Arene Mono Research Articles

Synthesis of diamido-bridged bis-pillar[5]arenes and tris-pillar[5]arenes for construction of unique [1]rotaxanes and bis-[1]rotaxanes.

The pillar[5]arene mono- and di(oxyalkoxy)benzoic acids were successfully prepared in high yields by sequential alkylation of ω-bromoalkoxy-substituted pillar[5]arenes with methyl or ethyl p-hydroxybenzoate followed by a hydrolytic reaction under basic conditions. Under catalysis of HOBt/EDCl, the amidation reaction of pillar[5]arene mono(oxybutoxy)benzoic acid with monoamido-functionalized pillar[5]arenes afforded diamido-bridged bis-pillar[5]arenes. 1H NMR and 2D NOESY spectra clearly indicated that [1]rotaxanes were formed by insertion of longer diaminoalkylene unit into the cavity of one pillar[5]arene with another pillar[5]arene acting as a stopper. The similar catalysed amidation reaction of pillar[5]arene di(oxybutoxy)benzoic acid with monoamido-functionalized pillar[5]arenes resulted in the diamido-bridged tris-pillar[5]arenes, which successfully form the unique bis-[1]rotaxanes bearing longer than diaminopropylene diamido bridges.

Internal charge transfer based Hg-sensing Azocalix[4]arene Mono anthracenate derivatives

The present study describes the synthesis and characterization of mono anthracenate derivatives of azocalix[4]arene. The azocalix[4]arene anthracenates (6a-e) were performed by the esterification of the 2-bromoethyl antracenate (5) and azocalix[4]arene (3a-e) in dry acetonitrile. The prepared compounds were characterized by using the 1H NMR, IR, DTA/DTG techniques and elemental analysis. They were examined to observe their capabilities of recognizing various cations including K+, Ag+, Hg+, Hg2+, Co2+, Ni2+, Cu2+, Pb2+, Cr3+ and Al3+ with UV–vis spectroscopy. It was found that the extraction mechanisms of metal cations are highly effective with the azo (NN) groups and adjacent anthracenate electron density. The synthesized azocalix[4]arene ligands (6a-e) were obtained fluorescence emission with Na+, K+, Sr2+, Ag+, Hg2+, Co2+, Cu2+, Pb2+, Ba2+, Ca2+ and Mg2+ metal ions at a wavelength of 367nm.

A study on thermal behaviors of mono ethyl ester azocalix[4]arene derivatives

In the present study, thermal stabilities of five new family of azocalix[4]arene mono ethyl ester derivatives, 4a–e, were investigated using thermogravimetry, differential thermogravimetry, and differential thermal analysis methods. It was found that all compounds showed thermal stability up to 236 °C averagely. After this temperature, decomposition of compounds starts gradually. The decomposition routes of 4a–c compounds are similar and occur with two stages. Ester alkyl groups decompose and remove from the structure in the first stage. Second stage corresponds to rest of structure decomposition. The decomposition routes of the 4d–e compounds are different from the decomposition routes of the 4a–c compounds. These compounds include halogen, and decomposition reactions realize with three and four stages respectively.

Calix[4]arene α-hydroxymethylphosphonic acids as potential inhibitors of protein tyrosine phosphatases

Calix[4]arene are known to be a promising scaffold for designing inhibitors of protein tyrosine phosphatases. In this work calix[4]arene mono- and bis-α-hydroxymethylphosphonic acids have been tested in vitro for the inhibitory activity against some therapeutically important protein tyrosine phosphatases. The results obtained have shown that these macrocyclic compounds can inhibit CD45, PTP1B, and SHP2 with IC50 values in the micromolar range. At the same time the inhibitors have demonstrated lower activity toward other protein tyrosine phosphatases such as TC-PTP and PTPβ. It has been found that mono-substituted calix[4]arene is more potent inhibitor of CD45 than the bis-substituted one and shows about 2-15 fold selectivity over TC-PTP, PTPβ, SHP2 and PTP1B. Model 4-hydroxyphenyl-α-hydroxymethylphosphonate displays at least one order lower activity than the phosphonate derivatives of calix[4]arene. Thus, the combination of a macrocyclic platform and α-hydroxymethylphosphonate group is essential for the inhibition activities of these compounds. Computer-simulated docking studies have been performed using AutoDock 4.2 programme by the example of PTP1B. The data obtained indicate that the inhibitors can bind in the active site of the enzyme. To clarify the inhibition mechanism the possible enzyme-inhibitor complexes have been considered using several crystal structures of PTP1B and all stereoisomeric forms of the inhibitors.

