Abstract: In acetone or chloroform/water,a series of S-(N-substituted carbaminomethylene)-O,O-dialkyl phosphorodithioates were prepared by the reaction of ammonium O,O-dialkyl phos-phorodithioate with α-haloalkanoamide,the substituent effect of which was studied.All of the compounds were confirmed by elemental analysis,IR,¹H NMR and MS.The results from the preliminary herbicidal tests show that introducing dithiophosphoryl group the herbicidal potency of the compounds were not only the same as that of a-chloroacetamide,but also their selectivity increased for the broadleaved plants.The relationship between chemical structure and activity was discussed.

Key words: α-Haloacetamides, Phosphorodithioates, Synthesis, Biological activity