Bromine → 5-Bromo-2-ethylbenzaldehyde

A stirred suspension of 2-ethylbenzaldehyde (0.98 mL, 7.45 mmol) and AlCl3 (1.74 g, 13 mmol) in DCM (4.5 mL) at 0° C. is treated with a solution of Br2 (0.38 mL, 7.45 mmol) in DCM (4.5 mL) dropwise over 6 h then stirred 16 h at RT. After this time, the reaction mixture is poured over ice-water (50 mL), the layers separated and the aqueous layer extracted with DCM (3×50 mL). The organic phases are combined and washed with 2M HCl (100 mL), aqueous NaHCO3 (100 mL) and brine (100 mL), dried over Na2SO4 then the solvents removed in vacuo. Purification by column chromatography (gradient elution—100% heptane increasing to 10% EtOAc in heptane) gives the title compound.