Scramble-Free Synthesis of Unhindered trans -A 2 B 2 -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-A 2 B 2 porphyrin intermediates that are otherwise very difficult to obtain, through use of removable blocking bromide substituents.