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

A tetrasulfate-resorcin[6]arene cavitand as the host for organic ammonium guests

“…2), a coalescence for ArCH 2 Ar AX systems of 2a was observed at 323 K, which led to an energy barrier of 14.6 kcal mol −1 . 16 In analogy with the data previously reported for calixarenes bearing 1,3-dioxocine moieties, 14,15 this energy barrier should be associated with an interconversion process between the distorted-boat and the boat-chair conformation of the 8-membered rings of 2a to give 2b. By increasing the temperature, a second coalescence was ascertained at 363 K (400 MHz), corresponding to an energy barrier of 16.5 kcal mol −1 , to give an averaged symmetrical spectrum (Fig.…”

“…Such distortedboat conformation was already observed in macrocyclic compounds containing 6H,12H-dibenzo[d,g][1,3]dioxocine rings. 14,15 The above variable temperature 1 H NMR experiments (TCDE, 400 MHz) (Fig. 2) clearly indicated that, notwithstanding the presence of sulphate bridges, the resorcin [6]arene skeleton of 2 still shows a residual conformational mobility, likely due to the presence of the four free OH groups.…”

Large Calixarenes: Synthesis and Properties

“…43 Assignment of the bridging pattern of 16-20 was mainly based on chemical shift of OH groups and chemical correlations. 43 Assignment of the bridging pattern of 16-20 was mainly based on chemical shift of OH groups and chemical correlations.…”