[Br:1][C:2]1[CH:7]=[CH:6][C:5]([C:8]2[CH2:9][CH2:10][CH2:11][N:12]=2)=[CH:4][C:3]=1[F:13].[BH3-]C#N.[Na+].C(O)(=O)C>CO>[Br:1][C:2]1[CH:7]=[CH:6][C:5]([CH:8]2[CH2:9][CH2:10][CH2:11][NH:12]2)=[CH:4][C:3]=1[F:13]To a solution of 5-(4-bromo-3-fluorophenyl)-3,4-dihydro-2H-pyrrole ((12.7 g, 52.7 mmol) in 360 mL methanol was added NaBH3CN (6.6 g, 105 mmol) at 0° C. The resulting solution was adjusted to pH=6 with acetic acid. The reaction mixture was stirred at room temperature overnight. The reaction was quenched with 2 N HCl and the methanol was removed by evaporation. The residue was diluted with water, the aqueous phase adjusted to pH=10 with NaOH, extracted with ethyl acetate, dried by Na2SO4, concentrated and the residue was purified by chromatography on silica gel to give 2-(4-bromo-3-fluorophenyl)pyrrolidine as a yellow solid (12.5 g, yield 98%). LC-MS (ESI) m/z: 244 (M+1)+.
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