Our group has recently reported the hydroaryloxylation reaction of phenols with olefins such as propylene, ethylene and 1-butene using pincer-ligated iridium catalysts (iPrPCOP)Ir, (tBu3MePCP)Ir and (MeO-iPrPCP)Ir. Initial results revealed that this represents a very rare example of O-H addition to an olefin that is genuinely catalyzed by a transition metal complex and not by so-called �hidden Bronsted Acids�.1 The addition products, alkyl aryl ethers, are important industrial reagents currently synthesized on a large scale from alkyl halides and metal alkoxides (the Williamson ether synthesis). More recently, we have reported catalysis of the back reaction, i.e. ether C-O bond cleavage. This reaction is of great interest in contexts such as the processing of lignocellulosic biomass or removal of protecting groups in organic synthesis.                                                                                                                     DFT calculations indicate that the mechanism for the hydroaryloxylation reaction proceeds via formation of (pincer)Ir(H)(OAr)(olefin), followed by olefin insertion into the iridium-aryloxy bond, followed by C-H reductive elimination to give the ether product. The results of kinetic studies are consistent with this mechanism. However, while the C-H reductive elimination is calculated to be rate determining, Hammett-type structure-property relationships and kinetic isotope effects indicate that the rate-determining step is actually olefin insertion into the Ir-O bond.(1) Hintermann, L. In C-X Bond Formation; Vigalok, A., Ed.; Springer Berlin Heidelberg: 2010;  Vol. 31, p 123-155.

Hydroaryloxylation of olefins and dehydroaryloxylation of ethers catalyzed by pincer iridium catalysts: A mechanistic/computational study

248th National Meeting (2014)

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