Synthesis of novel chiral Schiff base and amino alcohol derivatives of calix[4]arene and chiral recognition properties

In the present study, the synthesis and liquid phase extraction properties towards some amino acid methylesters and amino alcohols of Schiff base and amino alcohol substituted calix[4]arene are reported. The Schiff base substituted calix[4]arene 5 has been synthesized via condensation reaction involving 5,17-diformyl-11,23-di-tert-butyl-25,27-di[3-(4-formylphenoxy)propoxy]-26,28 dihydroxycalix[4]arene 4 and (R)-(?)-2-phenylglycine methyl ester in CHCl₃:MeOH. To give the amino alcohol substituted calix[4]arene 6, the synthesized chiral compound 5 was reduced by LiAlH₄. The new chiral Schiff base and amino alcohol derivatives of calix[4]arene have been characterized by a combination of FT-IR, ¹H NMR, ¹³C NMR, FAB-MS and elemental analysis. Also, the extraction behaviors of 5 and 6 towards some selected amino acid methylesters and amino alcohols have been studied by liquid–liquid extraction.     

Design and Synthesis of New Chiral Calix[4]arenes as Liquid Phase Extraction Agents for α-Amino Acid Methylesters and Chiral α-Amines

The article describes the synthesis and extraction properties of new (S)-(-)-1-phenylethylamine substituted p-tert-butylcalix[4]arene/calix[4]arene. These compounds have been synthesized via nucleophilic substitution reactions involving 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetra(2-hydroxyethoxy)calix[4]arene (4a), or 5,11,17,23-tetra-H-25,26,27,28-tetra(2-hydroxyethoxy)calix[4]arene (4b) with (S)-(-)-1-phenylethylamine in dry THF. The extraction properties of ligands 5a and 5b towards the some selected α-amino acid methylesters and chiral α-amines are also reported. It has been observed that receptor 5a was an excellent ionophore for α-amino acid methylesters/α-amines and good extractant than 5b. However, both of the ligands did not display any selectivity towards the configurations of this species. in final form: 17 January 2005     

Synthesis and amino acid extraction abilities of chiral calix[4]arene triamides containing amino alcohol units

Herein the synthesis and extraction abilities of new d-/l-phenylalaninol substituted p-tert-butylcalix[4]arene triamide derivatives (3 and 4) towards amino acids are reported. These compounds (3 and 4) have been easily synthesized via aminolysis of p-tert-butylcalix[4]arene trimethylester (2) with d-/l-phenylalaninol in methanol-toluen solvent system at one step. The extraction properties of the prepared chiral calix[4]arene triamide derivatives (3 and 4) towards some selected amino acid methylesters are studied by liquid–liquid extraction. Results show that these chiral calix[4]arene triamide derivatives (3 and 4) exhibited a good affinity towards all amino acid species without any remarkably discrimination.     

Synthesis of new chiral calix[4]arene diamide derivatives for liquid phase extraction of α-amino acid methylesters

The synthesis of chiral diamide derivatives of calix[4]arene from the reaction of p-tert-butylcalix[4]arene diester 1a and calix[4]arene diester 1b with various amino alcohols were reported. The ¹H and ¹³C NMR, data showed that the compounds synthesized exist in the cone conformation. The extraction study properties of these new compounds 3a,b–4a,b towards some selected α-amino acid methylesters are also reported.     

Synthesis and chiral recognition abilities of new calix[6]arenes bearing amino alcohol moieties

Herein the synthesis and recognition abilities towards amino acids and amino alcohols of new d-/l-phenylalaninol substituted p-tert-butylcalix[6]arenas are reported. These compounds, 6 and 7 have been synthesized via nucleophilic substitution reactions involving 5,11,17,23,29,35-tert-butyl-37,38-dimethoxy-39,40,41,42-(p-tosylethoxy)calix[6]arene 5 with d-/l-phenylalaninol in dry THF. The extraction properties of 6 and 7 towards some selected amino acid methylesters and amino alcohols have been studied by liquid–liquid extraction. These results show that chiral calix[6]arene derivatives exhibit a good affinity towards all amino acids and amino alcohols.     

