Heterocycles from ylides. Part III. Reactivity of allylic phosphonium ylides with 1,3-dipoles

Abstract

3-Cyano-, 3-formyl-, and 3-methoxycarbonyl-allylidenetriphenylphosphorane react with nitrile imides and nitrile oxides yielding the corresponding substituted pyrazoles and isoxazoles, through elimination of a methyltriphenylphosphonium salt. The differences in reactivity between the foregoing phosphoranes and simple carbonyl-stabilised phosphoranes are discussed.