Radical Formation by Direct Single Electron Transfer between Nitrobenzene and Anionic Organo Bases

The presence of unpaired electrons, i.e., radicals, equips organic molecules with unique magnetic and reactivity properties. However, due to the reactive nature of radicals and the nontrivial chemistry required for their preparation, strict structural and electronic limitations are imposed on the available systems, limiting their potential applications. Thus, developing mechanisms that enable facile radical formation in simple reaction conditions, employing available and inexpensive reactants and applicable to general types of molecules, holds the key to capitalize on the extraordinary properties that radicals have to offer. Here, combining electron paramagnetic resonance spectroscopy and ab initio calculations, we uncover an unprecedented single electron transfer from multiple anionic organic bases (B^-X⁺) to nitrobenzene [1], leading to the formation of stable nitrobenzenide radical ion-pair [1 ^•- ]-[X ⁺ ] (X = Li, Na, K) and transient oxidized, radical bases B^•. Our results establish nitroarenes as versatile radical precursors, providing a broadly applicable protocol for generating heteroatom-centered radicals and enabling radical transformations under mild conditions from inexpensive and readily available starting materials. Finally, we propose the [1]-[B^-X⁺] couple as an unexplored platform with the potential to advance the field of frustrated radical pairs.