Abstract: The isomerization/chlorination of O,O-dialkyl thiophosphate(-onate)₁ with phosphorus oxychloride gives S-alkyl thiophosphorochloride(-nochloride)₂,then,the reaction of compounds 2 with polychlorophenol in the presence of triethylamine afford the title compounds 4.Compounds 4 have also been prepared by using the traditional method, thus,the reaction of S-alkyl thiophosphorodichloride 5 with polychorophenol, then with another nucleophile R' Hin the presence of triethylamine can also give the title compounds(4).The results of the tests in the fungicidal activity towards the twelve plant disease fungus show that the twenty-eight compounds 4 prepared possess a satisfactory or excellent fungicidal activity.

Key words: Phosphorothiolate, Phosphonothiolate, Isomerization, Chlorination