Schiff Base Macrocycles Containing Pyrroles and Pyrazoles

摘要

A double nucleophilic substitution reaction of 3,5-bis(chloromethyl)pyrazole with pyrroles generates a novel pyrroleCpyrazole hybrid building block, the pyrazole analogue to tripyrrane. VilsmeierCHaackformylatio n produces the corresponding dialdehyde, which was used in the formation of a series of nonaromatic Schiff base macrocycles. NMR and UV/Vis spectroscopy and single-crystal diffractometry were used to characterize the novel macrocycles. The solid-state structures of select free bases and protonated members of this class of macrocycles display a range of intra- and intermolecular hydrogen-bonding patterns that suggest their use in molecular-recognition systems. They also contain an acidsensitive chromophore. Their acidCbase and anion-recognition properties were ascertained; alas, only modest anion-selective spectroscopic signatures could be detected by using UV/Vis and 1H NMR spectroscopy. The macrocycles proved resistant toward oxidation to their aromatic congeners. The pyrroleCpyrazole building blocks presented are potentially useful for the synthesis of a range of pyrazole analogues of all-pyrrole macrocycles.