Catalytic Cleavage of Ether CO Bonds by Pincer Iridium Complexes

Abstract

The development of efficient catalytic methods to cleave the relatively unreactive C-O bonds of ethers remains an important challenge in catalysis. Building on our group's recent work, we report the dehydroaryloxylation of aryl alkyl ethers using pincer iridium catalysts. This method represents a rare fully atom-economical method for ether C-O bond cleavage.

Computational Studies of Synthetically Relevant Homogeneous Organometallic Catalysis Involving Ni, Pd, Ir, and Rh: An Overview of Commonly Employed DFT Methods and Mechanistic Insights

“…In 2014, catalytic C−O bond cleavage based on this study has been presented by the same group. 554 The novel insights gained in this study may, according to the principle of microscopic reversibility, also be applied to C−O bond formation as shown by Krogh-Jespersen and Goldman in the Ir−PCP-catalyzed olefin hydroaryloxylation. 555 DFT studies have excluded the usual "hidden Brønsted acid" mechanism proposed for similar catalytic systems 556,557 and suggested an olefin insertion into Ir−O bond, followed by the ratedetermining C−H elimination to afford the ether product.…”

Formation of 5-membered metallacycles at iPrPCPIr by C–H, O–H, and C–CO bond cleavage

“…Pincer iridium species have been shown to form metallacycles by C-H activation of phosphine alkyl substituents in POCOP [23] and PCP [24] systems, by metalation of a second pincer ligand in less sterically demanding systems [25], as well as during the catalytic cleavage of C-O bonds in substituted alkyl aryl ethers [26]. However, while the use of pincer iridium species has been extensively investigated in alkane dehydrogenation and similar reactions [19,22,27], examples of processes or complexes employing metallacycles are limited.…”

Platinum(0)-mediated C–O bond activation of ethers via an SN2 mechanism

“…11 He followed this investigation with catalytic conversion of ethers such as 3,5-Me 2 C 6 H 3 O-iPr to the corresponding phenol and alkene at 150 or 200 °C (dehydroaryloxylation). 12 Intramolecular CO alkyl cleavage at Pd(0) and Pt(0) has also been reported briefly. 13 Additionally, C(sp 3 ) O bond activation reactions have been achieved using esters at Ir, Fe, and Pt complexes.…”