Design, Synthesis and Biological Evaluation of Novel 6,7,8,9-Tetrahydro-2-(2-aryloxypyrimidin-4-yl)-2H-[1,2,4]triazolo [4,3-a]azepin-3(5H)-ones

A series of novel 6,7,8,9-tetrahydro-2-(2-aryloxypyrimidin-4-yl)-2H-[1,2,4]triazolo[4,3-a]azepin-3(5H)-ones were designed and efficiently synthesized. Their structures were determined by IR, 13C and 1H NMR, mass spectroscopy, and elemental analysis. These compounds were screened for herbicidal activities against rape and barnyard grass. Compounds 5a-5f and 5m exhibited moderate herbicidal activity against rape. In addition, the synthesis of the intermediate 1-(azepan-2-ylidene)-2-(2-chloropyrimidin-4-yl)-hydrazine (3) was studied and the reason for the low yield in the initial procedure is discussed as well.