Radical and ionic mechanisms in rearrangements of o-tolyl aryl ethers and amines initiated by the Grubbs-Stoltz reagent, Et3SiH/KOtBu

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Abstract

Rearrangements of o-tolyl aryl ethers, amines, and sulfides with the Grubbs-Stoltz reagent (Et3SiH + KOtBu) were recently announced, in which the ethers were converted to o-hydroxydiarylmethanes, while the (o-tol)(Ar)NH amines were transformed into dihydroacridines. Radical mechanisms were proposed, based on prior evidence for triethylsilyl radicals in this reagent system. A detailed computational investigation of the rearrangements of the aryl tolyl ethers now instead supports an anionic Truce-Smiles rearrangement, where the initial benzyl anion can be formed by either of two pathways: (i) direct deprotonation of the tolyl methyl group under basic conditions or (ii) electron transfer to an initially formed benzyl radical. By contrast, the rearrangements of o-tolyl aryl amines depend on the nature of the amine. Secondary amines undergo deprotonation of the N-H followed by a radical rearrangement, to form dihydroacridines, while tertiary amines form both dihydroacridines and diarylmethanes through radical and/or anionic pathways. Overall, this study highlights the competition between the reactive intermediates formed by the Et 3SiH/KOtBu system.

Original languageEnglish
Article number6879
Number of pages18
JournalMolecules
Volume26
Issue number22
DOIs
Publication statusPublished - 15 Nov 2021

Keywords

  • Truce–Smiles rearrangement
  • Grubbs–Stoltz reagent
  • radical
  • electron transfer
  • aryl substitution
  • diarylmethanes
  • dihydroacridines
  • triethylsilane
  • potassium tert-butoxide
  • DFT
  • carbanion

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