b) Preparation of ethyl methylsulfonylacetate
To a solution of ethyl methylsulfanylacetate (Example 61a, 73.4 g, 0.547 mol) in dichloromethane (1000 mL) was added 3-chloroperoxybenzoic acid (m-CPBA, 217 g, 1.094 mol) in batches, and the temperature of the reaction was controlled to be less than 10 °C. After addition, the reaction mixture was stirred at room temperature for 24 hours. After completion of the reaction, the solid was removed by filtration and the filtrate was neutralized with potassium carbonate to pH=7. The organic layer was separated, washed with saturated sodium chloride solution, dried over anhydrous sodium sulfate, and concentrated under reduced pressure to give ethyl methanesulfonyl acetate (90 g, 100% yield) as a solid.LC-MS m/e 167 (MH+).
