Benzyl chloroformate → 4-Benzyl 9-tert-butyl 1-oxa-4,9-diazaspiro[5.5]undecane-4,9-dicarboxylate

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Reaction Steps

To a mixture of tert-butyl 1-oxa-4,9-diazaspiro[5.5]undecane-9-carboxylate (5.80 g) and dioxane (100 mL), 1 M aqueous sodium hydroxide (24.9 mL) and benzyl chloroformate (3.55 mL) were added sequentially under ice cooling and stirred at room temperature for 16 hours. The reaction mixture was concentrated under reduced pressure and then extracted with ethyl acetate. The organic layer was concentrated under reduced pressure, and the residue was purified by silica gel column chromatography (eluent; n-hexane:ethyl acetate=9:1-1:1) to give 4-benzyl 9-tert-butyl 1-oxa-4,9-diazaspiro[5.5]undecane-4,9-dicarboxylate (8.06 g) as a colorless syrup.

Provenance & Evidence