[CH3:1][N:2]1[CH:6]=[C:5]([C:7]2[CH:8]=[CH:9][C:10]3[N:11]([CH:13]=[CH:14][N:15]=3)[N:12]=2)[CH:4]=[N:3]1.[Br:16]N1C(=O)CCC1=O.CCOC(C)=O>CN(C=O)C>[Br:16][C:13]1[N:11]2[N:12]=[C:7]([C:5]3[CH:4]=[N:3][N:2]([CH3:1])[CH:6]=3)[CH:8]=[CH:9][C:10]2=[N:15][CH:14]=16-(1-Methyl-1H-pyrazol-4-yl)-imidazo[1,2-b]pyridazine (Stage 8.2, 2.22 g, 11.1 mmol) was dissolved in DMF (33 mL) and cooled down to 0° C. with an ice-water bath. Then N-bromo-succinimide (2.3 g, 12.3 mmol) was added and the RM was stirred at the same temperature for 1 h45. It was then taken up with EtOAc and washed with a saturated solution of NaHCO3 and brine. The organic layer was dried over Na2SO4 and the solvent was removed. The residue was triturated with Et2O and the precipitate was filtered off to afford the title compound as a yellow solid (tR 1.3 min (conditions 2), MH+=278).
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