C–O cleavage via InIII alkoxide intermediates: In situ 13C NMR analysis of the mechanism of an enantioselective in-mediated cyclopropanation reaction

Jennifer L. Slaughter, Guy C. Lloyd-Jones

Research output: Contribution to journalArticlepeer-review

Abstract

The mechanism of asymmetric cyclopropanation of dibenzylideneacetone and benzylideneacetone by in situ generated allyl indium reagents in the presence of methyl mandelate as a chiral modifier has been studied by in situ 13C{1H} NMR in conjunction with 13C/2H labelling and mass spectrometry. Two indium alkoxides were identified, the first arising from indium mediated allylation of the ketone, the second arising from reaction of an in situ liberated homoallylic via a LiI mediated reaction with excess allyl indium reagent. On acidification, protonation at oxygen induces C–O rather than In–O cleavage and the incipient tertiary allylic cation is stereoselectivly allylated with approximately 90% si selectivity, via what is assumed to be a mandelate-chelated indium allyl reagent.

Original languageEnglish
Article number131786
Number of pages6
JournalTetrahedron
Volume78
Issue number11
Early online date25 Nov 2020
DOIs
Publication statusPublished - 8 Jan 2021

Keywords

  • C-labelling
  • In situ NMR
  • Indium
  • Mechanism
  • Stereoselective reactions

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