Photochemical Carbene Transfer Reactions of Aryl/Aryl Diazoalkanes – Experiment and Theory

The photochemical carbene transfer reaction is a timely strategy in organic synthesis and generally proceeds via singlet carbene intermediates. In this combined experimental and computational studies, we show that the photolysis reaction of diaryl diazoalkanes gives access to both singlet and triplet diarylcarbene intermediates. The electronic properties of substituents of the aryl substituents show a strong influence on the electronic properties of the carbene intermediate and result in significantly reduced singlet triplet energy gaps. Depending on the spin state and electronic properties of the carbene intermediate, the reaction with alkynes provides access towards chemoselective cyclopropenation, cascade, or C-H functionalization reactions.