From Formyl-Corroles to Non-Aromatic Porphyrinoids

In 1998, it would have been impossible to imagine that only 20 years later the chemistry of one of corroles would expand to create an independent field of study. The synthesis of corroles has undergone incredible changes. From multistep strategies that attracted only practitioners in the field, the procedure has been transformed into a one-pot process from commercially available reagents. The synthesis of meso -substituted corroles evolved quickly during the first seven years after Paolesse’s and Gross’s discovery [1,2]. The methodology which led to trans -A 2 B-corroles (i.e., corroles bearing substituents A at positions 5 and 15 and substituent B at position 10) from dipyrranes and aldehydes was discovered in 2000 and optimized several times prior to 2006, when we discovered that as long as aldehydes and dipyrranes were relatively small and/or hydrophilic, performing this reaction in a mixture of water and methanol in the presence of HCl allowed the yields to increase from 6-30% to ~55% [3,4]. The synthetic revolution made it possible to try risky ideas in diverse areas of materials chemistry and in various biology- and medicine-oriented applications. Multiple challenges still remain in the preparation of corroles. One of those challenges is the preparation of corroles possessing CHO groups. Free formyl groups can be reacted with multiple nucleophiles forming more complex and more advanced structures. At the same time CHO is the reacting group pivotal in the corrole synthesis. Attempting to solve this conundrum we recently developed the synthesis of tris(4-formylphenyl)corrole in straightforward fashion. During the realization of this project we discovered that 10-(2-formylphenyl)corrole undergoes intramolecular Friedel-Crafts reaction leading to non-aromatic, π-expanded corrole. This divalent macrocycle possess intriguing photophysical properties and has an ability to form complexes with various metals. References Gross, Z.; Galili, N.; Saltsman, I. Angew. Chem. Int. Ed. 1999 , 38 , 1427−1429. Paolesse, R.; Jaquinod, L.; Nurco, D. J.; Mini, S.; Sagone, F.; Boschi, T.; Smith, K. M. Chem. Commun. 1999 , 1307−1308. Koszarna, B.; Gryko, D. T. J. Org. Chem . 2006 , 71 , 3707−3717. Orłowski, R.; Gryko, D.; Gryko, D. T. Chem. Rev . 2017 , 117 , 3102-3137. Figure 1