Synthesis
General procedure for the synthesis of 2-hydroxy-3-bromo-5-trifluoromethylpyridine from 2-hydroxy-5-trifluoromethylpyridine: to a solution of 5-(trifluoromethyl)pyridin-2-ol (10.52 g, 62 mmol) and sodium acetate (5.29 g, 64 mmol) in glacial acetic acid (38 mL) was added slowly with bromine (3.36 mL, 65 mmol) and the reaction was at room temperature. The reaction was carried out at room temperature. After observing the gradual transformation of the white turbid solution into a clarified brown solution, the reaction mixture was heated and refluxed at 80 °C for 2.5 h. After the reaction was completed, the mixture was cooled and refluxed for 2.5 h. The reaction was carried out at room temperature. Upon completion of the reaction, the mixture was cooled to room temperature and the solvent was subsequently removed by evaporation under reduced pressure. The residue was neutralized with saturated sodium bicarbonate solution to pH=8. The neutralized aqueous phase was extracted three times with ethyl acetate. The organic phases were combined, dried with anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to give the crude product 15.1 g (99.8% yield) as a white solid. The purity of the product was confirmed by LC-MS with a calculated value of [M+H]+ of C6H3BrF3NO of 241.9 and a measured value of 241.9/243.9.
References
[1] Patent: US2005/267146, 2005, A1. Location in patent: Page/Page column 22-23
[2] Patent: WO2004/82682, 2004, A1. Location in patent: Page 47-48
[3] Patent: WO2004/94371, 2004, A2. Location in patent: Page 59
[4] Patent: US2008/81803, 2008, A1. Location in patent: Page/Page column 25
[5] Patent: US2007/117797, 2007, A1. Location in patent: Page/Page column 23
