Is Phenylnitrene a Missing Link in the Formation of Polycyclic Aromatic Nitrogen Heterocycles?

The incorporation of heteroatoms into the framework of polycyclic aromatic hydrocarbons (PAHs), in particular of nitrogen to yield polycyclic aromatic nitrogen heterocycles (PANHs), has been proposed for both astronomical and combustion environments, but no suitable precursors and pathways have been found. Analogous pathways to PAH formation are kinetically or energetically inhibited in the presence of a nitrogen heteroatom. We report on the reaction of phenylnitrene (³PhN, c-C₆H₅N) with resonance-stabilized propargyl radicals (C₃H₃) and find that the association reaction bifurcates depending on the orientation of the attacking propargyl radical and yields multiple isomeric products. Among them, we identify the condensed-ring quinoline and conclude that nitrenes are viable candidates to drive the formation of PANHs.