Complexation of alkali metal cations by conformationally rigid, stereoisomeric calix[4]arene crown ethers: a quantitative evaluation of preorganization

Abstract

Selective bridging of p-tert-butylcalix[4]arene (1) with tetra- and pentaethylene glycol ditosylate gives the 1,3- dihydroxy-p-tert-butylcalix[4]arene crown ethers 7 and 9 in good yields. The subsequent alkylation of the two phenolic groups of 7 and 9 with substituents (R) bulkier than CH 3 gives a series of conformationally rigid 1,3-dialkoxy-p-tert-butylcalix[4]arene crown ethers.