Novel HPPD inhibitors: triketone 2H‐benzo[b][1,4]oxazin‐3(4H)‐one analogs

BACKGROUND Herbicides that inhibit 4‐hydroxyphenylpyruvate dioxygenase (HPPD, EC 1.13.11.27) are very important for grass weed control. In order to discover novel HPPD herbicides, a series of triketone 2 H ‐benzo[ b ] oxazin‐3(4 H )‐one analogs was designed and synthesized. RESULTS In comparison with the commercial triketone HPPD herbicide mesotrione (IC 50 = 0.252 μ M), some of these new triketone analogs displayed excellent HPPD inhibitory potency in vitro , for example B39 (IC 50 = 0.172 μ M) and B41 (IC 50 = 0.156 μ M). In addition, some of these compounds exhibited pre‐ and post‐emergence herbicidal activity similar to mesotrione when applied at 375 g/ha. CONCLUSION Many of the title compounds described in this paper could be important lead structures for the further development of novel HPPD herbicides.