Synthesis of Novel Azamacrocyclic Metal Ion Receptors Using a Modified Mannich Aminomethylation Reaction

A modified Mannich aminomethylation reaction was used to prepare a series of N-substituted-phenol-containing azacrown ether ligands. Ligands synthesized include aza-15-crown-5, aza-18-crown-6, azapyridino-18-crown-6, diaza-18-crown-6, diaza-21-crown-7 and diaza-24-crown-8 containing various substituted phenols, salicylaldehyde, and 5-chloro-8-hydroxyquinoline (CHQ) groups as side arms. The modified Mannich reaction was also used to prepare bi- and tricyclic azamacroheterocycles containing phenol units, benzoazacrown ethers, benzocryptands, and cryptohemispherands. The phenol- and CHQ-substituted azacrown ligands interact more strongly with metal ions than do the parent unsubstituted azacrown ethers. Bis-CHQ-substituted diaza-18-crown-6, wherein the CHQ groups are attached through their 7 positions, are particularly selective for K^+ over other alkali metal ions and for Ba^(2+) over all other metal ions studied.