A solution of 6-chloro-3-isopropyl-[1,2,4]triazolo[4,3-b]pyridazine (20.0 g, 102 mmol, Preparation #G.1) in DMF (300 mL) was evacuated and purged with nitrogen 3 times. To the reaction mixture was added 1-ethynyl-2,4-difluorobenzene (21.1 g, 153 mmol), CuI (0.969 g, 5.09 mmol), TEA (42.5 mL, 305 mmol) and bis(triphenylphosphine)palladium(II) chloride (3.57 g, 5.09 mmol). The reaction mixture was evacuated and purged with nitrogen 3 times. The reaction mixture was heated to about 60° C. for about 6 h, cooled to ambient temperature, and diluted with EtOAc (500 mL). The organic solution was washed with water (3×500 mL), brine (500 mL), dried over MgSO4, filtered, and concentrated in vacuo. The crude material was dissolved in a minimal amount of hot DCM and allowed to cool to ambient temperature. The solid 1,2-bis(2,4-difluorophenyl)ethyne (6.7 g, 26.3%) was filtered off and the filtrate was purified by silica gel chromatography using heptane/EtOAc (gradient, 1:1 to 0:1) to give product. The product was then precipitated by dissolving in EtOAc (500 mL) and adding heptane (100 mL portions) while concentrating in vacuo. The solid was collected by vacuum filtration and dried under vacuum to give the title compound (19.5 g, 64%) as an off white solid. LC/MS (Table 1, Method a) Rt=2.72 min; MS m/z: 299.1 (M+H)+.
