Abstract: The cyclization of Lawesson's reagent with the bifunctional cornpounds containing two amino groups has been studied.Lawesson' s reagent reacted with 1, 2-diamines 2a-2b,1, 2-phosphinodiamides 7a-7b, and 1, 3-diamines 4a-4b in anhydrous toluene at 110℃ togive the "N-P-N" type 5-membered phosphorus heterocycles 3a-3b, 1, 3, 2, 4-di-azadiphospholidines (8a-8b) and 6-membered rings 5a-5b, respectively.In addition, LRwas treated with 1, 2, 4-triazoles at 100℃ in toluene to from cyclic compounds containingphosphorus.However, LRreacted with oximide at refluxing temperature in dry acetonitrileto give dithiooxamide, a O-Sexchange product of carbonyl, instead of the expected productformed as a result of heterocyclization.As to the formation of cyclizational products, one canassume that the electrophilic center of phosphorus of the monmetric part of LRcould attackthe nucleophilic center namely the amino group of the bifunctional substates, to form adithiophosphonamide which looses hydrogen sulfide to yield phosphorus heterocycles.Theresult of preliminary bloassays shows that all heterocycles prepared by cyclization with LRhave selective herbicidal activity.So the cyclization with Lawesson's reagent is a novel routeleading to biological active heterocycles.

Key words: Lawesson's reagent, Phosphorus-heterocycles, Cycllzation, Herbicidal activity