A series of 3-[substituted pyridyl (or thiazolyl)methyl]-1,2,3-triazolo[4,5-d]pyrimidin-7-ones were synthesized via the tandem Aza-Wittig reaction annulation。The carbodiimides 5，obtained from the aza-Wittig reaction of iminophosphorane 4 with aromatic isocyanates，reacted with a variety of primary ali-phatic amines in the presence of a catalytic amount of EtONa to give the target compounds 7 in moderate yields。The preliminary bioassay indicated that some of the target compounds displayed good herbicidal ac-tivity against Brassica campestris L at the dosage of 100 mg/L。

Key words: substituted pyridine, thiazole, 1,2,3-triazolo[4,5-d]pyrimidin-7-one, aza-Wittig reaction, herbicidal activity