[F:1][CH2:2][C:3]([CH2:10][F:11])([CH3:9])[C:4](=O)[CH2:5][C:6]#[N:7].[OH-:12].[Na+].S(O)(O)(=O)=O.[NH2:19]O>CCO.O>[F:1][CH2:2][C:3]([C:4]1[CH:5]=[C:6]([NH2:7])[O:12][N:19]=1)([CH3:9])[CH2:10][F:11]To a solution of 5-fluoro-4-(fluoromethyl)-4-methyl-3-oxopentanenitrile (1.00 g, 6.2 mmol) and NaOH (0.272 g, 6.8 mmol) in EtOH (5 mL) and water (5 mL) at room temperature was added a solution of hydroxylamine sulfate (1.12 g, 6.8 mmol) in water (5 mL). To the mixture was added additional NaOH until the pH was about 8. After heating at 100° C. for 2 hours, it was quenched with water and extracted with CH2Cl2. Extracts were washed with water, dried over MgSO4, and concentrated under reduced pressure. The residue was purified by silica gel chromatography eluted with gradient of 0-50% EtOAc/hexane to afford 3-(1,3-difluoro-2-methylpropan-2-yl)isoxazol-5-amine as a solid (0.191 g, 17%). 1H NMR (300 MHz, CDCl3) δ 5.16 (s, 1H), 4.63 (q, 2H), 4.5 (q and br, 4H), 1.37 (s, 3H); LC-MS (ESI) m/z 177 (M+H)+.
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