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.     

Epoxide Polymerization and Copolymerization with Carbon Dioxide Using Diethylaluminum Chloride-25,27-Dimethoxy-26,28-dihydroxy-p-tert-butyl-Calix[4]arene System as a New Homogeneous Catalyst

ABSTRACT

Previously unknown substituted chelate phenolatoaluminum chloride, (25,27-dimethoxy-p-tert-butylcalix[4]arene-26,28-diolato) aluminum chloride, was derived from the reaction of diethyl-aluminum chloride and 25,27-dimethoxy-26,28-dihydroxy-p-tert-butylcalix[4]arene at reactants 1:1 mole ratio. It was applied successfully for the polymerization of propylene oxide and cyclohexene oxide, and their copolymerization with carbon dioxide, leading to respective oligomers and co-oligomers. The catalyst structure and the structure of the obtained low-molecular-weight polymers and copolymers were studied using NMR spectroscopy. Poly(propylene oxide) obtained in the presence of the studied catalyst appeared to contain isotactic diads predominantly, whereas the obtained poly(cyclohexene oxide) did not exhibit any significantly prevailing sequences of either isotactic nor syndiotactic diads. The polymerization mechanism has been proposed and discussed in view of the obtained results.     

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 Solid-State Conformation of a Calix[8]arene 1,5-Diquinone Derivative

The first example of a calix[8]quinone derivative, hexamethoxy-p-tert-butylcalix[8]-1,5-diquinone 5, has been synthesized from p-tert-butylcalix[8]arene 1by exploiting a protection-deprotection procedure. The structure of the 5·toluene inclusion compound has been determined by a single crystal X-ray diffraction study. The calix[8]arene molecule possesses a crystallographic inversion centre and assumes a ‘pseudo-chair-like’ conformation, with two opposite 3/4-cone moieties, which resembles the previously reported chair-like conformation of p-tert-butylcalix[8]arene. The 4 toluene molecules per unit cell occupy interstitial voids and are released in the temperature range of 30–160 °C.This revised version was published online in July 2005 with a corrected issue number.     

Synthesis, characterization, and conformational analysis of new perfunctionalized calix[9]arenes

The synthesis of a series of six new per-substituted p-tert-butylcalix[9]arenes derivatives has been achieved. Functions such as ester, nitrile, or carbonate have been grafted on the phenolic oxygens of calix[9]arene: p-tert-butylcalix[9]arene nona-ethyl acetate, p-tert-butylcalix[9]arene nona-carboxylic acid, p-tert-butylcalix[9]arene nona-cyanopropyloxy, p-tert-butylcalix[9]arene nona-tert-butoxycarbonyle, p-tert-butylcalix[9]arene nona-acetyl, and p-tert-butylcalix[9]arene nona-trifluoroacetyl have been obtained in good yields (from 48% to 78%) and fully characterized. The X-ray structures of p-tert-butylcalix[9]arene nona-tert-butoxycarbonyl and p-tert-butylcalix[9]arene nona-ethyl acetate have been determined. A dynamic NMR study has revealed the high conformational mobility of such structures, even at low temperature.     

Preparation and biological properties of inclusion compounds of calix[4]arene and 1,4-benzodiazepinone derivatives

The possibility of enhancing the oral bioavailability of certain 1,4-benzodiazepinones by using them as complexes with a series of calix[4]arene derivatives was examined. All the inclusion compounds prepared exhibit anticonvulsant activity by antagonism with Corazol spasmodic agent. Complexes with 25,27-bis[(hydrazinocarbonyl)methoxy]-26,28-dihydroxy-p-tert-butylcalix[4]arene exhibit higher pharmacological activity compared to the starting 7-bromo-5-(o-chloro)phenyl-and 1-hydrazinocarbonylmethyl-7-bromo-5-phenyl-1,2-dihydro-3H-1,4-benzodiazepin-2-ones.     

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 conformation studies of multiple bridged p-tert-butylcalix[7]arene diphosphates

p-tert-Butylcalix[7]arene reacting with phosphorus pentachloride and then with water afforded two stereoisomers p-tert-butylcalix[7]arene diphosphates 2a and 2b, representing the first phosphorus multiple bridged calix[7]arene. The more accurate structure of 2a was investigated with the aid of Gaussian03 calculations.     

