Synthesis and herbicidal activity of α-[(substituted phenoxybutyryloxy or valeryoxy)]alkylphosphonates and 2-(substituted phenoxybutyryloxy)alkyl-5,5-dimethyl-1,3,2-dioxaphosphinan-2-one containing fluorine

Abstract

Based on our previous work on the structural modification of the lead compound I, three series of novel fluorine-containing phosphonates derivatives (II, III and IV) were designed and synthesized. Their post-emergence herbicidal activities against some species of weeds were evaluated in a green house. The compounds II were synthesized by introducing of two methylene into the structure I. Compared with the commercial herbicidal clacyfos, compounds II showed moderate herbicidal activity with 60–85% inhibition effect against chingma abutilon (Abutilon theophrasti), common amaranth (Amaranthus retroflexus) and white eclipta (Eclipta prostrate) at a rate of 150g ai/ha. The compounds III were designed by introducing open-chain phosphonates, which displayed notable herbicidal activity. Especially, the compounds III-1–III-4, III-6, III-8, III-11 and III-12 exhibited significant herbicidal activity (80–100%) comparing to the clacyfos against all tested broadleaf weeds, while compounds IV with five carbon atoms in the carboxylic acid chain were inactive against all of the tested weeds. Structure-activity relationship analyses indicated that the length of the carbon chain had a great effect on the herbicidal activity. Furthermore, a broad spectrum test confirmed that compounds III-4 and III-8 were comparable with glyphosate against all of the tested weeds at a rate of 75g ai/ha.