Two important types of a-heterolytic fragmentation reactions of aminium radicals are discussed. In these fragmentation processes, transfer of electrofugal groups from the aminium radicals to either Lowry-Bronsted or
Lewis bases produces a-amino radicals. The results of recent studies that provided key information about the dynamics of the important aminium radical fragmentation reactions, deprotonation, desilylation, are summarized.
Finally, selected examples, which demonstrate how knowledge of the relative rates of aminium radical cleavage can be used to design synthetically relevant SET-promoted photocyclization reactions, are presented.