Lithium Hydroxide → 1-cyclopentyl-5-methyl-1H-pyrazole-4-carboxylic acid

Participants

Reaction Steps

A solution of ethyl 1-cyclopentyl-5-methyl-1H-pyrazole-4-carboxylate (15.5 g, 70 mmol) in EtOH (200 mL) was treated with a solution of LiOH (6 g, 250 mmol) in water (100 mL) and the resultant mixture was stirred at 60° C. overnight. The reaction was concentrated in vacuo and the residue was partitioned between EtOAc and water. The aqueous layer was acidified with aq HCl (2 M) to pH 3 and was extracted with EtOAc. The extract was concentrated under reduced pressure to give 1-cyclopentyl-5-methyl-1H-pyrazole-4-carboxylic acid (8.7 g, 64% yield). 1H NMR (300 MHz, DMSO-d6): δ 12.05 (br s, 1 H), 8.10 (s, 1 H), 4.60 (m, 1 H), 2.28 (s, 3 H, 2.04-1.97 (m, 2 H), 1.89-1.85 (m, 2H), 1.78-1.71 (m, 2 H), 1.62-1.59 (m, 2 H); MS (ESI) m/z: 194.99 [M+H]+.

Provenance & Evidence