Synthesis of 7H-indolo[1,2-a]quinolinium derivatives via oxidative photocyclization of 3H-indolium salts using blue LED photoreactor

Oxidative photocyclization of 1-phenyl-2-(2-arylethenyl)-3,3-dimethyl-3H-indolium perchlorates leading to 7H-indolo1,2-a]quinolinium salts was investigated. The synthesis was performed under Vis irradiation. Blue LEDs emitting at 454.5 nm were used as the light source. The reaction progress was followed by UV-Vis spectroscopy. The products were characterized by IR, ¹H and ¹³C NMR spectroscopy. Reaction time depended on the position of the UV-Vis absorption band of both the substrates and products. The results revealed that the application of blue LED photoreactor makes the synthesis of 7H-indolo1,2-a]quinolinium easier and more convenient.