The design of cone-fixed calix[4]arene analogs by takingsyn-[2.n]metacyclophanes as a building block

Rigidified calix4]arene analogs were synthesized fromsyn-2.n]metacyclophanes as a building block. Their structure was firmly locked in the cone conformation. An enlarged calix4]arene analog was obtained after the cyclobutane ring cleavage of the parent analog by Birch reduction. Several ionophores have been derived from the analogs and been found to select the larger ions during the extraction of alkali metals, transition metals, and lanthanoids. The ionophore having oligoethylene glycol units showed an effective catalytic activity for S_N2 reactions such as ester synthesis, Williamson ether synthesis, and Finkelstein reaction in several media.This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes.