General procedure for the synthesis of methyl 5-formyl-2-methoxybenzoate from 5-formyl-2-hydroxybenzoic acid and iodomethane: 5-formyl-2-hydroxybenzoic acid (2.0 g, 12.0 mmol), iodomethane (1.5 mL, 25 mmol) and potassium carbonate (3.06 g, 22.2 mmol) were mixed in dimethylformamide (15 mL). The reaction mixture was stirred at room temperature for 16 hours. After completion of the reaction, the solvent was removed by distillation under reduced pressure. The crude product was dissolved in ethyl acetate, washed sequentially with water (2×), saturated saline (2×) and the organic phase was dried with anhydrous sodium sulfate. After filtration, the filtrate was concentrated under reduced pressure and the resulting residue was purified by column chromatography to afford the target product methyl 5-formyl-2-methoxybenzoate 1.85 g (79% yield). The structure of the product was confirmed by 1H-NMR (CDCl3, 500 MHz) and mass spectrometry: 1H-NMR δ 9.91 (s, 1H), 8.31 (d, J = 2.1 Hz, 1H), 8.02 (dd, J = 8.5, 2.5 Hz, 1H), 7.11 (d, J = 8.6 Hz, 1H), 3.99 (s, 3H), 3.91 (s, 3H); mass spectrometry: 195 (s, 3H); mass spectrometry: 196 (s, 3H); mass spectrometry: 196 (s, 3H). 3H); MS: 195.05 (MH)+.
