N[C:2]1[CH:18]=[CH:17][C:5]2[CH2:6][CH2:7][N:8]([C:11](=[O:16])[C:12]([F:15])([F:14])[F:13])[CH2:9][CH2:10][C:4]=2[CH:3]=1.[OH:19]S(O)(=O)=O.N([O-])=O.[Na+]>O>[F:13][C:12]([F:15])([F:14])[C:11]([N:8]1[CH2:9][CH2:10][C:4]2[CH:3]=[C:2]([OH:19])[CH:18]=[CH:17][C:5]=2[CH2:6][CH2:7]1)=[O:16]Into a 250 ml flask, the product of step (c) (2 g, 7.75 mmol) dissolved in water (8.5 ml) and concentrated H2SO4 (1.5 ml) was added. The stirred mixture was heated to 70° C., followed by the addition of a solution NaNO2 (615 mg, 8.91 mmol) in water (20 ml). The reaction mixture was stirred at 70° C. for 1 hour. The mixture was then allowed to cool to room temperature and diluted with water (50 ml). The aqueous mixture was extracted with EtOAc (3×). The combined EtOAc extracts were washed with brine, dried over Na2SO4, and solvent evaporated in vacuo to give the sub-title compound as a brown solid (1.8 g) that was used without further purification. MS: ESI (positive): 260 (M+H).
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