S-Methyl thiosulfonate (CAS NO.: ), with other names like Methanesulfonothioic acid, S-, could be produced through the following synthetic methods.

A 1-L, three-necked, round-bottomed flask equipped with a large magnetic stirring bar, a thermometer, reflux condenser, and a 100-mL pressure-equalizing addition funnel with a rubber septum is charged with 49 g (0.75 mol) of zinc dust, 1.0 mL (0.012 mol) of 1,2-dibromoethane , 2.0 mL (0.016 mol) of chlorotrimethylsilane , and 500 mL of ethyl acetate. After the mixture is stirred for 15 min at room temperature, it is ed to reflux by means of an oil bath and 38.7 mL (0.500 mol) of methanesulfonyl chloride is added dropwise through the addition funnel. The reaction is highly exothermic. At the end of the addition (1 hr), a large part of the zinc is consumed. The resulting grey suspension is stirred for an additional 15 min. , 35.7 mL (0.502 mol) , is then added dropwise through the addition funnel with care taken to maintain vigorous stirring of the reaction mixture. After completion of the addition, the resulting mixture becomes clear and no zinc remains. Heating is maintained for an additional 15 min, and the mixture is allowed to cool to room temperature. The resulting clear solution is poured into a 1 M aqueous hydrochloric acid solution (ca. 200 mL) and the phases are separated. The aqueous phase is extracted with ethyl acetate (ca. 200 mL) and the combined organic phases are washed with brine (ca. 200 mL) and dried over anhydrous magnesium sulfate . The solvent is removed under reduced pressure and the residual yellow oil is distilled under reduced pressure to give 24.1 g (76% yield) of as a colorless liquid, bp 80-83°C/0.5 mm.

Notice: The reaction must be performed in a well-ventilated hood.