Abstract: In search of safe and more efficacious herbicidal compounds,nine novel derivatives of N-(7-fluoro-3-oxo-3,4-dihydro-2H-benzo oxazin-6-yl) acetamide were prepared from the reaction of 2-substitued acetyl chloride with the corresponding 2H benzo oxazine-3-one. Their chemical structures were confirmed by elemental analysis, IR and 1H NMR. The primary bioassay results showed that 5d exhibited control efficacy of more than 90% against Amaranthus spinosus at 75 g a.i./hm2.