Polymer Supported Calix[4]arene Schiff Bases: A Novel Chelating Resin for Hg2+ and Dichromate Anions

This article describes the synthesis and characterization of two new calix[4]arene Schiff bases and their polymeric resins. The extraction properties of these “proton switchable extractants” with alkali, transition, post transition metal cations and for dichromate anions are reported. The two new calix[4]arene based Schiff bases (5 and 6) have been synthesized from 5,17‐diformyl‐25,27‐dipropoxy‐26,28‐dihydroxycalix[4]arene (4) by treatment with 3‐amino‐methylpyridine and 1,8‐diaminooctane in two separate reaction flasks following the same procedure. Compounds 5 and 6 have been appended to a polymeric resin by treatment with Merrifield resin through a nucleophilic substitution reaction. The receptor compounds (3 and 5–8) do not extract alkali metal cations, but show some selectivity toward transition metal cations, and a particularly high selectivity to Hg²⁺ and Pb²⁺. The protonated forms of all of the calixarene‐based receptors are good extractants for transferring Cr₂O₇ ^2?/HCr₂O₇ ^? anions from an aqueous into a dichloromethane layer.     

Synthesis of di-substituted calix[4]arene-based receptors for extraction of chromate and arsenate anions

The article describes the synthesis of a family of novel calix[4]arene ionophores, 25,27-bis-(2-aminomethylpyridine-propoxy)-26,28-dihydroxycalix[4]arene (5a), 25,27-bis-(3-aminomethylpyridine-propoxy)-26,28-dihydroxycalix[4]arene (5b) and two chromogenic calix[4]arenes, 5,17-dinitro-25,27-bis-(2-aminomethylpyridine-propoxy)-26,28-dihydroxycalix[4]arene (5c), 5,17-dinitro-25,27-bis-(3-aminomethylpyridine-propoxy)-26,28-dihydroxycalix[4]arene (5d) bearing pyridinium units. In the synthesis, the upper and lower rims of p-tert-butylcalix[4]arene were modified in order to acquire binding sites for the recognition of arsenate and dichromate anions. It has been observed that protonated alkylammonium forms of the ionophores showed high affinity toward dichromate and arsenate anions.     

Synthesis and dichromate anion extraction ability of p-tert-butylcalix[4]arene diamide derivatives with different binding sites

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.     

A Schiff basep-tent-butylcalix[4]arene. Synthesis and metal ion complexation

This communication describes the synthesis of Schiff base calix[4]arene (1) in which the Schiff base unit bridges two opposite hydroxy groups ofp-tert-butylcalix[4]arene. The synthesis of (1) has been achieved by refluxing in acetonitrile-methanol the appropriate 1,3-dicarbaldehyde-p-tert-butyl-calix[4]arene (4) with 1,3-diaminopropane. The yield of the reaction is 19%. Ligand (1) possesses a compartment containing two nitrogen atoms, four ether-type oxygen atoms, and two ionizable hydroxy groups likely to complex metal cations.     

Synthesis and Properties of Upper Rim Schiff Base Calix[4]arenes

The synthesis and properties of upperrim Schiff base calix[4]arenes are described in thisarticle. Tetrakis-p-bromomethylcalix[4]arene(1) reacts with hexamethylenetetramine to givetetrakis-p-formylcalix[4]arene (2) in highyield. Then upper rim Schiff base calix[4]arenes 3 can be easily synthesized by 2 reacting withappropriate alkylamines. The complexation ability of3 toward transition metals Pb²⁺, Cu²⁺and Co²⁺ was studied by UV-VIS spectrophotometry.     

Anion‐binding properties of two calix[4]arene derivatives containing two ferrocene imine or ferrocene amine units at the upper rim

Calix[4]arene derivatives containing ferrocene units at the upper rim have been synthesized and their anion‐binding and sensing investigated towards anions such as chloride, bromide and hydrogen sulfate by cyclic voltammetry. Electrochemical studies show that these redox‐active ligands electrochemically recognize chloride and bromide anions. These compounds have excellent selectivity for chloride and bromide ions, in the comparison with hydrogen sulfate anion. With ferrocenyl Schiff base calix[4]arene 1 an anodic shift as large as 302 mV is observed on addition of four equivalents of Cl⁻ anion. Also electrochemical and UV–vis spectroscopic titrations ferrocenyl calix[4]arene derivatives 1 with chloride and bromide ions and 2 (only with Cl⁻) indicate a 1:1 binding‐stiochiometry. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis of a novel calix[4]azacrown ionophore and its extraction ability toward Cr(VI)

