General procedure for the synthesis of 3-bromo-2-fluoroacetophenone from N-methoxy-N-methyl-3-bromo-2-fluorobenzamide and methylmagnesium bromide:
1. methylmagnesium bromide (3M in ether, 21mL) was slowly added to a solution of tetrahydrofuran (100mL) containing 3-bromo-2-fluoro-N-methoxy-N-methylbenzamide (10.89g) at -78°C.
2. The reaction mixture was gradually warmed to room temperature and stirred continuously for 16 hours.
3. Upon completion of the reaction, the mixture was cooled to 0 °C and the reaction was quenched by slow addition of 2 M HCl solution up to pH=1 .
4. The solvent was removed by rotary evaporator and the product was subsequently extracted with ethyl acetate (3 x 100 mL).
5. The organic layers were combined, dried over anhydrous sodium sulfate and the solvent was again removed by rotary evaporator to give a light brown solid product.
6. The resulting solid was dissolved in dichloromethane (200 mL) and washed with saturated aqueous NaHCO3 (200 mL).
7. The dichloromethane layer was separated, dried with anhydrous sodium sulfate, and finally the solvent was removed by rotary evaporator to give 1-(3-bromo-2-fluorophenyl)-acetophenone as a yellow oil (8.8 g, 97% yield).
1H NMR (CDCl3) data: δ 2.67 (3H, d, ArCOCH3), 7.11 (1H, t, Ar), 7.69-7.81 (2H, m, Ar).
