Structure and Reactivity of Lithiated Phosphine Oxide Anions

3 Structure and Reactivity of Lithiated Phosphine Oxide Anions 

Warren and co-workers continue to develop the use of phosphine oxides, and the Horner-Wittig elimination, to control the stereoselectivity of organic reactions  

The Wittig-Homer reaction between C-metallated a-phosphoryl sulfides and carbonyl compounds provides a common route to a,P-unsaturated sulfides, but one which usually results in poor yields of the desired product when enolisable ketones are used. Stephan et al. have investigated the role of boron trifluoride in promoting the Wittig-Horner reaction of enolisable ketones, which usually follows a two-step process the initial condensation of the anion followed by an elimination step. It was found that when the second step occurred at a slow rate then addition of boron triflouride was necessary for completion.  

A widely used first step in Horner-Wittig reactions is the lithiation of a 

On the synthetic side, single diastereomers of P-keto phosphine oxides have been generated from intermolecular acylation of phosphine oxides using either chiral esters or chiral phosphine oxides. In most cases, reduction of the ketone products was not affected by the presence of extra chiral centres. Addition of metallated phosphine oxides to proline-derived ketoaminals provides a new route to optically active P-hydroxy phosphine oxides. The P-hydroxy phosphine oxide 97 has been prepared by the caesium fluoride mediated reaction of silyl-substituted phosphine oxide 98 and benzaldehyde. The synthesis of two (E)-(6-hydroxy-2-hexen-l-yl)diphenylphosphine oxides (99) has been reported. The Horner-Wittig reactions of these compounds with various carbonyl compounds 

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