[F:1][C:2]([CH3:9])([CH3:8])[C:3](=O)[CH2:4][C:5]#[N:6].[OH-:10].[Na+].S(O)(O)(=O)=O.[NH2:17]O>O.CCO>[F:1][C:2]([C:3]1[CH:4]=[C:5]([NH2:6])[O:10][N:17]=1)([CH3:9])[CH3:8]To a stirred solution of 4-fluoro-4-methyl-3-oxopentanenitrile from Step 1 (12.9 g, 0.1 mol) and sodium hydroxide (8.20 g, 0.11 mol) in 1:1 water/EtOH (184 mL) was added hydroxylamine sulfate (17.23 g, 0.11 mol). The mixture was adjusted to pH 7.5 with 1N NaOH, then heated at 80° C. for 15 h. After cooling to rt, the mixture was concentrated to dryness under reduced pressure. The resulting solid was partitioned between water and dichloromethane, and the separated organic layer was washed with brine, dried over MgSO4, and concentrated under reduced pressure. The residue was purified by silica gel chromatography eluting with 0-10% EtOAc in petroleum ether to afford 3-(2-fluoropropan-2-yl)isoxazol-5-amine as a yellow solid (5 g, 35%). LC-MS (ESI) m/z 145 (M+H)+.
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