Cyclization of p-tert-Butylcalix[6]arene with Diols Under the Mitsunobu Protocol. A Conformational Study of the Peralkylated Derivatives

p-tert-Butylcalix[6]arene was attempted to O-alkylate with alcohols and diols under the Mitsunobu protocol. Regio-and conformation-selective reactions were not observed with alcohols and oligoethylene glycols, but 1,6-hexaneand 1,8-octanediols effected cone-selective A,D-bridging. Exhaustive alkylation of the remaining four OH groups in a cyclized molecule was carried out under base-promoted conditions and the conformation of the products along with the metal ion binding properties were studied by NMR methods.