TY - JOUR
T1 - Pd-catalysed mono- and dicarbonylation of aryl iodides: Insights into the mechanism and the selectivity
AU - Fernández-Alvarez, Victor M.
AU - De La Fuente, Verõnica
AU - Godard, Cyril
AU - Castillõn, Sergio
AU - Claver, Carmen
AU - Maseras, Feliu
AU - Carbõ, Jorge J.
PY - 2014/8/25
Y1 - 2014/8/25
N2 - The mechanism of the experimentally reported phosphine-free palladium-catalysed carbonylation of aryl iodides with amines in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as base was investigated at the DFT level. Paths were identified for both di- and monocarbonylation, and the calculated selectivity for three different substrates was in agreement with experiment. In dicarbonylation yielding α-ketoamides, formation of the second carbon-carbon bond occurs through reductive elimination in the Pd acyl amide intermediate after DBU-assisted nucleophilic attack of an amine at a terminal CO ligand. This path yields the major product with iodobenzene and the almost exclusive product with p-methoxyiodobenzene. Two different possible pathways yield the monocarbonylated amide product. In one of them, which affords the minor product for iodobenzene, base-assisted nucleophilic attack of the amine takes place on a Pd-bound acyl ligand. For substrates with electron-withdrawing substituents, such as p-cyanoiodobenzene, aryl migration to the CO ligand is disfavoured, and this allows base-assisted amine attack at a terminal CO ligand early in the catalytic cycle. From the resulting Pd amide aryl complex, the subsequent reductive elimination occurs easily, and monocarbonylation becomes favoured. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
AB - The mechanism of the experimentally reported phosphine-free palladium-catalysed carbonylation of aryl iodides with amines in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as base was investigated at the DFT level. Paths were identified for both di- and monocarbonylation, and the calculated selectivity for three different substrates was in agreement with experiment. In dicarbonylation yielding α-ketoamides, formation of the second carbon-carbon bond occurs through reductive elimination in the Pd acyl amide intermediate after DBU-assisted nucleophilic attack of an amine at a terminal CO ligand. This path yields the major product with iodobenzene and the almost exclusive product with p-methoxyiodobenzene. Two different possible pathways yield the monocarbonylated amide product. In one of them, which affords the minor product for iodobenzene, base-assisted nucleophilic attack of the amine takes place on a Pd-bound acyl ligand. For substrates with electron-withdrawing substituents, such as p-cyanoiodobenzene, aryl migration to the CO ligand is disfavoured, and this allows base-assisted amine attack at a terminal CO ligand early in the catalytic cycle. From the resulting Pd amide aryl complex, the subsequent reductive elimination occurs easily, and monocarbonylation becomes favoured. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
KW - carbonylation
KW - chemoselectivity
KW - density functional calculations
KW - palladium
KW - reaction mechanisms
U2 - 10.1002/chem.201403022
DO - 10.1002/chem.201403022
M3 - Article
SN - 0947-6539
VL - 20
SP - 10982
EP - 10989
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 35
ER -