Five new 5,7-disubstituted-2-(2,4-dichlorophenoxyacetylimino)-2H-1,2,4-thiadiazolo[2,3-a]pyri~mi~di~nes were synthesized, and their structures were confirmed by ¹H NMR andelemental analysis. Biological test showed that some of the target compounds displayed herbicidal activity to some extent. In order to investigate the relationship between the structure of these compounds and their herbicidal activities, acrystal structure of the target compound 5bwas determined by X-ray diffraction analysis.

Key words: 2H-1,2,4-thiadiazolo[2,3-a]pyrimidines, 2,4-dichlorophenoxyacetylimine, crystal structure, synthesis, herbicidal activity