Synthesis of Benzoxazinones Sulphur Analogs and Their Application as Bioherbicides: 1.4-Benzothiazinones and 1.4-Benzoxathianones for Weed Control

Abstract

Eight different compounds inspired by benzoxazinones were synthesized in one simple step with easy purification. These compounds have a sulfur atom instead of the oxygen atom present in benzoxazinones. Furthermore, a new derivative obtained by a Rutkauskas–Beresnevicius reaction was synthesized. These compounds were evaluated in vitro to assess their phytotoxicity in plant cells by the elongation of wheat coleoptiles. The novel compounds showed higher inhibition than benzoxazinones and the positive control, especially at higher concentrations (1000 and 300 μM). Benzoxazinones have been described as histidine deacetylase inhibitors and we therefore evaluated the effect of 1.4-benzothiazinones and 1.4-benzoxathianones against HDA6, one of the most important enzymes of the family, in silico by molecular docking and molecular dynamics. In vitro studies against Echinochloa crus-galli, Lolium rigidum and Portulaca oleracea weeds gave interesting results against the growth of the roots for both monocots and dicots. Specifically, the inhibition was more pronounced against dicots, as in the case of common purslane, whose inhibition at a concentration of 1000 μM was similar to that of the classical herbicide employed as a positive control. Higher inhibition was obtained when an aliphatic group was present in the C2 position of 1.4-benzothiazinones.