p-Toluenesulfonic acid → 5-Hydroxy-1H-pyrazole-3-carboxylic acid methyl ester

Participants

Reaction Steps

To a solution of (E)-2-hydrazino-but-2-enedioic acid dimethyl ester (500 mg, 2.87 mmol) in xylene (10 mL) was added para-toluenesulfonic acid (45 mg, 0.24 mmol) and the resulting mixture heated at reflux for 4 h. After cooling to room temperature the mixture was stirred overnight and the resulting solid was filtered off and dried to afford the title compound (283 mg, 69%) as a white solid after trituration with dichloromethane. MS: m/e=141.1 [M+H]+.

Provenance & Evidence