General procedure for the synthesis of 1-(5-bromo-2-chlorophenyl)ethanone using 1-(5-bromo-2-chlorophenyl)ethanol as starting material: to a solution of 1-(5-bromo-2-chlorophenyl)ethanol (1.09 g, 4.6 mmol) in dichloromethane (20 mL) was added pyridinium dichromate (2.6 g, 6.94 mmol). The reaction mixture was stirred for 15 hours and then pyridinium dichromate (2.6 g, 6.94 mmol) was added again. After continued stirring for 24 hours, diatomaceous earth was added and the mixture was stirred for 20 minutes. The reaction mixture was filtered through a diatomaceous earth pad and the filter cake was washed with ether. The filtrates were combined and concentrated to give a brown oil. Purification of the crude product by fast silica gel column chromatography (eluent: hexane/ethyl acetate, 0% to 10% ethyl acetate gradient) afforded 1-(5-bromo-2-chlorophenyl)ethanone as a clear oil (0.92 g, 85% yield).1H NMR (400 MHz, CDCl3): δ 2.64 (s, 3H), 7.29 (d, J = 8.6 Hz, 1H) , 7.51 (dd, J = 8.6, 2.3 Hz, 1H), 7.66 (d, J = 2.3 Hz, 1H).
