Cl.[Br:2][C:3]1[CH:8]=[CH:7][C:6]([CH:9]2[CH2:13][CH2:12][NH:11][CH2:10]2)=[CH:5][CH:4]=1.[CH2:14](N(CC)CC)C.C=O.C(O[BH-](OC(=O)C)OC(=O)C)(=O)C.[Na+]>CO.C(O)(=O)C>[Br:2][C:3]1[CH:4]=[CH:5][C:6]([CH:9]2[CH2:13][CH2:12][N:11]([CH3:14])[CH2:10]2)=[CH:7][CH:8]=1To a mixture of 3-(4-bromophenyl)pyrrolidine hydrochloride (200 mg, 0.76 mmol) in methanol (6 mL) was added triethylamine (77 mg, 0.76 mmol) and several drops of acetic acid. The reaction mixture was stirred at room temperature for 5 min and treated with aqueous formaldehyde (37%, 0.2 mL) and sodium triacetoxyborohydride (322 mg, 1.52 mmol). The reaction mixture was stirred for 18 h at room temperature. The methanol was evaporated in vacuo and the residue was partitioned between water and EtOAc. The phases were separated and the aqueous phase was back-extracted with EtOAc. The combined organic phases were washed with brine, dried over Na2SO4, and concentrated in vacuo to give 3-(4-bromophenyl)-1-methylpyrrolidine (0.247 g) as a solid, which was used in the next step without further purification. MS (ES+) 239.9 (M+H)+.
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