[NH2:1][C:2]1[CH:17]=[CH:16][C:5]([O:6][C:7]2[CH:14]=[CH:13][C:12]([F:15])=[CH:11][C:8]=2[C:9]#[N:10])=[CH:4][C:3]=1[CH3:18].Cl.[N:20]([O-])=O.[Na+].CC([O-])=O.[K+]>CC(O)=O.O.CCOC(C)=O>[F:15][C:12]1[CH:13]=[CH:14][C:7]([O:6][C:5]2[CH:4]=[C:3]3[C:2](=[CH:17][CH:16]=2)[NH:1][N:20]=[CH:18]3)=[C:8]([CH:11]=1)[C:9]#[N:10]
Intermediate (25t) (13.2 g, 54.5 mmol) and NH4BF4 were dissolved in 550 mL of mixed solvent of AcOH and water (2:1) and cooled to 0° C. Added concentrated HCl (12N, 23 mL, 272 mmol) and NaNO2 (4.14 g, 59.9 mmol) to the solution at 0° C., then the mixture was allowed to warm to room temperature and stirred. After 3 hours of stirring, the solution was concentrated under reduced pressure and azeotroped with toluene 4 times to dryness to obtain a pale yellow crude solid. The solid was dissolved in 600 mL of EtOAc and KOAc was added to the solution then the mixture was stirred under room temperature. In 30 minutes, the yellow solution became orange and was stirred further. After overnight stirring, the orange suspension was filtered and washed with EtOAc a few times to 1000 mL total volume. The organic solution was transferred to a separatory funnel and washed with saturated NaHCO3 and brine, dried with MgSO4, filtered and evaporated. The obtained crude orange solid was purified on silica gel with EtOAc/hexane (1:2-1:1) to afford an orange solid (13.2 g), which was washed with toluene. The orange colored toluene solution was concentrated and washed with toluene again. Repeating the same toluene washing afforded compound (26t) as a slightly orange colored solid (11.7 g, 84% yield over 2 steps). 1HNMR (400 MHz, CDCl3) δ 12.12 (s, 1H), 8.03 (s, 1H), 7.58 (d, J=9.4 Hz, 1H), 7.40 (d, J=2.3 Hz, 1H), 7.37 (dd, J=7.9, 3.1 Hz, 1H), 7.18 (ddd, J=9.4, 7.9, 3.1 Hz, 1H), 7.13 (dd, J=8.5, 2.3 Hz, 1H), 6.80 (dd, J=9.3, 3.9 Hz, 1H) ppm.
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