Sodium Hydroxide → 5,7-Dimethylpyrazolo[1,5-a]pyrimidine-3-carboxylic acid

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Reaction Conditions

Reaction Steps

Pentane-2,4-dione (1.46 ml, 14.2 mmol), ethyl 3-amino-1H-pyrazole-4-carboxylate (2.00 g, 12.9 mmol) were heated in a sealed tube with acetic acid (10 ml) at 110° C. overnight. The reaction reached completion by LCMS (LC-MS: rt (min)=3.08). The acetic acid was removed by blowing air with the flask being heated to 75° C. The crude residue of ethyl 5,7-dimethylpyrazolo[1,5-a]pyrimidine-3-carboxylate (assumed to be 12.89 mmol) was suspended in MeOH (15 ml) and treated with 7.2 M sodium hydroxide (5.37 ml, 38.7 mmol). The mixture was heated to 80° C. (at this temperature the solid dissolved) and then stirred for 3 h. The reaction was cooled and the neutralized to pH 6-7. The slurry was filtered via a Büchner funnel under house vacuum, the solid residue was washed with water and then diethyl ether to obtain 5,7-dimethylpyrazolo[1,5-a]pyrimidine-3-carboxylic acid (1.4 g, 7.3 mmol, 57% yield). LC-MS: rt (min)=2.61. 1H NMR (400 MHz, DMSO-d6) δ ppm 2.57 (s, 3H), 2.71 (s, 3H), 7.10 (s, 1H), 8.50 (s, 1H).

Provenance & Evidence