Antimicrobial ferrocene containing quinolinones: Synthesis, spectral, electrochemical and structural characterization of 2-ferrocenyl-2,3- dihydroquinolin-4(1H)-one and its 6-chloro and 6-bromo derivatives

Abstract

Syntheses of three new ferrocene containing heterocycles - 2-ferrocenyl-2,3-dihydroquinolin-4(1H)-one and its 6-chloro and 6-bromo derivatives - starting from 2-aminoacetophenones and ferrocenecarboxaldehyde was achieved in two steps. The aldol condensation of these substrates gave the corresponding 2′-aminochalcones in the first stage, whereas a further intramolecular cyclization gives the final products. This cyclization was performed by either a solvent-free microwave irradiation (500 W/5 min) of a mixture of chalcones and mortmorillonite K-10 or by using an acidic catalyst (the mixture of acetic and orthophosphoric acid). The latter method, which can be performed by simple stirring at room temperature or by irradiation in an ultrasonic bath, gave much better results. The obtained compounds were spectrally and electrochemically (cyclic voltammetry) fully characterized, as well as by single-crystal X-ray analysis. A microdilution assay revealed that the three dihydroquinolinones can be regarded as potential lead compounds in the discovery of new antimicrobial drugs due to their very strong and unselective activity towards pathogenic bacteria and one yeast with MIC values (0.01-10.0 μg/mL) lower than that of tetracycline. © 2011 Elsevier Ltd. All rights reserved.