Functional modification,self-assembly and application of calix[4]resorcinarenes

As a special subset of calix[4]arene, calix[4]resorcinarene is an excellent molecular platform which could be modified by introducing functional groups to multiple sites at the upper and lower rims. There are mainly three ways to build functionalized calix[4]resorcinarene derivatives: (1) modification on the C-2 sites of calix[4]resorcinarenes; (2) modification on the phenolic hydroxyl groups of calix[4]resorcinarenes; (3) modification on the bridging methylenes at lower rim of calix[4]resorcinarenes. Functionalized calix[4]resorcinarene derivatives play an important role in the development of self-assembly chemistry, among which hydrogen bonding and metal coordination are the two most common interactions to obtain multicomponent structures. Moreover, due to the excellent topological structures and various active substituents of functionalized calix[4]resorcinarene derivatives, their applications in various fields, such as nanoparticles, catalysts, fluorescent materials, and sensors, have been briefly presented in this paper.

     

Syntheses and Crystal Structures of Functionalized Tetramethyl Resorcinarenes

Tetramethyl resorcinarene, which was obtained by acidic condensation of resorcinol with paraacetoaldehyde, was chemically modified to the functionalized O-acyl, O-tosyl and O-acetate derivatives by corresponding acylation, p-toluenesulfonylation and alkylation reactions. The single crystal structures of these functionalized resorcinarenes and the complex of tetramethyl resorcinarene with 2,2'-bipyridine were determined by X-ray diffraction method. All these resorcinarenes adopt the all-cis configuration with four methyl groups stretching to the down rim and form 1D or 2D structures through H-bonds.     

Synthesis of calix[4]resorcinarenes with phosphorylaryl substituents at the lower rim of the molecule

Reaction of resorcinarenes with 4-phosphorylbenzaldehydes afforded calix[4]resorcinarenes, bearing phosphorylaryl substituents at the lower rim of the molecule. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2269–2271, November, 2007.     

Complexes of dirhodium(II) carboxylates with calix[4]resorcinarenes functionalized at the upper and lower rim of the molecule with P,N-containing Fragments

The features of the reaction between dirhodium(II) carboxylate and calix[4]resorcinarenes modified with various type functional groups at the upper and lower rim of the molecule in protic anhydrous solvent (ethanol) under inert atmosphere were investigated. Neutral complex compounds were isolated formed as a result of substitution of a water molecule by the macroligand in the axial position with respect to the R $ \tilde h The features of the reaction between dirhodium(II) carboxylate and calix[4]resorcinarenes modified with various type functional groups at the upper and lower rim of the molecule in protic anhydrous solvent (ethanol) under inert atmosphere were investigated. Neutral complex compounds were isolated formed as a result of substitution of a water molecule by the macroligand in the axial position with respect to the RRh bond occurring with the conservation of the latter. The compounds were characterized by 31P NMR, UV, IR, Raman, and ESR spectroscopy. Their composition was confirmed by elemental analysis. Original Russian Text ? E.V. Guseva, E.L. Gavrilova, A.A. Naumova, V.I. Morozov, N.I. Shatalova, D.T. Karimova, V.K. Polovnyak, 2008, published in Zhurnal Obshchei Khimii, 2008, Vol. 78, No. 12, pp. 1963–1971.     

Syntheses, crystal structures, and electrochemical properties of multi-ferrocenyl resorcinarenes

Tetraaryl and tetraferrocenyl resorcinarenes 1a-1c have been synthesized by the HCl-catalyzed condensation of resorcinol with aromatic aldehydes or ferrocenecarbaldehyde, which were fully alkylated with ethyl α-chloroacetate to give the activated ethyl resorcinarylacetates 2a-2c. Reaction of 2a-2c with hydrated hydrazine yielded the resorcinarene acylhydrazine derivatives 3a-3c, from which the multi-ferrocenyl functional groups were selectively and efficiently introduced on the upper rim, or on the lower rim, or both on the upper and lower rims of resorcinarenes 4a-4c and calixarenes 4d-4f based upon the condensation reactions of acylhydrazones with ferrocenecarboxaldehyde.     

Synthesis of calix[4]resorcinarenes,containing phosphoryl fragments at the lower rim of the molecule

Reaction of resorcinol with phosphorylated acetals or ethoxyvinylphosphonic acid esters in acidic media leads to calix[4]resorcinarenes, containing dialkoxyphosphoryl fragments at the lower rim of the molecule. When the alkyl substituent in alkoxy groups at phosphorus atom is not very long, a partial hydrolysis of the initially formed products takes place to give calixarenes with alkoxyhydroxyphosphoryl fragments. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1102–1106, June, 2007.     

