[Synthesis]
Aluminum trichloride (1.25 eq.) was dissolved in dichloromethane and cooled to 0°C under the protection of an inert atmosphere. To this solution was added m-bromoanisole (1 eq.) dropwise over a period of 10 minutes. The reaction mixture was continued to be stirred at 0°C for 1 hour. Subsequently, a dichloromethane solution of acetyl chloride (1.05 eq.) was added dropwise. After addition, the reaction mixture was stirred at 0°C for 2 hours. Upon completion of the reaction, the mixture was quenched by careful pouring into ice water. The organic phase was separated, washed with saturated brine and dried over anhydrous magnesium sulfate. The solvent was removed by concentration under reduced pressure to give the crude product. The crude product was purified by silica gel column chromatography (elution gradient: petroleum ether/ethyl acetate from 98/2 to 90/10) to isolate 1-(2-bromo-4-methoxyphenyl)ethanone (colorless oil) and 1-(4-bromo-2-methoxyphenyl)ethanone (white solid). The yields were 55% and 18%, respectively. Thin layer chromatography (TLC) analysis (unfolding agent: petroleum ether/ethyl acetate 95/5) showed Rf values of 0.33 and 0.5, respectively.Nuclear magnetic resonance hydrogen spectroscopy (1H NMR, CDCl3) data were as follows:1-(2-bromo-4-methoxyphenyl)ethanone: δ 2.60 (s, 3H), 3.82 (s, 3H), 6.85 (d, 1H, J = 1.9 Hz), 7.13 (s, 1H), 7.58 (d, 1H, J = 5.0 Hz); 1-(4-bromo-2-methoxyphenyl)ethanone: δ 2.61 (s, 3H), 3.94 (s, 3H), 7.15 (m, 2H), 7.64 (d, 1H, J = 8.3 Hz). |