Red light-induced conjugation of amines through amide bond formation triggered via photooxidation of 3-acylindolizines

The development of a conjugation method initiated by irradiation of long-wavelength light (>500 nm) to prepare densely functionalized molecules while avoiding undesired photodegradation has attracted considerable attention. Here we show an amide bond formation method based on the photoreaction of 3-acylindolizines in the presence of amines triggered via red-light irradiation. Photooxidation of 3-acylindolizines using a catalytic amount of a photosensitizer and red light-emitting diodes (660 nm) affords the corresponding conjugated amides in nearly quantitative yields within <5 min. This transformation can be performed in aqueous organic solvents and is applicable to diverse aliphatic amines with various functional groups, including the moieties responsive to short-wavelength light. Photoinduced conjugation has been broadly used for functionalization of molecules but is limited by possible photodegradation. Here, the authors report a robust amide bond formation method based on the photoreaction of 3-acylindolizines with amines triggered via red-light irradiation in nearly quantitative yields within less than 5 min.

Automated summary

We introduce a new method for amide bond formation based on the photoreaction of 3-acylindolizines with amines triggered by red-light irradiation. This method allows for the synthesis of conjugated amides in a short time with high yields. It is applicable to various aliphatic amines with different functional groups and can be conducted in aqueous organic solvents.