64067-99-8

5469-69-2

70-23-5

64067-99-8

To a suspension of 6-chloropyridazin-3-amine (10.00 g, 77 mmol) in ethanol (30 mL) at 0 °C, a solution of ethyl 3-bromo-2-oxopropanoate (20.07 g, 93 mmol) in ethanol (5 mL) was slowly added by pipette. After addition, the ice bath was removed and the reaction mixture was stirred at room temperature for 15 min, followed by warming to 80 °C for 30 min. After 2 hours of reaction, the mixture was cooled to room temperature and the precipitated beige solid was collected by vacuum filtration and washed with cold ethanol. The resulting solid was suspended in saturated aqueous NaHCO3 solution and stirred for 30 minutes. The solid was again collected by vacuum filtration and the filter cake was washed with water, dried over a filter and further dried under vacuum to give ethyl 6-chloroimidazo[1,2-b]pyridazine-2-carboxylate as a brown solid (8.8 g, 39.0 mmol, 51% yield). The product was characterized by NMR (400 MHz, chloroform-d3): δ 8.46 (s, 1H), 8.13 (d, J=9.5 Hz, 1H), 7.23 (d, J=9.5 Hz, 1H), 4.49 (q, J=7.2 Hz, 2H), 1.46 (t, J=7.1 Hz, 3H). the LC retention time was 2.29 min (Analytical HPLC method A). LC/MS showed (M+H)+ peaks of 226/228 (ratio about 3:1).