The present study describes the synthesis of a novel extractant p-tert-butyl-calix[4]azacrown ionophore (5) and evaluation of its extraction capability toward dichromate ion from aqueous solution. At first, p-tert-butyl-calix[4]azacrown ionophore (5) has been synthesized from the condensation of p-tert-butyl-calix[4]arene diamine (3) with N-(4-formylphenyl)-aza-15-crown-5 (4). The studies regarding the removal of dichromate ion from the aqueous solutions have been carried out in the liquid–liquid extraction systems. The extraction results showed that p-tert-butyl-calix[4]azacrown derivative (5) exhibited generally higher affinity towards dichromate ion than both 3 and 4 at all studied pHs.     

Synthesis of two new p-tert-butylcalix[4]arene β-ketoimin derivatives for extraction of dichromate anion

In this study the selective derivatization of p-tert-butylcalix[4]arene was carried out and two new p-tert-butylcalix[4]arene β-ketoimin, 5,11,17,23-tetra-tert-butyl-25,27-bis-3-methyl-[(β-ketoimine)-ethoxy]-26,28-dihydroxycalix[4]arene (4), and 5,11,17,23-tetra-tert-butyl-25,27-bis-3-chloro-[(β-ketoimine)-ethoxy]-26,28-dihydroxycalix[4]arene (5) have been synthesized. In the synthesis, the lower rim of p-tert-butylcalix[4]arene was modified in order to acquire binding site for the recognition of dichromate anion. It was observed that these ionophores 4 and 5 showed high affinity towards dichromate anion. The protonated Schiff-base forms of the receptors were effective for transferring the HCr₂O₇ ^? anion from aqueous phase to a dichloromethane phase.     

SYNTHESIS AND COMPARATIVE COMPLEXATION STUDIES OF SCHIFF BASE DERIVATIVES OF p-TERT BUTYLCALIX[4]ARENE COPOLYMERS

Two different Schiff base derivatives of p-tert butylcalix[4]arene 3, 6 in which one of them carrying two oxime groups, while the other has a 1,8-octylenediimino bridge, are synthesized. Treatment of these monomers with triethylene ditosylate provided corresponding copolymers 5, 7. Their complexing properties with selected alkali and transition metals are reported here. It has been concluded that the binding ability of Schiff base-calix arene derivatives in transferring the metal cations is due to the presence of soft π-donor systems in the macrocyclic structure.     

Synthesis and chiral recognition properties of two novel chiral calix[4]arene tartaric ester derivatives

Two new chiral calix[4]arene derivatives containing tartaric acid ester moieties were synthesized. The chiral calix[4]arenes are in a ‘cone’ conformation according to NMR spectroscopy. The chiral recognition capabilities of 1–4 toward the guests, 1,2-propanediol and serine methyl ester hydrochloride (SerOMe), were investigated (¹H NMR spectroscopy). The extraction properties of compounds 1 and 2 toward selected α-amino acid methyl esters were also studied.     

Chiral calix[4]arenes bearing α-hydroxy amide units as membrane carriers for amino acid methyl esters

Novel chiral calix[4]arene derivatives functionalized at the lower rim have been prepared from the reaction of p-tert-butylcalix[4]arene diamine or acylhydrazine derivative with mandelic acid or hydroxyisovaleric acid. The structures of these receptors were characterized by FTIR, ¹H, ¹³C and 2D COSY NMR spectroscopy and elemental analysis. The transport of amino acid derivatives (phenylalanine, phenylglycine and tryptophan methyl ester hydrochlorides) was studied through bulk liquid membrane in the presence of chiral calix[4]arene derivatives. The receptors have been found to act as carriers for transport of aromatic amino acid methylesters from the aqueous source phase to the aqueous receiving phase. The transport rate and L/D selectivity of amino acid esters studied depend strongly upon the structure of the chiral receptors and guests. The best enantioselectivity was obtained in the case of phenylglycine methyl ester for all chiral carriers.     

