Synthesis
To a stirred suspension of 5-bromo-2-furoic acid (15.0 g, 78.54 mmol) in 225 mL of dichloromethane was slowly added oxalyl chloride followed by a catalytic amount of N,N'-dimethylformamide at room temperature. After 1 hour of reaction, ethanol (20 mL) was added followed by triethylamine (22 mL). The reaction was continued with stirring for 15 hours. Upon completion of the reaction, the mixture was concentrated to dryness under reduced pressure to give a residue. Extraction was carried out with excess hexane and hexane-dichloromethane (3:1, v/v) solvent mixture. The organic phases were combined, filtered and the filtrate was concentrated to give a yellow oil. Finally, the product was dried under high vacuum to give ethyl 5-bromofuran-2-carboxylate 17.2 g in 93% yield.
References
[1] Patent: WO2004/11418, 2004, A1. Location in patent: Page 133
[2] Patent: WO2005/68460, 2005, A1. Location in patent: Page/Page column 314-315
[3] Journal of Materials Chemistry A, 2014, vol. 2, # 18, p. 6589 - 6597
[4] Chemical Communications, 2015, vol. 51, # 15, p. 3166 - 3168
[5] Patent: CN106977476, 2017, A. Location in patent: Paragraph 0106-0108
