[Synthesis]
General procedure for the synthesis of 2-chloro-3-trichloromethoxypyridine (8) from 2-chloro-3-trichloromethoxypyridine (7, 32.9 g, 0.13 mol): 2-chloro-3-trichloromethoxypyridine (7) was added slowly and dropwise to a molten mixture of SbF3 (46.5 g, 0.26 mol, 2.0 equiv) and SbCl5 (5.8 g, 2.5 mL, 19.5 mmol, 0.15 equiv) in a molten mixture. The reaction mixture was stirred at 120°C for 7 h. The progress of the reaction was monitored by gas chromatography (GC) to confirm complete conversion of the feedstock and disappearance of the by-product OCF2Cl. Upon completion of the reaction, the mixture was cooled to 0°C and dissolved in dichloromethane (300 mL). Subsequently, the reaction was quenched with saturated aqueous sodium bicarbonate solution (300 mL) and potassium fluoride solution (20%, 150 mL), and the aqueous layer was extracted with dichloromethane (2 x 150 mL). The organic layers were combined, dried over anhydrous sodium sulfate, and the solvent was removed by distillation under reduced pressure. The crude product was purified by vacuum distillation to afford 2-chloro-3-trifluoromethoxypyridine (8, 14.9 g, 75.6 mmol, 60% yield) as a colorless oil with a boiling point of 57-59 °C/19 mbar.The structure of the product was confirmed by 1H NMR, 13C NMR and mass spectrometry (MS): 1H NMR (CDCl3, 300 MHz): δ = 8.37 ( dd, J = 4.7, 1.5 Hz, 1H), 7.68 (dt, J = 8.1, 1.5 Hz, 1H), 7.41 (dd, J = 8.1, 4.7 Hz, 1H); 13C NMR (CDCl3, 75 MHz): δ = 147.4, 144.9, 142.2, 130.8, 123.2, 120.2 (q, J = 260 Hz); MS (EI): m/z = 197 [M+], 162 [M+-Cl]. |