Methanol → Methyl 4,5-Dibromo-2-furancarboxylate

Participants

Reaction Steps

To a solution of 69.91 g (0.259 mol) of 4,5-dibromo-2-furoic acid in 700 mL of methanol was carefully added 42.4 mL (0.777 mol) of 98% sulfuric acid at room temperature. The mixture was refluxed for 7 hours. The resulting solution was concentrated to slurry under reduced pressure and diluted with 0.5 L of MTBE. To this ice-cooled solution 0.5 L of 30% trisodium citrate and 0.25 L of 2N NaOH were slowly added, under vigorous stirring. The aqueous layer (pH=6) was separated and extracted again with 300 mL of MTBE. Some insoluble solid (residual starting material) was removed from the organic extracts by filtration. The clear extracts were dried over Na2SO4 then concentrated to dryness to afford a light brown solid that was purified by crystallization with 30 mL of hot MTBE and 60 mL of n-heptane. The mixture was cooled to 0/+4° C., aged for 1 hour then filtered to yield 57.13 g of cream-colored product. From the mother liquors a further amount of 12.65 g of product could be recovered by chromatography (eluent: ethyl acetate/cyclohexane 5:95). Thus, the overall amount of isolated product was 69.78 g.

Provenance & Evidence