Calixarenes and Resorcarenes

Stibor, I. and Lhotak, P. Calixarenes and their Analogues molecular complexation , in Encyclopedia of Supramolecular Chemistry, Atwood, J. L., Steed, J. W., eds. Marcel Dekker New York, 2004 vol. 1, pp. 628-635. 

The synthesis and nomenclature of calixarenes such as 3.118 has already been in introduced (Section 3.14 - For an introduction to calixarenes and the history of their development see Box 3.4) in the context of their widespread applications as hosts for cations, generally binding to metals through 

In aqueous solution, water-soluble calixarenes have the potential to bind much more strongly to organic guests than in lipophilic media because of the hydrophobic effect (Section 1.9). Unfortunately, p-alkylcalixarenes are not water-soluble and must be derivatised in order to take them up into aqueous 

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In this chapter we present an overview of chiral structures realized on the basis of calixarenes and resorcarenes.8 Clearly this cannot be an exhaustive survey, due to the enormous development calixarene chemistry has experienced during the last decade (mainly the last 5 years). Rather, it is a survey of the potential possibilities that are offered by this class of macrocyclic molecules—illustrated by selected examples of what has been done and indicating what might be done in the future. 

It seems appropriate at the outset to review some basic features of calixarenes and resorcarenes. Four basic conformations have been discussed for calix[4]arenes... 

The three structures shown at the right of the second line represent important families of receptor molecules that have been extensively studied in their own right. The aromatic spherand grew out of crown ether chemistry while calixarene chemistry developed on a separate evolutionary pathway. Still, their similarity is apparent. The structures of calixarenes and resorcarenes (also resorcinarenes) are included here because they have often been fused to macrocycles to form complex receptor systems. A few examples of fused receptor systems are discussed below. 

This last example demonstrates already one of the future lines. As the chemistry of calixarenes and resorcarenes is more and more understood, these fascinating molecules lend themselves as building blocks for the construction of increasingly larger and more and more sophisticated structures. It is hoped that this fascination could be transferred at least in part to the reader. 

The term cyclophane literally means any organic molecule containing a bridged aromatic ring. Thus specific cyclophanes such as the calixarenes and resorcarenes that we encountered in Section... 

The synergistic effect was only found in mixed stationary phases that have a special selectivity. Those stationary phases were CD, crown ether, liquid crystalline, resorcarene, calixarene, AgNOs, and others. Crown ether, CD, calixarene, and resorcarene possess cyclic moieties with cavity-like structures that are able to form inclusion complexes with metal ions and organic molecules. Liquid crystalline stationary phases have temperature-dependent ordered stmctures and the... 

Calixarenes, for example, 2.120, have already been discussed as hosts for cations and both cation and neutral molecules simultaneously in Sections 2.3.6 and 2.5.5, respectively. Resorcarenes e.g. 2.121) are very closely related to calixarenes and are sometimes referred to as calixresorcarenes. They are prepared from the acid-catalysed condensation of resorcinol (1,3-dihydroxybenzene) with aldehydes, a reaction first carried out by Baeyer in 1872. This macrocycle is arguably one of the most important molecules in the field, as resorcarenes serve as the basic building blocks for many cavitands and (hemi)carcerands. Both calixarenes and resorcarenes posses a shallow bowl-shaped conformation in their most stable forms. However, [4]resorcarenes (the [4] prefix refers to the ntimber of resorcinol units that make up the molecule, just as in calix[n]arenes) tend to produce a... 

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