Competitive Aryl–Fluorine and Aryl–Halogen (Halogen = Cl, Br) Bond Cleavage with Iridium Porphyrin Complexes
摘要:
Base-promoted competitive Ar-F and Ar-X (X = Cl, Br) bond cleavage with iridium porphyrin complexes was investigated. Mechanistic studies suggested that Ir(ttp)(-) (ttp = 5,10,15,20-tetra-p-tolylporphyrinato dianion) cleaves the Ar-F bond via nucleophilic aromatic substitution and Ir-2(ttp)(2) cleaves the Ar-X (X = Cl, Br) bond via metalloradical ipso substitution. Therefore, a stronger base, polar solvent, lower temperature, and iridium anion precursor favor Ar-F bond cleavage, while a weaker base, nonpolar solvent, higher temperature, and Ir-2(ttp)(2) precursor favor Ar-X (X = Cl, Br) bond cleavage.