Mesoionic Carbenes in Single Electron Transfer Reactions
Much of classical organic chemistry is focused on two-electron reactions. Indeed, it is common to teach sophomore organic chemistry with only the bare minimum of radical chemistry, such as free radical halogenation of alkanes. However, there is a wide world of single-electron chemistry to explore if we look beyond classical organic reactivity.
This dissertation will explore some of this hidden single electron chemistry, specifically as it pertains to stable mesoionic carbenes (MICs). MICs are so differentiated from other carbenes by the inability to draw a fully neutral resonance form without assigning formal charges. In practical terms, this results in a carbene that does not have the usual propensity of carbenes to dimerize and is nucleophilic but not electrophilic. Another property is that they are good leaving groups (weak bases) and so are adept at organocatalytic reactions just as N-heterocyclic carbenes (NHCs) are.
While the polar two electron chemistry of MICs has been well explored, single electron transfer reactions are not considered part of their repertoire. This dissertation will detail new single electron reactivity of MICs through super electron donating Breslow Intermediates, MIC-isocyanide adducts, and the free carbenes themselves. In this way, we find that the 1,2,3-triazolium framework of these carbenes is supportive of a range of single electron transfer reactions.