STUDIES ON ORGANOPHOSPHORUS HETEROCYCLES (VIII) - CYCLIZATION OF LAWESSON REAGENT WITH THE BIFUNCTIONAL SUBSTRATES CONTAINING 2 AMINO-GROUPS

The cyclization of Lawesson's reagent with the bifunctional compounds containing two amino groups has been studied. Lawesson's reagent react ed with 1,2-diamines 2a-2b, 1,2-phosphinodiamides 7a-7b, and 1,3-diami nes 4a-4b in anhydrous toluene at 110 degrees C to give the ''N-P-N'' type 5-membered phosphorus heterocycles 3a-3b, 1,3,2,4-diazadiphosphol idines (8a-8b) and 6-membered rings 5a-5b, respectively. In addition, LR was treated with 1,2,4-triazoles at 100 degrees C in toluene to fro m cyclic compounds containing phosphorus. However, LR reacted with oxi mide at refluxing temperature in dry acetonitrile to give dithiooxamid e, a O-S exchange product of carbonyl, instead of the expected product formed as a result of heterocyclization. As to the formation of cycli zational products, one can assume that the electrophilic center of pho sphorus of the monmetric part of LR could attack the nucleophilic cent er namely the amino group of the bifunctional substates, to form a dit hiophosphonamide which looses hydrogen sulfide to yield phosphorus het erocycles. The result of preliminary bioassays shows that all heterocy cles prepared by cyclization with LR have selective herbicidal activit y. So the cyclization with Lawesson's reagent is a novel route leading to biological active heterocycles.