Synthesis of Imidazo[1,2-a]pyridines: Water-Mediated Hydroamination and Silver-Catalyzed Aminooxygenation

Aqueous syntheses of methylimidazo[1,2-a]pyridines without any deliberate addition of catalyst are reported. Imidazo[1,2-a]pyrazine and imidazo[2,1-a]isoquinoline were also obtained in good yields under similar conditions. With acetonitrile as solvent, Ag-catalyzed intra-molecular aminooxygenation produced imidazo[1,2-a]pyridine-3-carbaldehydes in moderate to good yields.