Base-Promoted Selective Aryl Carbon−Bromine Bond Cleavage by Iridium(III) Porphyrin for Iridium(III) Porphyrin Aryl Synthesis: A Metalloradical Ipso Addition−Elimination Mechanism

K2CO3 was found to promote selective aryl carbon−bromine bond (Ar−Br) cleavage by a high-valent iridium(III) porphyrin carbonyl chloride (IrIII(ttp)(CO)Cl, ttp = 5,10,15,20-tetra-p-tolylporphyrinato dianion) in benzene solvent at elevated temperature to give iridium(III) porphyrin aryls (IrIII(ttp)Ar) in high yields. Ir(ttp)(CO)Cl is reduced in alkaline media to give an [Ir(ttp)]2 intermediate. [Ir(ttp)]2 then cleaves the Ar−Br bond via a radical-type addition−elimination reaction (radical ipso -substitution) to yield Ir(ttp)Ar and a bromine radical.

研究表明，碳酸钾（K₂CO₃）可在升温的苯溶剂中，促进高价铱(III)卟啉羰基氯化物（high-valent iridium(III) porphyrin carbonyl chloride，缩写为IrIII(ttp)(CO)Cl，其中ttp为5,10,15,20-四对甲苯基卟啉二阴离子（5,10,15,20-tetra-p-tolylporphyrinato dianion））选择性断裂芳基碳-溴键（aryl carbon−bromine bond，Ar−Br），并以高收率得到铱(III)卟啉芳基化合物（IrIII(ttp)Ar）。IrIII(ttp)(CO)Cl在碱性介质中被还原，生成[Ir(ttp)]₂中间体。随后，[Ir(ttp)]₂通过自由基型加成-消除反应（radical ipso取代，radical ipso -substitution）断裂Ar−Br键，生成Ir(ttp)Ar与溴自由基。