Calixarenes calixarene-related compounds

Interesting calixarenes and calixarene-related compounds have been obtained in one-step reactions from 1-naphthol, from the naphthalenediol disulfonate 11, and from and the bis-phenols 13, 15, and 17. Although 2-naphthol reacts with formaldehyde to yield a simple bis-naphthol, 1-naphthol produces a mixture containing 9.6% of the symmetrical cxo-OH cyclic tetramer 10 accompanied by 5% and 16% of two other cyclic tetramers in which the naphthol residues are unsymmetrically placed in the cyclic array. When the disodium salt of 1,8-dihydroxy-3,6-naphthalenedisulfonic acid (chromotropic acid) (11) is treated with an aqueous solution of formaldehyde and the mixture is allowed either to stand at room temperature for a week or is refluxed 6 h, a high yield of the endo-OH cyclic tetramer 12 is formed. The ease with which this condensation occurs is surprising in view of the deactivating effect of the sulfonic acid groups... 

Hetero-calixarenes represent another interesting group of calixarene-related compounds that can be used for the interaction with nucleic acids and related compounds. Due to their constitutional variation their structural features significantly differ from the corresponding original calixarene scaffolds. Still there is a number of examples worth considering in the broad context of calixarenes and nucleic acids. 

For earlier reviews on inherently chiral calixarenes and related compounds see (a) Bohmer, V. Kraft, D. Tabatabai, M. J. Incl. Phenom. Mol. Recogn. 1994,19,17-39. (b) Otsuka, H. Shinkai, S. Supramolecular Science 1996,3,189-205. 

This subject was covered previously in pages 993-1022 in CHEC-II(1996) (volume 9, chapter 36). This chapter is intended to update the previous work on major preparative and structural aspects of various types of rings containing silicon to lead that have been reported since 1995. As compared to previous work, two novel topics are covered reactivity and transformations of heterocyclic rings in Section 14.19.4 and application of computational methods in Section 14.19.5. Moreover, silacrown ethers and related compounds such as calixarenes, cyclophanes, and metallacenes are covered in Section 14.19.3.6. 

There are some 3,000 publications reporting calixarenes, many of which can be obtained by searching databases under the term calix. In addition, several books have been written on calixarenes, and metal complexes are described in all of them.1-6 Reviews on metal complexes of calixarenes has been published,7-10 and a book published in 2001 also makes numerous references to them.11 Among the other calixarenes are the calix[4]arene thiol (7) and the thiacalix[4]arene (8). Related compounds are the oxacalix[3]arene (9) and the azacalix[3]arene (10), both of which have been used as complexants for metal ions. 

Conjugates of nucleic acid related compounds (nucleobases, nucleosides and nucleotides) and calixarene scaffolds are potential candidates for the formation of well-defined supramolecular structures. Nucleobases are structurally predetermined to mediate non-covalent interactions, e.g. base pairing via hydrogen bonds and r-stacking to aromatic moieties. The versatile nature of the cahxarene corpus provides a convenient entry to multiple pre-oriented functionahties. By this combination a broad range of supramolecular architectures becomes accessible. Over the years a number of calixarene DNA hybrids have been constructed and investigated in their complexation properties towards nucleic acid related compounds. A valuable summary on this topic is given by Kumar et al. in Advances in Heterocyclic Chemistry [38]. 

As suggested by the title, Calixarenes and Beyond aims to give an update on the chemistry of this ever-growing family of macrocycles, including related compounds beyond any strict or rigorous definitimi. In addition to their ostensibly similar structural features, the fil-rouge connecting the macrocycles discussed in... 

S. Pappalardo, L. Giunta, P. Neri, and C. Rocco Proceedings 2nd Workshop on Calixarenes and Related Compounds, Kurume (Japan), 2-4 June 1993, OP-5. 

T. Thiemann, Y. Lee, Y Nagano, M. Tashiro Book of Abstr. Second Workshop on Calixarenes and Related Compounds in Krume, Fukuoka, Japan, PS/A28 (1993). 

THIRD INTERNATIONAL CONFERENCE ON CALIXARENES AND RELATED COMPOUNDS... 

Three macrobicycles 40b (216), 40h (212), and 40k (211) were characterized by X-ray crystallography. Fig. 31 displays the structure of 40h. The compounds adopt a highly folded conformation, reminiscent of calixarenes (23) and related Schiff-base macrocycles (181). 

The reaction of 13, in which the (3-pyridyl)carbonyloxy groups can be either in syn or in anti position, with spiro[cyclopropene-3,9 -fluorene] creates two new stereogenic centers.35 Thus two diastereomers are possible for each the syn- and the anri-isomer which form a pair of C2-symmetrical enantiomers (R,R/S,S) and a Cs- or Cj-symmetrical meso form (R,S) n The resulting calixarenes 14, bearing dihydroindolizine units, were studied as chromogenic compounds ( calixo-chromes ) in quenching experiments not related to their chirality. 

Further examples of related multi redox-active macrocycles 89 — 91 have also been synthesised and their electrochemistry examined [108 — 110], Calix-4-arenes have also been derived from ferrocene to form monomeric macrocycles of type 92 or 93 together with dimeric compounds of type 94 [102] and crystal structures of the latter two compounds were reported. Solution HNMR and electrochemical studies in CH3CN, CHCI3, or CH2CI2 showed, however, that there was no complex formation between these calixarenes and either aliphatic or aromatic amines. 

Although not formally classified as calixarenes, compounds closely related in architecture to the calix[4jarenes have been prepared by the condensation of furans, thiophenes, and pyrroles with aldehydes and ketones. Furan undergoes acid-catalyzed condensation with aldehydes and ketones to give 15 76-79), as shown in Fig. 9. 

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