Simple route to meso-substituted trans-A2B2-porphyrins bearing pyridyl units

We have developed a methodology that affords regioisomerically pure trans-A2B2-porphyrins bearing pyridyl substituents. The optimal conditions for their synthesis were identified by the modification of known conditions for the reaction of dipyrromethanes with aromatic aldehydes. A total of five new porphyrins were synthesized.