P-Chirogenic Phosphines Supported by Calix[4]arene: New Insight into Palladium-Catalyzed Asymmetric Allylic Substitution

The first P-chirogenic mono- and diphosphine ligands supported on the upper rim of a calix[4]arene moiety were synthesized using the ephedrine methodology. The lithiated calix[4]arene mono- and dianions both react with the oxazaphospholidine–borane, prepared from ephedrine, to afford regio- and stereoselectively the corresponding calix[4]arenyl aminophosphine–boranes, by cleavage of the heterocyclic ring at the P–O bond position. Subsequent reactions with HCl and then organolithium reagent and finally decomplexation with DABCO lead to the corresponding calix[4]arenyl mono- or diphosphines. Both enantiomers of the calix[4]arenyl phosphines were obtained either by using (+)- or (−)-ephedrine or by changing the addition order of the organolithium reagents during the synthesis. The enantiomeric excesses of the phosphines were determined either by HPLC on a chiral column of their borane complexes or by 31P NMR in the presence of a chiral palladium complex. The absolute configurations of the mono- and diphosphinocalix[4]arenes were assigned by X-ray analysis of their crystalline borane complexes. The P-chirogenic calix[4]arenyl phosphines were tested for asymmetric palladium-catalyzed allylic substitution of (E)-1,3-diphenylprop-2-en-1-yl acetate, by dimethyl malonate or benzylamine. When the bis-methylphenylphosphino calix[4]arene was used, the allylic products were obtained with 82% and 79% ee, respectively. In both cases, the use of a diphosphine affords better results than using 2 equivalents of monophosphine. Despite the C2 symmetry of the P-chirogenic diphosphine calix[4]arene ligand, computer modeling of the corresponding Pd(allyl) complex shows a clear dissymmetry of the LUMO, which is in good agreement with a complexed η1-allyl moiety and with the regio- and enantioselectivity of the Pd-catalyzed allylations.

ChemInform Abstract: A New Effective Synthesis of Arene Mono‐ and Disulfonyl Chlorides.

AbstractThe title compounds are prepared by a three‐step sequence.

Synthesis and Characterisation of Asymmetrically Bridged Calix[4]Arene and Tetrathiacalix[4]Arene Mono Amido Crown Derivatives

The synthesis of asymmetrically bridged calix[4]arene and tetrathiacalix[4]arene amido crown derivatives has been achieved by the aminolysis of distal diester derivatives of calix[4]arene and tetrathiacalix[4]arene with 1,2-diamino-propane or 1,2-diaminocyclohexane (stereoisomeric mixture, mainly trans). The title compounds have been characterised by detailed analysis of their NMR spectra. The assignment of NMR signals and stereo differentiation in the amido crown ring formation has been studied using a chiral shift reagent.

A New Effective Synthesis of Arene Mono- and Disulfonyl Chlorides

Arene mono- and disulfonyl chlorides have been easily synthesized starting from the corresponding anilines via aqueous oxidative chlorination of S-aryl O-ethyl dithiocarbonates intermediates, aryl methyl sulfides, or from arenethiols.

Inhibition of Yersinia protein tyrosine phosphatase by phosphonate derivatives of calixarenes

Inhibition of Yersinia protein tyrosine phosphatase by calix[4]arene mono-, bis-, and tetrakis(methylenebisphosphonic) acids as well as calix[4]arene and thiacalix[4]arene tetrakis(methylphosphonic) acids have been investigated. The kinetic studies revealed that some compounds in this class are potent competitive inhibitors of Yersinia PTP with inhibition constants in the low micromolar range. The binding modes of macrocyclic phosphonate derivatives in the enzyme active center have been explained using computational docking approach. The results obtained indicate that calix[4]arenes are promising scaffolds for the development of inhibitors of Yersinia PTP.

