Intermolecular amination of allenes via twofold photocatalytic nitrene transfer reactions

The amination with monovalent, nitrogen-based intermediates constitutes an important reaction for the construction of valuable amines. The high basicity of reagents, reaction intermediates or products however poses significant challenges to metal-catalyzed amination through coordination and blocking of catalytically active sites and hampering their efficiency. In this context, high-yielding intermolecular amination reaction of allenes remain an unsolved challenge in organic synthesis and general methods are not available. Herein, we describe a photochemical approach towards the intermolecular amination of allenes via free nitrene radical anions as the key reactive intermediate. This reaction proceeds without the participation of catalyst-bound nitrogen species and can thus overcome current limitations. We report on the application in the amination of allenes to give azetidine and cyclopropyl amines with a broad and general substrate scope. Experimental and theoretical studies were performed to provide an understanding of the reaction mechanism and rationalize the high efficiency of this photocatalytic approach.