External photocatalyst-free photocycloaddition between triplet vinylnitrenes with 1,3-biradical character and activated olefins under 420 nm LEDs.

Herein, we report that triplet vinylnitrenes with 1,3-biradical character can directly participate in photocycloaddition reactions with olefins to produce single diastereomers of the corresponding 1-pyrrolines under 420 nm LEDs in acetonitrile solvent. Moreover, a one-pot method has been developed to produce pyrroles directly through photocycloaddition and oxidation sequences. The excited state of the substrate olefin can sensitize vinyl azide energy transfer, eliminating the need for an external photocatalyst or sensitizer.