derivatives, carried out under oxidative conditions using a simple catalytic system consisting of PdI2 (1 mol%) in conjunction with KI (1 equiv.), in the presence of AcONa as additive (1 equiv.) at 100 °C under 20 bar of a 4 : 1 mixture CO‐air. Under the optimized conditions, several N‐(prop‐2‐yn‐1‐yl)pyridin‐2‐amines were smoothly converted into alkyl 2‐(imidazo[1,2‐a]pyridin‐3‐yl)acetates in fair yields
We report herein the silver-catalyzed cycloisomerization of readily available N-(prop-2-yn-1-yl)pyridine-2-amines as a new and practical method for the synthesis of differently substituted 3-methylimidazo[1,2-a]pyridines. The isomerization reactions proceeded under mild reactions conditions to give good yields and excellent regioselectivity. A DFT-based mechanistic analysis is also reported.
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.