The stereochemistry of Wittig reactions of ylide-anions derived from semi-stabilized phosphonium ylides 

 -  Tetrahedron Letters, 29(4), p.485-488, 1988 .
<br/><br/> Ylide-anions derived from a variety of benzylphos honium salts react with one or two equivalents of benzaldehyde to stilbene. Reactions of these ylide-anions with one equiva ent of aldeh B