Dimethyl Sulfoxide → tert-Butyl 1-oxa-6-azaspiro(2.5)octane-6-carboxylate

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Reaction Steps

55% sodium hydride (6.02 g) was added under ice-cooling to a DMSO (250 mL) suspension of trimethylsulfoxonium iodide (33.1 g), and stirring was performed at room temperature for 1 hour. A DMSO (125 ml) solution of tert-butyl 4-oxopiperidine-1-carboxylate (25.0 g) was added, and heated and stirred at 60° C. for 1 hour. Purified water was added to the mixture, and extraction was performed with EtOAc. The organic layer was dried over anhydrous sodium sulfate and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (EtOAc/hexane) to obtain tert-butyl 1-oxa-6-azaspiro[2.5]octane-6-carboxylate (21.5 g),

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