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Synthesis 1992; 1992(5): 453-455
DOI: 10.1055/s-1992-26133
short paper
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α-Pyranones; I. Reaction of 4-Ethoxy- and 4-Chloromethylene-2-phenyl-5(4H)-oxazolone with Ethyl 3-Oxo-4-(triphenylphosphoranylidene)butyrate: A New Synthesis of 2H-pyran-2-one Compounds

M. L. Gelmi* , D. Pocar
  • *Istituto di Chimica Organica-Facoltà di Farmacia dell'Università, Via Venezian 21, I-20133 Milano, Italy
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Publication Date:
17 September 2002 (online)

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The reaction of 4-ethoxymethylene-5(4H)-oxazolone (2a) with ethyl 3-oxo-4-(triphenylphosphoranylidene)butyrate (1) affords ethyl 3-benzoylamino-2-oxo-6-triphenylphosphoranylidenemethyl-2H-pyran-5-carboxylate (3). Starting from the corresponding 4-chloromethylene compound 2b and 1, besides 3, ethyl 3-benzoylamino-6-[2-(4,5-dihydro-5-oxo-2-phenyl -4-oxazolylidene)-1-(triphenylphosphoranylidene)ethyl]-2-oxo-2H-pyran-5-carboxylate (5) is formed. The phosphorane 3 is a reactive synthetic intermediate for the preparation of ethyl 6-(1-alkenyl)-3-benzoylamino-2-oxo-2H-pyran-5-carboxylates 7 through reaction with aldehydes.