C([O:5][C:6]1[N:15]=[CH:14][CH:13]=[C:12]2[C:7]=1[C:8]1[CH:22]=[C:21]([F:23])[CH:20]=[CH:19][C:9]=1[C:10]([C:16]([CH3:18])=[CH2:17])=[N:11]2)CCC.S(=O)(=O)(O)O.[OH-].[Na+]>O.CCOC(C)=O>[F:23][C:21]1[CH:20]=[CH:19][C:9]2[C:10]([C:16]([CH3:18])=[CH2:17])=[N:11][C:12]3[CH:13]=[CH:14][NH:15][C:6](=[O:5])[C:7]=3[C:8]=2[CH:22]=1To a stirred suspension of 1-butoxy-9-fluoro-6-isopropenylbenzo[c]-1,6-naphthyridine (30 mg, 0.097 mmol) in water (0.5 ml) was added sulfuric acid (0.5 ml) (CAUTION: EXOTHERM). The reaction mixture was stirred for 15 h at 100° C. The reaction was diluted with EtOAc (30 mL) and water (30 mL). To the resulting biphasic mixture was added NaOH (0.85 g, 21 mmol) portionwise to make the aqueous layer basic. The organic layer was dried over sodium sulfate, filtered and concentrated. The crude residue was dissolved in 3 ml DMF and 100 uL of TFA, and purified by preparative reverse phase HPLC eluting with an acetonitrile/water+(with 0.05% TFA as a modified) gradient, to afford 9-fluoro-6-isopropenylbenzo[c]-1,6-naphthyridin-1(2H)-one. 1H NMR (500 MHz, DMSO-D6) δ 11.92 (br s, 1H), 9.74 (dd, 1H), 8.41 (dd, 1H), 7.64-7.60 (overlapping m, 2H), 6.78 (d, 1H), 5.70 (s, 1H), 5.22 (s, 1H), 2.25 (s, 3H). LRMS (ESI) calc'd for (C15H11FN2O) [M+H]+, 255.1; found 255.0.
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