General procedure for the synthesis of 5-fluoro-2-nitrobenzaldehyde from 5-fluoro-2-nitrobenzyl alcohol: 5-fluoro-2-nitrobenzyl alcohol (13.92 g, 81.08 mmol) was dissolved in dichloromethane (284 mL). To the solution was added 4?molecular sieves (73 g) and pyridinium dichromate (36.58 g, 97.3 mmol). The reaction mixture was stirred at 20 °C for 6 hours. After completion of the reaction, the crude reaction mixture was filtered through a short silica gel column. The filtrate was concentrated under reduced pressure to remove the solvent and the residue was purified by fast column chromatography (silica gel, 10-20% ethyl acetate/hexane as eluent) to afford 9.43 g (69% yield) of the target compound 5-fluoro-2-nitrobenzaldehyde as a colorless oil.1H-NMR (CDCl3) data: δ 10.44 (d, 1H), 8.22 (dd, 1H) , 7.62 (dd, 1H), 7.41 (ddd, 1H).
