Synthesis and alkali metal picrate extraction capabilities of novel cage-functionalized 17-crown-5 and 17-crown-6 ethers

The syntheses of three novel cage-functionalized 17-crown-5 and 17-crown-6 ethers, i. e., 10-12, are reported and the results of alkali metal picrate extraction experiments performed by using each of these crown ethers in turn as the extractant are described. Their respective relative extraction efficiencies toward alkali metal picrates were compared with the corresponding efficiencies of 15-crown-5 and benzo-15-crown-5 solutions at the same concentration. The extraction profile of 10 (17-crown-5) toward alkali metal picrates is similar to that of 15-crown-5; however, 10 displays 33% greater avidity toward Na+ picrate. The ability of 11 (benzo-17-crown-5) to extract Li+, Rb+, and Cs+ picrates is similar to that of benzo-15-crown-5. Crown ether 10 is ca. 3 times more effective than 11 toward extraction of K+ picrate. The alkali metal picrate extraction profile of 12 (17-crown-6) resembles that of 10; however, 12 shows enhanced avidity vis-a-vis 10 toward Na+, K+, Rb+, and Cs+ picrates. (C) 1997 Elsevier Science Ltd.