Electrophilic Attack at the Porphyrin Periphery
Paine, J.B. and David Dolphin
J. Am. Chem. Soc.
Rates of D incorporation into the meso-positions of various octaalkylporphyrins were measured in refluxing deuterioacetic acid. The rates were similar for both the metal-free porphyrins, and for their complexes with Co(II), Co(III) and Fe(III), thereby showing that N-protonation is responsible for the strong deactivation in stronger acids, and that metal d-π-p-π overlap with N is not a significant feature of the transition state for meso electrophilic attack.