Synthesis
General procedure for the synthesis of 1,2-dibromo-4,5-dimethoxybenzene from o-anisidine: 16.16 g (117 mmol) of 1,2-dimethoxybenzene was dissolved in 120 mL of carbon tetrachloride at 0 °C with stirring. 13.2 mL (257.4 mmol, 41.13 g) of bromine (2.2 eq.) dissolved in 25 mL of carbon tetrachloride was slowly added dropwise for a controlled time of 30 min while maintaining the reaction temperature in the range of 0-5 °C (by inserting bubbles into the reaction solution to expel the hydrogen bromide generated and neutralizing with Na2CO3). After dropwise addition, the reaction mixture was continued to be stirred at 0°C for 2 hours. Upon completion of the reaction, the mixture was poured into an ice-water mixture, and the organic phase was separated and washed sequentially with 10% aqueous NaHSO3 and 10% aqueous NaOH. The organic phase was concentrated by evaporation and dried to give 33.42 g of white solid product as 1,2-dibromo-4,5-dimethoxybenzene in 97% yield. The melting point of the product was unspecified.1H NMR (CDCl3): δ=7.06 (s, 2H); 3.86 (s, 6H).13C NMR (CDCl3): δ=148.8; 115.9; 114.7; 56.2.
References
[1] Tetrahedron Letters, 2004, vol. 45, # 37, p. 6851 - 6853
[2] CrystEngComm, 2011, vol. 13, # 20, p. 6050 - 6056
[3] Chemistry - An Asian Journal, 2012, vol. 7, # 10, p. 2240 - 2252
[4] Patent: US8859763, 2014, B1. Location in patent: Page/Page column 5
[5] Chemistry - A European Journal, 2016, vol. 22, # 24, p. 8113 - 8123
