Synthesis Candidates Herbicide Through Optimization Quinclorac Containing 3-Methyl-1H-pyrazol-5-yl

Dingfeng Luo; Haodong Bai; Xiaomao Zhou; Lamei Wu; Chengjia Zhang; Zhongchi Wu; Zuren Li; Lianyang Bai

doi:10.3389/fchem.2021.647472

Synthesis Candidates Herbicide Through Optimization Quinclorac Containing 3-Methyl-1H-pyrazol-5-yl

Front Chem. 2021 Apr 14:9:647472. doi: 10.3389/fchem.2021.647472. eCollection 2021.

Authors

Dingfeng Luo^{1

2}, Haodong Bai², Xiaomao Zhou^{1

2}, Lamei Wu², Chengjia Zhang², Zhongchi Wu², Zuren Li^{1

2}, Lianyang Bai^{1

2}

Affiliations

¹ Long Ping Branch, Graduate School of Hunan University, Changsha, China.
² Hunan Provincial Key Laboratory for Biology and Control of Weeds, Hunan Academy of Agricultural Sciences, Changsha, China.

Abstract

To enhance quinclorac potency, twenty-five derivatives were synthesized containing 3-methyl-1H-pyrazol-5-yl by intermediate derivatization methods (IDMs). These compounds were confirmed by melting point (mp), ¹HNMR, ¹³CNMR, and HRMS. The compound 1,3-dimethyl-1H-pyrazol-5-yl 3,7-dichloroquinoline-8-carboxylate (10a) was determined by X-ray diffraction. The activity of these compounds substituent on the phenyl was: electron-drawing group > neutral group > donor-drawing group, the results was like that of substituted benzyl group on pyrazole. The herbicidal activity assays showed that compounds 1-(2-fluorophenyl)-3-methyl-1H-pyrazol-5-yl 3,7-dichloroquinoline-8-carboxylate (8l, EC₅₀ = 10.53 g/ha) and 10a (EC₅₀ = 10.37 g/ha) had an excellent inhibition effect on barnyard grass in greenhouse experiment. Greenhouse safety experiment of rice exhibited almost no difference in plant height and fresh weight treated 10a at stage 1∼2-leaf of rice after 14 days but 8l had a detrimental effect. Two season field assays showed 10a herbicidal activity on barnyard grass at 150 g/ha as equal as 300 g/ha quinclorac in fields in 2019 and 2020. The study demonstrated that 10a could be further researched as a potential herbicide to control barnyard grass in fields.

Keywords: barnyard grass; field assay; herbicidal activity; intermediate derivatization methods (IDMs); quinclorac.