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Issue 46, 2011
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P–H activation using alkynylgold substrates: steric and electronic effects

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Abstract

The susceptibility of a prototypical hydrogen phosphonate to undergo P–H activation upon treatment with alkynylgold complexes has been studied. Dynamic solution behavior was observed during reactions involving triphenylphosphine ligated substrates and was attributed to rapid phosphine exchange between the alkynylgold starting material and the gold phosphonate product. The use of bulky biaryldialkylphosphine ligands eliminated the fluxional behavior, but did not significantly slow the rate of P–H activation. Similarly, changing the supporting ligand to an N-heterocyclic carbene did not significantly slow the rate of the reaction. Despite a number of reports outlining the functionalization of propargyl alcohols using gold catalysts, incorporating these groups into the architecture of the alkynylgold substrates did not alter the product distributions. Although the chemistry tolerated a range of supporting ligands, incorporating electron donating groups into the alkyne increased the rate of the reaction while electron-withdrawing groups slowed the reaction. A possible mechanism for the process includes a transition state containing significant pi-contribution from the alkyne. Due to the high yields of gold phosphonates obtained in this chemistry as well as the mild conditions of the reactions, the interception of intermediates/catalysts by substrates or ligands containing labile P–H donors is an issue that must be circumvented when designing or developing a gold catalyzed reaction that proceeds through alkynylgold intermediates.

Graphical abstract: P–H activation using alkynylgold substrates: steric and electronic effects

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Publication details

The article was received on 15 Jul 2011, accepted on 06 Sep 2011 and first published on 20 Oct 2011


Article type: Paper
DOI: 10.1039/C1DT11337B
Citation: Dalton Trans., 2011,40, 12595-12606
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    P–H activation using alkynylgold substrates: steric and electronic effects

    G. F. Manbeck, M. C. Kohler, M. R. Porter and R. A. Stockland Jr., Dalton Trans., 2011, 40, 12595
    DOI: 10.1039/C1DT11337B

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