Mild Photocatalytic Synthesis of Azimines

Abstract

We report the photocatalytic formation of azimines upon visible light irradiation of mixtures of sulfonyl azides and electron‐rich azo reagents in the presence of IrIII complexes. The method was applied to a series of alkyl‐ and arylsulfonyl azides and azo reagents. The azimines were previously prepared using toxic reagents such as lead‐tetraacetate, or harsher UV photons. The reactions can be carried out either in batch or flow conditions. The observation that the azo reagent equilibrates under the reaction conditions and the high energy of the azide triplet state suggests that the reaction may proceed through a photocatalytic cycloaddition, rather than via a nitrene.