Hydrochloric Acid → ethyl 3-amino-6,6-dimethyl-5,6-dihydropyrrolo[3,4-c]pyrazole-1(4H)-carboxylate dihydrochloride

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Reaction Steps

To a stirred slurry of 5-tert-butyl 1-ethyl 3-amino-6,6-dimethyl-4,6-dihydropyrrolo[3,4-c]pyrazole-1,5-dicarboxylate (I(H), 30.0 g, 92.5 mmol) in ethanol (200 mL) was drop wise added HCl 4 M solution in hexanes (116 mL) drop wise. The resulting clear solution was stirred at room temperature for 12 h. The reaction mixture was concentrated under vacuum to a residue and stirred with hexane (250 mL) for 10 min. The solid product was collected by filtration, washed with hexane (100 mL) and dried under vacuum at 40° C. for 15 h to get ethyl 3-amino-6,6-dimethyl-5,6-dihydropyrrolo[3,4-c]pyrazole-1(4H)-carboxylate dihydrochloride (54a, 27.0 g, 98.5%) as white solid. 1H NMR (300 MHz, dmso-d6): δ 1.31 (td, J=7, 1.3 Hz, 3H), 1.59 (s, 6H), 4.09 (t, J=3.7 Hz, 2H), 4.36 (qd, J=7.2, 1.2 Hz, 2H), 10.12 (br s, 2H).

Provenance & Evidence