ( 5 ) with 25,27‐bis(3‐bromopropoxy)‐26,28‐dihydroxy‐5,11,17,23‐tetra(tert‐butyl)calix[4]arene ( 4 ) in high yield (92%). The other derivative 10 was prepared from 3‐methylalloxazine‐1‐acetic acid ( 7 ) and 25,27‐bis(3‐cyanopropoxy)calix[4]arene ( 3 ). All new compounds were characterized by a combination of FT‐IR and ¹H‐NMR spectroscopy, and elemental‐analysis techniques.     

Synthesis, conformational studies and inclusion properties of N-substituted tetrahomodiazacalix[4]arenes

A series of tetrahomodiazacalix[4]arenes (1–8) with different substituents (or substituted) at the upper rim and/or N-side arm has been synthesized with acceptable yields. The compounds were characterized by elemental analysis, IR, MS and NMR methods. In particular, 5 was shown by X-ray crystallography to adopt the cone conformation in the solid state. Two-phase picrate extraction showed that 2 and 6, bearing N-2-picolyl arms, are the best extractants. Of the cations tested, Ag(I) is the best extracted by almost all ligands and the extraction efficiency follows the order 2-picolyl > 3-picolyl > 4-picolyl.     

Synthesis of New Rigid Dimeric Calix[4]arene

A new Dimeric calixarene from the head to head linkage of two calix[4]arene units fixed in the cone conformation was synthesized via Sonogashira cross-coupling reaction. The structure of 10 was confirmed by NMR, MS and IR-spectroscopy.     

Synthesis of Calix[4]resorcinarene Schiff Bases

Introduction Calix[4]resorcinarenes are cyclic tetramers in which four resorcinol units are linked via alkylmethylene bridges in the o-position to each resorcinic hydroxyl group[1]. Their structures resemble that of p-butylcalix[n]arenes and render them of interest as host compounds in many contemporary fields of supramolecular chemistry.     

杯[4]芳烃对单糖及嘧啶衍生物的分子识别和分子开关

用AM1和INDO/SCI方法对八羟基杯[4]芳烃与单糖及嘧啶衍生物形成的超分子体系进行理论研究,结果表明,主体通过CH-π相互作用对单糖类进行分子识别,尤其对赤藓糖识别效果更好;主体与嘧啶没有明显的π-π堆砌作用,但能识别含吸电子基团的嘧啶衍生物,据此可设计酸碱调控的分子开关.讨论了配合物的UV谱带与主体相比发生红移的原因.     

Calix[4]arene Schiff bases—potential ligands for fluorescent studies

A series of novel double-armed calix[4]arene derivatives incorporating imine substituents were synthesised from the Schiff-base reaction of 25,27-bis[2-[(1-formyl-2-phenyl)oxy]ethyl]-p-tert-butylcalix[4]arene (1) with the appropriate amine or hydrazone. All compounds were characterised by various spectroscopic and analytical techniques, and in three cases, by X-ray crystallographic studies. In the case of compound 2, inclusion compounds were synthesised with both m-xylene and dimethylformamide and their X-ray structures revealed these inclusion sites—between the pendant arms and in the upper cavity, respectively. In all cases, the pendant arms are bent away from each rather than adopting a face-to-face conformation.     

Efficient synthesis of water-soluble calix[4]arenes via thiol-ene “click” chemistry

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.     

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.     

Calix[4]arene based molecular probe for sensing copper ions

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.     

Calix[4]arene bisphosphite ligands bearing two distal 2,2′-biphenyldioxy or 2,2′-binaphthyldioxy moieties: conformational flexibility and allyl-palladium complexes

Achiral and chiral calix[4]arene bisphosphite ligands (2 and 3) bearing two distal 2,2′-biphenyldioxyphosphinoxy and 2,2′-binaphthyldioxyphosphinoxy moieties, respectively, have been synthesized. Each of these ligands exists in two pairs of interconverting conformations in solution. The partial cone conformer (A) of the (bis)biphenyldioxyphosphinoxy ligand 2 has been separated by fractional crystallization and its structure established by X-ray crystallography. The mechanism of interconversion of the pairs of conformers (A/B and C/D) has been probed by two-dimensional NMR spectroscopy. The ¹H and ³¹P NMR evidence strongly supports a similar kind of exchange mechanism for ligand 3. Freezing of the cone conformer from the interconverting C/D pair of conformers of ligand 2 has been achieved by complexation with (allyl)palladium moieties. The methyl-allyl complex (2d) is moderately effective for catalytic regioselective allylic alkylation of crotyl acetate.     

Synthesis of Calix[4]pyrroles: A Class of New Molecular Receptor

RecentlySesslerandco-workersdiscoveredthatthemeso-octaalkylporphyrinogensshowedinterestinganionandneutralsubstratebindingpropertiesandmightserveasaclassofneweasy-to-makemolecularreceptorintheareaofsupramolecularchemistry'.However,themeso-octaalkylpor...     

Dendritic octa-CMPO derivatives of calix[4]arenes

Calix[4]arenes substituted at the narrow or wide rim by eight carbamoylmethyl-phosphine oxide (CMPO) functions in a dendritic manner were synthesised and studied in extraction of Eu³⁺ and Am³⁺ from aqueous nitric acid into o-nitrophenylhexyl ether. ¹H NMR relaxivity titrations for a wide rim octa-CMPO reveal the clear formation of a solvent-free 1:2 ligand/metal complex, while the wide rim tetra-CMPO formed oligomeric complexes under similar conditions.     

Synthesis and self-assembly of novel calix[4]arenocrowns: formation of calix[4]areno[2]catenanes

A series of novel calix[4]arenocrowns 1a-c were efficiently synthesized by a one-pot reaction of calix[4]monohydroquinone diacetate 5 with ditosylate 6 and its analogues in the presence of sodium hydroxide. It was found that the calix[4]arenocrowns could form stable pseudorotaxane-type complexes 2a-c with paraquat, and further self-assemble into calix[4]areno[2]catenanes 3a-c with dicationic salt 8 and p-bis(bromomethyl)benzene.     

Synthesis and complexing properties of four imidazolyl acetamido p-tert-butylcalix[4]arenes

Four imidazolyl acetamido p-tert-butylcalix[4]arenes 5–8 have been prepared by reacting the corresponding methyl esters derivatives 1–4 with histamine in 1:1 mixture of methanol:toluene. The yields ranged from 56 to 68%. 5–8 have been shown to be in cone conformation. The complexation behaviour of 5–8 towards monovalent metal picrates M⁺Pic⁻ with M⁺ = Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺ and divalent metal picrates M²⁺(Pic⁻)₂ with M²⁺ = Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Pb²⁺, Cd²⁺, Zn²⁺ and Co²⁺ are given. Tentative localisation of the metal cations in the receptors is given. The binding properties towards these cations have been determined along with stoichiometries of the complexes.     

Calix[4]quinones. Part 4: The ClO2 oxidation of calix[4]arene dialkyl ethers

Except for the special case of calix[4]arene diethyl ether 1, the chlorine dioxide oxidation of dialkyl ethers 2-5 yielded only the corresponding calix[4]diquinone dialkyl ethers 8-11. Chlorine dioxide oxidation of calix[4]arene diethyl ether 1 produced two isomeric products 6 and 7, which were stable enough to be isolated by column chromatography. However, a slow conformational interconversion between isomeric pair 6 and 7 was observed at room temperature, and the equilibrium was reached after 400 h at 18 °C with an amount of 5:3 in favor of syn-isomer.