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Issue 16, 2019
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Palladium-catalysed alkyne alkoxycarbonylation with P,N-chelating ligands revisited: a density functional theory study

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Abstract

A revised in situ base mechanism of alkyne alkoxycarbonylation via a Pd catalyst with hemilabile P,N-ligands (PyPPh2, Py = 2-pyridyl) has been fully characterised at the B3PW91-D3/PCM level of density functional theory. Key intermediates on this route are acryloyl and η3-propen-1-oyl complexes that readily undergo methanolysis. With two hemilabile P,N-ligands and one or both of them protonated, the overall computed barrier is 16.8 kcal mol−1. This new mechanism is consistent with all of the experimental data relating to substituent effects on relative reaction rates and branched/linear selectivities, including new results on the methoxycarbonylation of phenylacetylene using (4-Me2N-Py)PPh2 and (6-Cl-Py)PPh2 ligands. This ligand is found to decrease catalytic activity over PyPPh2, thus invalidating a formerly characterised in situ base mechanism.

Graphical abstract: Palladium-catalysed alkyne alkoxycarbonylation with P,N-chelating ligands revisited: a density functional theory study

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Publication details

The article was received on 15 Mar 2019, accepted on 26 Mar 2019 and first published on 26 Mar 2019


Article type: Paper
DOI: 10.1039/C9CP01471C
Citation: Phys. Chem. Chem. Phys., 2019,21, 8543-8552

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    Palladium-catalysed alkyne alkoxycarbonylation with P,N-chelating ligands revisited: a density functional theory study

    S. Ahmad, A. Lockett, T. A. Shuttleworth, A. M. Miles-Hobbs, P. G. Pringle and M. Bühl, Phys. Chem. Chem. Phys., 2019, 21, 8543
    DOI: 10.1039/C9CP01471C

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