2-Hydroxy-5-trifluoromethylpyridine synthesis

5006-66-6

33252-63-0

General procedure for the synthesis of 2-hydroxy-5-trifluoromethylpyridine from 6-hydroxynicotinic acid: 6-hydroxynicotinic acid (18.2 g, 0.13 mol), anhydrous hydrofluoric acid (2.6 mL, 0.13 mol, ≥95 wt%) and sulfur tetrafluoride (42.1 g, 0.39 mol) were added to a stainless steel pressure tank. The mixture was heated to 100 °C and reacted at 0.15 MPa pressure for 12 hours. The gaseous product generated during the reaction was treated by an exhaust gas absorption unit. Upon completion of the reaction, the remaining product was transferred to a polytetrafluoroethylene vessel and heated to 40°C to remove residual hydrogen fluoride. Subsequently, the product was dissolved in 150 mL of water and the pH was adjusted to 6.8-7.2 with saturated sodium carbonate solution. the aqueous phase was extracted with chloroform, and the organic phases were combined and dried. After filtration and drying, 2-hydroxy-5-trifluoromethylpyridine (15.3 g, 0.094 mol) was obtained in 72% yield.