Novel Functionalized Symmetrical Dibenzosulfoxo-Crown Ethers with High Selectivity for Pb^2+, K^+, and Ba^2+

A new series of crown ether-based macrocycles bearing two hydroxyl groups and a dibenzosulfoxide moiety was synthesized. These symmetrical dibenzosulfoxo- (aza)-crown ethers were synthesized by the reaction of an active symmetrical bisepoxide pod and with diol reagents in the presence of sodium hydride as a strong base and dry tetrahydrofuran as the solvent. In fact, the reaction begins with the opening of the epoxide rings via the nucleophilic attack (SN2) of dialkoxide and ends with the formation of a macrocyclic ring. The final compounds were characterized by FT-IR, 1H NMR, 13C NMR, and FAB-MS spectroscopic methods. They were evaluated for their extraction ability and selectivity for various metallic cations in the form of picrate salt in dichloromethane solvent at room temperature. The new macrocycles showed good extraction ability especially for Pb^2+ (72%), K+ (66%), and Ba^2+ (56%) among the used cations, for 3b, 3c, and 3a respectively. Compound 3b (dibenzosulfoxo-20-aza-crown-4-ether) showed the excellent selectivity for Pb^2+ (72%).