endo-Cavity Complexation and Through-the-Annulus Threading of Large Calixarenes Induced by Very Loose Alkylammonium Ion Pairs

A general mode to obtain endo-complexation and through-the-annulus threading of scarcely efficient macrocyclic hosts was obtained by exploiting the inducing effect of the weakly coordinating tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (TFPB) anion that gives free naked cations. This method works very well with simple, conformationally mobile calix[6-7]arene ethers, which give conformationally blocked endo-calix or [2]pseudorotaxane complexes.