Synthesis and Herbicidal Activity of 3-Acetyl-4-hydroxy-2,1-benzothiazine Derivatives

摘要

In order to develop a novel herbicide containing the 2,1-benzothiazine motif, a series of 3-acetyl-4- hydroxy-2,1-benzothiazine derivatives was synthesized. All the target compounds were confirmed by 1H NMR,13C NMR, and high-resolution mass spectrometry(HRMS).In addition,the crystal structure of compoimd T27 was detemiined by single crystal X-ray diflraction. The bioassay results showed that some of the 3-acetyl-4-hydroxy- 2,1-benzothiazine derivatives(T13, T15, T22, and T24) showed good herbicidal activity at a dosage of 100 pg/mL. Among them,compounds T22 and T24 showed promising post-emergent herbicidal activities against Brassica campestris and Amaranthus retroflexus even at a dosage of 375 g/ha(1ha=104 m^2) in the greeiiliouse test. Studies on the structure-activity relationship demonstrated that the type of acetyl group played an important role in the herbicidal activity, and that the introduction of a phenoxyacetyl group at the 3-position of 2,1-beiizothiazine was beneficial in improving the herbicidal activity. The present study also indicated that 3-phenoxyacetyl-4-hydroxy-2,1-benzothiazine could be a potential lead compound for fiirther development of novel 2,1 -benzothiazine-containing herbicides.