An efficient method for the synthesis of 2, 5-dihydroisoxazoles and isoxazoles using iodocyclization of N-alkoxycarbonyl O-propargylic hydroxylamines has been developed. 2, 5- Dihydro-4-iodoisoxazole underwent the cross-coupling reactions without aromatization to afford polyfunctionalized 2, 5-dihydroisoxazoles. This process was applied to the preparation of valdecoxib and its 2, 5-dihydro-derivative.