Uses
Vinyl lithium is a reactive intermediate for the formation of vinyl alcohols from aldehydes, vinyl ketones from organic acids, vinyl sulfides from disulfides, and monosubstituted alkenes from organic halides.
Definition
ChEBI: Vinyllithium is a vinyllithium compound and an alkenyllithium compound.
Preparation
Vinyllithium is prepared by a variety of methods. Direct metalation of Ethylene with Lithium metal in
dimethoxymethane yields vinyllithium contaminated with lithium hydride, and other organolithio species, such as butyllithium
and 1,4-dilithiobutane. Direct formation from ethylene can also be accomplished using Potassium t-Butoxide, n-Butyllithium, and TMEDA (N,N,N′,N′-Tetramethylethylenediamine) in hexane at -40 °C, followed by treatment of the
vinylpotassium with Lithium Bromide. The lithium-halogen exchange reaction has been used, starting from vinyl chloride
and lithium/sodium dispersions, or from vinyl bromide with 2 equiv of t-Butyllithium in either a Trapp solvent mixture at -
120 °C or ether at -78 °C. This is the most convenient procedure, but lithium halide is formed during the reaction and is
present as a contaminant. Halide-free vinyllithium can be prepared by transmetalation of Tetravinylstannane with phenyl- or
butyllithium, of tetravinyllead with either lithium metal or Phenyllithium, or of divinylmercury with lithium dispersion in
pentane.
storage
As with most alkyllithium reagents, vinyllithium reacts readily with moisture. Solid
vinyllithium should be maintained at -25 °C or below, under an inert atmosphere. The solid suffers a loss in activity with time
and should be used immediately upon preparation. Solutions of the reagent in ether or THF, under an inert atmosphere, are
stable for up to 1 week at rt. Solid vinyllithium is violently pyrophoric, yielding a brilliant red flash on contact with air.
Purification Methods
Purification of Vinyllithium: ether solutions can be evaporated under an inert atmosphere and the resulting solid washed with anhydrous
pentane or hexane.
