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Potassium carbonate (K2CO3, 12 g, 88 mmol, 3.0 eq.) was added to acetone (10 mL) as 4-azepinone hydrochloride (1-18, 4.4 g, 29 mmol) and benzyl bromide (5.0 g, 29 mmol, 1.0 eq.). The reaction mixture was stirred at room temperature for 16 hours. After completion of the reaction, the crude reaction mixture was concentrated by evaporation, the residue was dissolved in ethyl acetate and the organic layer was washed with water. The crude product was purified by silica gel column chromatography to afford 1-benzylhexahydroazepin-4-one (1-19, 5.6 g, 95% yield). Mass spectrometric (ESI) analysis showed m/z 204.1 (M + H+).

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