To a solution of 2-pyrrolidone (10.0 g, 118 mmol) in acetonitrile (118 mL) was sequentially added triethylamine (19.6 mL, 141 mmol), 4-dimethylaminopyridine (7.18 g, 58.8 mmol) and di-tert-butyl dicarbonate (32.7 g). The reaction mixture was stirred to room temperature at 0 °C and continued to stir overnight. After completion of the reaction, the mixture was partitioned between ethyl acetate and water. The organic layer was separated and washed sequentially with 1N aqueous hydrochloric acid, 1N aqueous sodium hydroxide and saturated saline. The organic layer was dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (n-hexane: ethyl acetate = 1:1) to afford 1-(tert-butoxycarbonyl)-2-pyrrolidinone (21.0 g, 96%) as a light yellow oil.1H-NMR (CDCl3, Varian, 400 MHz): δ 1.53 (9H, s), 2.00 (2H, quintuple peak, J = 8.0 Hz), 2.52 (2H, triple peak, J = 8.0 Hz), 3.75 (2H, triple peak, J = 7.6 Hz).
