646055-62-1

1-Benzyl-1,7-diazaspiro[4.4]nonane (1.30 g, 6.01 mmol) and triethylamine (1 mL) were dissolved in 25 mL of dichloromethane, followed by addition of di-tert-butyl dicarbonate (1.45 g, 6.64 mmol). The reaction mixture was stirred at room temperature overnight. Upon completion of the reaction, the mixture was poured into 10 mL of saturated aqueous sodium bicarbonate solution and extracted with chloroform (4 x 25 mL). The organic phases were combined, dried with anhydrous potassium carbonate and subsequently concentrated by rotary evaporation. The crude product was purified by column chromatography (using Merck silica gel 60, 70-230 mesh), eluting with concentrated eluent to afford 1.85 g (97.4% yield) of the target product tert-butyl 1-benzyl-1,7-diazaspiro[4.4]nonane-7-carboxylate as a colorless viscous oil.

[1] Patent: WO2004/5293, 2004, A2. Location in patent: Page 60
[2] Patent: WO2006/23630, 2006, A2. Location in patent: Page/Page column 57-58