Metal-Ligand Cooperative Iron Catalysis Enabling the One-Pot Synthesis of Imidazo[1,2-a]Quinolines and...

Herein, we present an atom-economical sustainable protocol for the synthesis of imidazo[1,2-a]pyridines and imidazo[1,2-a]quinolines catalyzed by a well-defined Fe(II)-catalyst 1a supported by the redox-noninnocent pincer ligand 2-((4-chlorophenyl)diazenyl)-1,10-phenanthroline. The method provides a broad range of imidazopyridine and imidazoquinoline derivatives from primary alcohols, terminal alkynes, and amines, affording products in yields of up to 80% with only 3.0 mol% catalyst loading. Under the same conditions, isoquinolin-1-amine furnished the corresponding imidazoisoquinoline derivative in moderate yield. Control experiments suggest that the catalytically active species is the one-electron-reduced azo-anion radical [1a]^-, generated in situ. The redox transformations occur at the aryl-azo ligand, while the Fe(II)-center primarily serves as a structural template.