Synthesis and herbicidal activities of urea compounds containing of pyrimidine and 1,3,4-thiadiazole rings

A series of novel urea compounds containing of pyrimidine and 1,3,4-thiadiazole rings were designed and synthesized viathe multi-step reactions using 4,6-dimethoxypyrimidinylsulphone and salicylic aldehyde as starting materials.4,6-Dimethoxypyrimidinylsulphone reacted with salicylic aldehyde to give 2-(4,6-dimethoxypyrimidinyloxy)benzaldehyde 1,which condensated with aminothiourea,followed by the cyclization to yield 5-amino-2-[2-(4,6-dimethoxypyrimidinyloxy)phenyl]-1,3,4-thiadiazole 2,2 reacted with isocyanates to form the target compounds 3.Their structures of the target compounds 3 were confirmed by IR,1 H NMR,EI-MS and elemental analyses.The preliminary bioassay indicated that some of the target compounds 3 displayed moderate inhibitory activities against Brassica campestris L at the concentration of 100mg/L.