Trifluoroacetic acid → 2-(4-Fluorophenyl)pyrazolo[1,5-a]pyridine

Participants

Reaction Steps

Solid t-butoxycarbonyl-O-mesitylenesulfonylhydroxylamine (17.26 54.6 mmol) was added portionwise with stirring to TFA (50 ml) over 10 min then stirred for a further 30 minutes. The solution was poured onto ice (˜250 ml) and left until the ice melted. The resulting white solid was filtered off, washed with water, and dissolved in chloroform (200 ml). The solution was dried over 4 Å mol. sieves for 1.5 hours, filtered and 1-(4-fluorophenyl)-2-pyridin-2-ylethanone oxime (6.29 g 27.3 mmol) in chloroform (100 ml) was added. The reaction was stirred at room temperature for 18 hours, washed with water (2×50 ml) and dried. Removal of solvent gave a brown solid which was purified by biotage chromatography. Elution with cyclohexane/ethyl acetate (20/1) gave the title compound as a yellow solid (4.09 g 71%). MH+: 213; NMR: (CDCl3): δ 6.75 (2H, m) 7.10 (3H, m) 7.50 (1H, d) 7.95 (2H, m) 8.45 (1H, d).

Provenance & Evidence