Hydrochloric Acid → (1,3-Dimethyl-1H-pyrazol-5-yl)acetic acid

Participants

Reaction Steps

To a solution of (2,5-dimethyl-2H-pyrazol-3-yl)-acetic acid N-methyl-hydrazide (9.1 g, 41 mmol) in dioxane (50 mL) aqueous sodium hydroxide solution was added (5 N, 50 mL) and the and the resulting mixture was heated under reflux for 4 h. After addition of hydrochloric acid (5 N, 50 mL), all volatiles were evaporated. The residue was extracted with refluxing ethanol (150 mL) and the solvent was evaporated. Residual volatiles were azeotropically removed by coevaporation with toluene to afford (2,5-dimethyl-2H-pyrazol-3-yl)-acetic acid as a viscous oil. It was dissolved in ethanol (100 ml), p-toluene sulfonic acid (2.0 g, catalytic) was added and the resulting mixture was heated under reflux for 16 h. After evaporation of the solvent, the residue was extracted with ethyl acetate and water. The organic phase was dried over sodium sulfate, concentrated and chromatographed (SiO2, heptanes:ethyl acetate=100:0 to 40:60) to afford the title compound as a colorless oil (7.6 g, 100%). 1H-NMR (400 MHz, CDCl3): δ=1.22 (t, J=7 Hz, 3H), 2.22 (s, 3H), 3.61 (s, 2H), 3.75 (s, 2H), 4.18 (q, J=7 Hz, 2H), 5.95 (s, 1H).

Provenance & Evidence