Memory effects in Pd-catalysed allylic alkylation: Stereochemical labelling through isotopic desymmetrization

GC Lloyd-Jones*, SC Stephen

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

H-2-Labelled and O-18-labelled cyclopentenyl esters (+/-)-4 and (+/-)-5 are used as probes for memory effects in Pd-catalysed allylic alkylation. H-2-Labelled alkylation product 6 arising from stereospecific Pd-catalysed reaction of (+/-)-4 was analysed by a novel C-13 NMR method involving H-2-isotope shifts and paramagnetic diastereotopic shifts. When catalysts bearing the Trost modular ligand (R,R)-3 were employed, variable memory effects were observed with the slower reacting chirality mismatched (R)-4 substrate-catalyst pairing. The memory effect is dependent on nucleofuge steric bulk and not pK(a). Attack by [LiCH(CO2CH3)(2)] occurs with reversed site selectivity but (R)-4 remains the mismatched substrate. Mismatched ionisation leading to a Pd-pi-allyl in which (R,R)-3 acts as a monophosphine ligand may explain the memory effect.

Original languageEnglish
Pages (from-to)2539-2549
Number of pages11
JournalChemistry - A European Journal
Volume4
Issue number12
Publication statusPublished - Dec 1998

Keywords

  • allyl complexes
  • asymmetric catalysis
  • isotopic labeling
  • P ligands
  • palladium
  • SYN-ANTI DICHOTOMY
  • ASYMMETRIC CATALYSIS
  • (PI-ALLYL)PALLADIUM COMPLEXES
  • ENANTIOSELECTIVE CATALYSIS
  • NUCLEOPHILIC-SUBSTITUTION
  • HOMOGENEOUS CATALYSIS
  • PALLADIUM COMPLEXES
  • CHIRAL LIGANDS
  • MECHANISM
  • SELECTIVITY

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