832710-65-3

(C) Tert-butyl 1-oxo-2,8-diazaspiro[4.5]decane-8-carboxylate (400 mg) was used as a raw material and it was mixed with ethyl acetate (10 mL). Ethanol (2.0 mL) and 4M HCl/ethyl acetate solution (5.0 mL) were sequentially added to the reaction mixture at room temperature. The reaction system was heated to 60°C with continuous stirring for 2 hours. Upon completion of the reaction, the solvent was removed by distillation under reduced pressure. The residue was diluted with ethyl acetate and the precipitated solid was collected by filtration to give the final 2,8-diazaspiro[4.5]decan-1-one hydrochloride (240 mg). The product was characterized by 1H NMR (300 MHz, CDCl3): δ 1.47-1.64 (2H, m), 1.77-1.92 (2H, m), 1.93-2.03 (2H, m), 2.81-3.03 (2H, m), 3.11-3.34 (4H, m), 7.72 (1H, brs), 8.62-9.33 ( 2H, m).

[1] Patent: WO2015/17305, 2015, A1. Location in patent: Page/Page column 106
[2] Patent: EP2933247, 2015, A1. Location in patent: Paragraph 0335
[3] Patent: WO2016/60941, 2016, A1. Location in patent: Page/Page column 56