[Br:1][C:2]1[CH:3]=[N:4][C:5]2[CH:6]=[CH:7][CH:8]=[N+:9]([O-])[C:10]=2[CH:11]=1.[Cl-].C(=O)([O-])[O-:15].[K+].[K+]>C(Cl)(Cl)Cl.O>[Br:1][C:2]1[CH:11]=[C:10]2[C:5]([CH:6]=[CH:7][C:8](=[O:15])[NH:9]2)=[N:4][CH:3]=1To a mixture of 3-bromo-1,5-naphthyridine-5-oxide (C-3) (70.0 g, 311 mmol, 1.0 eq) and 4-toluolsulfonyl chloride (71.16 g, 373 mmol, 1.2 eq) in CHCl3 (1200 mL) was added a solution of potassium carbonate (146 g, 1056 mmol, 3.4 eq) in H2O (500 mL) at RT. The resulting mixture was stirred overnight and diluted with H2O (500 mL). The solid was collected by filtration, washed with water, dried in vacuo to afford the desired product 7-bromo-1,5-naphthyridin-2(1H)-one (C-4) (28.8 g, 41.2% yield). 1H NMR (300 MHz, DMSO-d6) δ: 11.90 (bs, 1H), 8.51 (s, 1H), 7.88 (d, J=9.6 Hz, 1H), 7.81 (s, 1H), 6.74 (d, J=9.6 Hz, 1H); ESI-MS m/z: 225.1 [M+H]+.
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