Branched Selectivity in the Pd-Catalysed Methoxycarbonylation of 1-Alkenes

Charmaine Arderne, Llia A. Guzei, Cedric W. Holzapfel, Tyler Bredenkamp

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)

Abstract

The methoxycarbonylation of alkenes by palladium(II) complexes with P,O-donor ligands [(2-methoxyphenyl)diphenylphosphine (L-2), bis(2-methoxyphenyl) phenyl phosphine (L-3) and tris(2-methoxyphenyl) phosphine (L-4)] has been investigated. The results show that the Pd complexes derived from these ligands provide high regioselectivity for the branched esters from 1-pentene and 1-hexene (>80 %). Various parameters (including temperature, pressure, acid concentration) were optimized to improve the performance of the catalyst system. Higher temperatures afforded higher regioselectivity; but effected rapid catalyst decomposition. Acceptable turnover frequencies, conversions as well as catalyst stability could be obtained at higher L/Pd ratios. The dramatic change in regioselectivity is rationalised on the basis of the hemi-lability of the o-methoxy moiety, which may lead to ligand dissociation from L2PdX2 (L=ligand, X=Cl) rather than the expected dissociation of X. In support of our hypothesis, direct evidence for the coordination of the o-methoxy to the Pd centre was demonstrated by the crystal structure. To the best of our knowledge, this work provides the first reported route to valuable branched esters through the methoxycarbonylation of alkenes at suitable rates.

Original languageEnglish
Pages (from-to)1084-1093
Number of pages10
JournalChemCatChem
Volume8
Issue number6
DOIs
Publication statusPublished - 18 Mar 2016

Keywords

  • branched esters
  • hemi-labile
  • methoxycarbonylation
  • palladium

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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