Key points are not available for this paper at this time.
Benzene wins the battle for aromaticity against 18annulene. The first fully conjugated, benzene-containing porphyrin analogue 1 is not an 18 π aromatic system; only the tautomer with the intact arene is observed. This compound is synthesized from the corresponding tripyrranedicarboxylic acid and isophthalaldehyde and forms black-blue crystals.
Berlin et al. (Mon,) studied this question.