Compounds having imidazo[5, 1‐a]isoquinoline nucleus have been synthesised. Selenium dioxide oxidation of a mixture of various aldehydes and 1‐isoquinolinemethylamine yielded the respective 3‐substituted imidazo[5, 1‐a]isoquinolines in good yields. When 1‐isoquinolinemethylamine was employed without any aldehyde, 3‐(1‐isoquinolinyl)imidazo[5, 1‐a]isoquinoline (IQ‐1) was isolated. This IQ‐1 is fluorescent and all the compounds were thoroughly characterized. Molecular structures of IQ‐1 and 3‐(2‐hydroxyphenyl)imidazo[5, 1‐a]isoquinoline (IQ‐4) have been confirmed by single crystal X‐ray diffraction technique.

We report an efficient protocol for the synthesis of 3‐trifluoromethylquinoxalin‐2(1H)‐ones, 3‐trifluoromethylimidazo[1,2‐a]pyridines and 3‐(trifluoromethyl)‐2H‐indazoles under metal‐, photocatalyst‐, light‐ and electrochemical‐free conditions. The combination of Langlois’ reagent (sodium triflinate) with the oxidant (NH4)2S2O8 in DMSO: H2O (10 : 1) works as an efficient reagent system to promote this free radical trifluoromethylation reaction. The trifluoromethyl radical generated by the oxidation of sodium triflinate with (NH4)2S2O8 attacks on to the C‐3 position of quinoxalin‐2(1H)‐ones, imidazo[1,2‐a]pyridines and 2H‐indazoles; and the excess SO4•− completes the reaction furnishing their respective 3‐trifluoromethyl derivatives in very good to excellent yields. Radical scavenging experiments with (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO), butylated hydroxy toluene (BHT), and 1,1‐diphenylethylene also prove the participation of radical.

A new convenient route for the synthesis of 3‐substituted‐imidazo[1,5‐a]pyridines has been described as well as the scope and limitations of the method are evaluated. By reacting 2‐picolylamine and different aldehydes in presence of selenium dioxide as the oxidant, a series of 3‐substituted imidazo[1,5‐a]pyridines was isolated in good yields. Different kinds of aldehydes such as aliphatic, aromatic, heterocyclic as well as aromatic ring carrying some substituents have been used.

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