Optimized Synthesis of Tetrakis(4-methoxyphenyl)porphin-Co(II)

Detailed kinetic investigation of Rothemund synthesis of porphyrins was conducted in different solvents. A one-pot synthesis of tetrakis(4-methoxyphenyl)porphin-Co(II) from pyrrole, anisic aldehyde, and cobalt acetate was developed that gave 35% isolated yield. Chlorobenzene was found to be the best solvent for the reaction. The synthesis can be done with either propionic or chloroacetic acid as catalyst with about the same yield. Cobalt prevents the synthesis of the porphyrin, so it has to be added in the reaction mixture only after the synthesis of the free porphyrin is finished. Optimum time is 2-2.5h at a temperature of 130C. Lower temperatures reduce the yield. Potentially, these dependencies can be applied to synthesis of other analogous porphyrins.