An Efficient One-Pot Synthesis of 2-(Aryloxyacetyl)cyclohexane-1,3-diones as Herbicidal 4-Hydroxyphenylpyruvate Dioxygenase Inhibitors.

4-Hydroxyphenylpyruvate dioxygenase (EC 1.13.11.27, HPPD) is an important target for new bleaching herbicides discovery. As a continuous work to discover novel crop selective HPPD inhibitor, a series of 2-(aryloxyacetyl)cyclohexane-1,3-diones were rationally designed and synthesized by an efficient one-pot procedure using N,N'-carbonyldiimidazole (CDI), triethylamine, and acetone cyanohydrin in CHCl. A total of 58 triketone compounds were synthesized in good to excellent yields. Some of the triketones displayed potent in vitro Arabidopsis thaliana HPPD (AtHPPD) inhibitory activity. 2-(2-((1-Bromonaphthalen-2-yl)oxy)acetyl)-3-hydroxycyclohex-2-en-1-one, II-13, displayed high, broad-spectrum, and postemergent herbicidal activity at the dosage of 37.5-150 g ai/ha, nearly as potent as mesotrione against some weeds. Furthermore, II-13 showed good crop safety against maize and canola at the rate of 150 g ai/ha, indicating that II-13 might have potential as a herbicide for weed control in maize and canola fields. II-13 is the first HPPD inhibitor showing good crop safety toward canola.