Eighty-four 3-[(substituted phenylamino)carbonyl]-2-pyrazinecarboxylic acids (3) and the same numbers of N-(substituted phenyl)pyrazine-2, 3-dicarboximides (4) were synthesized starting from various substituted anilines and 2, 3-pyrazinedicarboxylic anhydrides prepared by the condensation of diaminomaleonitrile with 1, 2-diketones, and examined for biological activities. Five compounds of 4 showed certain protective activity against rice bacterial leaf blight and eight compounds of 4 protective activity against rice blast.
All dialkyl 1,3-dithiolan-2-ylidenemalonates examined are considerably stable in rice plants, showing their t1/2 of 2.0-3.8 days. A non-cyclic analog with the t1/2 of 0.8 day, however, is rapidly metabolized probably through the oxidation at its thioether groups. Although the rat liver homogenate has both oxidation and hydrolysis activities, it shows predominantly the esterase activity in the absence of NADPH. In the rat liver homogenate, again, the non-cyclic analog is much more susceptible to oxidative metabolism in the presence of NADPH than, but as stable against the ester hydrolysis as the cyclic counterparts. The ester hydrolysis rates of the compounds well relate to the branching(s) at the ce-position or the resulting electronic (o*) or steric (ECS) effects of alcoholic alkyl groups.
Abstract:Fifteen pyrazino [2, 3-d] pyridazines were prepared by condensing four kinds of 2, 3-disubstituted pyrazinedicarboxylic anhydrides with hydrazine, methylhydrazine, phenylhydrazine and dimethylhydrazine.The condensates underwent chemical modifications and additional reactions to four kinds of dicyanopyrazines with hydrazine to prepare total thirty-two compounds, which were examined for pesticidal activity. Among them 2-phenyl-5, 8-diacetoxypyrazino [2, 3-d]pyridazine showed protective activity against downy mildew of cucumber.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.