Synthesis of Unique Cagelike Thiacalix[4]arene Derivatives in a 1,3-Alternate Conformation

A novel type of doubly bridged thiacalix[4]arenes in the 1,3-alternate conformation has been prepared by direct aminolysis reaction of easily accessible thiacalix[4]arene tetraacetates
with α,ω-diamines. Despite the high excess of diamine, both
sites of a 1,3-alternate conformer can be intramolecularly
bridged to form the cagelike structures in high yields.
Optimum results were obtained using 1,2-ethanediamine as
bridging units. X-ray analysis of the novel cagelike molecules
revealed a highly preorganized array of −C(O)−NH− bonds
pointing to the interior of the cavity.