Synthesis and dichromate anion sorption of silica gel-immobilized calix[4]arenes

Three new silica gel-immobilized calix[4]arene polymers 9–11 have been prepared via modification of calix[4]arene mono amido derivatives 3–5 with 3-aminopropyl triethoxysilane (APTES) and activated silica gel, respectively. The polymers were characterized by Fourier transform infrared spectroscopy, elemental analysis and thermal gravimetric analysis. The solid–liquid extraction properties of ligands 3–5 along with their immobilized derivatives 9–11 towards dichromate (HCr 2O 7 −/Cr 2O 7 2−) anions were reported. It was found that these calix[4]arene-based polymers have high extraction abilities towards dichromate anions as compared to their monomeric precursors.

Synthesis of Calix[4]arene Mono and Diamide Derivatives and Selective Complexation of Alkali and Alkaline Earth Cations

The synthesis of mono and diamide derivatives of the p‐tert‐butylcalix[4]arenes/calix[4]arenes from the reaction of 5,11,17,23‐tetra‐tert‐butyl‐25,27‐diethoxycarbonyl‐methoxy‐26,28‐dihydroxycalix[4]arene 1 and 25,27‐diethoxycarbonyl‐methoxy‐26,28‐dihydroxycalix[4]arene 2 with various primary amines were reported. The effect of reaction time and steric hindrance of the primary amines used on the reactions have been investigated. All the amide derivatives of calix[4]arene are in a cone conformation according to the 1H‐NMR doublet–doublet pattern of the protons of the methylene groups between the aromatic rings. The complexing properties of these compounds toward selected alkali and alkaline earth metal cations are also studied. It has been observed that receptor 8 is a selective extractant for Cs+ and Sr2+ cations.

Synthesis of calix[4]arene(amido)monocrowns and their photoresponsive derivatives

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 (Cr 3+, Fe 2+, Co 2+, Ni 2+, Cu 2+, Ag +, Cd 2+, Pb 2+, Hg +, Hg 2+, Pd 2+, and Pt 2+) 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.

PH‐Switchable Cesium Nitrate Extraction with Calix[4]arene Mono and bis(Benzo‐crown‐6) Ethers Bearing Amino Functionalities

Results obtained in this work show that four calix[4]arene mono and bis(benzo‐crown‐6) ethers functionalized with primary amine groups feature markedly enhanced cesium stripping under acidic conditions compared with nonfunctionalized analogs. The four amine‐derivatized calixarenes were surveyed in nitrobenzene diluent at 25°C, demonstrating the effect under controlled conditions, where it was seen that the amino functionalization entailed at most a mild sacrifice of cesium extraction strength or selectivity. Limited solubility of the protonated forms of the extractants appears to be a potential issue for future development, however. In the best case, calix[4]arene bis[4‐(2‐ethylhexyl)benzo‐crown‐6], possessing an aminomethyl group on the upper rim, (AMBEHB) exhibited a cesium extraction strength comparable to that of a control system containing calix[4]arene bis(tert‐octylbenzo‐crown‐6) (BOB) under alkaline conditions, whereas stripping of the cesium from AMBEHB was 56‐fold more effective than BOB. A proof‐of‐principle extraction, scrubbing, and stripping (ESS) cycle using AMBEHB in Isopar L modified with 0.75 M 1‐(2,2,3,3‐tetrafluoropropoxy)‐3‐(4‐sec‐butylphenoxy)‐2‐propanol (Cs‐7SB) showed that a greater than three‐fold more efficient stripping may be obtained with AMBEHB vs. its nonfunctionalized control BEHB. A slope analysis of systematic extraction data under caustic and acidic conditions confirmed that the extraction of cesium nitrate by AMBEHB in dodecane modified by 0.5 M Cs‐7SB involves the formation of a 1:1:1 metal:ligand:nitrate organic species.

