GB947778A - Improvements in or relating to the production of carbamylmethyl phosphorothioates - Google Patents

Abstract

A thiophosphate ester of the general formula: <FORM:0947778/C2/1> is obtained by reacting together a phosphoro-thiolate salt of the formula: <FORM:0947778/C2/2> with a haloacetamide compound of the formula: <FORM:0947778/C2/3> wherein R1 is methyl, R2 is methyl or other alkyl group containing up to 5 carbon atoms, X1 and X2 are oxygen or sulphur, at least one being sulphur, R3 and R4 are hydrogen, alkyl containing up to 5 carbon atoms, or together with the N atom form a heterocyclic residue e.g. morpholine residue, Y is an alkali metal, alkaline earth metal or ammonium, and Z is chlorine or bromine, the reaction being carried out in a two phase liquid system comprising an aqueous phase and a water-immiscible organic solvent phase, the phosphorothioate salt appearing preferentially in the aqueous phase and the thiophosphate ester appearing preferentially in the solvent phase. The phosphorothioate salt may be formed in situ by introducing into the reaction the free phosphorothioic acid and an alkaline compound of an alkali metal, alkaline earth metal, or ammonium e.g. a hydroxide, carbonate, or bicarbonate. The volume ratio of the aqueous phase to the organic solvent phase may vary from 1:4 to 4:1. Specified solvents are ketones, alcohols and ethers having 4 or more carbon atoms, e.g. methyl isobutyl ketone, cyclohexanone, methyl cyclohexanone, 2,2-dichlorodiethyl ether, 3, 5, 5-trimethyl hexanol, and hydrocarbons or halogenated hydrocarbons, e.g. benzene, xylene, chlorobenzene, chloroform and carbon tetrachloride, or mixtures of such solvents. Preferred reaction temperatures are from 15 to 90 DEG C. Suitable 0, 0-dimethyl phosphorodithioates which may be used as starting material may be obtained by extracting the commercial product with water, separating the oily impurities and neutralising the aqueous extracts with a suitable base or the commercial product may be extracted with aqueous ammonia and the oily impurities separated off. The pH of the aqueous phase during reaction should preferably be not above 10 and the reaction mixture may be buffered e.g. with bicarbonate ions. Examples are given for the production of O, O-dimethyl -S-(N-methyl) carbamylmethyl phosphorodithioate, O, O-methyl ethyl -S-(N-methyl)-carbamylmethyl phosphoromonothiate and O, O-dimethyl -S-(N-methyl -N-ethyl) carbamoylmethyl phosphorodithioate. Specifications 663,270 and 791,824 are referred to. Reference has been directed by the Comptroller to Specification 886,319.