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

Abstract

A revised mechanism of alkyne alkoxycarbonylation via a Pd catalyst with P,N-ligands is validated through joint DFT modeling and experiments.

Palladium-catalysed methoxycarbonylation of ethene with bidentate diphosphine ligands: a density functional theory study

“…We recently identified highly reactive ketenelike intermediates during the formation of MMA at palladium catalyst with P,N-chelating ligands. 27,28 These ketene species undergo rapid alcoholysis leading to the final product. Based on this work, we have characterised a ketene cycle for the production of MePro, which requires an a,b insertion of ethene into the Pd-H bond followed by an a,a insertion of the ethyl group into coordinated carbon monoxide.…”

Design of a Highly Active Pd Catalyst with P,N Hemilabile Ligands for Alkoxycarbonylation of Alkynes and Allenes: A Density Functional Theory Study

“…We recently applied state‐of‐the‐art density functional theory (DFT) studies to disclose the mechanistic details of homogenous methoxycarbonylation of propyne using hemilabile Pd(P,N) catalyst . Our mechanism involves proton shuffling by the pyridyl groups in the initiation and termination steps.…”

“…Both complexes are interconvertible under the turnover conditions (Δ G 9 + →9L + =−0.7 kcal mol −1 and Δ G ≠ 9 + →9L + =8.8 kcal mol −1 ). In 9 + , proton transfer to the terminal carbon of propadiene gives an agostic intermediate 2 ii + , which is an isomer of 2 i + . 2 ii + rearranges into 2 (Figure ), which then follows the same steps as in mechanism E to give the final branched product, MMA (Scheme ).…”

“…An electron‐withdrawing group at the same position helps towards this desired selectivity and also increases the reaction rate . We have thus evaluated the effect of chloro and methyl substituents at 6‐position of the 2‐pyridyl moiety on the selectivity with propadiene as substrate.…”

“…We found previously that in the (4‐Me 2 N‐Py)PPh 2 ligand, the Me 2 N substituent at the para position increases the basicity of the pyridyl moiety, which makes protonation of propyne more difficult . To make 8 + as a stable intermediate with minimal effects on the proton transfer step, we have considered another ligand system, (6‐Cl‐3‐Me‐Py)PPh 2 .…”