[NH2:1][C:2]1[C:7]([NH2:8])=[CH:6][CH:5]=[C:4]([Br:9])[N:3]=1.[C:10](OCC)(OCC)(OCC)[CH3:11]>C(O)(=O)C.ClCCl.C(=O)([O-])[O-].[K+].[K+].C>[Br:9][C:4]1[N:3]=[C:2]2[N:1]=[C:10]([CH3:11])[NH:8][C:7]2=[CH:6][CH:5]=12,3-Diamino-6-bromopyridine (8.16 g) and triethyl orthoacetate (12.0 ml) were mixed in acetic acid (41 ml), and the mixture was refluxed under heating for 29 hr. After allowing to cool, the solvent was evaporated under reduced pressure to give a crude product (10 g). This was dissolved in a sufficient amount of dichloromethane and anhydrous potassium carbonate and active charcoal were added. The mixture was stirred at room temperature. The insoluble matter was removed by filtration and the solvent was evaporated to give 5-bromo-2-methyl-1H-imidazo[4,5-b]pyridine (7.59 g) as a pale-yellow powder.
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