General procedure for the synthesis of 5-nitro-2-(trifluoromethyl)pyridin-4-ol from 2-trifluoromethyl-4-hydroxypyridine: Nitric acid (12 mL) was added slowly and dropwise to a solution of 2-(trifluoromethyl)pyridin-4-ol (10 g, 11.9 mmol) in concentrated sulfuric acid (4.8 mL) under ice bath cooling conditions. The reaction mixture was transferred to a sealed tube and stirred at 120°C for 48 hours. The progress of the reaction was monitored by thin layer chromatography (TLC) and after confirming the completion of the reaction, the reaction mixture was cooled to room temperature. The reaction was quenched with ice water and subsequently extracted with ethyl acetate (3 x 100 mL). The organic phases were combined, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure to give the brown solid product 5-nitro-2-(trifluoromethyl)pyridin-4-ol. Yield: 3.0 g (23% yield). Product characterization data: 1H NMR (400 MHz, DMSO-d6) δ 9.08 (s,1H), 7.43 (s,1H); mass spectrum (ESI+) m/z 208.98 [M+H]+.