Novel Calix[4]resorcinarenes with Side Azobenzo-15-crown-5 Residues

New calix[4]resorcinarenes having two or four azobenzo-15-crown-5 residues on the lower rim have been synthesized by the condensation of resorcinol with the corresponding aldehyde (acetal).     

Ion‐Pair Complexation with a Cavitand Receptor

The capability of resorcinarenes to bind anions within the alkyl feet at the lower rim has been exploited as the starting point for developing a new cavitand able to engulf contact ion pairs of primary ammonium salts in chlorinated solvents with association constants (K_ass) in the range of 10³–10⁴ M ^?1. Methylene bridges were introduced into the upper rim to freeze the resorcinarene in the cone conformation with the four H_down protons converging in the lower pocket, thereby maximizing the CH–anion interactions responsible for the anion binding. Four additional phosphate moieties were introduced into the lower rim in close proximity to the anionic site to provide hydrogen‐bonding‐acceptor P?O groups and promote cation complexation at the bottom of the cavitand. The binding ability of the synthesized ligands was analyzed by ¹H NMR spectroscopy and, when possible, by isothermal titration calorimetry (ITC); the data were in agreement when complementary techniques were used.     

Resorcinarenes的合成及其边缘化学修饰（Ⅰ）

探讨了烷基醛类（乙醛,丙醛）的Ｒｅｓｏｒｃｉｎａｒｅｎｅｓ的合成及其边缘化学修饰（乙酰化,甲基化）,研究了各种因素对Ｒｅｓｏｒｃｉｎａｒｅｎｅｓ的影响。确定了较佳反应条件。     

Regioselective acylation of aminoresorcinarenes

The acid catalyzed hydrolytic cleavage of the oxazine rings in the readily available tetraoxazine derivatives of resorcinarenes results in tetraaminoresorcinarenes. A similar process applied to C₂-symmetrical bisoxazine resorcinarene tetratosylates affords C_2v-symmetrical resorcinarenediamines. The mild acylation of these resorcinareneamines with BOC-anhydride or para-nitrophenyl ester proceeds selectively at the nitrogen atoms without affecting the hydroxyl groups. Most of the resulting resorcinareneamides are thus obtained in preparative yields and can be easily purified by simple crystallizations. In the crystalline state the compounds obtained are found to bind chloride anions through hydrogen bonds and electrostatic interactions and to display a chiral arrangement of hydrogen bonded functional groups at the wide rim of the macrocycle.     

Mannich reaction involving calix[4]resorcinarenes and aminoacetals

The Mannich reaction involving calyx[4]resorcinarenes, aminoacetals, and formaldehyde in the molar ratio 1:4:4 yields calixarenes containing aminoacetal fragments on the upper molecule rim. Four oxazinyl rings formed with the retention of acetal groups as the formaldehyde amount was twofold increased.     

Guest controlled aggregation of amphiphilic sulfonatomethylated calix[4]resorcinarenes in aqueous solutions

Supramolecular nanoaggregates formed through the association of amphiphilic sulfonatomethylated calix[4]resorcinarenes with different substituents on the lower rim (methyl, pentyl, heptyl) and number of aromatic, aliphatic, and cationic guests differing in their shapes and sizes were investigated in aqueous solution by various NMR techniques ((1)H, 2D NOESY, FT-PGSE). It was shown that slight variations of the alkyl chain length on the lower rim of calixresorcinarenes dramatically change their aggregation behavior. Unlike the other calixresorcinarenes studied, the "head-to-tail" packing mode is observed for calixresorcinarene with pentyl moieties on the lower rim, which is unusual for amphiphilic calixarene aggregates. This calixresorcinarene demonstrates the stronger binding capacity toward the guest molecules due to their encapsulation into the capsule-like aggregate subunits. The guest-host complexation modifies the properties of both components, with the size of the resulted colloid particles being controlled by the guest nature.     

