Calixarenes double

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. 

Figure 6.5 Combination of a double calixarene koilartd (6.14) with a long, linear guest such as hexadiyne gives an inclusion polymer or koilate (two repeat units shown).4...

Double calixarenes containing O- and S-heterocyclic fragments 93SL719. 

It should be mentioned, that larger assemblies consisting of nine calixarenes are available with the calixarene-monocyanurate 139,208a while the double-calixarene 140 forms a double-box with 136 consisting of 15 molecules (3 x 140 and 9 x 136).283 Polymeric aggregates are formed between bis-melamine and bis-cyanurate calix[4]arenes.284 In all these cases, chiral induction still remains to be explored. 

One of the important applications of butylcalix[4]arenes arises from their ability to trap alkali metal ions. In particular, Cs+-calixarene complexes have received much attention because of the need to remove the Cs radionucleotide from nuclear wastes. Benevelli et al. have used one-pulse solid state NMR experiments to directly observe Li, Na and Cs ions in the host cavity [52]. More advanced experiments, which allow the investigation of metal lattice interactions were also reported. Rotational-echo double resonance (REDOR) NMR is a useful tool for obtaining structural details of butylcalix[4]arene [53]. Gullion and coworkers used REDOR to determine the position of the... 

A recent improvement involves the rearrangement in the presence of bis(trimethylsilyl)-urea to protect intermediately the phenolic hydroxy groups formed during the rearrangement. Thus, the / -allylcalix[4]arene was obtained in 99% yield and the larger p-allylcalix[4]arenes also became available . Multiple tandem rearrangements have also been used to convert O-linked double calixarenes into p-linked double calixarenes (see Section VIII. A). 

VIII. MOLECULES CONSISTING OF SEVERAL CALIXARENE STRUCTURES A. Double Calixarenes... 

M. Saadioui and V. Bohmer, Double and Multi-Calixarenes, in Reference lb, p. 130. Examples for Al ... 

The fullerene-rich calix[6]arene complexes. (C60 or C7o)2calix[6]arene, were structurally authenticated as isomorphous complexes,showing the calixarene in the double-cone conformation with a fullerene perched in each of the shallow cavities, resembling the jaws of a pincer acting on two adjacent cage molecules the... 

The four-fold symmetry of calixarenes and resorcinar-enes relates to complexation of the siloxane. 8, with 50 in toluene. " Here the fullerenes are arranged in double columnar arrays shrouded by edge on siloxanes (Fig. 2f), the siloxanes interlocking by one of the phenyl groups of one molecule residing in the cavity of another. 

Scheme 28.8 The synthesis of amphiphilic calixarenes by mercuration at the para position, followed by crosslinking from the subphase by exchanging the trifluoracetate counterion (with a single negative charge) with the malonate (with a double-negative charge, 02CCH2C02 ).

Steric effects are shown to affect the outcome of the aroylation reaction as illustrated, for example, by the reaction with 3,5-dinitrobenzoyl chloride which affords an excellent yield of a di-aroylate and provides a starting material for the synthesis of a double cavity calixarene, as illustrated in Figure 4. 

Fig. 9. Complexation of a double cavity calixarene with carboxylic acids.

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