New Calix[4]arene Dibenzocrown Ethers for Selective Sensing of Cesium Ion in an Aqueous Environment

1,3-Dialkoxycalix[4]arene dibenzocrown ethers (6-9) were successfully synthesized in the fixed 1,3-alternate conformation, with greater than 90% yields by reaction of the corresponding 1,3-dialkoxycalix[4]arenes 2-5 with dibenzodimesylate 13 in acetonitrile as a solvent in the presence of cesium carbonate as a base. In view of the cyclization yield, dimesylate is better than dibenzoditosylate. Because of an unusual AB pattern in the ¹H NMR spectrum for compound 9, it is suggested that the conformational structure of 1,3-diallyloxy calix[4]arene dibenzocrown ether is less flexible than that of usual 1,3-alternate calixcrown ether, probably due to steric effects of two allyl groups. Complexation of the corresponding calix[4]arene ethers 6-9 to alkali metal ions using the single-flux method through a bulk liquid membrane system was found to give high cesium selectivity.