External Oxidant-Dependent Reactivity Switch in Copper-Mediated Intramolecular Carboamination of Alkynes: Access to a Different Class of Fluorescent Ionic Nitrogen-Doped Polycyclic Aromatic Hydrocarbons

An
interesting case of external oxidant-controlled reactivity switch
leading to a divergent set of ionic nitrogen-doped polycyclic aromatic
hydrocarbons (N-doped PAHs), is presented here, which is quite unrecognized
in copper-mediated reactions. In the current scenario, from the same
pyridino-alkyne substrates, the use of the external oxidant PhI­(OAc)2, in combination with Cu­(OTf)2, gave N-doped spiro-PAHs
via a dearomative 1,2-carboamination process; whereas, without the
use of oxidant, an alkyne/azadiene [4 + 2]-cycloaddition cascade occurred
to exclusively afford ionic N-doped PAHs. These newly synthesized
N-doped PAHs further exhibit tunable emissions, as well as excellent
quantum efficiencies.