185-72-8

Trimethylsulfonium oxide iodide (286 mg, 13 mmol) was dissolved in dimethyl sulfoxide (DMSO, 20 mL) under nitrogen protection. Sodium hydride (60% dispersed in mineral oil, 520 mg, 13 mmol) was then added in batches (note: vigorous bubble generation was observed). The resulting suspension was stirred at room temperature for 1 h. Tetrahydro-4H-pyran-4-one (0.93 mL, 10 mmol) was then added slowly and dropwise. The reaction mixture was continued to be stirred for 1 h at room temperature and then the reaction was quenched by pouring into an ice-water mixture. The aqueous phase was extracted with ether (3 x 20 mL), the organic phases were combined, washed sequentially with water and saturated brine and dried over anhydrous magnesium sulfate. After concentration under reduced pressure, 1,6-dioxaspiro[2.5]octane was obtained as a light yellow oil (725 mg, 6.3 mmol, 63% yield).

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