[Cl:1][C:2]1[N:7]=[C:6]([NH:8][CH2:9][C:10]2[CH:11]=[C:12]3[C:17](=[CH:18][CH:19]=2)[N:16]=[CH:15][CH:14]=[CH:13]3)[C:5]([NH2:20])=[CH:4][CH:3]=1.[N:21]([O-])=O.[Na+].S(=O)(=O)(O)O.C(=O)(O)[O-].[Na+]>C(O)(=O)C.O>[Cl:1][C:2]1[N:7]=[C:6]2[N:8]([CH2:9][C:10]3[CH:11]=[C:12]4[C:17](=[CH:18][CH:19]=3)[N:16]=[CH:15][CH:14]=[CH:13]4)[N:21]=[N:20][C:5]2=[CH:4][CH:3]=1
Intermediate 9 (0.220 g, 0.772 mmol) was dissolved in acetic acid (1.3 ml) and cooled to 5° C. Sodium nitrite (0.063 g, 0.927 mmol) in 0.35 ml water was added slowly followed by sulphuric acid (0.09 ml). The reaction mixture was warmed to RT and stirred for 30 min. The reaction mixture was poured into ice water and pH adjusted to ca. 8 with sodium bicarbonate solution, extracted with ethyl acetate, washed with brine, dried over sodium sulphate and concentrated to afford the title compound as a brown solid (0.220 g, 96%). 1H-NMR (δ ppm, DMSO-d6, 400 MHz): δ 8.88 (s, 1H), 8.69 (d, J=8.6 Hz, 1H), 8.35 (d, J=8.1 Hz, 1H), 8.01 (d, J=8.6 Hz, 1H), 7.90 (s, 1H), 7.74 (d, J=8.5 Hz, 1H), 7.61 (d, J=8.5 Hz, 1H), 7.53 (dd, J=8.0, 4.0 Hz, 1H), 6.12 (s, 2H).
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