Detection of the Elusive Nitrogen-Centered Radicals from Catalytic Hofmann-Loffler Reactions

The catalytic Hofmann-Loffler reaction represents a uniquely effective protocol for the formation of pharmaceutically relevant heterocycles and is based on the reactivity of N-halogenated amines. Herein, we report stoichiometric experimentation toward the detection of a sulfonamidyl radical as the decisive intermediate in this C-H amination reaction. It can be observed by EPR after homolytic cleavage of the in situ formed N-halogen bond under the conditions of the iodine or bromine catalyzed Hofmann-Loffler reaction.