Organic and Biomolecular Chemistry
For functional nitrogen-bridged calix(hetero)aromatic platforms to be further used in the design of more sophisticated receptors, the azacalixarenetriazine nitrogen bridges were functionalised with methyl bromoacetate. Three new macrocycles with four N-methyl ester pendant arms were straightforwardly prepared in good yields from the undecorated azacalixarenetriazine precursors with chlorine, dimethylamine or dihexylamine substituted triazines. These intermediate macrocycles exhibited different reactivity towards the nucleophilic replacement, which was rationalized from the computed electrostatic potential for these molecules. Subsequently, the N-methyl ester appendages were hydrolyzed with each dialkylamine derivative providing a single macrocycle with four carboxylic groups. In contrast, the hydrolysis of the dichlorinated azacalixarene triazine analogue yielded a mixture of three isomeric macrocycles having two N-methyl esters and two carboxylmethyl pendant arms and the triazine chlorine atoms replaced by hydroxyl groups. The coordination ability of two macrocycles with four carboxylic groups for transition metals was evaluated with copper(ii) by UV-vis titrations. © The Royal Society of Chemistry.
Year of publication: 2014