Scramble-free synthesis of unhindered trans-A₂B₂-mesoaryl porphyrins via bromophenyl dipyrromethanes

Trans-disubstituted porphyrins are highly valuable intermediates across diverse fields, but they pose a significant synthesis challenge in some cases due to scrambling and formation of complex mixtures. Conditions that minimize scrambling also lower yields, but steric hindrance around the meso-aryl substituent can effectively suppress scrambling altogether. Here we report a straightforward approach to valuable trans-A2B2 porphyrin intermediates that are otherwise very difficult to obtain, through use of removable blocking bromide substituents.