Cleavage of Carbonyl Carbon and α-Carbon Bond of Acetophenones by Iridium(III) Porphyrin Complexes

Abstract

Selective carbonyl carbon (C(═O)) and α-carbon (C(methyl)) bond activation of acetophenones was discovered by the high-valent, iridium(III) 5,10,15,20-tetrakis-4-tolylporphyrinato carbonyl chloride (Ir(ttp)Cl(CO)), which also acted as a Lewis acid in catalyzing the aldol condensation of acetophenones together with release of the coproduct water. Preliminary mechanistic studies suggest that both aliphatic and aromatic carbon−hydrogen bond activation products are kinetic products, which can be converted by reaction with water to iridium porphyrin hydride (Ir(ttp)H) via iridium porphyrin hydroxide (Ir(ttp)OH). Both Ir(ttp)OH and Ir(ttp)H were the possible intermediates to cleave the C(═O)−C(methyl) bond of acetophenones and to generate iridium porphyrin acyl complexes as the thermodynamic products.