Spectroscopic and Structural Characterization of Unexpected Porphyrinoid Byproducts Resulting from the Reaction of a Cyclopentadiene Trialdehyde with N-Alkyltripyrranes.

Acid-catalyzed condensation of N-alkyltripyrranes with a cyclopentadiene trialdehyde, followed by oxidation with aqueous ferric chloride solutions, gave unusual tripyrrolic byproducts in addition to previously reported carbaporphyrins and oxycarbaporphyrins. These stable nonaromatic structures incorporate aldehyde substituents, macrocyclic ketones, two conjugated pyrrole units, and a pyrrolo[1,2-a]pyrrole moiety. The NMR and UV-vis data were consistent with a nonaromatic system, and single-crystal X-ray diffraction confirmed that these structures are highly distorted. Structural characterization of a related aromatic carbaporphyrin triketone was also accomplished.