Calix arene esters

Other recent works in this field, studies on the transport of alkali and alkaline earth cations with p-zerr-butyl calix[n]arene esters and amides, were carried out by Arnaud-Neu et al. [20] and Casnati et al. [21]. They prepared 1,3-alternate calix[4]arene-crown-6 as a new class of cesium selective ionophore. 

Beer, P. D., Gale, P. A., Chen, Z., Drew, M. G. B., New bis- and tris-ferrocenoyl and tris-benzoyl lower-rim substituted calix[5]arene esters Synthesis, electrochemistry and X-ray crystal structures. Supramol. Chem. 1996, 7, 241-255. 

Diamba HM et al (2009) Towards calixarene-based prodrugs drug release and antibacterial behaviour of a water-soluble nalidixic acid/calix[4]arene ester adduct. Bioorg Med Chem Lett 19 2679-2682... 

Hg(II) Crown 18C6, 4 -nitrobenzo[15-crown-5], calix oligomer deriv., bis-calix[4]arene ester derivative [178-186] ... 

Lynch, A., Eckhard, K., McMahon, G. et al. (2002) Cation binding selectivity of partially substituted calix[4]arene esters. Electroanalysis, 14 (19-20), 1397-1404. 

The size of the calixarene macrocycle can govern the selectivity with regard to the different cations. For example, the ester derivative of calix[4]arene presents a high selectivity for the smaller cations Na" and However, the analogous ester derivative of calix[5]arene and calix[6]arene interact strongly with Cs =Rb >K. No selectivity with regard to cations is observed for the calix[7]arene and calix[8]arene ester derivatives. 

Functional calixarenes can be used as plurifunctional ATRP initiators for the synthesis of star polymers. Show the structures of 2-bromopropionate and 2-bromoisobutyrate esters of 4-ten-butyl calix[ ] arene used as tetrafunctional ( = 4), hexafunctional (h = 6), and octafunctional (n = 8) initiators for ATRP. 

In an attempt to mimic the highly sophisticated ion transport properties found in biological membranes for the development of an ion channel sensor, a comprehensive study on artificial systems was carried out [10]. It was shown that the permeability of orientated monolayers of various calixarene esters is strongly influenced by the complexation with metal ions [11]. It was reported that the membrane permeability of calix[6]arene esters for a neutral redox-active... 

Danil de Namor, A.F. Gil, E. Tanko, M.A.L. Tanaka, D. Salazar, L. Schulz, R. Wang, J. (1995) Thermodynamics of Calix(4)arene Esters. 1. Complexation of Alkyl p-tert-Butylcalix(4)arenetetraethanoates and Alkali-Metal Cations in Acetonitrile and in Benzonitrile, /, Phys. Chem., 99 16776-16780. 

Cadogan A, Diamond D, Smyth MR, Svehla G, McKervey MA, Seward EM, Harris SJ (1990) Caesium-selective poly(vinyl chloride) membrane electrodes based on calix[6]arene esters. Analyst 115 1207—1210... 

Thus, it has been shown that calix[4]aryl esters exhibit remarkably high selectivity toward Na [11-14]. This is attributable to the inner size of the ionophoric cavity composed of four 0CH2C=0 groups, which is comparable to the ion size of Na, and to the cone conformation that is firmly constructed on the rigid ca-lix[4]arene platform (Scheme 2). 

Kimura and coworkers [17], Diamond [18], and Damien et al. [19] have described that the polymeric calix-[4]arenes have been used as ionophores in ion selective electrodes for Na (based on calixarene esters and amides) and for Na and Cs (based on p-alkylcalixarene acetates). The electrodes are stated to function as poten-tiometric sensors as well, having good selectivity for primary ion, virtually no response to divalent cations, and being stable over a wide pH range. 

Recently, Deligoz and Yilmaz [24,25] described the preparation of two polymeric calix[4]arene tetra esters (Scheme 4) and their Na -complexation. Based on phase-transfer experiments with these compounds using alkali picrates in water-dichloromethane, they confirmed that polymers are as Na selective as monomers. 

It was observed that while the ester (3) and ketone (4) derivatives of p-/erf-butyl calix[4]arene extracted negligibly small amounts of Cu " and Cr " ions, its oxime derivative efficiently extracted these ions. Furthermore, 5 was found to be more effective than 6 in extracting Cr ion. 

Calixarenes, which are macrocyclic compounds, are one of the best building blocks to design molecular hosts in supramolecular chemistry [158]. Synthesis of calix[4]arenes, which have been adamantylated, has been reported [105, 109]. In calix[4]arenes, adamantane or its ester/carboxylic acid derivatives were introduced as substituents (Fig. 29). The purpose of this synthesis was to learn how to employ the flexible chemistry of adamantane in order to construct different kinds of molecular hosts. The X-ray structure analysis of p-(l-adamantyl)thiacalix[4]arene [109] demonstrated that it contained four CHCI3 molecules, one of which was located inside the host molecule cavity, and the host molecule assumed the cone-like conformational shape (Fig. 30). 

Macrocycles containing isoxazoline or isoxazole ring systems, potential receptors in host—guest chemistry, have been prepared by multiple (double, triple or quadruple) 1,3-dipolar cycloadditions of nitrile oxides, (prepared in situ from hydroxamoyl chlorides) to bifunctional calixarenes, ethylene glycols, or silanes containing unsaturated ester or alkene moieties (453). This one-pot synthetic method has been readily extended to the preparation of different types of macrocycles such as cyclophanes, bis-calix[4]arenes and sila-macrocycles. The ring size of macrocycles can be controlled by appropriate choices of the nitrile oxide precursors and the bifunctional dipolarophiles. Multiple cycloadditive macrocy-clization is a potentially useful method for the synthesis of macrocycles. 

Cuest-Induced Changes in Membrane Permeability. Calixarene derivatives are also used for sensing systems other than ISEs or optodes. Recently, a systematic investigation on the control of membrane permeability by use of oriented monolayers composed of calixarene esters was carried out. The hosts used were short alkyl chain esters of calix[6]arene [28 (R = Bu )] and calix[4]arene [26 (R = Bu ), 30 both cone conformers]. The permeabilities through the intermo-lecular voids of these monolayers were evaluated by cyclic voltammetry, as described earlier for oriented membranes of nucleobase derivatives. Cationic, anionic, and neutral electroactive compounds were used as the permeability markers. The voltammetric measurements were carried out either for a monolayer... 

With the idea that crown ethers based on the p-tert-butylcalix[5]arene platform could provide an interesting extension of our catalytic studies, several calix[5]-crown-ethers were investigated as potential catalysts of ester methanolysis in the presence of a Ba + salt [22]. Of the various structures investigated, the calixcrown-5 derivative 7 gave the... 

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