[NH:1]1[CH2:5][CH2:4][CH2:3][CH2:2]1.Br[C:7]1[CH:12]=[C:11]([Cl:13])[N:10]=[N:9][C:8]=1[Cl:14].C(=O)([O-])[O-].[K+].[K+].O>CN(C=O)C>[Cl:14][C:8]1[N:9]=[N:10][C:11]([Cl:13])=[CH:12][C:7]=1[N:1]1[CH2:5][CH2:4][CH2:3][CH2:2]1
Pyrrolidine (3.36 ml, 40 mmol) was added to a stirred solution/suspension of 4-bromo-3,6-dichloropyridazine (8.3 g, 36 mmol) and potassium carbonate (13.8 g, 0.1 mol) in dry DMF (100 ml) at room temperature under nitrogen. The mixture was stirred at room temperature for 16 hours, then at 60° C. for 3 hours. The reaction was poured into water (250 ml). The aqueous was extracted with ethyl acetate (×3). The combined extracts were dried (MgSO4), filtered and evaporated. The residue was purified by chromatography on silica gel, eluting with 0.5% methanol/dichloromethane to afford the title pyridazine (7.2 g, 92%) as a colourless oil. 1H NMR (250 MHz, CDCl3) 2.00-2.05 (4H, m) 3.61-3.69 (4H, m), 6.46 (1H, s). MS (ES+) 218 [MH]+, 220 [MH]+.
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