Synthesis, crystal structure and herbicidal activity of 5,7-disubstituted-2-(2,4-dichlorophenoxyacetylimino)-2H-1, 2,4-thiadiazolo[2,3-a] pyrimidine derivatives

Five new 5,7-disubstituted-2-(2,4-dichlorophenoxyacetylimino)-2H-1,2,4-thiadiazolo[2,3-a]pyrmidines were synthesized, and their structures were confirmed by H-1 NMR and elemental 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, a crystal structure of the target compound 5b was determined by X-ray diffraction analysis.