Trimethylsulfonium methyl sulfate

To dimethyl sulfate (19 ml, 0.2 mol) in acetone (80 ml) was added dimethyl sulfide (15 ml. 0.2 mol). After a few minutes, the reaction mixture became turbid and warm. It was then cooled with cold water. The salt crystallized slowly, and after 4-5 h it was filtered. The white crystals were washed several times with acetone and dried under vacuum 26-28 g of the very hygroscopic salt were obtained (70-75% yield), m.p. 100-104°C. 

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To a solution of benzaldehyde (1.06g. lOmmol) in CH2CI2 (10ml) were added trimethylsulfonium methyl sulfate (2.17 g, 11.5 mmol) and 50% aqueous NaOH (5 ml). The reaction mixture was magnetically stirred at room temperature for 2.5 h. Water (20-30 ml) was added and the organic phase was decanted. The aqueous phase was extracted twice with ether (2 X 20ml). The combined organic solution was washed twice with water and dried (CaCl2). The solvents were evaporated under vacuum (rotatory evaporator, cold bath) and the epoxide distilled (l-2g, 80%), b.p. 82°C/38 torr. 

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