Hydrochloric Acid → 5-chloro-1-phenyl-1H-pyrazole-4-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

To a solution of 5-chloro-1-phenyl-1H-pyrazole-4-carboxylic acid ethyl ester (Intermediate 1; 7.3 g, 29.1 mmol) in tetrahydrofuran (70 mL) was added a solution of lithium hydroxide in water (7.3 g, 305 mmol) in water (70 mL). Methanol (˜10 mL) was added dropwise to the reaction mixture until only one layer was visible. The reaction mixture was stirred at 70° C. for 1 hour (reaction progress monitored by TLC). The reaction mixture was acidified to pH 3 with 1N hydrochloric acid and washed with dichloromethane (3×200 mL). The organic layer was dried over magnesium sulfate and evaporated to give 5-chloro-1-phenyl-1H-pyrazole-4-carboxylic acid (5.8 g, 91%), which HPLC analysis indicated was 85% pure. This material was used directly in the next step without further purification.

Provenance & Evidence