General procedure for the synthesis of 2-chloro-4-iodo-6-trifluoromethoxypyridine from 6-chloro-3-iodo-2-(trifluoromethoxy)pyridine: diisopropylamine (1.4 g, 1.9 mL, 13.6 mmol, 1.1 eq.) was added slowly and dropwise at 0 °C to a butyl lithium (1.56 M hexane solution, 9.0 mL, 13.6 mmol, 1.1 eq.) in a tetrahydrofuran (THF, 20 mL) solution. Subsequently, a solution of 2-chloro-5-iodo-6-trifluoromethoxypyridine (41, 4.0 g, 12.4 mmol, 1 eq.) in THF (10 mL) was added dropwise at -78 °C and the reaction mixture was stirred for 1 hour at 0 °C. Upon completion of the reaction, it was neutralized with 2N hydrochloric acid solution (10 mL), followed by treatment with saturated aqueous sodium bicarbonate solution (30 mL) and extraction with diethyl ether (3 x 20 mL). The organic layers were combined, dried over sodium sulfate and the solvent evaporated. The crude product was purified by vacuum distillation (boiling point 104-107 °C/16 mbar) to afford 2-chloro-4-iodo-6-trifluoromethoxypyridine (42, 3.2 g, 10.9 mmol, 80% yield) as a colorless oil. The structure of the product was determined by 1H NMR (CDCl3, 300 MHz): δ=7.66 (d, J=1.0 Hz, 1H), 7.34 (d, J=1.0 Hz, 1H); 19F NMR (CDCl3, 282 MHz): δ=-57.1; 13C NMR (CDCl3, 75 MHz): δ=155.1, 149.4, 130.7, 120.3, 119.1 (q, J=262 Hz), 108.3 confirmed.
