Synthesis of Methylene-bridged Cyclic Resorcinol Oligomer

Abstract

A convenient synthesis of methylene-bridged cyclic resorcinol oligomer (calix[4]resorcinarene) was reported. First, calix[4]resorcinarene octamethyl ether was prepared by the HCl-catalyzed condensation of 1, 3-dimethoxybenzene with paraformaldehyde in ethylene glycol monoethyl ether. The methoxy group was easily converted to hydroxy group by treatment with BBr₃ in chloroform. In ¹H NMR spectra, each proton signal of these compounds is singlet. A novel ionophore based on calix[4]resorcinarene octaester was prepared. The ionophore showed higher affinity for larger alkali cations, K⁺, Rb⁺ and Cs⁺, than for smaller ones, Na⁺ and Li⁺. The ionophore based on C-methylated calix[4]resorcinarene, which was synthesized from resorcinol with acetaldehyde, on the contrary, did not bind alkali cations.