General procedure for the synthesis of 4-amino-2-bromobenzaldehyde from m-bromoaniline: 5.5 g (32 mmol) of 3-bromoaniline was dissolved in 50 mL of DMSO and 4 mL of concentrated hydrochloric acid, and 8.1 g (60 mmol) of cuprous chloride (CuCl) was added. The reaction mixture was heated at 100°C for 5.5 hours. After completion of the reaction, the reaction mixture was neutralized with sodium carbonate solution and subsequently extracted with dichloromethane (CH2Cl2). The extract was purified by silica gel column chromatography with the eluent being a mixed solvent of dichloromethane-hexane, resulting in 1.9 g of a yellow solid product in 30% yield, with a melting point of 129°C. Thin-layer chromatography (TLC) showed an Rf value of 0.3 (unfolding reagent: dichloromethane), and a violet coloration in reaction with ninhydrin. Nuclear magnetic resonance hydrogen spectrum (1H NMR, CDCl3) data were as follows: δ 10.1 (1H, s, CHO), 7.75 (1H, d, J = 8.5 Hz, H-6), 6.83 (1H, d, J = 2.2 Hz, H-3), 6.60 (1H, dd, J = 8.5, 2.2 Hz, H-5), 4.20 (2H, br.s, NH2 ).
