p-Toluenesulfonic acid → 8-Bromo-6-chloroimidazo(1,2-b)pyridazine

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Reaction Steps

A solution of 4-bromo-6-chloropyridazin-3-amine (15.7 g, 75.3 mmol), 2-chloro-1,1-diethoxyethane (13.9 g, 90.3 mmol) and PTSA (17.2 g, 90.3 mmol) in isopropanol (150 mL) was heated to 80° C. for 20 h. After cooling to room temperature, the solution was concentrated in vacuo. The resulting mixture was treated with a saturated NaHCO3 solution (300 mL), extracted with dichloromethane (200 mL×3), dried over Na2SO4, filtered and concentrated. The residue was purified by chromatography (silica gel, 200-300 mesh, petroleum ether:ethyl acetate=3:1) to give 8-bromo-6-chloroimidazo[1,2-b]pyridazine (17.2 g, 98%) as an orange solid. LC-MS: [M+H]+, 231.9, 233.9, tR=1.46 min.

Provenance & Evidence