A New Synthesis of 5-Hydroxy-2-Isoxazolines and Their Conversion into Isoxazoles

The reaction of 1,5-diarylpent-1-yne-3, 5-diones or 2,6-diaryl-4H-pyran-4-ones with hydroxylamine in ethanol led to the formation of 5-hydroxyisoxazolines as well as isoxazoles as minor products. The isoxazolines could be converted into the latter isoxazoles on prolonged heating in xylene. The structure of the intermediate 5-hydroxyisoxazolines was established from their I. R., UV. 1H-N.M.R. and mass spectral data.