Synthesis and characterization of manganese(II), nickel(II), copper(II) and zinc(II) Schiff-base complexes derived from 1,10-phenanthroline-2,9-dicarboxaldehyde and 2-mercaptoethylamine

The synthesis of a new Schiff base containing 1,10-phenanthroline-2,9-dicarboxaldehyde and 2-mercaptoethylamine is described. The reaction of 1,10-phenanthroline-2,9-dicarboxaldehyde with 2-mercaptoethylamine leads to 2,9-bis(2-ethanthiazolinyl)-1,10-phenanthroline (I) which undergoes rearrangement when reacted with manganese, nickel, copper or zinc ions to produce complexes of the tautomeric Schiff base 2,9-bis[2-(2-mercaptoethyl)-2-azaethene]-1,10-phenanthroline (L). The [M(L)Cl₂] complexes [where M = Mn(II), Ni(II), Cu(II) and Zn(II) ions] were characterized by physical and spectroscopic measurements which indicated that the ligand is a tetradentate N₄ chelating agent.     

Synthesis and characterization of azocalix[4]arene ester and ketone derivatives incorporated in a polymeric backbone with bisphenol-A and their cation-binding properties

This study comprises synthesis and characterization of azocalix[4]arene compounds having copolymeric structures. The novel bisazocalixphenol-A and copolymer containing pendant azocalix[4]arene units with ester (5) and ketone (6) functionalities at their lower rim have been synthesized via diazo-coupling reaction. The phase transfer study is performed by liquid?Cliquid extraction method. It has been deduced from the observations that their precursors 25,26,27-tribenzoyloxy-28-hydroxy-5-(4-aminophenylazo)calix[4] arene (3), 25,27-diacetoniloxy-26,28-dihydroxy-5,17-(4-aminophenylazo)calix[4]arene (4) and bisazocalixphenol-A (5) show a good phase transfer affinity towards selected transition metal cations, unlike copolymer (6). These compounds are studied by the selective extraction of Fe³⁺ cation from the aqueous phase into the organic phase and it is carried out using compounds 1?C6. It is observed that the reduced azocalix[4]arene 4 is the most efficient (82.93?%) carrier of all compounds (3?C6) in the extraction of Fe³⁺ at pH 5.4.     

Synthesis of Oligomer and Styrene Polymer-supported Calix[4]arene Derivatives and Selective Extraction of Fe3+

Five new polymeric compounds containing more than one calix[4]arene have been synthesized by reacting an oligomer with 5,11,17,23-tetrakis[(diethylamino)methyl]-25,26,27,28-tetrahydroxycalix[4]arene (L1), 25,27-dimethyl-26,28-dihydroxy-p-tert-butylcalix[4]arene diketone (L2), and p-nitrocalix[4]arene (L3), and chloromethylated polystyrene with 25,27-dimethyl-26,28-dihydroxy-p-tert-butylcalix[4]arene diketone (L4) and p-nitrocalix[4]arene (L5). These compounds were studied by the selective extraction of Fe³⁺ cation from the aqueous phase into the organic phase and was carried out by using compounds L1–L5. It was observed that the polymer support attached to the lower rim of p-nitrocalix[4]arene was the most efficient carrier of Fe³⁺ in the extraction process.     

Synthesis and Extraction Studies of a Versatile Calix[4]arene-Based “Proton-Switchable Extractant” for Toxic Metals and Dichromate Anions

The article describes the syntheses and extraction properties of a new calixarenebased extractant 5, which has been synthesized from5,11,17,23-tetra-tert-butyl-25,27-bis(chlorocarbonyl-methoxy)-26,28-dihydroxycalix[4]arene(4) by treatment with isoniazid (isonicotinic acid hydrazide) in the presence ofpyridine. The compound 5 was converted to its methyl iodide salt (6) by refluxing 5 with methyl iodide in acetonitrile. In this synthesis it was thought to explore the role of pyridinium sites in the extraction of HCr₂O ₇ ^- /Cr₂O ₇ ^2- anions. The complexing properties of 5 toward selected alkali/transition metal cationsand HCr₂O ₇ ^- /Cr₂O ₇ ² - anions are reported. It has been observed that receptor 5 does not extract alkali metal cations but shows an excellent selectivity toward transition metals. The protonated pyridinium form of 5 is an effective formfor transferring the HCr₂O ₇ ^- /Cr₂O ₇ ^2- anions from an aqueous into adichloromethane layer.