Pyridine → Methyl 4-bromo-5-cyanothiophene-2-carboxylate

Beteiligte Stoffe

Reaktionsschritte

To a solution of 16.48 g (66.17 mmol) of methyl 4-bromo-5-formylthiophene-2-carboxylate in 165 mL of acetonitrile was added 5.06 g (72.78 mmol) of hydroxylamine hydrochloride. To this suspension 32.05 mL (397 mmol) of pyridine was added dropwise over a period of 20 min at 20-25° C. After 90 min stirring, neat trifluoroacetic anhydride (22.5 mL, 158.8 mmol) was dropped in over 30 min at room temperature. After 2.5 hours stirring, the reaction mass was poured in a mixture of HCl 0.5 M (200 mL) and ethyl acetate (150 mL); the aqueous layer was extracted again with 150 mL of ethyl acetate. The combined organic extracts were concentrated under reduced pressure and washed again with 120 mL of HCl 1 M. The organic was concentrated under vacuum to afford a raw solid product. This crude material was taken up in 75 mL of ethanol and treated with 75 mL of water under efficient stirring. The resulting suspension was cooled to 0/+4° C., then filtered off to afford 15.4 g of product as light cream solid.

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