Under nitrogen atmosphere, a solution of Na2CO3 (138 mg) in water (0.8 ml) was added to a suspension of 3-amino-5-chloro-6-(1-isopropyl-6-oxo-1,6-dihydro-3-pyridazinyl)-2-pyrazinecarboxamide (100 mg), 2-thienylboronic acid (104 mg) and tetrakis(triphenylphosphine)palladium (11.3 mg) in dioxane (2 ml) and the mixture was stirred at 100-105° C. for 4 hours. After addition of water (10 ml), a precipitate was collected by filtration and purified by column chromatography on silica gel eluting with a mixture of n-hexane and EtOAc (40:60 v/v) to give 3-amino-6-(1-isopropyl-6-oxo-1,6-dihydro-3-pyridazinyl)-5-(2-thienyl)-2-pyrazinecarboxamide as a solid (85 mg).
