Potassium Fluoride → 2-(4-Fluorophenyl)-3-(4-pyridinyl)pyrazolo[1,5-a]pyridine

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Reaction Steps

To a solution of 2-(4-fluorophenyl)-3-bromopyrazolo[1,5-α]pyridine (0.2 g, 0.68 mmol) and 4-(tributylstannyl)pyridine (0.38 g, 1 mmol) in dry toluene (10 mL) was added tetrakis(triphenylphosphine)palladium (0) (0.03 g, 0.03 mmol) and the mixture was heated at reflux temperature under a nitrogen atmosphere for about 48 hours. The mixture was cooled to room temperature and diluted with diethyl ether (40 mL). The mixture was poured into a 10% aqueous solution of potassium fluoride (20 mL) and the mixture was stirred for 1 hour. The biphasic mixture was filtered through a pad of diatomaceous earth and the organic phase was separated. The aqueous phase was extracted with diethyl ether (10 mL) and the combined organic phases are washed with brine, dried over anhydrous magnesium sulfate, filtered and the solvent evaporated under reduced pressure. The residue was purified using silica gel chromatography with 20% ethyl acetate in hexanes, followed by 50% ethyl acetate in hexanes, as eluent to give the title compound as an off white solid, 0.16 g (80%). 1H NMR (CDCl3) δ 8.58 (br s, 2H), 8.50 (d, 1H, J=7.2 Hz), 7.63 (d, 1H, 9 Hz), 7.52 (m, 2H), 7.27–7.20 (m, 3H), 7.06 (t, 2H, 8.7 Hz), 6.86 dt, 1H, J=7, 1 Hz). MS (+ve ion electrospray) 290 (100), (MH+).

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