To a room temperature solution of 4-chloro-7-ethyl-7H-imidazo[4,5-c]pyridazine (Preparation 8, 9.6 g, 52.4 mmol) in dioxane (300 mL) was added 4-fluorobenzene boronic acid (8.8 g, 63 mmol) and an aqueous solution of Na2CO3 (1M, 260 mL, 262 mmol). The reaction mixture was degassed and purged with nitrogen gas 3 times. Tetrakis(triphenylphosphine)palladium(0) (1.2 g, 1.0 mmol) was then added and the mixture was heated to reflux for 4 hours. The organic solvent was removed in vacuo and the resulting aqueous mixture filtered. The filter cake was dried under vacuum to afford the title compound as a yellow solid in 55% yield, 7 g.
