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Oxidant speciation and anionic ligand effects in the gold-catalyzed oxidative coupling of arenes and alkynes


Hofer, Manuel; de Haro, Teresa; Gómez-Bengoa, Enrique; Genoux, Alexandre; Nevado, Cristina (2019). Oxidant speciation and anionic ligand effects in the gold-catalyzed oxidative coupling of arenes and alkynes. Chemical Science, 10(36):8411-8420.

Abstract

The mechanism of the gold-catalyzed oxidative cross-coupling of arenes and alkynes has been studied in detail combining stoichiometric experiments with putative reaction intermediates and DFT calculations. Our data suggest that ligand exchange between the alkyne, the Au(I)-catalyst and the hypervalent iodine reagent is responsible for the formation of both, a Au(I)-acetylide complex as well as a more reactive “non-symmetric” I(III) oxidant, responsible for the crucial Au(I)/Au(III) turnover. Further, the reactivity of the in situ generated Au(III)-acetylide complex is governed by the nature of the anionic ligands transferred by the I(III) oxidant: while halogen ligands remain unreactive, acetato ligands are efficiently displaced by the arene to yield the observed Csp2-Csp cross-coupling products through an irreversible reductive elimination step. Finally, the nature of competitive processes and catalyst deactivation pathways has also been unraveled. This detailed investigation provides insights not only on the specific features of the species involved in oxidative gold-catalyzed cross couplings but also highlights the importance of both ancillary and anionic ligands on the reactivity of the key Au(III) intermediates.

Abstract

The mechanism of the gold-catalyzed oxidative cross-coupling of arenes and alkynes has been studied in detail combining stoichiometric experiments with putative reaction intermediates and DFT calculations. Our data suggest that ligand exchange between the alkyne, the Au(I)-catalyst and the hypervalent iodine reagent is responsible for the formation of both, a Au(I)-acetylide complex as well as a more reactive “non-symmetric” I(III) oxidant, responsible for the crucial Au(I)/Au(III) turnover. Further, the reactivity of the in situ generated Au(III)-acetylide complex is governed by the nature of the anionic ligands transferred by the I(III) oxidant: while halogen ligands remain unreactive, acetato ligands are efficiently displaced by the arene to yield the observed Csp2-Csp cross-coupling products through an irreversible reductive elimination step. Finally, the nature of competitive processes and catalyst deactivation pathways has also been unraveled. This detailed investigation provides insights not only on the specific features of the species involved in oxidative gold-catalyzed cross couplings but also highlights the importance of both ancillary and anionic ligands on the reactivity of the key Au(III) intermediates.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Scopus Subject Areas:Physical Sciences > General Chemistry
Uncontrolled Keywords:General Chemistry
Language:English
Date:1 January 2019
Deposited On:29 Jul 2020 09:14
Last Modified:30 Jul 2020 20:00
Publisher:Royal Society of Chemistry
ISSN:2041-6520
OA Status:Gold
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1039/c9sc02372k

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