An aqueous solution (50 mL) of potassium cyanide (22.5 g, 0.335 mol) was slowly added dropwise over a period of 5 minutes to a mixture of water (90 mL) and methanol (110 mL) containing N-tert-butoxycarbonyl-4-piperidone (32.48 g, 0.1598 mol) and ammonium carbonate (33.8 g, 0.351 mol). Upon completion of the dropwise addition, an off-white precipitate rapidly appeared in the reaction mixture. Subsequently, the reaction flask was sealed and the suspension was stirred continuously at room temperature for 72 hours. Upon completion of the reaction, the light yellow precipitate was collected by filtration and washed with a small amount of water to afford 8-Boc-2,4,8-triazaspiro[4.5]decane-1,3-dione (37.1 g, 86% yield) as a colorless solid.
