Stereochemically pure E- and Z- alkenes by the Wittig–Horner reaction

Abstract

Pure Z-alkenes are obtained stereospecifically from erythro-alcohols (3) formed on addition of Ph₂PO-stabilised anions to aldehydes; acylation of the same anions, reduction of the α-Ph₂P(O) ketones (5) to the threo-alcohol (6), and elimination gives pure E-alkenes.