Cyclic(alkyl)(amino)carbene (CAAC)- and bicyclic (alkyl)(amino)carbene (BICAAC)-derived glyoxal radical cations with excellent stability.

Examples of air- and water-stable main-group radicals are scarce in the literature due to the higher reactivity of radical compounds as well as several synthetic challenges. Herein, we report two stable structurally characterized glyoxal radical cations (1˙ + and 2˙ + ) stabilized by cyclic(alkyl)(amino)carbene (CAAC) and bicyclic (alkyl)(amino)carbene (BICAAC), respectively. Both 1˙ + and 2˙ + are stable under harsh conditions such as strong acids, bases, mild oxidizing agents, and reducing agents, as well as towards bovine serum. Radical (2˙ + ) represents the first isolated radical stabilized by a BICAAC ligand.