1-Butyl-3-methylimidazolium tetrafluoroborate → 3-Bromo-5-fluoro-2,4-dimethylpyridine

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A mixture of 5-bromo-4,6-dimethyl-pyridin-3-amine (500 mg, 2.49 mmol) and nitrosyl tetrafluoroborate (445 mg, 3.73 mmol) in 1-butyl-3-methylimidazolium tetrafluoroborate (9.48 mL, 49.74 mmol) was heated at 60° C. for 2 hours (caution: exothermic). The reaction mixture was diluted with ethyl acetate (50 mL) and washed with water (2×20 mL), and then saturated aqueous sodium bicarbonate (20 mL). The organic layer was separated, dried over sodium sulfate, filtered and concentrated in vacuo to provide a residue that was purified by flash chromatography (4 g, Silica, 0-50% ethyl acetate in heptane). Desired fractions were combined and evaporated in vacuo to afford the title compound as pale yellow oil (220 mg, 43%), which was used in the next step without further purification.

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