Unusual thermodynamic stabilities of the four conformers of tetraacetoxy-p-tert-butylcalix[4]arene

Abstract

The relative stability of four conformers of tetraacetoxy-p-tert-butylcalix[4]arene 2 is determined by ¹H NMR spectroscopy; the four conformers are not flexible in Me₂SO at room temperature, but equilibrate at a higher temperature into a mixture with relative stability in the order 1,3-alternate (most stable) > 1,2-alternate > partial cone > cone (most unstable).