Polycyclic Dicationic Heteroaromatic Compounds From One-Step Multiple Condensation Reactions: Synthesis and Reactivity

The synthesis of nitrogen-containing polycyclic aromatic compounds (NPACs) from simple condensation reactions is described. 2,6-diformylpyridine was reacted with aniline derivatives in the presence of sulfuric acid as catalyst, giving rise to the formation of NPACs in one-step reaction. Aniline and derivatives, including p-Cl and m-B(OH)₂ substituents, have been used as starting materials; in all three cases, the main core of the resulting compounds includes a dicationic five-fused cyclic system. The core of the whole structure is related to the polycyclic aromatic hydrocarbon dihydrocyclopenta[hi]aceanthrylene. The absorption bands are similar for all three cases; the small variations in the absorption coefficient were associated with the pyridyl substituent. The Lewis acid behavior of the boronic acid groups was explored by titration with Ca(OH)₂. In addition, the reactivity of the boronic acid groups was proven with aminodiols. N–B dative bonds favor the formation of five-membered bicyclic structures.