[NH2:1]OS(O)(=O)=O.[NH:7]1[CH:11]=[CH:10][N:9]=[C:8]1[C:12]([O:14][CH2:15][CH3:16])=[O:13].C([O-])([O-])=O.[K+].[K+]>O>[NH2:1][N:7]1[CH:11]=[CH:10][N:9]=[C:8]1[C:12]([O:14][CH2:15][CH3:16])=[O:13]To a stirred solution of hydroxylamine-o-sulfonic acid (26.64 g, 235.8 mmol, 3.0 eq) in H2O (17 mL) at 0° C., ethyl 1H-imidazole-2-carboxylate (11.0 g, 78.6 mmol, 1.0 eq) was added and the resulting mixture was stirred at 90° C. for 30 min. The mixture was cooled to RT and K2CO3 (3.6 g, 26.2 mmol, 1.0 eq) was added in portions. The resulting mixture was stirred at RT overnight, filtered and rinsed with H2O (10 mL×3). The filtrate was extracted with ethyl acetate (50 mL×5). The combined organic layer was washed with brine, dried over Na2SO4 and filtered. The filtrate was evaporated in vacuo and the residue was purified by flash column chromatography on silica gel (1% MeOH in DCM) to afford ethyl 1-amino-1H-imidazole-2-carboxylate (800 mg, 6.5% yield). ESI-MS m/z: 156.1 [M+H]+.
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