[Br:1][C:2]1[CH:3]=[C:4]([C:8]([NH:12][C:13](=[O:19])[O:14][C:15]([CH3:18])([CH3:17])[CH3:16])([CH3:11])[CH:9]=O)[CH:5]=[CH:6][CH:7]=1.[CH3:20][NH2:21].C(O[BH-](OC(=O)C)OC(=O)C)(=O)C.[Na+]>ClC(Cl)C.O.CC(O)=O>[Br:1][C:2]1[CH:3]=[C:4]([C:8]([NH:12][C:13](=[O:19])[O:14][C:15]([CH3:18])([CH3:17])[CH3:16])([CH3:11])[CH2:9][NH:21][CH3:20])[CH:5]=[CH:6][CH:7]=1
To a solution of tert-butyl 2-(3-bromophenyl)-1-oxopropan-2-ylcarbamate (CD2; R4=Me) (1.0 g, 3 mmol) in dichloroethane (50 mL) was added methylamine (0.48 g, 6.1 mmol, 2 eq) in water (40%) and 1 mL of AcOH. The solution was allowed to stir at RT for 1 h followed by the addition of sodium triacetoxyborohydride (1.8 g, 8.5 mmol, 2.8 eq). The resulting mixture was stirred at RT for 16 h and quenched with MeOH. After stirring for 30 min the mixture was concentrated in vacuo. The residue was purified by chromatography on silica gel by eluting with EtOAc/MeOH to give 0.62 g (60%) of tert-butyl 2-(3-bromophenyl)-1-(methylamino)propan-2-ylcarbamate (CD3; R1=Me, R4=Me) as a colorless oil. 1H NMR (CDCl3) δ 7.47 (bs, 1H), 7.37 (m, 1H), 7.27 (m, 1H), 7.23 (m, 1H), 5.97 (bs, 1H), 3.18-2.82 (m, 2H), 2.45 (s, 3H), 1.74 (s, 3H), 1.40 (s, 9H). MS (ESI) m/e 342.9 (M+H)+.
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