A 500 mL round bottom flask was charged with 3-(6-chloropyridazin-3-yl)-2-(2,4-difluorophenyl)-6,7-dihydro-5H-pyrrolo[1,2-a]imidazole (7.50 g, 22.5 mmol), 1-propanol (225 mL) and hydrazine hydrate (11.3 g, 225 mmol). The mixture was then heated at about 105° C. for about 10 h. The reaction mixture was cooled to ambient temperature and stirred overnight. The mixture was concentrated under reduced pressure to remove about ¾ of the volume. The remaining mixture was stirred with DCM (250 mL) and saturated aqueous NaHCO3 (200 mL). The layers were partitioned, the aqueous layer was diluted with water (100 mL) and extracted with DCM (2×200 mL). The combined organic extracts were washed with brine (100 mL), dried over MgSO4, filtered, and concentrated under reduced pressure. The resulting residue was triturated with Et2O (50 mL) and the solid was collected by vacuum filtration. The filter cake was washed with additional Et2O (10 mL) and then dried in a vacuum oven for about 1 h at about 60° C. to give the title compound (4.59 g, 62%): LC/MS (Table 1, Method g) Rt=1.41 min; MS m/z: 329.1 (M+H)+.
