A New Route to meso-Formyl Porphyrins

Abstract

Prior syntheses of porphyrins bearing meso-formyl groups have generally employed the Vilsmeier formylation of an acid-resistant copper or nickel porphyrin. A new approach for the synthesis of free base porphyrins bearing one or two (cis or trans) meso-formyl substituents entails the use of a dipyrromethane bearing an acetal group at the 5-position, a dipyrromethane-1-carbinol bearing an acetal group at the 5-position or carbinol position, or a dipyrromethane-1,9-dicarbinol bearing an acetal group at a carbinol position. Treatment of the resulting meso-acetal-substituted free base porphyrin to gentle acidic hydrolysis yields the corresponding meso-formyl porphyrin.

Synthesis and Photophysical Characterization of Porphyrin, Chlorin and Bacteriochlorin Molecules Bearing Tethers for Surface Attachment

“…The porphyrin bearing a cyanoacrylic acid ( ZnP‐A ) tether is readily prepared by derivatization of a meso ‐formylporphyrin. A number of routes to meso ‐formylporphyrins have been devised (73). A new route for the synthesis of meso ‐formylporphyrins, which was discovered serendipitously, is shown in Scheme 2.…”

Design and synthesis of water-soluble bioconjugatable trans-AB-porphyrins

“…The emission maxima were typical for free base trans -AB-porphyrins bearing meso -aryl substituents for H 2 P-1 (625 and 686 nm) and H 2 P-3 (629 and 688 nm), but were shifted bathochromically for H 2 P-2 (641 and 707 nm). The shift in the emission spectrum of H 2 P-2 stems from the presence of the meso-formyl substituent, which is known to be a potent auxochrome 58,59…”

β-Formyl- and β-Vinylporphyrins: Magic Building Blocks for Novel Porphyrin Derivatives

“…The Vilsmeier–Haack formylation of meso -tetraarylporphyrins like TPP ( 1 ) at the β-positions are usually carried out by using the corresponding Ni(II) or Cu(II) complexes due to the compromise between electronegativity and acid lability they offer ( Scheme 2 ) [ 75 , 76 , 77 , 78 , 79 ]. Under the acidic Vilsmeier conditions, the Zn(II) and Mg(II) complexes are demetallated and protonated and consequently the macrocycle reactivity is highly reduced for the β-formylation [ 80 , 81 ].…”