89691-88-3

773837-37-9

1191-95-3

506-87-6

89691-88-3

34 General procedure for the synthesis of 5,7-diazaspiro[3.4]octane-6,8-dione from the compound (CAS: 773837-37-9), cyclobutanone and ammonium carbonate: 34.1 Sodium cyanide (1.47 g, 30 mmol) and ammonium carbonate (7.5 g, 78 mmol) were added to the reaction flask under argon protection. Subsequently, a mixed ethanol-water solvent (16 mL) solution of cyclobutanone (1.49 mL, 20 mmol) was added to the reaction system at 23°C. The reaction mixture was heated to 70 °C with continuous stirring for 6 hours. Upon completion of the reaction, the reaction mixture was cooled, poured into water (15 mL), and then concentrated hydrochloric acid (13 mL) solution was slowly added. Stirring was continued at 23 °C for 10 hours. After that, ethanol and some water were removed from the reaction mixture using a rotary evaporator. The precipitate was filtered through a glass filter and washed with distilled water. The target compound 5,7-diazaspiro[3.4]octane-6,8-dione was finally obtained as a beige powder in 39% yield (1.1 g). 1H NMR (400 MHz, DMSO-d6) δ: 10.49 (s, 1H, NH), 8.27 (s, 1H, NH), 2.31-2.37 (m, 2H, CH2), 2.19-2.27 (m, 2H, CH2), 1.83-1.90 (m, 1H, CHA), 1.71-1.76 (m, 1H, CHB ). Melting point: 223-225°C.