Abstract: A series of novel N-[(1-aryl-3-phenyl-pyrazol-4-yl)methylene]-2-hydroxybenzohydrazide derivatives were designed and synthesized by combining o-hydroxyl phenyl and phenyl pyrazole with hydrazone bond, according to the superposition principle of biological activities. Six compounds are all novel. Substituted aniline was diazotized and subsequently reduced to give substituted phenylhydrazine, acetophenone arylhydrazone were obtained by the condensation of acetophenone with substituted phenylhydrazine. 1-Aryl-3-phenyl-4-formylpyrazoles were obtained with N,N-dimethylformamide and phosphorus oxychloride, which was reacted with salicylic hydrazide to get the title compounds. The structures of all title compounds were confirmed by ¹H NMR, IR and elemental analysis. The reaction mechanism of acquiring 3a—3f show that catalytic reaction activity is enhanced by electron-donating groups of the first phenyl ring, but reduced by electron-withdrawing groups of the first phenyl rings. The result of preliminary bioassay show that the inhibitory rate against Monilia albican and Escherichia coli of the title compounds can be high to 100% at 0.01% mass fraction, inhibitory rate against Staphlococcus aureus is over 70%. They will be a series of potential antibacterial compounds against fungi and gram-negative bacteria. The analysis of structure-activity relationship show that the antibacterial activities of title compounds are enhanced by the halogen groups of the phenyl ring, but reduced by electron-donating and electron-withdrawing groups of the phenyl ring, such as NO₂ and CH₃.

Key words: N-[(1-Aryl-3-phenyl-pyrazol-4-yl)methylene]-2-hydroxybenzohydrazide, Derivative, Antibacterial-activity