Synthesis of cone, partial-cone, and 1,3-alternate 25,27-bis[1-(2-ethyl)hexyl]- and 25,27-bis[1-(2-tert-butoxy)ethyl]calix[4]arene-crown-6 conformersas potential selective cesium extractants

The preparation of 25,27-bis [1-(2-ethyl)hexyl]- and 25,27-bis [1-(2-tert-b utoxy)ethyl]calix[4]arene-crown-6 combining one polyether crown-6 and one a lkylchain O-attached on each side of a calix[4]arene in the cone, partial-c one, and 1,3-alternate conformations are reported. The control over 25,27-b isalkylcalix[4]arene-crown-6 conformation via varying specific reaction con ditions was studied. The series of calix[4]arenes have been prepared by two routes, which differ in the order in which the alkyl or polyether groups w ere introduced. Moreover, methods have been developed to selectively prepar e the cone and partial-cone conformers by using an appropriate base in the alkylation reactions. The conformations of these new derivatives have been probed by H-1:NMR analysis and X-ray crystallography. The H-1 and C-13 NMR spectra of 25,27-bis[1-(2-ethyl)hexyl]calix[4]arene-crown-6, 1,3-alternate 1, cone 2, and partial-cone 3 are also discussed.