Heteroarylmethyl phosphorothiolates and phosphorodithioates

An important group of insecticides of the phosphorus ester type are those compounds in which the sulfur atom of the phosphorothiolic acid or of the phosphorodithioic acid is linked through a methylene bridge to a heteroaromatic ring. They are mostly prepared by the reaction of the sodium, salt of the desired phosphorothiolic acid or phosphorodithioic acid with the chloromethyl derivative of the respective heterocyclic compound. 

The most important of the phosphorothiolic acid derivatives within this group is 0,0-dimethyl-S-[(5-methoxy-4-oxo-4H-pyran-2-yl)methyl] phosphorothioate (endothion, 77) prepared by Metivier (1955a 1955b) by the reaction of 2-chloromethyl-5-methoxy-4-oxo-4H-pyran with the sodium salt of 0,0-dimethyl phosphorothioate  

Endothion is a systemic insecticide with an action lasting for 8-14 days. Its for rats is 30-50 mg/kg. 

The other members of this family of compounds are phosphorodithioic acid derivatives. Of these, menazon, 0,0-dimethyl-S-(4,6-diamino-l,3,5-triazin-2-yl)-methyl phosphorodithioate (78), distinguishes itself by its low toxicity to warmblooded animals. It is prepared by cyclisation of biguanide and ethyl chloroacetate, upon which the 2-chloromethyl-4,6 iaminotriazine formed is reacted with sodium 0,0-dimethyl phosphorodithioate (Anonym, 1958). 

It has a long residual action. Spraying with its aqueous solution protects plants for 18-26 days against sucking insects. 

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