[Cl:1][C:2]1[C:3]([NH2:12])=[C:4]([NH:8][CH:9]([CH3:11])[CH3:10])[N:5]=[N:6][CH:7]=1.[CH:13](OCC)(OCC)OCC>>[Cl:1][C:2]1[C:3]2[N:12]=[CH:13][N:8]([CH:9]([CH3:10])[CH3:11])[C:4]=2[N:5]=[N:6][CH:7]=1A mixture of 5-chloro-N3-isopropylpyridazine-3,4-diamine (Preparation 5, 1020 mg, 5.47 mmol) in triethyl orthoformate (9 mL) was heated at 130° C. for 80 minutes. The solvent was removed in vacuo and the residue dissolved in MeOH/DCM and purified by silica gel column chromatography eluting with EtOAc:heptane 0-63% to provide the titled product as a white solid in 76% yield, 816 mg.
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