Theoretical study of the Bergman cyclization of 2,3-diethynyl-1-nitrotropylium ion: formation of a nitroxide radical amenable to EPR detection for biological applications.

We report a DFT study of a Bergman cyclization producing a stable triplet nitroxide diradical and monoradical (after H abstraction from an external source). The monoradical is predicted to be amenable to detection by EPR methods to potentially probe the structure and dynamics of enediyne molecules for drug interactions.