Dioxamethylene intramolecular bridging of p-tert-butylcalix[8]arene

The first examples of dioxamethylene bridged calix[8]arenes 2–6 have been obtained by Cs2CO3-promoted direct O-alkylation of p-tert-butylcalix[8]arene with BrCH2Cl. Assignment of the 1,2-, 1,2:3,4-, 1,2:3,4:6,7-, 1,4:2,3:5,6:7,8-, and 1,2:3,4:5,6:7,8-bridging pattern of 2–6, respectively, was mainly based on chemical shift of OH groups and chemical correlations. Dynamic 1H NMR studies and MM3 calculations indicated that in these compounds the dioxocine subunit adopts a boat–chair conformation.