Ion‐Pair Recognition of Tetramethylammonium Salts by Halogenated Resorcinarenes

The non‐covalent interactions of different upper‐rim‐substituted C₂‐resorcinarenes with tetramethylammonium salts were analyzed in the gas phase in an Electrospray Ionization Fourier‐transform ion‐cyclotron‐resonance (ESI‐FTICR) mass spectrometer and by ¹H NMR titrations. The order of binding strengths of the hosts towards the tetramethylammonium cation in the gas phase reflects the electronic nature of the substituents on the upper rim of the resorcinarene. In solution, however, a different trend with particularly high binding constants for halogenated resorcinarenes has been observed. This trend can be explained by a synergetic effect originating from the interaction of the halogenated resorcinarenes with the counter anions through hydrogen bonding. This study highlights the importance of weak interactions in recognition processes and points out the benefits of comparing the gas‐phase data with results obtained from solution experiments.     

Photoresponsive upper-rim azobenzene substituted calix[4]resorcinarenes

Photoswitchable calix[4]resorcinarenes with different numbers of azo groups in the upper rim were synthesised by the reaction of bromomethylcavitand with 4-aminoazobenzene. UV-vis, ¹H and ¹³C NMR, MALDI TOF-MS spectral data have been used to elucidate the structures of compounds.     

Synthesis and characterization of chiral, bridged resorcinarenes as templates for asymmetric catalysis

A full study of the synthesis of chiral, bridged resorcinarenes (3a-3l, 13a, 13b) is presented using Mannich condensation of C_2v-tetraprotected resorcinarenes with chiral 1,n-diamines bearing homochiral α-methylbenzyl auxiliaries at each terminal nitrogen. The study has revealed the methodology to be applicable to preparing a broad range of bridged structures with varying lengths of bridge, different functionality in the bridge and various protecting groups on the upper rim. Reproducible and satisfactory yields in the reaction were only obtained with the pendant R group as methyl. The bridged adducts have been fully characterized by a range of spectroscopic techniques, and NMR has revealed varying trends in the way the various bridges protrude into the cavity. Low temperature NMR as well as X-ray structures of tetramesylate 15 and tetratoluate 3g has revealed hydrogen bonding to the amine nitrogens in the bridge to be an important control element for positioning the bridge relative to the cavity of the bowl. The derivatives provide chiral templates for asymmetric catalysis studies using cooperative effects in the bowl.     

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.     

Phosphorylation of Dialkylaminomethylated Calix[4]-Resorcinarenes with Some P(III) and P(IV) Derivatives

Abstract

The phosphorylation of dialkylaminomethylated calix[4]resorcinarenes with P(m)-amides and P(TV)chlorides under various conditions results in the formation of different structures with phosphorus containing fragments fixed on the cavity rim. Hydrophosphoryl compounds based on dialkylaminomethylated calix[4]resorcinarenes have been synthesized and some of their properties investigated.     

Preparation of partially functionalised resorcinarene derivatives

The conditions for synthesis of mono-, di- and trifunctionalised resorcinarenes by catalysed Mannich reaction are described. A series of these compounds are functionalised with different functional groups.     

Selective hetero-trisfunctionalization of the large rim of a biomimetic calix[6]arene using host-guest chemistry as a synthetic tool

A calix[6]arene has been selectively functionalized by three different groups at the large rim. The strategy relies on the hostguest recognition chemistry of a biomimetic metal complex at the small rim (so-called "funnel complex") and the Huisgen cycloaddition. The intramolecular thermal reaction proceeds with a high efficiency, chemio- and regioselectivity, allowing the monofunctionalization of one aromatic unit among three. Thanks to the high yield and selectivity of the reaction, it can be applied successively twice on the same compound, which opens the route for inherently chiral calix[6]arenes. This methodology not only is of wide potential for obtaining and exploiting calix[6]arenes that are dissymmetrized at the large rim, but also stands as an exemplary strategy for the selective appending of a functional group on a host platform.     

Liquid extraction of La<Superscript>III</Superscript>, Gd<Superscript>III</Superscript>, and Yb<Superscript>III</Superscript> ions by phosphorylated calix[4]resorcinarene derivatives

New phosphorylated calix[4]resorcinarene and cavitands were synthesized. Their extraction ability toward La^III, Gd^III, and Yb^III ions was studied. The cavitands are more efficient extracting agents than octasubstituted calix[4]resorcinarenes. The nature of substituents at the nitrogen atom at the upper rim and hydrophobic substituents at the lower rim exerts a substantial effect on the solubility of the extracted complex in chloroform. Coordination of two lanthanide ions with an extragent molecule results in their efficient but non-selective extraction. The literature and our spectral (³¹P NMR) data suggested that the ligand in the extracted complex has most probably a “kite” conformation. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 303–308, February, 2007.