252882-60-3

252882-61-4

24424-99-5

252882-60-3

Spiro[indoline-3,4'-piperidin]-2-one (2.73 g, 11.42 mmol) and di-tert-butyl dicarbonate (2.74 g, 12.57 mmol) were used as the raw materials. Spiro[indoline-3,4'-piperidin]-2-one was dissolved in tetrahydrofuran (100 mL), and then di-tert-butyl dicarbonate and triethylamine (2.38 mL, 17.135 mmol) were added in turn at room temperature. 17.135 mmol). The reaction mixture was stirred at room temperature for 4 hours. Upon completion of the reaction, the solvent was removed by evaporation under reduced pressure and the residue was treated with a mixture of water and dichloromethane. The aqueous layer was extracted three times with dichloromethane, the organic layers were combined, dried over anhydrous sodium sulfate, filtered and concentrated to give tert-butyl 2-oxospiro[dihydroindole-3,4'-piperidine]-1'-carboxylate (4.02 g, quantitative yield) as a white foam. The product was confirmed by 1H NMR (400 MHz, DMSO-d6): δ 1.44 (s, 9H), 1.56-1.73 (m, 4H), 3.55-3.79 (m, 4H), 6.86 (dd, J = 7.70, 0.40 Hz, 1H), 6.95 (td, J = 7.59, 1.10 Hz, 1H), 7.19 (td , J = 7.70, 1.10 Hz, 1H), 7.43 (dd, J = 6.80, 0.70 Hz, 1H), 10.41 (br.s., 1H); m/z = 303.05 (M + H).