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Issue 11, 2000
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Selective C-acylation of CH-active dicarbonyl compounds with ketenylidenetriphenylphosphorane: syntheses and structures of 3-phosphoranylideneacyltetronic acids, 3-phosphoranylideneacyl-4-oxocoumarins, and 4-phosphoranylideneacylpyrazol-5-ones

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Abstract

Selective C- over O-/N-acylation of acyclic, carbocyclic and heterocyclic carbonyl compounds bearing active α-CH groups is described. β-Ketoesters give the corresponding α-acylylidic derivatives in good yields. Likewise, tetronic acids and 4-hydroxycoumarins furnish the respective 3-acylylidic derivatives, and pyrazol-5-ones exclusively yield the corresponding 4-acylylidic compounds despite the possibility of tautomerism. X-Ray single crystal structure and NMR analyses of the product tricarbonyl ylides are presented and structure–reactivity interdependencies are discussed. As a rule, compounds with wide-spread conjugation of the π-system like 9/13 do not readily undergo Wittig olefination. Acylylides 11 with separated β-keto moieties react normally.

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Publication details

The article was received on 24 Feb 2000, accepted on 07 Apr 2000 and first published on 12 May 2000


Article type: Paper
DOI: 10.1039/B001541P
Citation: J. Chem. Soc., Perkin Trans. 1, 2000,0, 1723-1730
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    Selective C-acylation of CH-active dicarbonyl compounds with ketenylidenetriphenylphosphorane: syntheses and structures of 3-phosphoranylideneacyltetronic acids, 3-phosphoranylideneacyl-4-oxocoumarins, and 4-phosphoranylideneacylpyrazol-5-ones

    R. Schobert, S. Siegfried, M. Nieuwenhuyzen, W. Milius and F. Hampel, J. Chem. Soc., Perkin Trans. 1, 2000, 0, 1723
    DOI: 10.1039/B001541P

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