Large parent homooxacalixarenes: formation and transformation

The mixtures obtained on thermally dehydrating concentrated solutions of a bishydroxymethylated diphenol could be reliably analysed through the signal s of the phenol protons in the H NMR spectra. This allowed two oxygenated h omologues of calix[6]arene and one homologue of calix[8]arene to be prepare d in favourable conditions along with two homooxacalix[4]arenes. The obtain ed compounds are regular products of a cyclooligomerization reaction, namel y dimer, trimer, and tetramer, and modified structures with one CH2OCH2 bri dge less than expected. The latter compounds and lower regular cyclooligome rs appear to be formed when cyclooligomers are thermally decomposed. The th ermal lability of the compounds increases along the series dimer, trimer, t etramer. The strict relationship between parent homooxacalixarenes and typi cal calixarenes becomes increasingly evident in the light of the obtained r esults. (C) 2001 Elsevier Science Ltd. All rights reserved.