Iodine → 2-Fluoro-3-iodo-6-(trifluoromethyl)pyridine

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Reaction Conditions

Reaction Steps

A solution of N,N-diisopropylamine (1.4 mL, 10.0 mmol) in anhydrous THF (15 mL) is cooled under N2 to −78° C. and nBuLi (2.5 M in hexanes, 4.0 mL, 10.0 mmol) is added dropwise at a rate to maintain the temperature below −65° C. A solution of 2-fluoro-6-(trifluoromethyl)pyridine (1.65 g, 10.0 mmol) in anhydrous THF (15 mL) is added dropwise over 10 min and the resulting orange solution is stirred for 2 h at −78° C. Iodine (2.54 g, 10.0 mmol) in anhydrous THF (12.5 mL) is then added dropwise over 15 min (keeping the temperature under −65° C.), causing the colour of the solution to change to red-brown and a precipitate to form. After 30 min the mixture is allowed to warm to 10° C. and the solvent is evaporated under reduced pressure. The residue is diluted with diethyl ether (25 mL) and washed with Na2S2O3 (2 M aq., 10 mL), HCl (2 M aq., 2×12.5 mL), NaHCO3 (sat. aq., 12.5 mL) and brine (12.5 mL). The organic solvents are dried over Na2SO4 and evaporated under reduced pressure to afford a yellow oil. The product is purified by silica chromatography, eluting with cyclohexane, to afford the title compound as a white solid (1.36 g). Alternatively, this compound may be used directly in the next step without further purification.

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