5-Bromo-2-methylbenzaldehyde

529-20-4

90050-59-2

The general procedure for the synthesis of 5-bromo-2-methylbenzaldehyde from 2-methylbenzaldehyde was as follows: a solution was prepared by dissolving 15.1 g (113 mmol) of AlCl3 in 30 mL of CH2Cl2 at 20 °C, followed by the dropwise addition of 7.50 mL (64.8 mmol) of 2-methylbenzaldehyde over a period of 20 min. Next, a solution of 3.35 mL (64.8 mmol) Br2 dissolved in 60 mL CH2Cl2 was added dropwise to the reaction system at 0 °C. Upon completion of the reaction, the solution was allowed to warm slowly to room temperature over a period of 12 hours, after which the reaction mixture was quenched by pouring it into 500 g of ice. The mixture was extracted with 400 mL of CH2Cl2 and the organic phase was washed sequentially with 250 mL of 1.0 N HCl (aq), 250 mL of saturated NaHCO3 (aq) and 250 mL of brine. The organic layer was dried with Na2SO4 and concentrated, and the resulting solid was purified by twice recrystallizing from 50 mL hexane to give 2.92 g (21% yield) of 5-bromo-2-methylbenzaldehyde as an off-white solid. Its 1H NMR (400 MHz, CDCl3) data were as follows: δ 10.21 (s, 1H), 7.94 (s, 1H), 7.57 (d, 1H, J = 8.5 Hz), 7.16 (d, 1H, J = 8.5 Hz), 2.64 (s, 3H).