Hydrochloric Acid → 5-(2-hydroxy-phenyl)-1-methyl-1H-pyrazole-3-carboxylic acid

Participants

Reaction Steps

To a solution of 5-(2-benzyloxy-phenyl)-1H-pyrazole-3-carboxylic acid ethyl ester (0.25 g, 0.00078 mole) in DMF (5 mL) was added K2CO3 (0.225 g, 0.00163 mole) followed by methyl iodide (0.116 g, 0.00081 mole) and at the resulting mixture was stirred at ambient temperature for 1 hour. The mixture was then quenched with iced water and the resulting precipitate was isolated by filtration. The solid was recrystallized from ethyl acetate to afford 0.251 g (96%) of 5-(2-benzyloxy-phenyl)-1-methyl-1H-pyrazole-3-carboxylic acid ethyl ester. LCMS: 337.15 (M+1)+, 90.13%. To a stirred solution of 5-(2-benzyloxy-phenyl)-1-methyl-1H-pyrazole-3-carboxylic acid ethyl ester (0.251 g, 0.00075 mole) in methanol (40 mL) was added 10% Pd/C (0.05 g) and the resulting mixture was stirred under an atmosphere of hydrogen for 1 hour. The mixture was then filtered through celite and the celite was washed with methanol. The combined filtrate was concentrated under reduced pressure to afford 0.169 g (92%) of 5-(2-hydroxy-phenyl)-1-methyl-1H-pyrazole-3-carboxylic acid ethyl ester. LCMS: 247.1 (M+1)+, 99%. To a stirred solution of 5-(2-hydroxy-phenyl)-1-methyl-1H-pyrazole-3-carboxylic acid ethyl ester (0.169 g, 0.00069 mol) in a mixture of THF (10 mL), methanol (5 mL) and H2O (5 mL), was added LiOH.H2O (0.087 g, 0.00206 mol) at ambient temperature and the resulting mixture was stirred overnight. The reaction mixture was then diluted with cold water and acidified with 10% HCl. The product was extracted with ethyl acetate. The organic layer was dried over sodium sulfate and concentrated under reduced pressure to afford 0.13 g (87%) of 5-(2-hydroxy-phenyl)-1-methyl-1H-pyrazole-3-carboxylic acid. LCMS: 219.07 (M+1)+, 81.5%

Provenance & Evidence