Carbolithiation of meso-aryl-substituted 5,15-diazaporphyrin selectively provides 3-alkylated diazachlorins

Treatment of meso-mesityl 5,15-diazaporphyrin with alkyllithiums in toluene at low temperature provided monoalkylated diazachlorins through highly regioselective nucleophilic addition at the beta-position near the meso-nitrogen atom.