Alkyl Carbon–Oxygen Bond Cleavage of Aryl Alkyl Ethers by Iridium–Porphyrin and Rhodium–Porphyrin Complexes in Alkaline Media

Abstract

Alkyl C–O bond cleavage in aryl alkyl ethers was achieved with Rh(ttp)Cl (1a; ttp = 5,10,15,20-tetrakis(p-tolyl)porphyrinato dianion) together with competitive alkyl C–H bond activation in alkaline media. In contrast, selective alkyl C–O bond cleavage occurred with the iridium–porphyrin Ir(ttp)(CO)Cl (1b)/KOH. Mechanistic investigations indicate the coexistence of MI(ttp)− and M2II(ttp)2 (M = Rh, Ir) under basic conditions. With a weaker Rh(ttp)–Rh(ttp) bond, RhII(ttp)· metalloradical exists in an appreciable amount to cleave the alkyl C–H bond, competing with the alkyl C–O bond cleavage via RhI(ttp)−. In contrast, the more nucleophilic IrI(ttp)− cleaves the alkyl C–O bond exclusively.