[N:1]1[C:2]([C:10]([O:12][CH2:13][CH3:14])=[O:11])=[CH:3][N:4]2[CH:9]=[CH:8][CH:7]=[CH:6][C:5]=12.C=O.[C:17]([O-])(=[O:19])C.[Na+].[OH-].[Na+]>C(O)(=O)C.ClCCl>[OH:19][CH2:17][C:3]1[N:4]2[CH:9]=[CH:8][CH:7]=[CH:6][C:5]2=[N:1][C:2]=1[C:10]([O:12][CH2:13][CH3:14])=[O:11]To a solution of ethyl imidazo[1,2-a]pyridine-2-carboxylate (5.0 g) in acetic acid (30 ml) were added 37% formaldehyde (14 ml) and sodium acetate (8.0 g) at room temperature, and the reaction mixture was heated under reflux for 15 hr. The reaction mixture was cooled to room temperature and dissolved in dichloromethane. The mixture was adjusted to pH 8 with 10% aqueous sodium hydroxide solution at 0° C. The organic layer was separated, washed with water and dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure. The residue was subjected to silica gel column chromatography, and a fraction eluted with dichloromethane-methanol (15:1) was concentrated under reduced pressure to give the object product (2.1 g).
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