Synthesis and Evaluation of Herbicidal Activity of [4-(2-Nitrobenzyl)piperazin-1-yl](phenyl)methanone Derivatives

A series of novel [4-(2-nitrobenzyl)piperazin-1-yl](phenyl)methanone derivatives containing piperazine structures were designed and synthesized. (3,7-Dichloroquinolin-8-yl)[4-(2-nitrobenzyl)piperazin-1-yl]methanone was selected to confirm the spatial structure through X-ray diffraction. Herbicidal activity of the target compounds was evaluated against the pre-emergence of Echinochloa crusgalli L., Lolium perenne L., Amaranthus retroflexus L. and Lactuca sativa var. ramosa Hort. Herbicidal activity of compounds with different substituent on the phenyl followed an order of magnitude that was given as: donor-drawing group > neutral group > electron-drawing group on Lactuca sativa var. ramosa Hort. (2,3-Dimethylphenyl)[4-(2-nitrobenzyl)piperazin-1-yl]methanone showed stronger herbicidal activity against the pre-emergence of Echinochloa crusgalli L. and Lolium perenne, while (2-chlorophenyl)-[4-(2-nitrobenzyl)piperazin-1-yl]methanone showed stronger herbicidal activity against Amaranthus retroflexus L. and Lactuca sativa var. ramosa Hort.