Stereochemically controlled synthesis of unsaturated alcohols by the Horner–Wittig reaction

Abstract

Single isomers (E or Z) of unsaturated alcohols with two to five carbon atoms between the double bond and the OH group may be made by the phosphine oxide version of the Horner–Wittig reaction. Hydroxyalkyldiphenylphosphine oxides react with aldehydes either directly or as silyl ethers to give a moderately Z-selective synthesis, while rearrangement of esters of the same alcohols by acyl transfer or acylation of alkyldiphenylphosphine oxides with lactones gives hydroxy ketones whose reduction and elimination leads to an E-selective synthesis. In most cases, separation of the diastereoisomers of the Horner–Wittig intermediates leads to the preparation of pure E- or Z-alkenols.