The stereocontrolled Horner-Wittig reaction: synthesis of disubstituted alkenes

Abstract

Addition of the lithium derivatives of phosphine oxides Ph2P(O)CH2R1 to aldehydes gives erythro adducts (11) with good stereoselectivity. Reduction of α-diphenylphosphinoyl ketones (12) gives threo adducts (11) with even better stereoselectivity. Purification by flash chromatography and/or crystallisation followed by elimination of Ph2PO2) gives pure Z- or E-alkenes with high material conversion. Explanations are offered for the stereoselectivities, conditions defined for full stereochemical control, and guidelines suggested for approaches to a given alkene.