The product from above (3.4 g, 22 mmol) in concentrated 48% aqueous HBr (20 mL) at 0 C was treated with a 0 C solution of NaNO2 (1.5 g, 22 mmol) in water (30 mL). The reaction mixture was stirred for 30 min and then transferred cold to a stirred solution of CuBr (4.44 g, 31 mmol) in 48% aqueous HBr (20 mL) at 23 C (significant frothing!). Water (40 mL) was added, the solution was heated at 60 C for 45 min, cooled, diluted with EtOAc (200 mL) and water (50 mL), and the layers were separated. The aqueous layer was extracted with EtOAc (2x, 50 mL). The organic layers were combined, washed with 1 M HCl (2x, 100 mL) and brine (50 mL), dried (Na2SO4), filtered, and concentrated to provide 3-bromo-4-chlorobenzaldehyde as a pale yellow powder (3.9 g, 82%). 3-Bromo-4-chlorobenzaldehyde, yield 3.9 g, 82%
