[CH3:1][O:2][C:3]([C:5]1[N:6]=[N:7][C:8]([Cl:12])=[CH:9][C:10]=1Cl)=[O:4].[CH3:13][N:14]1[CH:18]=[CH:17][C:16]([NH2:19])=[N:15]1>CN1CCCC1=O>[CH3:1][O:2][C:3]([C:5]1[N:6]=[N:7][C:8]([Cl:12])=[CH:9][C:10]=1[NH:19][C:16]1[CH:17]=[CH:18][N:14]([CH3:13])[N:15]=1)=[O:4]4,6-Dichloro-pyridazine-3-carboxylic acid methyl ester (165 mg, 0.8 mmol) and 1-methyl-1H-pyrazol-3-amine (81 mg, 0.837 mmol) were dissolved in of N-methylpyrrolidinone (3.2 mL). The reaction was heated at 110° C. for 2 h, then cooled and concentrated in vacuo. The residue was diluted with water and then extracted with ethyl acetate. The combined organic extracts were washed with brine, dried (sodium sulfate), filtered and concentrated in vacuo. Purification by chromatography (silica, 10 to 70% ethyl acetate in hexanes) gave 6-chloro-4-(1-methyl-1H-pyrazol-3-ylamino)-pyridazine-3-carboxylic acid methyl ester (69 mg, 32%) as a light brown solid. 1H NMR (300 MHz, CHLOROFORM-d) δ ppm 10.09 (br. s., 1H) 8.24 (s, 1H) 7.34 (d, J=2.3 Hz, 1H) 6.02 (d, J=2.3 Hz, 1H) 4.08 (s, 3H) 3.91 (s, 3H); LCMS (EI/CI) m/z: 268 [M+H].
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