1-(2-Fluoroethyl)-1H-pyrazole-4-carboxylic acid synthesis

Yield:1401727-16-9 67%

Reaction Conditions:

with lithium hydroxide in tetrahydrofuran;methanol;water at 20; for 6 h;

Steps:

31.2

To a solution of 1-(2-fluoro-ethyl)-1H-pyrazole-4-carboxylic acid ethyl ester (4.0 g, 21.48 mmol) in THF: CH₃OH:water (20:60:20 mL) was added LiOH (1.8 g, 42.96 mmol) and the mixture was stirred at room temperature for 6 h. The volume was concentrated under reduced pressure and pH was adjusted to 2-3 using 1N HCl. The mixture was extracted with EtOAc (3×50 mL) and the combined organic layers were washed with water (2×30 mL), dried over Na₂SO₄ and evaporated to dryness to give the title compound IM31 as a colorless solid (2.3 g, 67%).1H NMR (DMSO, 400 MHz) δ 12.34 (1H, s), 8.28 (1H, s), 7.84 (1H,USD), 4.83-4.85 (1H, m), 4.71-4.73 (1H, m), 4.49-4.52 (1H, m), 4.43-4.45 (1H, m).

References:

US2012/252853,2012,A1 Location in patent:Page/Page column 31