The reactions of α-acetylenic esters with N-substituted hydroxylamines in the presence of strong bases afforded 2-substituted 4-isoxazolin-3-ones, which were also prepared from α-acetylenic acid chlorides and N-substituted hydroxylamines. 1-Phenyl-3-hydroxypyrazoles were obtained by the reaction of α-acetylenic esters with phenylhydrazine in the presence of alkoxides.
