1-Ethyloxycarbonyl-5-Boc-3-amino-4,6-dihydro-pyrrolo[3,4-c]pyrazole

398491-59-3

541-41-3

398495-65-3

The general procedure for the synthesis of ethyl 5-Boc-3-amino-4,6-dihydropyrrolo[3,4-C]pyrazole-1-carboxylate from 3-amino-5-Boc-pyrrolo[3,4-C]pyrazole and ethyl chloroformate was carried out as follows: a solution of THF (250 mL) with ethyl chloroformate (8.9 mL, 93 mmol) was slowly added at 0-5 °C to the solution containing 3 -amino-5-tert-butoxycarbonyl-pyrrolo[3,4-C]pyrazole (20 g, 89 mmol) and diisopropylethylamine (DIEA, 92 mL, 528 mmol) to a solution of THF (500 mL). The reaction was kept at the same temperature for 2 h, followed by raising to room temperature and stirring overnight. After completion of the reaction, the mixture was concentrated to dryness under vacuum. The resulting residue was extracted with ethyl acetate and water, the organic phase was separated, dried over anhydrous sodium sulfate and concentrated again to dryness. The crude product was purified by fast column chromatography (eluent: ethyl acetate/cyclohexane, ratio tapered from 4/6 to 7/3) to afford 19 g (72% yield) of the target compound ethyl 5-Boc-3-amino-4,6-dihydropyrrolo[3,4-C]pyrazole-1-carboxylate as a white solid.1H-NMR (400 MHz, DMSO-d6) δ: 10.06 (s, broad peak, 2H), 4.4-4.05 (m, 6H), 1.27 (t, 3H), 1.00 (s, 9H).