Expanding the scope of enantioselective ferroPHANE-promoted [3+2] annulations with alpha,beta-unsaturated ketones

Chemistry. 2010 Jan 18;16(3):1033-45. doi: 10.1002/chem.200901893.

Abstract

The planar chiral 2-phospha[3]ferrocenophane I has been shown to be the first efficient nucleophilic organocatalyst for the enantioselective synthesis of cyclopentenylphosphonates, through [3+2] cyclizations between diethyl allenylphosphonate and alpha,beta-unsaturated ketones. The same catalyst has also been applied to the highly enantioselective [3+2] cyclizations of allenic esters with dibenzylideneacetone and analogous bis-enones, leading to functionalised cyclopentenes with either monocyclic or spirocyclic structures (ee 84-95 %). It has been shown that the residual enone functions in the resulting cyclopentenes can be involved in subsequent cyclization steps to afford unprecedented C(2)-symmetric bis-cyclopentenylketones. In order to provide insight into the behaviour of FerroPHANE I as a chiral catalyst in [3+2] cyclisations, the energetically most favoured isomers of the key phosphine-allene adduct have been calculated by DFT methods. Factors likely to control the chiral induction process are highlighted.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Catalysis
  • Crystallography, X-Ray
  • Cyclization
  • Ferrous Compounds / chemistry*
  • Ketones / chemistry*
  • Molecular Conformation
  • Phosphines / chemistry
  • Phosphinic Acids / chemical synthesis
  • Phosphinic Acids / chemistry
  • Stereoisomerism

Substances

  • Ferrous Compounds
  • Ketones
  • Phosphines
  • Phosphinic Acids
  • phosphine