Preparation and characterisation of thiol functionalised p-tert-butylcalix[4]arene-embedded polymer inclusion membranes: performance and selectivity

ABSTRACT

Here in we report the syntheses of the thiol functionalised p-tert-butylcalix[4]arene from the reaction of p-tert-butylcalix[4]arene-dialkylbromide derivative with thiourea. The structure of the thiol functionalised p-tert-butylcalix[4]arene was determined by using ¹HNMR, ¹³CNMR and elemental analysis techniques. Furthermore, the thiol functionalised p-tert-butylcalix[4]arene, cellulose triacetate (CTA) and 2-nitrophenyl octyl ether (o-NPPE) in dichloromethane were used to make a new calixarene-embedded polymer inclusion membrane (Bu^t-C@PIM). The surface and structure morphology of Bu^t-C@PIM was detected using thermogravimetric analysis, elemental analysis techniques and scanning electron microscopy. The affinity (the percentage of metal ion transferred from the source solution) of a PIM towards a range of divalent cations was found to follow the order Pb²⁺ > Zn²⁺ > Ni²⁺ > Cu²⁺ > Cd²⁺ > Co²⁺. The results also indicated that the transport efficiency of Bu^t-C@PIM was repeatable and may be beneficial in the development of a simplistic and highly influential trace metal recovery method from aqueous solution.     

Synthesis and Host Properties of (1,3)- p-tert-Butylcalix[5]crown-6 Derivatives Incorporating the 1,1'-Binaphthalene-2,2'-dioxy Subunit

Alkylation of p-tert-butylcalix[5]arene (1) with 2,2'-bis(5-tosyloxy-3-oxa-1-pentyloxy)-1,1'-binaphthalene ((±)-2) in the presence of CsF affords selectively racemic 1,3-bridged calix[5] [5]crown-6-triol 3, along with very small amounts of the (1,2)-bridged regioisomer 4. Compound 3 has been converted into tri-methoxy and tri--picolyloxy derivatives 5 and 6, respectively, by exhaustive alkylation with the appropriate electrophile and base. The direct separation of the enantiomers of racemates 3 and 6 was achieved by HPLC, using a chiral stationary phase (Chiralpak AD). Hosts 5 and 6 are able to selectively form 1 : 1 endo-cavity complexes with the linear RNH₃ ⁺ ions.     

Thermodynamic and electrochemical aspects ofp-tert-butylcalix[n]arenes (n=4, 6, 8) and their interactions with amines

Attention is drawn to the need of detailed thermodynamics in calixarene chemistry. The reasons for increasing efforts in this area are underlined and suggestions for new issues to be addressed are given. The solution thermodynamics ofp-tert-butylcalix[n]arenes (n=4, 6, 8) is discussed with particular reference to transfer Gibbs energies which reflect the selective solvation that the tetramer and the octamer undergo in the various solvents. This is followed by recent solution studies on amine-p-tert-butylcalix[n]arene (n=4, 6, 8) in nitrobenzene and in benzonitrile at 298.15 K which indicate the lower acidic character of the tetramer relative to the hexamer and the octamer in these solvents. As an implication of these results, very low conductivities are observed in studies involving the interaction of the former with amines. Thus, thermodynamic studies suggest thatp-tert-butylcalix[4]arene interacts with triethylamine in benzonitrile and in nitrobenzene through hydrogen bonding or ion-pair formation. A thermodynamic cycle is used to investigate the effect associated with the interaction of the amine with the tetramer in these solvents.This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes.     

Synthetic and NMR Studies on Calix[n]Arene (n = 4,6,8) Triflates,Mesylates, and Tosylates

Abstract

The synthesis and full characterization of eight new calix[n]arene sulfonate esters including their conformational analysis were carried out. While p-tBucalix[6]arene and p-tBu-calix[8]arene esters are conformationally labile in the temperature interval of 25–100°C, p-tBu-calix[4]arene mono-and diesters were isolated as stable conformers at ambient temperature. Two 1,3-functionalised compounds of these derivatives, p-tert-butylcalix[4]arene ditriflate (5) and dimesylate (6) were shown unexpectedly high conformational stability up to 100°C by dynamic NMR measurements. The NMR measurements confirm the pinched-cone conformation for both derivatives. For the dealkylated calix[4]arene derivatives the partial cone conformer of the triesters have been obtained as major products in all cases.     

Calixarenes 11. Crystal and molecular structure ofp-tert-butylcalix[8]arene

Monoclinic prisms were obtained by slow evaporation of a pyridine solution ofp-tert-butylcalix[8]arene: space groupP2₁/c,a=20.312(3),b=23.020(2),c=20.006(6) ; =113.05(2)⁰;V=8707.6 ų;Z=4. Refinement led to anR value of 0.166 for 4231 reflections which, although high, is sufficient to establish the conformation of the molecule as a pleated loop in which the eight hydroxyl groups are arranged in a slightly undulating, almost planar, intramolecularly hydrogen bonded cyclic array. The possible inferences for the conformation ofp-tert-butylcalix[8]arene in solution are discussed. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82019.     

