Under nitrogen atmosphere, a solution of Na2CO3 (427 mg) in water (8.8 ml) was added to a suspension of N′-[6-chloro-3-cyano-5-(1-isopropyl-6-oxo-1,6-dihydro-3-pyridazinyl)-2-pyrazinyl]-N,N-dimethylimidoformamide (346 mg), (2-bromophenyl)boronic acid (503 mg) and tetrakis(triphenylphosphine)palladium (35 mg) in dioxane (22 ml) and the mixture was stirred at 100-105° C. for 4 hours. Dioxane was evaporated under reduced pressure to give a residue. The residue was dissolved in CHCl3, dried over MgSO4, concentrated under reduced pressure and purified by column chromatography on silica gel. By elution with a mixture of n-hexane and EtOAc (70:30 v/v) was obtained 3-amino-5-(2-bromophenyl)-6-(1-isopropyl-6-oxo-1,6-dihydro-3-pyridazinyl)-2-pyrazinecarbonitrile as a solid (42 mg) and by elution with a mixture of n-hexane and EtOAc (50:50 v/v) was obtained N′-[6-(2-bromophenyl)-3-cyano-5-(1-isopropyl-6-oxo-1,6-dihydro-3-pyridazinyl)-2-pyrazinyl]-N,N-dimethylimidoformamide as a solid (360 mg).
