Synthetic ionophores. Part 4. Phase transfer-catalysed synthesis of pyridine-containing macrocycles and their ionophore character
Abstract
Phase transfer-catalysed reactions of pyridine-2,6-dicarboxylic acid dichloride and 2,6-dichloropyridine with oligo(ethylene glycols) provide macrocycles in yields higher than those reported by high dilution or transesterification methods. Extraction and transport studies of some of these macrocycles towards picrates of Li+ Na+, K+, Tl+, Mg2+, Ca2+, and Ba2+ by using chloroform as the nonpolar layer showed that two examples, the pyridino crown ethers (3a) and (5b), transport barium and thallium picrates respectively with significant selectivity.