Hydrogen Bromide → (S)-methyl 2-bromo-2-phenylacetate
反応式
N[C@H:2]([C:7]1[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=1)[C:3]([O:5][CH3:6])=[O:4].[BrH:13].N([O-])=O.[Na+]>O>[Br:13][C@@H:2]([C:7]1[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=1)[C:3]([O:5][CH3:6])=[O:4]N[C@H:2]([C:7]1[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=1)[C:3]([O:5][CH3:6])=[O:4].[BrH:13].N([O-])=O.[Na+]>O>[Br:13][C@@H:2]([C:7]1[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=1)[C:3]([O:5][CH3:6])=[O:4](R)-methyl 2-amino-2-phenylacetate (5 g, 24.8 mmol, 1 equiv) was dissolved in a mixture of 48% hydrogen bromide (13 ml, 198 mmol, 8 equiv) and water (19 ml). An aqueous solution of sodium nitrite (5.48 g, 79.36 mmol, 3.2 equiv) was added slowly and the mixture stirred at 0° C. for 1.5 h. The reaction was degassed in vacuo and extracted with ether. The organic layer was further washed with water and brine, dried over MgSO4, and concentrated in vacuo. The resulting residue was purified using the Biotage flash chromatography system (SNAP 100 g cartridge, Rf=0.5, gradient—10% ethyl acetate/hexanes) to afford the (S)-methyl 2-bromo-2-phenylacetate as a light yellow oil (2.3 g, 40% yield); 1H NMR (400 MHz, DMSO-d6): δ 3.72 (s, 3H); 5.95 (s, 1H); 7.36-7.42 (m, 3H); 7.53 (d, 2H, J=1.2 Hz); 7.56 (d, 1H, J=2 Hz). MS for C9H9BrO2 m/z 229.98 (M+H)+.
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