Vinyllithium is an organolithium compound with the formula LiC<sub>2</sub>H<sub>3</sub>. A colorless or white solid, it is encountered mainly as a solution in tetrahydrofuran (THF). It is a reagent in synthesis of organic compounds, especially for vinylations.
Solutions of vinyllithium are prepared by lithium-halogen exchange reactions. A halide-free route entails reaction of tetravinyltin with butyllithium:
The reaction of ethylene and lithium affords vinyl lithium and lithium hydride, together with other organolithium compounds,
Like most organolithium compounds, vinyllithium crystallizes from THF as a cluster compound as a cubane-type cluster.
Vinyllithium is used to install vinyl groups on metal-based reagents, i.e., vinylations. It is a precursor to vinylsilanes, vinylcuprates, and vinylstannanes. It adds to ketones compounds to give allylic alcohols. Vinylmagnesium bromide is often used in place of vinyllithium.
Vinyl magnesium bromide, a Grignard reagent, is in many ways easier to generate in the laboratory and behaves similarly to vinyllithium.