Ethanol → Ethyl 3-hydroxypicolinate

Temperature

95 °C

To 3-hydroxypyridine-2-carboxylic acid (25 g, 179.5 mmol) in a 1 L dried flask was added 400 mL ethanol and 100 mL toluene followed by the addition of 10 mL sulfuric acid. The mixture was heated at reflux (95° C.) for 3 days. After cooling to rt, the mixture was concentrated to ¼ of its volume, and diluted with 600 mL ethyl acetate and 200 mL water. The aqueous layer was extracted with 200 mL ethyl acetate, and the combined organic layers were washed with sat NaHCO3 (3×200 mL), brine, and dried over Na2SO4. The solid was filtered off and the solvent was concentrated under reduced pressure to give 21.9 g of ethyl 3-hydroxypyridine-2-carboxylate (73%), which was used in the next step without purification. This ester (21.9 g, 131 mmol) was dissolved in pyridine and cooled to −40° C., followed by addition of trifluoromethanesulfonic anhydride (48 g, 170 mmol). The reaction mixture was then warmed to 0° C. for 30 min, and then warmed to rt for another 30 min. Water (100 mL) was added to quench the reaction. The mixture was extracted with ethyl acetate (3×200 mL), and the combined organic layers were washed with sat sodium bicarbonate (200 mL), water (200 mL), brine (200 mL), and dried over sodium sulfate. The solid was filtered off, and the solvent was removed under reduced pressure to give 39 g (99%) of desired product, which was used in the next step without further purification. 1H NMR (300 MHz, CD2Cl2) δ 8.73 (dd, 1H), 7.72 (dd, 1H), 7.62 (dd, 1H), 4.46 (q, 2H), 1.42 (t, 3H).

1. temperatureThe mixture was heated
2. temperatureAfter cooling to rt
3. concentrationthe mixture was concentrated
4. additiondiluted with 600 mL ethyl acetate and 200 mL water
5. extractionThe aqueous layer was extracted with 200 mL ethyl acetate
6. washthe combined organic layers were washed with sat NaHCO3 (3×200 mL), brine
7. dry with materialdried over Na2SO4
8. filtrationThe solid was filtered off
9. concentrationthe solvent was concentrated under reduced pressure

ORD record

ord-8d0f6f2f970847818bc5d27fc1a84a35

Source dataset

uspto-grants-2009_04

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07517878B2