A Calix[4]arene Monoalkyl Ether as a Model of a Tris(phenolate) Ligand with a Hemilabile Anisole Moiety: Syntheses, Molecular Structures and Bonding of Calix[4]arene Ether Supported Titanium Complexes and Their Catalytic Activity in Epoxidation Reactions

AbstractNew mononuclear titanium complexes [TiCl(Rcalix)] [R = Me (1), Bz (2), SiMe3 (3)] supported by p‐tert‐butylcalix[4]arene mono(organyl)ethers (Rcalix) were prepared in good yield from H2R2calix and [TiCl4(THF)2]. The crystallographically characterized complex [TiCl(Mecalix)] (1) reacts readily with NaCp and LiNR2 to afford the complexes [TiCp(Mecalix)] (4) and [Ti(NR2)(Mecalix)] [R = Me (5), Et (6), iPr (7), Ph (8)], respectively. Reactions of [Ti(NR2)(Mecalix)] (5) with alcohols, phenols and thiols proceed cleanly with amide exchange, as exemplified by the synthesis of [Ti(OR)(Mecalix)] [R = Me (10), iPr (11), tBu (12), 4‐tBuC6H4 (13), 2,6‐iPr2C6H3 (14)], and [Ti(StBu)(Mecalix)] (15). Depending on the steric demand of the ligand coordinated to the [Ti(Mecalix)] complex fragment these compounds are monomeric or dimeric in the solid state, as demonstrated by the molecular structures of monomeric [Ti(OC6H3‐2,6‐iPr2)(Mecalix)] (14) and [Ti(StBu)(Mecalix)] (15), or dimeric [{Ti(OMe)(Mecalix)}2] (10). In all complexes the calix[4]arene ligand adopts an elliptically distorted cone conformation in which the distance of the titanium atom from the anisole oxygen atom varies between 2.342 Å and 2.438 Å for the structurally characterized complexes, with the exception of the Cp complex 4. MP2 calculations on model complexes demonstrate that the titanium−anisole oxygen bond is weak, with a particularly shallow potential energy surface in the region between 2.30 Å and 2.80 Å. The Mecalix ligand system therefore might be described as a tris(phenolate) ligand with a hemilabile anisole group in the titanium compounds reported. Despite the labile anisole ether titanium bond, isomerization of the calix[4]arene ligand to a paco coordination mode, as described earlier for the Me2calix complexes [Ti(OC6H4‐4‐R)2(Me2calix)], has not been observed in these complexes. Preliminary results on the catalytic epoxidation of cyclooctene with TBHP using calix[4]arene‐stabilized titanium(IV) complexes are also briefly presented. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Synthesis of Calix

The formation of p-tert-butylcalix[4]arene mono-, bis-, tris-, and tetrakistriflates 3, 2, 4, and 5, respectively, and their respective reactions, under typical Pd-catalyzed carbonylative, Suzuki-Miyaura coupling, or deoxygenation conditions are described. A novel, nonsolvent-derived 1:1 clathrate (6) of benzophenone and 3 was formed from the palladium-catalyzed carbonylative reaction of phenylboronic acid and 2. The X-ray crystal structure of this first nonsolvent-derived clathrate of a calix[4]arene derivative is reported. Another 1:1 clathrate of triethylamine and 3 was formed during the attempted Pd-catalyzed deoxygenation of 2.

Selective Extraction of Cesium at Tracer Level Concentration from a Sodium Nitrate Solution with Calix-Crowns. Molecular Modeling Study of the Cs+/Na+ Selectivity

Calix[4]arene mono- and bis-crown6 in the 1,3 alternate conformation are highly selective extractants for cesium towards sodium in an acidic liquid waste. Extraction and selectivity are related to complexation properties which can be studied by Molecular Dynamics techniques. In this paper, we describe the results of Molecular Dynamics simulations in an explicit water phase for four complexes of 1,3-alternate mono- and bis-crown-calix[4]arenes. The structural features obtained are interpreted on the basis of cation/lignad complementarity and can explain the relative performances in Na+ extraction for the compounds simulated. The relative free energy of binding can be computed and is in a semi-quantitative agreement with complexation data in an homogeneous medium.

Anion recognition by novel ruthenium(II) bipyridyl calix[4]arene receptor molecules

Exotic calix[4]arene mono- and di-topic anion receptors containing one and two ruthenium(II) bipyridyl moieties have been prepared and shown by 1H NMR and CV to bind and electrochemically recognise halide, dihydrogen phosphate and hydrogen sulphate anions. The monotopic calix[4]arene anion receptor 8 selectively electrochemically recognises H2PO4– in the presence of tenfold excess amounts of HSO4– and Cl–.