Pd-catalysed mono- and dicarbonylation of aryl iodides: Insights into the mechanism and the selectivity

Victor M. Fernández-Alvarez, Verõnica De La Fuente, Cyril Godard, Sergio Castillõn, Carmen Claver, Feliu Maseras, Jorge J. Carbõ

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23 Citations (Scopus)

Abstract

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.
Original languageEnglish
Pages (from-to)10982-10989
JournalChemistry - A European Journal
Volume20
Issue number35
DOIs
Publication statusPublished - 25 Aug 2014

Keywords

  • carbonylation
  • chemoselectivity
  • density functional calculations
  • palladium
  • reaction mechanisms

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