Calix[4]arenes bridged at the lower rim

Calix[41 arenes, in which two opposite p-positions are linked by an aliphatic chain, and their derivatives show transport or complexation properties strongly dependent on the length of this chain. Bicyclo-calix[4]arenes, a special case of 1,3-bridged calix[41 arenes, and annelated calix[41 arenes, a special case of 1 ,&bridged calix [4] arenes, are also described. Although the preferred conformation of calix[4]arenes is the coneconformation due to its stabilization by a cyclic array of hydrogen bonds between the phenolic hydroxyl goups, these molecules are flexible, with a cone to cone inversion rate of about 150 8-1 for a calix[glarene at 47OC (ref. 1). The cone (or any other) conformation…