Synthesis and alkali metal picrate extraction studies of lower rim functionalized p-tert-butylcalix[4]arene crown ethers

Abstract The syntheses of four new calix[4]arene receptors, i.e. 4 – 7 , each of which contains an oxahexacyclic cage moiety, are reported. The structures of two of these receptors, i.e. 4 and 7 , have been established via single crystal X-ray structural analysis. The complexation properties of 4 – 7 were determined via a series of alkali metal picrate extraction experiments. Two of the cage-functionalized calix[4]arene-crown-5 hosts, i.e. 4 and 5 , display somewhat greater extraction avidity toward Na + picrate vis-a-vis the remaining alkali metal picrates. By way of contrast, host systems 6 and 7 function effectively as a moderately selective K + extractants and display significantly increased extraction avidity toward K + picrate vis-a-vis 4 and 5 .