Synthesis of calixarenes

Two general routes are available for the synthesis of calixarenes the base-and acid-promoted one-step synthesis and the convergent stepwise synthesis (fragment condensation).2,3 

Both the acid-catalysed and the base-promoted one-step syntheses provide the most powerful procedures to obtain symmetrically substituted calixarenes having only one type of phenolic unit in the cyclic array. 

Caution Carry out all procedures in a well-ventilated hood, and wear disposable vinyl or latex gloves and chemical-resistant safety goggles.3 

Position the heating mantle on a laboratory jack and place the 3 L flask on the heating mantle. 

Clamp the flask to a support and equip the flask with a mechanical stirrer, a nitrogen inlet and a still head connected to a tube dipped into a beaker of water. Close the fourth neck with a blowed glass stopper. 

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ZINKE ZIEGLER Synthesiso1 Cahxarenes Synthesis of calixarenes (a basket-llke macrocyclic compound)... 

Calix[n]arenes (n=4,6,8) are cyclic condensation products of ap-substituted phenol and formaldehyde [58]. Gutsche and co-workers [59,60] have developed procedures for the synthesis of calixarenes and caHxarene derivatives. 

Figure 7.2.2. Stepwise synthesis of calixarenes bearing different substituents.

Important works were devoted to the synthesis of calixarenes bearing different groups (malonamide, glycolamide, pyrazolone, thiopyrazolone, terpyridine, TTFA). Unfortunately, none of these compounds displayed a sufficient extracting ability. 

While the selective interactions of functionalised calixarenes with cations have been studied broadly for almost three decades, the application of cal-ixarene-based receptors for anion recognition is a relatively new research topic [2]. This review is focused on recent developments in the design and synthesis of calixarene-based anion receptors. Although the name calixarene was originally designated only for phenol-formaldehyde derivatives 1, recently many structural variations and mutations have been formed. Some of them, such as calixpyrroles [3], are widely used for anion recognition nevertheless, this review is restricted only to classical calixarenes 1 and newly discovered thiacalix-arenes 2 [4]. 

Scheme 3. Convergent, stepwise synthesis of calixarene[4]arenes (Bohmer, Chhim, and Kammerer method).

SCHEME 2. Synthesis of calixarenes by the stepwise strategy. In principle, each phenolic unit can have a different substituent (mainly alkyl groups) in the p-position... 

SCHEME 6. One-pot synthesis of calixarene analogues by condensation of bisphenols with formaldehyde... 

As a side product of the one-pot synthesis of calixarenes, compound 23 was isolated already in early studies. Here four f-butylphenol units were linked by three —CH2—bridges and one —CH2—O—CH2—bridge which explains the name bishomooxacalix[4]arene . Various other macrocyclic compounds are known now, in which the —CH2—bridges... 

A systematic study to design neutral, water-soluble calix[4]arenes has been carried out by Gansey et al., and this has led to the synthesis of calixarene derivatives with water solubility up to 0.3 M [80]. 

A new convenient strategy for the synthesis of calixarenes via a triple annulation of Fischer carbene complexes, V. Gopalsamuthiram and W. D. Wulff, J. Am. Chem. Soc.,... 

Direct synthesis of calixarenes with extended arms p-phenylcalix[4,5,6,8]arenes and their water-soluble sulfonated derivatives, M. Makha and C. L. Raston, Tetrahedron Lett., 2001, 42, 6215. 

Until recently, the acid-catalyzed synthesis of calixarenes was limited to the calixresorcarenes. A kinetic and molecular modeling study of the acid-catalyzed reaction of acetaldehyde and resorcinol comes to the conclusions that... 

The fragment condensation method for the synthesis of calixarenes (see Section... 

Trioxane has been employed as the formaldehyde source for the synthesis of calixarene derivatives during the cyclization step <1991JOC5527, 2002T2239,2002PSA1293>. Also, the Mannich reaction of dioxazasilacyclo-octane with 1,3,5-trioxane as the formaldehyde source has been reported <1989ZOB483>. 

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