Hydrazine → tert-Butyl (1S,9S)-9-amino-6,10-dioxooctahydro-6H-pyridazino[1,2-a][1,2]diazepine-1-carboxylate

In a 200 mL round-bottomed flask, (1S,9S)-tert-butyl 9-(1,3-dioxoisoindolin-2-yl)-6,10-dioxooctahydro-1H-pyridazino[1,2-a][1,2]diazepine-1-carboxylate (5 g, 11.7 mmol) was combined with ethanol (50 ml) to give a colorless suspension. Hydrazine (825 mg, 808 μl, 25.7 mmol) was added and stirred at room temperature for 2 hr. The crude reaction mixture was concentrated in vacuo and evaporated with toluene. 2M aqueous acetic acid (50 ml) was added and stirred at room temperature overnight. The precipitate was filtered and the filtrate was basified with sodium carbonate solution. It was extracted with CH2Cl2 (2×150 ml). The combined organic layer was dried with MgSO4 and concentrated in vacuo to afford (1S,9S)-tert-butyl 9-amino-6,10-dioxooctahydro-1H-pyridazino[1,2-a][1,2]diazepine-1-carboxylate as a sticky white solid (3.4 g, 97.8%). ESI-LRMS m/e calcd for C14H23N3O4 [M+] 297. found 298 [M+H+].