Sodium Hydroxide → 4-oxo-4,5,6,7-tetrahydro-1H-indazole-3-carboxylic acid

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Reaction Conditions

Reaction Steps

A solution of 4-oxo-4,5,6,7-tetrahydro-1H-indazole-3-carboxylic acid ethyl ester (purity 90%, 1.84 g, 8.0 mmol) in methanol (20 mL) is treated with 10 N NaOH (4 mL) and stirred under nitrogen at 60° C. for 90 min. The solvent is evaporated under reduced pressure and the residue is dissolved in water (30 mL), treated with brine (30 mL) and acidified to pH 2 with conc. hydrochloric acid to produce a white precipitate. The mixture is cooled to 0° C. The precipitate is filtered, washed with water (5 mL), and dried in a vacuum oven to give 4-oxo-4,5,6,7-tetrahydro-1H-indazole-3-carboxylic acid. 1H NMR (DMSO-d6) 2.18 (quintet, J=6.2 Hz, 2H), 2.66 (t, J=6.4 Hz, 2H), 2.95 (t, J=6.2 Hz, 2H).

Provenance & Evidence