Photocatalyzed C3-H Nitrosylation of Imidazo[1,2- a ]pyridine under Continuous Flow and External Photocatalyst-, Oxidant-, and Additive-Free Conditions.

This study reports a protocol for the highly regioselective photocatalyzed C-H nitrosylation of imidazo[1,2- a ]pyridine scaffolds at the C3 position under a combination of visible-light irradiation and continuous flow without any external photocatalyst. This protocol involves mild and safe conditions and shows good tolerance to air and water along with excellent functional group compatibility and site selectivity, generating various 3-nitrosoimidazo[1,2- a ]pyridines in excellent yields under photocatalyst-, oxidant-, and additive-free conditions.Notably, the proposed nitrosylation reaction, which introduces the chromophore NO into imidazo[1,2- a ]pyridine scaffolds, occurs efficiently under visible-light irradiation without any additional photocatalyst owing to the intense light-absorption characteristics of the nitrosylation products. This study could guide future studies on the development of green organic-synthesis strategies with a wide variety of potential applications.