Condensation and substitution products obtained in reactions of isomeric bromo-nitrofuraldehydes with ferrocenylamine: Electrochemistry and anti-parasitic evaluation

The reaction of 5-bromo-4-nitrofuraldehyde (4-NO2) with (η5-C5H4NH2)Fe(η5-C5H5) produces the Schiff base [(η5-C5H4)-NCH-(Br-NO2-2-C4HO)]Fe(η5-C5H5) (1a) as a condensation product and the amine complex [(η5-C5H4)-NH-(CHO-NO2-2-C4HO)]Fe(η5-C5H5) (1b) as a substitution product in a 1:4 ratio, whereas the reaction between 4-bromo-5-nitrofuraldehyde (5-NO2) and (η5-C5H4NH2)Fe(η5-C5H5) generates only the iminic derivative (2a). The structures of all the complexes were inferred from their FT-IR, 1H NMR, 13C NMR and mass spectra. The molecular structure of the ferrocenylamine (1b) determined by X-ray crystallography showed an unusual intramolecular H-bond (N-H⋅⋅⋅O), an [(η5-C5H4)-NH-(CHO-C4HO-NO2)] planar system, and an sp2-type hybridization on the amine nitrogen. Cyclic voltammetry study of 5-nitrofuran derivative 2a, exhibits a more anodic reduction potential (E½ = −0.60 V) compared with those registered for 1a (E½ = −1.03 V) and 1b (E½ = −1.14 V). All compounds were tested for their anti-parasitic activity against the tripomastigote form of the Dm28c strain of T. cruzi.