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A series of 2-(3-(trifluoromethyl)-5-(alkoxy)-1H-pyrazol-1-yl)-4-aryloxypyrimidine derivatives were designed and synthesized. The structures of all the title compounds were confirmed by 1H NMR and elementary analysis. These compounds were screened for herbicidal activity against rape and barnyard grass. Compound B13 exhibited moderate herbicidal activity.

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.

Ethyl 5-amino-3-trifluoromethyl-1H-pyrazole-4-carboxylate (1) was efficiently synthesized via the condensation of ethyl cyanoacetate and trifluoroacetic anhydride, followed by chloridization and the condensation with aqueous hydrazine. Its unique reactivity was exploited for the synthesis of trifluoromethylated pyrazolo[1,5-a]pyrimidine (5) and pyrazolo[5,1-d][1,2,3,5]tetrazine-4(3H)-ones (8a–j). Among them, 5 was firstly found to be a novel fluorescent molecule that might be exploited as an attractive fluorophore for possessing many binding sites, and its fluorescence intensity was obviously stronger than its methyl analogue. 8 were found to be a new chemical class of potential monocotyledonous Echinochloa crus-galli L. Beauv inhibitors, and were more active than their methyl analogues.

A series of novel sulfone-containing pyrazolo[1,5-a]pyrimidines (2-3) and pyrazolo[5,1-d][1,2,3,5]tetra-zine-4(3H)-ones (5a-5k) were designed and efficiently synthesized, some of which have been identified as being potential rape inhibitors. These results widen the structural diversity of rape inhibitors and confirm the perspectives of further investigations in this area. Moreover, a plausible reaction mechanism is outlined.