Allylic phosphine oxides as precursors of conjugated dienes of defined geometry

Abstract

Methods are described for the preparation in geometrically homogeneous form of allylic diphenylphosphine oxides. These compounds can be used in Horner reactions with carbonyl compounds to provide a convenient one-step synthesis of conjugated dienes in which the geometry present in the original allyl system is preserved. The method is exemplified by the preparation of the homogeneous Z- and E-forms of but-2-enylidenecyclohexane and of 3-methylpent-2-enylidenecyclohexane.