Synthesis and phytotoxic activity of novel acylthiourea and 2H-1,2,4-thiadiazolo[2,3-α]pyrimidine derivatives

Abstract

Eight N-[3-(2,4-dichlorophenyl)-5-methylisoxazol-4-ylcarbonyl]-N′-(4,6-disubstituted pyrimidin-2-yl)thioureas and eight 5,7-disubstituted-2-[3-(2,4-dichlorophenyl)-5-methyl isoxazol-4-ylcarbonylimino]-2H-1,2,4-thiadiazolo[2,3-α]pyrimidines were synthesized by multi-step reactions in yields of 50–85%. The structures of the target compounds were confirmed by IR, 1H NMR spectra and elemental analyses. Phytotoxic activities against Echinochloa crus-galli L., Digitaria ciliaris L., Brassica napus L. and Chenopodium serotinum L. were evaluated by the culture dish method. Preliminary bioassay results indicated that some target compounds exhibited good phytotoxic activity at a dose of 100 mg/L, with an inhibitory rate of 76.0–85.6% on root growth, even higher than the control herbicide, fenoxaprop-P-ethyl.