Horner-Wadsworth-Emmons Reaction

Metalated phosphonates are more reactive than analogous phosphonium ylids (Wittig reagents). The HWE reaction is usually used when the nucleophilic carbon bears a strong anion stabilizing group (CO2Me, COMe, COH, CN, SO2R, SOR). These reagents are trans-selective if the substituents on phosphorus are simple alkoxy groups.

Intramolecular reactions have been successfully used to close large rings. The example below is a key step in the synthesis of Rhyzoxin D. Williams. D. R.; Werner, K. M.; Feng, B. Tetrahedron Lett. 1997, 38, 6825

  
  
  
  
  

Horner-Wadworth-Emmons:
Olefin Synthesis with Organic Phosphonate Carbanions,
   J. Boutagy and R. Thomas, Chem. Rev. 1974, 74, 87.
Wadsworth-Emmons Reaction Revisited,
   W. J. Stec, Acc. Chem. Res. 1983, 16, 411.
Lithium Coordination by Wittig-Horner Reagents formed by β-Carbonyl Substituted Phosphonates and Phosphine Oxide,
   Seyden-Penne, J. Bull. Soc. Chim. France 1988, 238.
Vinylphosphonates in Organic Synthesis,
   Minami, T.; Motoyoshiya, J. Synthesis 1992, 333. Minami, T.; Okauchi, T.; Kouno, R.
α-Phosphonovinyl Carbanions in Organic Synthesis.
   Synthesis 2001, 349-57.

© Hans J. Reich

Fall 2004


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