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Issue 13, 1997
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Silyl enol ethers as new protecting groups for alkyl4-halo-3-oxobutanoates; the preparation of pure(3-alkoxycarbonyl-2-oxopropyl)triphenylphosphonium salts

Abstract

A new method has been developed for the preparation of pure (3-alkoxycarbonyl-2-oxopropyl)triphenylphosphonium salts 8. Alkyl 4-bromo-3-oxobutanoates and alkyl 4-chloro-3-oxobutanoates 7 are protected as the trimethylsilyl enol ethers prior to treatment of the resulting bromo(trimethylsilyl enol ether) esters 20c and 21c with triphenylphosphine in toluene and then addition of a little water to give pure (3-isopropoxycarbonyl-2-oxopropyl)triphenylphosphonium bromide 8c. Bromo(silyl enol ether) esters react more efficiently with triphenylphosphine than the chloro(silyl enol ether) esters. tert-Butyldimethylsilyl enol ethers of alkyl 4-bromo-3-oxobutanoates and alkyl 4-chloro-3-oxobutanoates 7 also react with triphenylphosphine. Protection of isopropyl 4-bromo-3-oxobutanoate 7c as the enol acetate followed by subsequent reaction with triphenylphosphine gives (Z)-(2-acetoxy-3-isopropoxycarbonylbut-2-enyl) triphenylphosphonium bromide 17.

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Article type: Paper
DOI: 10.1039/A700241F
J. Chem. Soc., Perkin Trans. 1, 1997, 1987-1996

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    Silyl enol ethers as new protecting groups for alkyl 4-halo-3-oxobutanoates; the preparation of pure (3-alkoxycarbonyl-2-oxopropyl)triphenylphosphonium salts

    C. M. Moorhoff, J. Chem. Soc., Perkin Trans. 1, 1997, 1987
    DOI: 10.1039/A700241F

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