Methanol → Methyl 4,5-dibromothiophene-2-carboxylate

To a suspension of 23.75 g (83.06 mmol) of 4,5-dibromo-2-thiophencarboxylic acid in 235 mL of methanol was slowly added 15.5 mL (284 mol) of 98% sulfuric acid at room temperature. The mixture was refluxed for 23 hours. The resulting solution was concentrated to thick slurry under reduced pressure and diluted with 240 mL of dichloromethane. To this ice-cooled solution 190 mL of 17% NaOH was slowly added, under vigorous stirring. The aqueous layer was separated and extracted again with 120 mL of dichloromethane. The combined organic extracts were dried over Na2SO4 then concentrated to dryness to afford 24.02 g of product as an off-white solid.

1. customat room temperature
2. temperatureThe mixture was refluxed for 23 hours
3. concentrationThe resulting solution was concentrated to thick slurry under reduced pressure
4. additiondiluted with 240 mL of dichloromethane
5. temperatureTo this ice-cooled solution 190 mL of 17% NaOH
6. additionwas slowly added, under vigorous stirring
7. customThe aqueous layer was separated
8. extractionextracted again with 120 mL of dichloromethane
9. dry with materialThe combined organic extracts were dried over Na2SO4
10. concentrationthen concentrated to dryness

ORD record

ord-9571742631764f03b383ecd87ff5322e

Source dataset

uspto-grants-2009_02

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07485661B2