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

Shahbaz Ahmad; Ashleigh Lockett; Timothy Shuttleworth; Alexandra Miles-Hobbs; Paul Pringle; Michael Buehl

doi:10.1039/C9CP01471C

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

Shahbaz Ahmad, Ashleigh Lockett, Timothy Shuttleworth, Alexandra Miles-Hobbs, Paul Pringle, Michael Buehl

Research output: Contribution to journal › Article › peer-review

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 (η³-propen-1-oyl) complexes that readily undergo methanolysis. With two hemilabile P,N-ligands and one of them protonated, the overall computed barrier is 24.5 kcal mol^-1, which decreases to 20.3 kcal mol^-1 upon protonation of the second P,N-ligand. 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-NMe₂Py)PPh₂ and (6-Cl-Py)PPh₂ ligand. This ligand is found to decrease catalytic activity over PyPPh₂, thus invalidating a formerly characterised in situ base mechanism.

Original language	English
Pages (from-to)	8543-8552
Number of pages	10
Journal	Physical Chemistry Chemical Physics
Volume	21
Issue number	16
Early online date	26 Mar 2019
DOIs	https://doi.org/10.1039/C9CP01471C
Publication status	Published - 28 Apr 2019

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Copyright © 2019 The Author(s). This work has been made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1039/C9CP01471C
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@article{d59b2a1895dc4c8a87a9d241fba24820,

title = "Palladium–catalysed alkyne alkoxycarbonylation with P,N chelating ligands revisited: a density functional theory study",

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 (η3-propen-1-oyl) complexes that readily undergo methanolysis. With two hemilabile P,N-ligands and one of them protonated, the overall computed barrier is 24.5 kcal mol-1, which decreases to 20.3 kcal mol-1 upon protonation of the second P,N-ligand. 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-NMe2Py)PPh2 and (6-Cl-Py)PPh2 ligand. This ligand is found to decrease catalytic activity over PyPPh2, thus invalidating a formerly characterised in situ base mechanism. ",

author = "Shahbaz Ahmad and Ashleigh Lockett and Timothy Shuttleworth and Alexandra Miles-Hobbs and Paul Pringle and Michael Buehl",

note = "Authors thank EaStCHEM and the School of Chemistry for support. The Bristol Chemical Synthesis Centre for Doctoral Training (BCS CDT) funded by the Engineering and Physical Sciences Research Council (EPSRC) (EP/G036764/1) and the University of Bristol are thanked for a PhD studentship (to T. A. S.).",

year = "2019",

month = apr,

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doi = "10.1039/C9CP01471C",

language = "English",

volume = "21",

pages = "8543--8552",

journal = "Physical Chemistry Chemical Physics",

issn = "1463-9076",

publisher = "Royal Society of Chemistry",

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TY - JOUR

T1 - Palladium–catalysed alkyne alkoxycarbonylation with P,N chelating ligands revisited

T2 - a density functional theory study

AU - Ahmad, Shahbaz

AU - Lockett, Ashleigh

AU - Shuttleworth, Timothy

AU - Miles-Hobbs, Alexandra

AU - Pringle, Paul

AU - Buehl, Michael

N1 - Authors thank EaStCHEM and the School of Chemistry for support. The Bristol Chemical Synthesis Centre for Doctoral Training (BCS CDT) funded by the Engineering and Physical Sciences Research Council (EPSRC) (EP/G036764/1) and the University of Bristol are thanked for a PhD studentship (to T. A. S.).

PY - 2019/4/28

Y1 - 2019/4/28

N2 - 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 (η3-propen-1-oyl) complexes that readily undergo methanolysis. With two hemilabile P,N-ligands and one of them protonated, the overall computed barrier is 24.5 kcal mol-1, which decreases to 20.3 kcal mol-1 upon protonation of the second P,N-ligand. 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-NMe2Py)PPh2 and (6-Cl-Py)PPh2 ligand. This ligand is found to decrease catalytic activity over PyPPh2, thus invalidating a formerly characterised in situ base mechanism.

AB - 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 (η3-propen-1-oyl) complexes that readily undergo methanolysis. With two hemilabile P,N-ligands and one of them protonated, the overall computed barrier is 24.5 kcal mol-1, which decreases to 20.3 kcal mol-1 upon protonation of the second P,N-ligand. 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-NMe2Py)PPh2 and (6-Cl-Py)PPh2 ligand. This ligand is found to decrease catalytic activity over PyPPh2, thus invalidating a formerly characterised in situ base mechanism.

UR - https://www.scopus.com/pages/publications/85064986906

U2 - 10.1039/C9CP01471C

DO - 10.1039/C9CP01471C

M3 - Article

SN - 1463-9076

VL - 21

SP - 8543

EP - 8552

JO - Physical Chemistry Chemical Physics

JF - Physical Chemistry Chemical Physics

IS - 16

ER -

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

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