Patent ID: 6943267

Claim:
A method for the preparation of the mono-protonated thiophosphonate salts of the general formula wherein R is selected from the group consisting essentially of hydrogen, methyl, ethyl, phenyl, a carboxyl, or naphthyl substituted or a carbonyl substituted, alkyl of from 3 to 20 carbon atoms, a mono cyclic, bicyclic or polycyclic aryl or substituted aryl comprising the steps of: (a) heating a mixture of dimethyl phosphite and Lawesson's reagent in the presence of suitable organic solvent to produce a thiophosphite ester; (b) performing an Michaelis-Becker alkylation reaction by contacting a halide of the general formula R—CH 2 —X, wherein X is a halide, in the presence of a base and a phase transfer catalyst with said thiophosphite ester to produce the corresponding R substituted O,O-dimethyl ester; (c) producing the corresponding O-methylphosphonothioic acid, tetramethylammonium salt by addition of an excess of trimethylamine; (d) heating the O-methylphosphonothioic acid, tetramethylammonium salt in the presence of a solvent with a stoicheiometric amount of methyl iodide to yield the corresponding O-S-dimethyl ester; (e) contacting the cooled O—S-dimethyl ester with iodotrimethylsilane to produce the corresponding disilyl ester; (f) hydrolyzing the corresponding disilyl ester; and, (g) precipitating the corresponding thiophosphonate salt from the corresponding disilyl ester in the presence of a base.