The synthesis of (Z)-penta-2,4-dien-1-ol and substituted (E)-pentadienols by the stereochemically controlled Horner–Wittig reaction

Acylation of Ph2P(O) Me with a lactone gives a Horner–Wittig intermediate with a Z-double bond protected as a Diels–Alder adduct with furan and hence (Z)-penta-2,4-dien-1-ol. Substituted (E)-penta-2,4-dien-1-ols are available by a more general route involving addition of enals to phosphine oxides, a regiochemically controlled allylic alcohol transposition, and a Horner–Wittig reaction. The geometry of only one double bond can be controlled.