Example 2B Synthesis of 5-bromo-2-chlorobenzaldehyde: 18 mL (0.26 mol) of DMSO was dissolved in 64 mL of dichloromethane at -78 °C and 16.1 g (0.127 mol, 11.1 mL) of oxalyl chloride was slowly added. After 30 minutes of reaction, 13.1 g (59 mmol) of 2-chloro-5-bromobenzyl alcohol dissolved in 100 mL of chloroform was added dropwise. After continuing the reaction for 20 minutes, 40 mL of triethylamine was added, followed by slow warming of the reaction mixture to room temperature. Upon completion of the reaction, 50 mL of water was added and the mixture was extracted several times with ethyl acetate. The organic phases were combined and washed sequentially with 2N hydrochloric acid, water, saturated sodium bicarbonate solution and saturated sodium chloride solution. The organic phase was dried over magnesium sulfate and concentrated in vacuum. The resulting solid was further dried until a constant weight was reached under high vacuum. Yield: 12.7 g (94% yield). HPLC (Method 11): Rt = 4.65 min. MS (EI): m/z = 218 (M)+. 1H-NMR (300 MHz, CDCl3): δ = 7.32 (d, 1H), 7.65 (dd, 1H), 8.03 (d, 1H), 10.4 (s, 1H).
