2434-03-9

2,3-Dibromofuran-5-carboxylic acid is used in a study of the effect of a furanyl halo-substituent on the intramolecular Diels-Alder reaction between the furan ring system and a pendant allylamide. The yield of the cycloaddition is improved with a C-5 bromide vs -chloro or -unsubstituted furan.

Step B: Synthesis of 4,5-dibromo-2-furoic acid. Methyl 4,5-dibromofuran-2-carboxylate (26.19 g, 92.2 mmol) was suspended in THF (60 mL) followed by addition of LiOH (3 M aqueous solution, 60 mL, 180 mmol). The resulting two-phase mixture was stirred at room temperature for 4 hours. Upon completion of the reaction, the mixture was slowly poured into 1 N HCl solution and extracted with dichloromethane (DCM, 4 x 60 mL). The organic phases were combined, dried over anhydrous sodium sulfate and concentrated under reduced pressure to give 24.59 g (99% yield) of the target product 4,5-dibromo-2-furoic acid as an off-white solid. The product was characterized by 1H NMR (CD3OD): δ 7.30 (s, 1H).

[1] Patent: WO2008/124518, 2008, A1. Location in patent: Page/Page column 18
[2] Patent: US2006/69286, 2006, A1. Location in patent: Page/Page column 25
[3] Chemical and Pharmaceutical Bulletin, 1997, vol. 45, # 5, p. 799 - 806
[4] European Journal of Organic Chemistry, 1999, # 9, p. 2045 - 2057