107-20-0

21717-96-4

139022-27-8

To a solution of 2-amino-5-fluoropyridine (10 g) in ethanol (200 mL) was slowly added 50% aqueous chloroacetaldehyde (56 mL, 4.0 equiv). The reaction mixture was heated under reflux conditions for 2 h and subsequently concentrated under reduced pressure to about 100 mL. The concentrated residue was diluted with ethyl acetate (AcOEt, 100 mL) and washed with saturated aqueous sodium bicarbonate (NaHCO3) (2 x 150 mL). The aqueous phases were combined, saturated with sodium bicarbonate and then back-extracted with ethyl acetate (2 × 100 mL). All organic phases were combined, washed with saturated brine (100 mL), dried over anhydrous sodium sulfate (Na2SO4), and concentrated under reduced pressure to remove the solvent. Purification by fast column chromatography (eluent: dichloromethane solution in 2.5% methanol) afforded 6-fluoroimidazo[1,2-a]pyridine as a milky white solid (8.7 g, 72% yield). Mass spectrum (M + H)+ m/z = 137.