Synthesis and Protoporphyrinogen Oxidase Activity Inhibition of 3-(4-Chloro-2-fluoro-5-substituent-phenyl)-7-methyl-3H-pyrazolo[3,4-d] [1,2,3]triazin-4(7H)-ones

In order to find new protoporphyrinogen oxidase inhibitors, a series of novel 3H-pyrazolo-[3,4-d][1,2,3]triazin-4-one derivatives were designed and synthesized according to biorational design. The target molecules were synthesized by diazotization of different 5-amino-N-phenyl-1H-pyrazole-4-carbox-amide derivatives prepared by a reaction of substituted 5-amino-pyrazole-4-carbonyl chloride with substituted anilines. Different halides were reacted with 3f to afford the pure target products 3g similar to 3w respectively. Their structures were identified by H-1 NMR, IR spectra and elemental analyses. The bioassay results showed that some of the title compounds exhibited high inhibition against protoporphyrinogen oxidase activity in vitro. The structure-activity relationship was discussed.