1.3.4- Thiadiazole substituents, highly activated

The activation in the orthoquinonoid structure (669) from the fusion of 1,2,5-thiadiazole makes the 7-chlorine substituent diplaceable under solvolytic conditions in aqueous acetic acid (70RTC5). The high activation is also manifested in the ease of halogen hydrolysis in the fused pyrazine (670) (75JHC451). 

Through structure-activity correlation studies with the new oxyacetamide substances, only 1,3,4-thiadiazole derivatives with specified substituents provided high herbicidal activity. Requisite properties of the compound for selection were (1) very good efficacy against grassy weeds, (2) very good compatibility for maize and soybeans, and (3) suitable water solubility (56 mg at 25 °C). Based on these results, flufenacet (FOE 5043 Fig. 8.1) was selected and developed as a second-generation heteroxyacetamide class for use as an upland herbicide. 

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