1H-Pyrazole-3-acetic acid, 2,5-dihydro-5-oxo- synthesis

Yield:924858-85-5 82%

Reaction Conditions:

Stage #1: ethyl (5-oxo-2,5-dihydro-1H-pyrazol-3-yl)acetatewith methanol;sodium hydroxide;water in tetrahydrofuran at 20 - 80; for 3 h;
Stage #2: with hydrogenchloride;water

Steps:

118

Reference Example 118 (5-oxo-2,5-dihydro-1H-pyrazol-3-yl)acetic acid To a suspension of ethyl (5-oxo-2,5-dihydro-1H-pyrazol-3-yl)acetate obtained in Reference Example 117 (5.00 g, 29.4 mmol) in THF (20 mL)-methanol (20 mL)-water (20 mL) was added 8N aqueous sodium hydroxide solution (11.0 mL, 88.0 mmol) at room temperature, and the mixture was stirred under heating at 80°C for 3 hr. The reaction mixture allowed to cool to room temperature, and concentrated under reduced pressure, and the residue was diluted with water, and acidified with 6N hydrochloric acid. The precipitated solid was collected by filtration, and washed with water, and dried under nitrogen stream to give the title compound as a white powder (3.43 g, 82%). ¹H-NMR (300MHz, DMSO-d₆) δ: 3.45 (2H, s), 5.33 (1H, s), 10.52-12.13 (3H, m).

References:

EP1953148,2008,A1 Location in patent:Page/Page column 165