TY - JOUR
T1 - Palladium-catalysed alkyne alkoxycarbonylation with P,N-chelating ligands revisited
T2 - a density functional theory study
AU - Ahmad, Shahbaz
AU - Lockett, Ashley
AU - Shuttleworth, Timothy A
AU - Miles-Hobbs, Alexandra M
AU - Pringle, Paul G
AU - Bühl, Michael
PY - 2019/4/17
Y1 - 2019/4/17
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 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.
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 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.
U2 - 10.1039/c9cp01471c
DO - 10.1039/c9cp01471c
M3 - Article (Academic Journal)
C2 - 30957820
SN - 1463-9076
VL - 21
SP - 8543
EP - 8552
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
IS - 16
ER -