Synthesis and characterization of new 3,5-dinaphthyl substituted 2-pyrazolines and study of their antimicrobial activity

Abstract

A number of chalcones were prepared by condensing either 1-acetylnaphthalene or substituted 1-acetylnaphthalenes with 1-naphthaldehyde or 4-dimethylamino-1-naphthaldehyde in ethanolic NaOH solutions. These chalcones were immediately reacted with hydrazine hydrochloride, phenyl hydrazine and semicarbazide hydrochloride in the presence of dry acetic acid to obtain the corresponding 2-pyrazolines. The synthesised heterocycles were characterized on the basis of their chemical properties and spectroscopic data. These compounds were tested for antimicrobial activity against a variety of test organisms: Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Proteus mirabillis, Shigella dysentry and Salmonella typhii. The compounds containing chloro, hydroxo and dimethylamino - N(CH3)2 group as substituents on the naphthalene rings have been found to be very effective antimicrobial agents. In addition, the presence of a carboxamido -CONH 2 substituent group at the N-1 position of the 2-pyrazoline rings is shown to contribute substantially to the antimicrobial activity.