Schlosser variant of the Wittig reaction

A different reaction mode of lithiobetaines is used in the Schlosser variant of the Wittig reaction. Here, too, one starts from a nonstabilized ylide and works under non-salt-free conditions. However, the Schlosser variant is an olefination which gives a pure frans-alkene rather than a trans.cis mixture. The experimental procedure looks like magic at first ... 

Fig. 11.6. Mechanism of the Schlosser variant of the Wittig reaction of nonstabilized ylides.

---