The general procedure for the synthesis of 7-benzyl-4,7-diazaspiro[2.5]octane-5,8-dione from 7-benzyl-4,7-diazaspiro[2.5]octane was carried out as follows: to a solution of 7-benzyl-4,7-diazaspiro[2.5]octane-5,8-dione (20 g, 86.8 mmol) in tetrahydrofuran (200 ml), cooled in an ice bath, was slowly Borane-tetrahydrofuran complex (0.93 M tetrahydrofuran solution, 375 ml, 0.35 mol) was added. Subsequently, the reaction mixture was heated to reflux for 19 hours. After completion of the reaction, methanol (130 ml) was slowly added to the reaction mixture under ice bath cooling and the mixture was stirred for 60 minutes. Afterwards, the solvent was removed by concentration under reduced pressure. To the concentrated residue, ethanol (450 ml), water (150 ml) and triethylamine (150 ml) were added and the mixture was heated to reflux for 2 hours. The solvent was again concentrated under reduced pressure to remove the solvent. The residue was diluted with ethyl acetate, washed sequentially with saturated aqueous sodium bicarbonate and saturated saline, and the organic phase was dried with anhydrous sodium sulfate. After removal of the solvent by evaporation under reduced pressure, the residue was purified by silica gel column chromatography (eluent ratio of chloroform:methanol=10:1) to afford 7-benzyl-4,7-diazaspiro[2.5]octane (10.4 g, 59% yield) as a colorless oil.1H-NMR (CDCl3) δ: 0.41-0.44 (2H, m), 0.57-0.60 (2H, m) , 1.49 (1H, br), 2.22 (2H, s), 2.45 (2H, brs), 2.97 (2H, t, J=4.9Hz), 3.50 (2H, s), 7.22-7.32 (5H, m).
![7-Benzyl-4,7-diazaspiro[2.5]octane](/CAS/20150408/GIF/1222106-45-7.gif)