The Mechanism and Stereochemistry of Wittig Reactions of Phosphonium Ylide-Anions

Schmidbaur's group have extensively investigated1 the coordination properties of phosphonium 1,3-ylide-anions (1) in organometallic chemistry and more recently Cristau2 has reported the potential usefulness of these compounds in synthetic organic chemistry. There have been a few studies3 of specific phosphonium 1,1-ylide-anions (2), however their only use in the Wittig reaction appears to be that of (2a).4 We have set out to study the stereochemistry and mechanism of Wittig reactions of (1) and (2) and to carry out some preliminary investigations on the arsenic analogues (3).