Mechanistic examination of AuIII-mediated 1,5-enyne cycloisomerization by AuBr2(N-imidate)(NHC) / AgX precatalysts - is the active catalyst AuIII or AuI?

Jonathan Paul Reeds, Mark P. Healy, Ian James Stewart Fairlamb

Research output: Contribution to journalArticlepeer-review

Abstract

Gold(III) catalysts mediate 1,5-enyne cycloisomerization or tandem nucleophilic substitution-1,5-enyne cycloisomerization processes in an efficient manner. This study examines the reaction kinetics of 1,5-enyne cycloisomerization, mediated by AuBr2(N-imidate)(NHC) catalysts {where N-imidate = N-tetrafluorosuccinimide (N-TFS) or N-phthalimide (N-phthal) and NHC = N,N′-di-tert-pentylimidazol-2-ylidene (ItPe)}, in the presence of AgOTf, in comparison with AuIIIBr3(NHC) and AuIBr(NHC). The nature of N-imidate anion influences catalyst efficacy. NMR spectroscopic investigations have allowed the ease of reduction of AuBr2(N-TFS)(NHC) to AuIX(NHC) (where X = N-TFS or Br) to be examined. Br2 is liberated from AuIII, which has been trapped by a sacrificial alkene. Under working catalyst conditions cationic AuIII is reduced to AuI.
Original languageEnglish
Pages (from-to)3524-3533
Number of pages10
JournalCatalysis Science and Technology
Volume4
Early online date24 Jul 2014
DOIs
Publication statusE-pub ahead of print - 24 Jul 2014

Keywords

  • GOLD CATALYSIS
  • CATALYSIS
  • KINETICS
  • MECHANISM
  • ENYNE CYCLOISOMERIZATIONS
  • NMR
  • GOLD CATALYSTS

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