Synthesis, Characterization and Antimicrobial Activity of Some Novel Quinoline Derivatives Bearing Pyrazole and Pyridine Moieties

Abstract

In continuation of our interest in synthesis of novel quinoline derivatives with anticipated biological activity, we have synthesized new quinoline derivatives bearing pyrazole and pyridine moieties by formylation of quinoline hydrazones through the Vilsmeier-Haack reaction which is a common method for the synthesis of 4-formyl pyrazoles. Condensation of 2-hydrazinylquinoline 1 with 4-substituted acetophenone gave the corresponding hydrazones 2a–c which in turn underwent the Vilsmeier-Haack reaction in POCl3/DMF to furnish the corresponding 4-formyl pyrazole derivatives 3a–c. One-pot reaction of compounds 3a–c with malononitrile and thiophenol or ethyl mercaptan gave the 3,5-pyridinedicarbonitrile derivatives 11a–f. The synthesized derivatives were screened for their antimicrobial activities against Gram negative bacteria, Gram positive bacteria and fungi. Most of compounds showed excellent antimicrobial activities compared to the reference drugs. All the newly synthesized compounds have been characterized by means of elemental analyses, IR, 1H-NMR and MS.