Calix resorcarene

M. Vazquez, J. Bobacka, M. Luostarinen, K. Rissanen, A. Lewenstam, and A. Ivaska, Potentiometric sensors based on poly(3,4-ethylenedioxythiophene) (PEDOT) doped with sulfonated calix[4]arene and calix[4]resorcarenes. J. Solid State Electrochem. 9, 312-319 (2005). 

Figure 6.3 Upper- and lower-rim intramolecular hydrogen-bonding interactions in calix[4] arenes and [4] resorcarenes, which stabilise the cone conformations.

Since the preparation of 6.97, an enormous range of carcerand and hemicarcerand species have been prepared based upon both [n]resorcarenes and calix[n]arenes (n = 4,5), all of which exhibit interesting binding behaviour and intra-cavity reactivity, as we will see in the next sections. 

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... 

If para-, meta- or ort/io-tetraacetyl-glucoxybenzaldehyde was used for the condensation with resorcinol in the presence of aluminium chloride, the formation of rett (major) and rccc (minor) isomers was observed.54 These compounds, which have carbohydrates attached to the resorcarene skeleton, were characterized as their Oacetyl derivatives 24b. (For further calix sugars see Section 2.4.)... 

Calixarenes are macrocyclic molecules synthesized with high yield by condensation of appropriate arenes and aldehyde derivatives. Calix means bowF in Latin and Greek, and this phrase reflects the shape of the tetramer, which usually adopts a bowl or beaker-like conformation. Gutsche first introduced the name calixarene for this class of compounds [38]. Several authors have exhaustively reviewed the chemistry and synthetic procedures, which lead to different structural modifications of calixarenes [39-42]. In general, three types of calixarenes derivatives are known first, metacyclophanes (type 1) second, those obtained by condensation of formaldehyde with phenol (type 11), and third, those obtained by reaction with resorcinol (type III) (Scheme 6). The latter modifications are also called resorcarenes to distinguish calixarenes of type III from those of type II. 

A strategy used by Reinhoudt, and others for constructing artificial receptor molecules as biochemical mimics makes use of medium-sized molecules as platforms to which functional groups can be attached. Included among such platforms are calix[4]arenes, calix[4]resorcarenes, cyclodextrins, and porphyrins (see Section 5.1.3.1), which have been combined in various ways. Several striking examples involve the intermolecular linking of calix[4]resorcarenes with... 

Joining the quest to find artificial receptors for large guests, Reinhoudt and coworkers have shown that the calix[4]resorcarene-substituted calix[4]arene... 

The complexation of sugars has been studied in some detail with the calix[4]resorcarenes but less so with the calixarenes themselves. Using the... 

Smith et have prepared 11 chiral calix[4]arenes, calix[4]resorcarenes, and anionic cyclodextrin derivatives and investigated the properties of their lanthanide (Yb, Dy +) complexes as chiral lanthanide shift reagents (LSR). Baldovini et alP report an application of a camphor-derived chiral complex, Yb(hfc)3 (hfc = tris[3-(heptafluoropropylhydroxymethylene)-(- -)-camphorate]) to differentiate the C NMR spectra of enantiomers of bornyl acetate. 

Fig. 4 Exemplary cases of enforced cavity hosts and their supramolecular compounds (guests symbolized in broken rings) (a) Cleft-type (b) tweezer-type (c) spherand (d) cyclophane (monocyclic) (e) cyclophane ibicyclic) (f) cavitand (g) carcerand (h) calixarene (calix[4]arene) (i) resorcarene (j) cryptophane (k) cyclodextrin (P-cyclodextrin) and (1) cucurbituril.

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... 

One of the earliest examples of a carcerand was prepared by joining two hemispherical bowl-shaped components together (cavitands, such as calix[4]arenes or the closely related [4]resorcarenes (Section 2.7.2). This was achieved by reacting a thiol-appended resorcarene with an analogous alkyl halide to form a thioether-bridged equatorial seam (2.123). This led to a challenging analysis as carcerand... 

Resorcinarene A cyclic oligomer (usually a tetramer) arising from the condensation of resorcinol and an aldehyde under acidic conditions. Other synonyms are resorcarene, calixresorcarene, calixresorcinarene, as well as resorcin-[n]-arene or calix-[n]-resorcinarene, where [n] specifies the number of monomers in the oligomer. 

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