Synthesis and anion binding behaviour of diamide derivatives of pyrrole-2,5-diacetic acid

Abstract

Four examples of bis-amidopyrrole derivatives of pyrrole-2,5-diacetic acid have been prepared. The reaction of diethyl pyrrole-2,5-diacetate with a large excess (24 equiv.) of N,N-dimethylethylenediamine gave N,N′-bis(2-dimethylaminoethyl)-1H-pyrrole-2,5-diacetamide (1). Three further examples, N,N′-bis[2-(2-pyridyl)ethyl]-1H-pyrrole-2,5-diacetamide (2), N,N′-bis(2-pyridylmethyl)-1H-pyrrole-2,5-diacetamide (3) and N,N′-dibenzyl-1H-pyrrole-2,5-diacetamide (4), were prepared in a one pot procedure by converting pyrrole-2,5-diacetic acid into the N-hydroxysuccinimide ester and then reacting this with four equivalents of the appropriate amine, 2-(2-aminoethyl)pyridine, 2-aminomethylpyridine or benzylamine, respectively. Compounds 1–4 are shown to be effective anion receptors in acetonitrile-d₃ solution, with comparable binding affinities to those found for simple pyrrole-2,5-dicarboxamides, despite possessing a more flexible hydrogen bonding array.