Wittig and Horner-Emmons reactions are useful reactions which react with aldehydes and ketones to form carbon-carbon double bonds and are frequently utilized in organic syntheses.1)
Recently, syntheses of α,β-unsaturated esters have increasingly been performed using Wittig and Horner-Emmons reagents. In Horner-Emmons reactions, carbon-carbon double bonds generally lead to the E-form. Attempts to selectively obtain Z-form are being investigated and reaction solvents, temperatures, and new Horner-Emmons reagents are being examined.2)
Ando has developed ethyl (diaryl) phosphonoacetate and found a method for the synthesis of selective Z-α,β-unsaturated ester.3) This method has received much attention as it utilizes quaternary ammonium hydroxide. The reaction is stable toward water and does not require special reactive technique. The reaction has an exceedingly high selectivity for Z-α,β-unsaturated ester.
Wittig Reaction
Horner-Emmons Reaction
Wittig Reaction
Horner-Emmons Reaction
Literature
2) S. K. Thompson, C. H. Heathcock, J. Org. Chem., 1990, 55, 3386 [DOI]; A. Redjal, J. Seyden-Penne, Tetrahedron Lett., 1974, 1733 [DOI].
3) W. C. Still, C. Gennari, Tetrahedron Lett., 1983, 24, 4405 [DOI].
4) K. Ando, Tetrahedron Lett., 1995, 36, 4105 [DOI]; K. Ando, J. Org. Chem., 1997, 62, 1934 [DOI]; K. Ando, Yuki Gosei Kagaku Kyokaishi (J. Synth. Org. Chem., Jpn.), 2000, 58, 869; K. Ando, T. Oishi, M. Hirama, H. Ohno, T. Ibuka, J. Org. Chem., 2000, 65, 4745 [DOI]; Tokyo Ksei Kogyo, Jpn. Kokai Tokkyo Koho 10 265486, 1998.
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