Ruthenium(II)-Catalyzed Annulation of 2-Arylimidazoles with Arylglyoxals: Synthesis of 5-Hydroxyimidazo[2,1-a]isoquinolin-6(5H)-ones and Their Photophysical Studies

Synthesis of novel 5-hydroxyimidazo[2,1-a]isoquinolin-6(5H)-ones have been achieved by Ru(II)-catalyzed reaction of 2-arylimidazoles with arylglyoxals. The method provided moderate to good yields of 5-hydroxyimidazo[2,1-a]isoquinolin-6(5H)-ones and is amenable to gram-scale synthesis. The reaction involves imidazole-directed Ru(II)-catalyzed ortho-dicarbonylation followed by nucleophilic cyclization of the NH-group with the carbonyl group. Photophysical properties of the newly synthesized 5-hydroxyimidazo-[2,1-a]isoquinolin-6(5H)-ones were investigated.