Potassium Fluoride → 4-Bromo-1-(trifluoromethyl)-1H-pyrazole

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Reaction Steps

HF-pyridine complex (129 mL) was added to a stirred and cooled (ice bath) solution of bromide 5 (72.68 g, 0.263 mol) in diisopropyl ether (196 mL) in a polypropylene reaction vessel. Mercuric oxide red (48.4 g, 0.222 mol) was then added in small portions over a period of 3 h at RT. The mixture was stirred for additional 4 h at RT and was poured onto a 25% aqueous KF (650 mL). The solid was filtered off and washed with ether (100 mL). The filtrate was extracted with ether (3×100 mL). Combined extracts were dried (MgSO4), concentrated under reduced pressure and distilled to afford 6 (31.05 g, 55%) as colourless liquid b.p. 35-37° C./25 mm Hg, which crystallized on standing in a refrigerator, m.p. 4° C. 1H NMR (400 MHz, CDCl3) δ 7.73 (s, 1H), 7.86 (s, 1H).

Provenance & Evidence