Process for the preparation of O,O-dialkyl-S-benzyl thiophosphates

A process for the preparation of O,O-dialkyl-S-benzyl thiophosphates of the general formula:

• ##STR63## where in R.sub.1 and R.sub.2 each stand for an alkyl group with 1-5 carbon atoms and Y for halogen, an alkyl with 1-4 carbon atoms, and alkoxyl with 1-4 carbon atoms or a nitro group, and n for zero or an integer of 1-4, with the proviso that when n is an integer of 2-4, Y may be the same or different, characterized by reacting (a) a diester of phosphorous acid of the general formula:
• ##STR64## wherein R.sub.1 and R.sub.2 have the same meanings as given above, in an organic solvent which is sparingly soluble or insoluble in water with (b) sulfur and (c) at least one compound selected from the group consisting of hydroxides and oxides of alkali and alkaline earth metals, and then reacting an aqueous extract of the resulting reaction product with a benzyl halide of the general formula:
• ##STR65## wherein X stands for halogen and Y and n have the same meanings given above.