[NH2:1][N:2]1[CH:6]=[CH:5][N:4]=[C:3]1[C:7]([O:9][CH2:10][CH3:11])=[O:8].CN(C=O)C.C(Cl)Cl.Cl[C:21]([O:23][CH2:24][CH3:25])=[O:22]>N1C=CC=CC=1>[CH2:24]([O:23][C:21]([NH:1][N:2]1[CH:6]=[CH:5][N:4]=[C:3]1[C:7]([O:9][CH2:10][CH3:11])=[O:8])=[O:22])[CH3:25]
(I9C): In 10 lit, round bottom flask charged ethyl 1-amino-1H-imidazole-2-carboxylate (70 g, 451 mmol) along with DMF and DCM (1200 ml) was added and cooled to 10-15° C. Then pyridine was added (35 ml) at single lot. Followed by slow addition of ethyl chloroformate (30 ml) and stirred at same temperature for 1.5 hrs. After 1.5 hrs additional pyridine (25 ml) and ethyl chloroformate (20 ml) was added. The reaction mixture was stirred for additional 30 minutes. The reaction mixture was concentrated under high vacuum and the crude residue was diluted with ethyl acetate and given saturated aqueous citric acid (250 ml) washing. The organic layer was separated. The citric acid layer was extracted with EtOAc (3×500 ml). All organic layers combined and washed with brine (2×150 ml), dried with sodium sulphate and concentrated to get the syrupy gel. The syrupy gel was triturated with ether-hexane mixture to give 65 g of ethyl 1-((ethoxycarbonyl)amino)-1H-imidazole-2-carboxylate as pale yellow solid.
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