B(Cl)(Cl)Cl.[NH:5]([CH:12]1[CH2:17][CH2:16][N:15]([CH3:18])[CH2:14][CH2:13]1)[C:6]1[CH:11]=[CH:10][CH:9]=[CH:8][CH:7]=1.[C:19](#N)[CH3:20].Cl.[OH2:23]>ClC(Cl)C>[C:19]([C:11]1[CH:10]=[CH:9][CH:8]=[CH:7][C:6]=1[NH:5][CH:12]1[CH2:17][CH2:16][N:15]([CH3:18])[CH2:14][CH2:13]1)(=[O:23])[CH3:20]To a 2.03M solution of boron trichloride (20×1.2 mmol) in dichloroethane (11.8 ml) is dropwise added a solution of 4-anilino-1-methylpiperidine (3.81 g, 20 mmol) in dichloroethane (38 ml), and acetonitrile (2.1 ml, 20×1.2 mmol) is added to the mixture, which is heated under reflux over a period of 20 hours. After cooling, the reaction mixture is mixed with 2N hydrochloric acid (15 ml) and water (30 ml) and stirred at 100° C. over a period of 20 minutes. After cooling, the reaction mixture is mixed with conc. aqueous ammoniac solution and separated. The organic layer is washed with water, dried over anhydrous potassium carbonate and concentrated in vacuo to give 4-(2-acetylanilino)-1-methylpiperidine (4.41 g) as an oil. The yield is 95%.
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