[OH-].[K+].N([CH2:5]NC(N)=O)=O.[CH2:10]([O:12][C:13]([N:15]1[C:23]2[C:18](=[C:19]([Br:24])[CH:20]=[CH:21][CH:22]=2)[C:17]([OH:25])=[N:16]1)=[O:14])[CH3:11]>CCOCC.C1COCC1>[CH2:10]([O:12][C:13]([N:15]1[C:23]2[C:18](=[C:19]([Br:24])[CH:20]=[CH:21][CH:22]=2)[C:17]([O:25][CH3:5])=[N:16]1)=[O:14])[CH3:11]To a 0° C. mixture of KOH (50% in H2O, 50 ml) and Et2O (150 ml), N-nitrosomethylurea (10.7 g, 103 mmol) was added portionwise over 40 minute period. After stirring for additional 20 minutes, the mixture was cooled to −78° C. and the upper bright yellow layer was poured into a 0° C. suspension of 4-Bromo-3-hydroxy-indazole-1-carboxylic acid ethyl ester CLXXXIV (2.96 g, 10.4 mmol) in a mixture of Et2O (100 ml) and THF (30 ml). After 2 hours, the yellow solution was warmed to room temperature and was left to stand at room temperature for 24 hours. The mixture was then washed with H2O and brine. The organic layer was dried over MgSO4, filtered, concentrated, and purified via flash chromatography (hexane/EtOAc) affording 4-Bromo-3-methoxy-indazole-1-carboxylic acid ethyl ester CLXXXV as an off-white solid (40% yield).
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