4-(bromomethyl) benzonitrile (1 g, 5.1 mmol) was dissolved in 10 mL of dry toluene and cooled at 0 oC and a portion of 1.08 M DIBALH in hexane (2 equiv.) was added dropwise under nitrogen atmosphere. The solution was stirred for 1 h at 0 oC. The reaction mixture was first diluted with chloroform (15 mL) followed by 34 mL of 10% HCl, and the solution was stirred at room temperature for another 1 h. The organic layer separated was washed with distilled water and dried over anhydrous Na2SO4. The solvent was almost completely removed from the filtrate under reduced pressure, and the residue was washed with ice-cold n-hexane and dried at 50 oC under vacuum to afford 4-(bromomethyl)benzaldehyde. Yield: 70%; 1 H NMR (300 MHz, CDCl3, TMS): δ = 10.02 (s, 1H), 7.86 (m, 2H), 7.57 (m, 2H), 4.52 (s, 2H) ppm[1].
