New macrocyclic ligands.: VIII -: Di- and tri-linked macrocyclic systems incorporating N2O2-donor atoms

The synthesis and characterization of new lipophilic di- and tri-linked O2N2-donor macrocycles is reported. The synthesis of the dilinked species involved the initial alkylation of one secondary nitrogen of the parent 15-membered, O2N2-donor macrocycle (1) with 2-bromoethanol or with ethylene oxide to yield (2), followed by protection of the appended alcohol group by reaction with t-butyldiphenylsilyl chloride to give (3). Two such moieties were then bridged via a diacylation reaction with ClCO(CH2)(8)COCl to yield the corresponding diamide product (4). Deprotection of the alcohol functions followed by reduction of the both amide linkages resulted in formation of the N,N'-alkyl-linked species (5) incorporating two pendant hydroxyethyl groups. This product was then converted [via the corresponding dichloro derivative (6)] into the diether (7) by condensation with 4-t-butylphenol. By use of analogous chemistry, the trilinked trismacrocycle species (12), based on a phloroglucinol core, has also been synthesized. An aim of the present study was thus the preparation of new 'linked' macrocyclic systems that might be expected to show higher lipophilicity than their corresponding single-ring systems. These were designed for future use as ionophores in metal ion membrane transport (and solvent extraction) experiments.