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Chemistry and Industry of Forest Products ›› 2020, Vol. 40 ›› Issue (3): 76-84.doi: 10.3969/j.issn.0253-2417.2020.03.010

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Synthesis and Herbicidal Activity of Citral-based Thiosemicarbazone Compounds

Yun HE1,Wengui DUAN1,*(),Guishan LIN1,Bo CEN1,Junwen BU1,Fuhou LEI2   

  1. 1. School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004, China
    2. Guangxi Key Laboratory of Chemistry and Engineering of Forest Products, Nanning 530008, China
  • Received:2020-01-14 Online:2020-06-28 Published:2020-06-29
  • Contact: Wengui DUAN E-mail:wgduan@gxu.edu.cn

Abstract:

Twenty-six novel citral-based thiosemicarbazone compounds 2a-2m (thirteen pairs of (2Z, 1E)/(2E, 1E)-isomers) were designed and synthesized in an attempt to develop potent herbicidal agents. The structures of the target compounds were characterized by FT-IR, NMR, and ESI-MS. The herbicidal activities of the target compounds were preliminarily evaluated in vitro against Brassica campestris and Echinochloa crusgalli. The bioassay results indicated that compounds (2Z, 1E)-2a (R=Me), (2E, 1E)-2a (R=Me), (2Z, 1E)-2b (R=Et), (2E, 1E)-2b (R=Et), and (2E, 1E)-2c (R=i-Pr) displayed inhibition rates of 82.6%, 88.7%, 80.2%, 80.5% and 82.0%, respectively, against the root-growth of rape (Brassica campestris) at the concentration of 100 mg/L. They were much better herbicidal activity than the commercial herbicide flumioxazin. It was found that the herbicidal activity of the compounds with aliphatic groups (R) was much better than that of the compounds with aromatic groups (R), and the (2E, 1E)-isomers bearing aliphatic groups (R) exhibited better inhibition activity than corresponding (2Z, 1E)-isomers, whereas the (2Z, 1E)-isomers bearing aromatic groups (R) showed better inhibition activity than their (2E, 1E)-isomers. The electrostatic potential and the frontier molecular orbitals of the best activity compound (2E, 1E)-2a were calculated and analyzed. This implied that the thiourea moiety was critical for the bioactive performance and the small R group was favorable for bioactivity.

Key words: citral, thiosemicarbazone, stereoisomer, herbicidal activity

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