Regioselective bridging of calixarenes - Syntheses, structural elucidationand extraction studies of 1,2-calix[n]dioxocrowns (n=6, 8)

A series of eater-containing 1,2-bridged calix[n]crowns (n = 6,8) have been synthesized in reasonable yields by treating p-tert-butylcalixarenes with oligoethylene glycol bischloroacetates in the presence of K2CO3. It was fou nd that K2CO3 not only acts as a weak base, but also plays the role of temp late. The template effect is based on the formation of a real active specie s derived from the bischloroacetates and K+. The longer spacer in bischloro acetates shows the stronger template effect and gives the higher yield. The extraction ability towards alkali metals and ammonium cations of the obtai ned 1,2-calix[6]dioxocrowns are superior to that of 1,2-calix[8]crown-5. Th e complexation abilities of calix[8]crowns are studied for the first time.