O-Phosphorylated calix[4]arenes as Li+-selective receptors

Phosphorylation of p-tert-butylcalix[4]arene 9 or calix[4]arene 10, having two diethoxyphosphoryl groups at distal positions on their narrow rim (phen olic oxygen atoms), by dibutyloxophosphinechloride or alkylation of 10 by m ethyl bromoacetate led to the corresponding tetrasubstituted calix[4]arenes 8b-d fixed in a cone conformation. The latter compounds and the similar de rivative of calix[4]arene 8a with four diethoxyphosphoryl groups were found to exhibit lithium cation selectivity, which was supported by UV-Vis spect ra of THF solutions of the alkali metal picrates and their water-chloroform extraction in the presence of ligands 8a-d. Calculated Ka(Li+)/Ka(Na+) sel ectivities range from 2.9 (8d) to 9.5 (8a), which are among the highest Val ues for the calixarene-based Li+- selective receptors reported to date. Cop yright (C) 2001 John Wiley & Sons, Ltd.