[CH2:1]([O:3][C:4](=[O:16])[CH2:5][N:6]1[C:14]2[CH2:13][CH2:12][CH2:11][C:10](=O)[C:9]=2[CH:8]=[N:7]1)[CH3:2].[Cl-].[OH:18][NH3+:19].N.[Cl-].[NH4+]>C(O)C>[CH2:1]([O:3][C:4](=[O:16])[CH2:5][N:6]1[C:14]2[CH2:13][CH2:12][CH2:11][C:10](=[N:19][OH:18])[C:9]=2[CH:8]=[N:7]1)[CH3:2]To a stirred solution of (4-oxo-4,5,6,7-tetrahydro-indazol-1-yl)-acetic acid ethyl ester (222 mg, 10 mmol) in ethanol (10 mL) was added hydroxylammonium chloride (74 mg, 10.5 mmol). The reaction mixture was heated at reflux for 1 hour. After cooling to room temperature, a solution of concentrated ammonia and saturated ammonium chloride (10 mL, 1:5, v/v) was added to the reaction mixture. The resulting solution was extracted with ethyl acetate (25 mL×3). The combined organic layers were washed with brine (30 mL), dried over sodium sulfate and concentrated in vacuo to give 4-hydroxyimino-4,5,6,7-tetrahydro-indazol-1-yl)-acetic acid ethyl ester (203 mg, 85%) as a white solid, which was used for the next step without further purification. The above white solid contained a pair of isomers in 10 to 1 ratio as determined by 1HNMR. for the major isomer, 1H NMR (400 MHz, CDCl3) δ ppm 8.29 (s, 1H), 4.89 (s, 2H), 4.26 (m, 2 H), 2.73 (t, J=6.4 Hz, 2 H), 2.58 (t, J=6.4 Hz, 2 H), 2.10 (t, J=6.4 Hz, 2 H), 1.31 (t, J=7.2 Hz, 3 H). MS calcd. for C11H15N3O3 237, obsd. (ESI+) [(M+H)+] 238.
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