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Mechanism of Alkyne Alkoxycarbonylation at a Pd Catalyst with P,N Hemilabile Ligands: A Density Functional Study
Author(s) -
Crawford L. Ellis,
ColeHamilton David J.,
Drent Eite,
Bühl Michael
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201403983
Subject(s) - propyne , alkyne , catalysis , ligand (biochemistry) , density functional theory , chemistry , methanol , proton , solvation , catalytic cycle , computational chemistry , medicinal chemistry , solvent , photochemistry , organic chemistry , physics , biochemistry , receptor , quantum mechanics
A detailed mechanism for alkyne alkoxycarbonylation mediated by a palladium catalyst has been characterised at the B3PW91‐D3/PCM level of density functional theory (including bulk solvation and dispersion corrections). This transformation, investigated via the methoxycarbonylation of propyne, involves a uniquely dual role for the P,N hemilabile ligand acting co‐catalytically as both an in situ base and proton relay coupled with a Pd 0 centre, allowing for surmountable barriers (highest Δ G ≠ of 22.9 kcal mol −1 for alcoholysis). This proton‐shuffle between methanol and coordinated propyne accounts for experimental requirements (high acid concentration) and reproduces observed regioselectivities as a function of ligand structure. A simple ligand modification is proposed, which is predicted to improve catalytic turnover by three orders of magnitude.