Nucleophilic substitution of hydrogen in meso-nitroaryl-substituted porphyrins—unprotected at the NH-centers in the core ring

Unprotected 5-(4-nitrophenyl)-10,15,20-triphenylporphyrin and 5,10-bis(4-nitrophenyl)-15,20-diphenylporphyrin react in the presence of a base at low temperature with carbanions (which bear a leaving group X at the carbanionic center) affording vicarious nucleophilic substitution of hydrogen (VNS) products in good yields (50–89%). The reactivity is explained in terms of the predominance of the porphyrin N-anion resonance forms at this temperature.