Synthesis
To a stirred solution of 2,4-dimethoxybenzaldehyde (20.0 g, 120.48 mmol) in methanol (200 mL), a methanolic solution of methylamine (33%, 15.0 g, 481.90 mmol) was slowly added at 0°C and the reaction mixture was kept stirring at 0°C for 1 hour. Subsequently, sodium borohydride (5.5 g, 144.57 mmol) was added in batches at 0 °C and the reaction mixture was kept stirring at room temperature for 12 hours. The reaction progress was monitored by thin layer chromatography (TLC). Upon completion of the reaction, the reaction mixture was acidified with dilute hydrochloric acid (200 mL) and methanol was removed by distillation under reduced pressure. The residue was diluted with water and alkalized with dilute sodium hydroxide solution (80 mL). The aqueous layer was extracted with ethyl acetate (5 x 200 mL). The organic layers were combined, dried over anhydrous sodium sulfate and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (50-80% ethyl acetate/hexane gradient elution) to afford 2,4-dimethoxy-N-methylbenzenemethanamine (20.0 g, 92.0% yield) as a light yellow liquid.1H NMR (400 MHz, DMSO-d6): δ 7.14 (d, J = 8.4Hz, 1H), 6.51 (brs, 1H), 6.47-6.45 (d, J = 8.4Hz, 1H), 6.47-6.45 (brs, 1H). 6.47-6.45 (m, 1H), 3.74 (s, 6H), 3.53 (s, 2H), 2.24 (s, 3H); LC-MS: m/z 181.80 [M + H]+.
References
[1] Patent: WO2018/165520, 2018, A1. Location in patent: Page/Page column 301
[2] Patent: WO2008/108380, 2008, A2. Location in patent: Page/Page column 103-104
[3] Bioorganic and Medicinal Chemistry Letters, 2009, vol. 19, # 2, p. 378 - 381
