Superacid-catalyzed reactions of pyridinecarboxaldehydes

A variety of pyridinecarboxaldehydes are shown to give condensation products in high yields (80-99%, 10 examples) by reacting with benzene and CF3SO3H (triflic acid). In the superacidic solution, pyridinecarboxaldehydes can react with deactivated arenes (o-dichlorobenzene and nitrobenzene) and with saturated hydrocarbons (methylcyclohexane and adamantane). Dicationic intermediates from pyridinecarboxaldehydes in superacid (FSO3H-SbF5) have been directly observed using low temperature 13C NMR spectroscopy. Diprotonated pyridinecarboxaldehydes have also been studies using ab initio computational methods.