Unusual cone conformation retention in calix[4]arenes

Use of a regioselective O-alkylation, C-dealkylation synthetic sequence generates an ‘ABAB’ calix[4]arene, 4, which contains only two upper rim t-butyl groups and yet retains the cone conformation. Further substitutions can then be carried out independently on the upper and/or lower rims of the A and/or B subunits, with retention of conformation. Complexation studies show that 4 retains its cone conformation in the presence of alkali metals from sodium to cesium. Thus 4 remains in the cone conformation in solid state, in solution and on complexation.