Synthesis
The general procedure for the synthesis of 2-bromothiophene-4-carboxaldehyde from 3-thiophenecarboxaldehyde was as follows: thiophene-3-carboxaldehyde (6.5 g, 0.06 mol) was dissolved in 200 mL of dry dichloromethane, followed by the addition of 14 g of aluminum chloride. The resulting dark-colored solution was stirred for 10 minutes and then a solution of bromine (10 g, 0.066 mol) dissolved in 10 mL of dichloromethane was added slowly and dropwise over 10 minutes. The reaction mixture was continued to be stirred for 12 hours, after which it was poured onto crushed ice. The organic layer was separated and washed sequentially with 2N HCl and water. The organic phase was dried and concentrated with anhydrous MgSO4. Ultimately, the white liquid product was purified by vacuum distillation in 88% yield (10 g).
References
[1] Bulletin of the Korean Chemical Society, 2013, vol. 34, # 4, p. 1170 - 1174
[2] Patent: EP2533783, 2015, B1. Location in patent: Paragraph 1044-1045
[3] Patent: WO2006/77412, 2006, A1. Location in patent: Page/Page column 85
[4] Chemical and Pharmaceutical Bulletin, 1999, vol. 47, # 10, p. 1393 - 1403
[5] Journal of Polymer Science, Part A: Polymer Chemistry, 2011, vol. 49, # 5, p. 1190 - 1194
