[F:1][C:2]1[CH:8]=[CH:7][C:5](N)=[CH:4][CH:3]=1.[BrH:9].N([O-])=O.[Na+].[C:14]([O:18][CH3:19])(=[O:17])[CH:15]=[CH2:16].N#N>O.CC(C)=O>[Br:9][CH:15]([CH2:16][C:5]1[CH:7]=[CH:8][C:2]([F:1])=[CH:3][CH:4]=1)[C:14]([O:18][CH3:19])=[O:17]A mixture of 4-fluoroaniline (27.75 g), acetone (500 ml) and hydrobromic acid (80 ml, 48%) stirred at -5° C. was treated over 30 minutes with a solution of sodium nitrite (21.0 g) in water (50 ml). Methyl acrylate (215 g) and cuprous bromide (0.04 g) were added. The internal temperature was allowed to rise in a carefully controlled manner; at 15° C. the evolution of N2 was vigorous. When the rate of N2 evolution decreased, the mixture was stirred at 25° C. for 1 hr to complete the reaction. The mixture was evaporated, and the residue was partitioned between water and toluene to give crude methyl 2-bromo-3-(4-fluorophenyl)propionate.
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