Synthesis
(1) Add 529 g of bromine dropwise to 500 g of 3,4-dimethoxybenzaldehyde dissolved in 2.5 L of methanol at room temperature (cooled if necessary) within 1 hour and stir the reaction mixture at the same temperature for 3 hours. Subsequently, 2.5 L of water was slowly added dropwise to the reaction solution to induce precipitation of crystals. A 20% aqueous sodium hydroxide solution was added to the crystal suspension at room temperature and the pH was adjusted to about 9-10, followed by cooling. The precipitated crystals were collected by filtration, washed with water and dried at 50 °C for 12 h. 718.78 g of 6-bromo-3,4-dimethoxybenzaldehyde was finally obtained (yield: 98%).
References
[1] Heterocycles, 2015, vol. 90, # 1, p. 730 - 739
[2] Patent: WO2007/40240, 2007, A1. Location in patent: Page/Page column 26
[3] Advanced Synthesis and Catalysis, 2015, vol. 357, # 14-15, p. 3255 - 3261
[4] Patent: EP1964925, 2016, B1. Location in patent: Paragraph 0068
[5] Journal of Asian Natural Products Research, 2012, vol. 14, # 4, p. 322 - 326
