General procedure for the preparation of 6-chloroimidazo[1,2-b]pyridazine: Bromoacetaldehyde diethyl acetal (13.7 g, 69.5 mmol, 1.8 eq.) was added to hydrobromic acid (4.0 mL) and heated to reflux for 1.5 hours. Upon completion of the reaction, the mixture was cooled to room temperature and subsequently poured into an isopropanol reaction flask containing an excess of sodium bicarbonate. After stirring for 3 minutes, filtration was performed. To the filtrate was added 3-amino-6-chloropyridazine (5.0 g, 38.6 mmol, 1.0 eq.) and the reflux was continued by heating for 2 hours. At the end of the reaction, the reaction mixture was quenched with water and extracted with ethyl acetate. Finally, the product was purified by column chromatography to give 5.1 g of brown solid in 86% yield. The product was characterized by 1H NMR (400 MHz, CDCl3): δ 7.89 (s, 1H), 7.88 (d, J = 9.3 Hz, 1H), 7.74 (s, 1H), 7.01 (d, J = 9.3 Hz, 1H).
![6-Chloroimidazo[2,1-f]pyridazine](/CAS/GIF/6775-78-6.gif)