Lithjations of Phosphane Oxides

Abstract

Two studies on lithiated phosphane oxides (Horner-Wittig reagents) are reported. In the first, attempted deprotonation of Ph₂P(O)CH₃ using the lithium amide (Me₃Si)₂NLi leads merely to an adduct between the two species and suggests thereby an initiation step for many lithiation reactions. The mechanism and energetics of deprotonation have been studied further by ab initio MO calculations on the model system H₂P(O)CH₃ + H₂NLi. In a related study the phosphane oxide Ph₂P(O)CH₂CHMeEt has been successfully lithiated in non-Lewis base media, affording a tetrameric (LiO)₄ cubane structure whose key feature is the presence of Li-C bonds.

Keywords::

• lithiations
• phosphane oxides
• X-ray structures