Dissymmetric calix(4)arenes with C(sub 4)- and C(sub 2)-symmetry: synthesis, X-ray structures, conformational fixation, and 1H NMR spectroscopic studies

The condensation of the associated 2- or 6-hydroxymethylated phenols yielded six dissymmetric calix (4) arenes with C4 symmetry containing four 3,4-disubstituted phenolic units. The p-methylcalix (4) arene possesses a higher energy barrier than calixarene 4a, which contains 3,4-dimethylphenol units for the gene-to-gene inversion in CDCl3. The alkylation of the phenolic hydroxyl group is used to structurally set the dissymmetric calixarenes 4. In addition to tetra derivatives, mono-acid 1, 3-di-derivatives could be used, because of the equivalence of all four phenolic units.