General procedure for the synthesis of 2-methoxy-5-nitrobenzaldehyde from 5-nitrosalicylaldehyde and iodomethane: Sodium hydride (NaH, 246 mg) and iodomethane (2.56 g) were added to a solution of 5-nitrosalicylaldehyde (1.00 g, 6.0 mmol) in N,N-dimethylformamide (DMF, 20 ml). The reaction mixture was stirred at 0°C for 8.5 hours. After completion of the reaction, the reaction mixture was extracted with ether and the organic phase was washed sequentially with aqueous sodium bicarbonate, saturated brine and 5% hydrochloric acid/saturated brine. The organic phase was dried with anhydrous magnesium sulfate and concentrated under reduced pressure to give 2-methoxy-5-nitrobenzaldehyde (0.95 g, 87.8% yield) as yellow needle-like crystals. The product was characterized by 1H NMR (CDCl3): δ 10.45 (s, 1H), 8.70 (d, J = 2.9Hz, 1H), 8.45 (dd, J = 8.8, 2.9Hz, 1H), 7.14 (d, J = 8.8Hz, 1H), 4.08 (s, 3H).
