Recent Advances in the Synthesis of meso-Substituted Corroles

 

Daniel T. Gryko

 

Institute of Organic Chemistry, Polish Academy of Sciences, Warsaw, Poland

 


Corroles  are aromatic tetrapyrrole macrocycles bearing a direct pyrrole-pyrrole link, and only in recent years has this area of research begun to attract attention as an independent rapidly evolving field. Interest in corroles was induced by the discovery of their remarkable ability to stabilize higher oxidation states of metals and by enormous synthetic developments made during the last four years. Progress in coordination chemistry of corroles  led to the use of their complexes as catalysts in hydrocarbon oxidations, as well as to the controversy over the ‘innocence’ of their core. 1

We devised the new method for the synthesis of 1,9-diacyldipyrromethanes – crucial intermediates in the synthesis of meso-substituted corroles and porphyrins with different substituents. The diacylodipyrromethanes formation involves the acylation of dipyrromethanes with salts made is situ from POCl3 and tertiary amides. This modified Vilsmeier approach gives higher yields and no concomitant formation of monoacyldipyrromethanes as compared with Grignard route. Moreover, compounds possessing groups previously inaccessible (CN, NO2 etc) can be synthesized. During the optimization of the transformation of DADPM into meso-substituted corroles it was found that if macrocyclization reaction mediated by DDQ is performed in the presence of big excess of pyrrole, meso-substituted [22]pentaphyrins(1.1.1.0.0) can be obtained in moderate yield. It constitutes the new method for the synthesis of these valuable porphyrynoids. Corroles possessing interesting, easy to transform functional groups were obtained in 3-40% yield. 2

 

We have also refined a one-pot synthesis of A3-corroles via condensation of an aldehyde with pyrrole followed by macrocyclization mediated by DDQ. After thorough examination of various reaction parameters we have elaborated three different sets of conditions for different types of aromatic aldehydes – (highly reactive, moderately reactive and sterically hindered) which allowed us to improve yields to ~15%. 3

 

 

 

 

 

 

 

 

 

  1. R. Paolesse in Porphyrin Handbook; K. M. Kadish, K. M. Smith, R. Guilard, Eds.; Academic Press: San Diego, CA, 2000; Vol.2, pp 201-232.
  2. D. T. Gryko, M. Tasior, B. Koszarna, J. Porphyrins Phthalocyanines 2003, 7, 239.
  3. D. T. Gryko, B. Koszarna, Org. Biomol. Chem. 2003, 1, 350.