Hydrochloric Acid → 2,4-dichloro-3-(1-methyl-3-methylcarbonyl-1H-pyrazol-5-yl)benzoic acid

Participants

Reaction Conditions

Reaction Steps

At room temperature and under protective gas, 2.0 g (6.7 mmol) of 2,4-dichloro-3-(5-methylcarbonyl-1H-pyrazol-3-yl)benzoic acid in 50 ml of tetrahydrofuran were added dropwise to 0.40 g (16.7 mmol) of sodium hydride. The mixture was stirred for 1 hour, 4.8 g (33.4 mmol) of methyl iodide were added, the mixture was stirred for 10 hours and another 4.8 g (33.4 mmol) of methyl iodide were added, the mixture was stirred at 50° C. for 5 hours and 0.16 g (6.7 mmol) of sodium hydride and another 4.8 g (33.4 mmol) of methyl iodide were then added and the mixture was heated at 50° C. for 1 hour. After cooling, the reaction mixture was stirred into 100 ml of a sodium chloride solution and a pH of 1 was adjusted using hydrochloric acid. The product was then extracted with methyl tert-butyl ether and the combined organic phases were washed with water, dried and concentrated. The residue was then chromatographed over silica gel (eluent: toluene/tetrahydrofuran/acetic acid=8/1/1). 1.25 g (60% of theory) of 2,4-dichloro-3-(1-methyl-3-methylcarbonyl-1H-pyrazol-5-yl)benzoic acid were obtained.

Provenance & Evidence