Encapsulating property of ap-t-butylcalix[6]arene derivative: Formation of charge-transfer complexes of alkadienes with iodine in the presence of octopus-type calix[6]arene

This paper deals with the ability ofp-tert-butylcalix[6]arene derivative1, which has six 3,6,9-trioxadecyl substituents at the phenolic oxygens, to encapsulate CT complexes of alkadienes with iodine. By adding I₂ to alkadienes in CH₂Cl₂ in the presence of1, the absorbance at 363 nm, which was ascribed to I ₃ ^– ion, increased in the order: 1,5-hexadiene<1,9-decadiene 1,7-octadiene. The reactivity features of the CT complexes in the presence of1 are discussed.     

新型多重氮杂杯[4]芳烃衍生物的合成

对叔丁基杯[4]芳烃-1,3-二醛基衍生物1与水杨酰肼、烟酰肼、异烟酰肼反应, 合成了具有开链结构新型杯[4]多重氮杂衍生物2a～2c, 产率分别为88%, 85%和90%. 化合物1与乙二酰肼、丙二酰肼、己二酰肼反应, 得到具有桥联结构的新型杯[4]多重氮杂衍生物3a～3c, 产率分别为86%, 89%和90%. 新化合物的结构经元素分析、质谱、核磁共振谱等表征证实, 杯[4]芳烃单元均为1,3-取代且采取锥式构象.     

Synthesis of derivatives of p-tert-butylcalix[4]arene containing on lower rim fragments of 2-aminoalkylbenzimidazoles

Reactions of calix[4]arene carboxymethoxy derivatives with 2-aminoalkylbenzimidazoles in the presence of dicyclohexylcarbodiimide and hydroxybenzotriazole afforded a series of p-tert-butylcalix[4]arene derivatives containing on the lower rim N-(2-benzimidazolylalkyl)carbamoylmethoxy fragments. The reaction carried out in the absence of hydroxybenzOtriazole resulted in macrocycles containing one N-(2-benzimidazolylalkyl)carbamoyl fragment and a fragment of N-(acyl)dicyclohexylisourea.     

Azobenzene-bridged calix[8]arenes

An azobenzene bridge was introduced into the lower (or smaller) rim of p-tert-butylcalix[8]arene (1) and 1,5-calix[8]crown-3 (2) to form 1,4-singly bridged (3) and 1,5:3,7-doubly bridged (4) calix[8]arene derivatives, respectively. Trans and cis isomers of conformationally rigid 4 were isolated. The quantum yields of the trans-cis photoisomerisation reactions have been measured.     

Synthesis and crystal structures of Ag and Hg complexes of bis(N-heterocyclic carbenes) on p-tert-butylcalix[4]arene platform

A series of p-tert-butylcalix[4]arene 1,3-diimidazolium salts were successfully prepared by the alkylation of p-tert-butylcalix[4]arene with dibromoalkanes, and sequential substitution reaction with 1-alkylimidazole. Furthermore, coordination reactions of p-tert-butylcalix[4]arene 1,3-diimidazolium salts with silver oxide and mercury acetate gave novel Ag and Hg complexes of bis(N-heterocyclic carbenes) on p-tert-butylcalix[4]arene platform. The single-crystal structures of four p-tert-butylcalix[4]arene 1,3-diimidazolium salts and three metal complexes were successfully determined by X-ray diffraction. An Ag–Ag argentophilic interaction (Ag–Ag bond length is 3.1599(6) Å) is formed between the two Ag–NHC complexes and a dimetallic coordination mode exists in Hg–NHC complexes.     

Two Stabilized Calix[6]Cryptand Stereo Isomers used as Stationary Phases for Capillary Gas Chromatography

ABSTRACT

A couple of stabilized calix[6]cryptand steroisomers were synthesized by capping 1,3,5-trimethoxy-p-tert-butylcalix[6]arene with 1,1,1-tri(tosyloxyethoxyethoxymethyl)-propane and used as stationary phases for capillary gas chromatography. Their chromatographic characteristics and separation mechanism for aromatic positional isomers and polycyclic aromatic hydrocarbons are discussed.     

A stability-indicating HPLC method for the determination of 17β-estradiol-3-phosphate in an ophthalmic solution

Summary Thep-tert-butylcalix[n]arenes (n=4,6,7,8) andp-tert-butyldihomooxacalix[4]arene have been separated by reverse phase liquid chromatography. Optimum conditions have been obtained on a Spherisorb ODS1, 5 m C18 column by isocratic ambient elution with acetonitrile-methyltert-butyl ether. Calibration plots have been obtained from purified calixarenes and the reliability of the method is confirmed from test mixtures of calixarenes of known composition.