endolexo preferences for double bonds in three-membered rings including phosphorus compounds

T. P.M. Goumans, Andreas W. Ehlers, Koop Lammertsma, Ernst Ulrich Würthwein

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)


Depending on the substituent and the heteroelements of an unsaturated three-membered ring system of the methylene-cyclopropane/1-methylcyclopropene type, the double bond may be preferentially exo- or endocyclic. This preference may be considered as a combination of substituent and ring-strain effects. The substituent effect is a composite one, encompassing both exocyclic olefinic strain and tautomeric preference. The preference for exocyclic unsaturation increases in the order =CH2 < =NH < =PH < =O for the considered substituents. The higher the ring-strain, the higher the propensity for exocyclic unsaturation. The low-strain 2H-phosphirenes favor endocyclic unsaturation, except for the 3-OH-substituted species where the strong C=O double bond is the determining factor.

Original languageEnglish
Pages (from-to)2941-2946
Number of pages6
JournalEuropean Journal of Organic Chemistry
Issue number15
Publication statusPublished - 28 Jul 2003
Externally publishedYes


  • Ab initio calculations
  • Heterocycles
  • Phosphorus heterocycles
  • Small-ring systems
  • Strained molecules
  • Tautomerism

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry


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