The controversial dynamic stereochemistry of bifluorenylidenes

P. Ulrich Biedermann, Amalia Levy, Michal Rachel Suissa, John J. Stezowski, Israel Agranat

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Two distinct Gibbs free energies of activation (ΔGc‡) have been determined by the dynamic NMR method for simple twisted homomerous overcrowded bistricyclic enes of the bifluorenylidene series: ΔGc‡ = 44 kJ/mol for the conformational inversion (enantiomerization) of 2-i-propyl-bi-9H-fluoren-9-ylidene, and ΔGc‡ = 104 kJ/mol for the E,Z-isomerization of 2,2′-dimethyl-bi-9H-fluorene-9-ylidene. These barriers are not biased by additional steric constraints and reflect the intrinsic dynamic properties of bifluorenylidenes. Mechanisms for the dynamic processes are proposed, based on the experimental evidence and semiempirical PM3 calculations.

Original languageEnglish
Pages (from-to)75-80
Number of pages6
JournalEnantiomer
Volume1
Issue number1
StatePublished - 1 Dec 1996
Externally publishedYes

Keywords

  • Bistricyclic enes
  • Chirality
  • Conformational behavior
  • Dynamic NMR
  • Overcrowding
  • Semiempirical calculations

ASJC Scopus subject areas

  • General Chemistry
  • Biochemistry
  • General Biochemistry, Genetics and Molecular Biology
  • Organic Chemistry

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