Synthesis and phase-transfer catalytic activity of novel chiral crown ethers immobilized onto polystyrene supports

Abstract

Polymer-supported novel optically active crown ethers were prepared by the reaction of chiral crown ethers derived from L-(+)-tartaric acid and 4-chloromethylated polystyrene resins crosslinked with 2 mol% of divinylbenzene. The ring substitution which indicates percentages of functionalized unit of the obtained polymers was in the range of 12–33%. The phase-transfer catalytic activity of the polymer-bound crown ethers has been studied on the reaction of 1-halo-octane with NaI or KI under liquid/liquid/solid tri-phase conditions. The catalyst with 18-crown-6 unit exhibited higher activity than the catalyst with 15-crown-5 unit. The activity of the catalyst with 18-crown-6 moiety for the reaction of 1-chloro-octane with KI was independent of catalyst particle size and increased with decreasing the degree of ring substitution, and the reaction rates were considered to be controlled only by the intrinsic reactivity at active site. On the other hand, the activity for the reaction of 1-bromo-octane with KI were dependent on catalyst particle size and exhibited maximum near 15–20% ring substitution, and the reaction rates were concluded to be limited by both the intrinsic reactivity and the intraparticle diffusion of reactants. The recovered catalyst could be reused repeatedly without a decrease in the activity.