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The mechanism of the Horner-Wadsworth-Emmons reaction. The ratio of alkene isomers 5 and 6 is not dependent upon the stereochemical outcome of the initial carbanion addition and upon the ability of the intermediates to equilibrate. The electron-withdrawing group (EWG) alpha to the phosphonate is necessary for the final elimination to occur.
Triethyl phosphonoacetate is a reagent for organic synthesis used in the Horner-Wadsworth-Emmons reaction (HWE) or the Horner-Emmons modification. Triethyl phosphonoacetate can be added dropwise to sodium methoxide solution to prepare a phosphonate anion. It has an acidic proton that can easily be abstracted by a weak base.
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This reaction is a variant of the Michael addition: CH 2 =CHCO 2 R + 3 H 3 PO 3 → (HO) 2 P(O)CH 2 CH 2 CO 2 R. In the Hirao coupling dialkyl phosphites (which can also be viewed as di-esters of phosphonic acid: (O=PH(OR) 2) undergo a palladium-catalyzed coupling reaction with an aryl halide to form a phosphonate.
The Horner-Wadsworth-Emmons reaction is a widely used olefination reaction in which a phosphonate-stabilized carbanion reacts with an aldehyde or ketone to form an alkene. In the standard HWE reaction, the phosphonate ester contains alkoxy substituents (typically methoxy or ethoxy), producing an E -alkene as the major product.
William D. Emmons (November 18, 1924 – December 8, 2001) was an American chemist and published with William S. Wadsworth a modification to the Wittig-Horner reaction using phosphonate-stabilized carbanions, now called the Horner-Wadsworth-Emmons reaction in his honor.
Réaction de Horner-Wadsworth-Emmons; Usage on it.wikipedia.org Reazione di Horner-Wadsworth-Emmons; Usage on it.wikibooks.org Chimica organica/Cose da fare; Usage on ja.wikipedia.org ホーナー・ワズワース・エモンズ反応; Usage on nl.wikipedia.org Horner-Wadsworth-Emmons-reactie; Usage on pt.wikipedia.org Reação de Horner ...
In the final steps a Horner–Wadsworth–Emmons reaction (methyl 2-(diethy1phosphono)acetate) give acrylate ester 12 as a mixture of cis and trans isomers which could be coached into the right (trans) direction by application of light in a photochemical rearrangement, the ester group was reduced (DIBAL / boron trifluoride) to isostrychnine 13 ...