I[C:2]1[CH:3]=[CH:4][C:5]2[N:6]([CH:8]=[C:9]([C:11]([O:13][CH2:14][CH3:15])=[O:12])[N:10]=2)[N:7]=1.[NH2:16][C:17]1[CH:18]=[C:19]([OH:23])[CH:20]=[CH:21][CH:22]=1.C(=O)([O-])[O-].[K+].[K+].CN(C)C=O>O.C(OCC)(=O)C>[NH2:16][C:17]1[CH:18]=[C:19]([CH:20]=[CH:21][CH:22]=1)[O:23][C:2]1[CH:3]=[CH:4][C:5]2[N:6]([CH:8]=[C:9]([C:11]([O:13][CH2:14][CH3:15])=[O:12])[N:10]=2)[N:7]=1A mixture of ethyl 6-iodoimidazo[1,2-b]pyridazine-2-carboxylate (951 mg, 3.00 mmol), 3-aminophenol (655 mg, 6.00 mmol), potassium carbonate (622 mg, 4.50 mmol) and N,N-dimethylformamide (9.0 mL) was stirred at 150° C. for 6 hr. After allowing the reaction mixture to cool to room temperature, ethyl acetate and water were added to the mixture and the insoluble material was filtered through celite. The organic layer was collected from the filtrate, washed with saturated aqueous sodium hydrogencarbonate solution, and dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure, and the residue was purified by silica gel column chromatography (ethyl acetate/hexane=1/19→ethyl acetate alone) to give the title compound (350 mg, 39%).
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