Calixarenes base-induced calixarene formation

Alkenes and Alkynes. A series of metal carbonyl cations, such as [Au(CO)n]+,287,288 [c-Pd( i-CO)2]2+,289 [Rh(CO)4]+,290 and [(Pt(CO)3)2]2+,291 was found to induce the formation of carboxylic acids from alkenes and CO in the presence of H2SO4 under mild conditions. A novel water-soluble Pd catalyst292 and Pd complexes of calixarene-based phosphine ligands293 showed high activity in the regioselective carboxylation of vinyl arenes to yield 2-arylpropionic acids or... 

Although the mechanism of the base-induced formation of calixarenes has been studied in some detail, the reaction pathways remain uncertain. The most intuitively reasonable proposal is that the immediate precursor of any particular calixarene, regardless of size, is the linear oligomer carrying the requisite number of aryl residues. Another proposal, however, postulates that calix[8]arenes, for example, arise from intermolecularly hydrogen-bonded dimers (hemicalixarenes) formed from a pair of crescent-shaped, intramolecularly hydrogen-bonded linear tetramers. Calix[4]arenes, formed under considerably more strenuous conditions, have been postulated to be the result not of direct cyclization of the linear tetramer but of reversion of the calix[8]arene. The cyclic octamer is viewed as the product of kinetic control, and the cyclic tetramer is viewed as the product of thermodynamic control. The particular efficacy of KOH and RbOH for the formation of calix[6]arenes suggests that the hexamer is the product of template control. 

Abstract. Several facets of calixarene chemistry have been investigated including the mechanism of their formation by the base-induced condensation of phenols and formaldehyde, procedures for introducing functional groups onto the upper rim and lower rim of calixarenes, the conformational behavior of calixarene oxyanions, the formation of complexes in aqueous and nonaqueous systems, and the application of calixarenes as catalysts. 

Anion-induced excimer formation in calixarene-based podands... 

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