Mechanism of Alkyne Alkoxycarbonylation at a Pd Catalyst with P,N Hemilabile Ligands: A Density Functional Study

作者：Crawford Luke; Cole Hamilton David J; Drent Eite; Buehl Michael

来源：Chemistry - A European Journal, 2014, 20(43): 13923-13926.

DOI：10.1002/chem.201403983

• alkynes
• density functional calculations
• homogeneous catalysis
• palladium
• reaction mechanisms

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 Delta G double dagger 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.

• 出版日期2014-10-20