(Invited) Synthesis of Unsymmetrically Meso-Substituted Porphyrins

Abstract

The continued development of new medicinal and industrial uses of highly substituted porphyrins, especially in the fields of photodynamic therapy, nonlinear optics and electron transfer systems, has led to a resurgent interest in developing new methodologies for porphyrin synthesis. The porphyrins in question, so called ABCD-type porphyrins, have mixed meso substituents, making them highly unsymmetric and thus not synthetically available through classical condensation routes. Synthetic strategies towards the formation of meso substituted porphyrins have been extensively researched over the last decade with various routes now available. While methods using mixed condensations are still preferred for systems with high symmetry, the number of possible products makes it an unviable route for the synthesis of the more useful non symmetric porphyrins. To this end novel syntheses of ABCD-type porphyrins have been developed using synthetic manipulations of pre-formed porphyrin scaffolds with various organolithium reagents and Pd-catalyzed metal couplings.