tert-Butyl 3-amino-6,6-dimethyl-4,6-dihydropyrrolo[3,4-c]pyrazole-5(1H)-carboxylate

946497-94-5

398491-61-7

Tert-butyl 4-cyano-2,2-dimethyl-3-oxopyrrolidine-1-carboxylate (11.5 g, 48.2 mmol) was used as a raw material and dissolved in ethanol (300 mL). To this solution was added hydrazine hydrochloride (4.95 g, 72.4 mmol) and the reaction mixture was stirred at 85 °C for 18 hours. Upon completion of the reaction, the mixture was concentrated under vacuum to remove the solvent. The concentrated residue was dissolved in ethyl acetate (200 mL) and washed with saturated aqueous sodium bicarbonate. The aqueous phase was dried with magnesium sulfate and again concentrated under vacuum. The product was purified by column chromatography (eluent: ethyl acetate solution containing 3% methanol) to give tert-butyl 3-amino-6,6-dimethylpyrrolo[3,4-C]pyrazole-5(1H,4H,6H)-5-carboxylate (5.5 g, 46% yield) as an off-white solid. The product was characterized by 1H NMR (DMSO-d6) with chemical shifts δ 11.12 (s, 1H), 5.05 (s, 2H), 4.11-4.07 (m, 2H), 1.50-1.48 (m, 6H), 1.44-1.41 (m, 9H).