Large parent homooxacalixarenes: formation and transformation

The mixtures obtained on thermally dehydrating concentrated solutions of a bishydroxymethylated diphenol could be reliably analysed through the signals of the phenol protons in the 1H NMR spectra. This allowed two oxygenated homologues of calix[6]arene and one homologue of calix[8]arene to be prepared in favourable conditions along with two homooxacalix[4]arenes. The obtained compounds are regular products of a cyclooligomerization reaction, namely dimer, trimer, and tetramer, and modified structures with one CH2OCH2 bridge less than expected. The latter compounds and lower regular cyclooligomers appear to be formed when cyclooligomers are thermally decomposed. The thermal lability of the compounds increases along the series dimer, trimer, tetramer. The strict relationship between parent homooxacalixarenes and typical calixarenes becomes increasingly evident in the light of the obtained results.