tert-Butyllithium

Description

tert-Butyllithium solution (tert-BuLi) is an organolithium compound, used as a strong base in organic chemistry. It facilitates lithium-halogen exchange reaction and also can be employed in the deprotonation of C-H compounds and amines. it has applications in organic synthesis since it is a strong base, capable of deprotonating many carbon molecules, including benzene. tert-Butyllithium is available commercially as hydrocarbon solutions; it is not usually prepared in the laboratory. Its synthesis was first reported by R. B. Woodward in 1941.

Chemical Properties

tert-Butyllithium is a colorless crystalline solid or colourless to pale yellow solution. It is more reactive than n- or sec-butyllithium and has similar properties. However, it is thermally stable. Dixon and co-workers have heated tert-Butyllithium to 100°C for 20 hr with little decomposition.

Uses

• There are no commercial uses of t-butyllithium, but it is used as a polymerization initiator and as a metalating agent in the laboratory.
• Alkylating and metalating agent. Reagent for the introduction of the tert-butyl group.
• tert-Butyllithium (t-BuLi) is the most reactive of the commercially available organolithium reagents. It is supplied as a standard solution in hydrocarbon solvents, usually in a bottle sealed with a septum.

Application

tert-Butyllithium solution can be used as a strong base in the synthesis of:
Alkyllithium derivatives form alkyl iodides and diiodoalkanes by halogen-lithium exchange reaction.
Inorganic polymer [(LiMo3Se3)n] from [(InMo3Se3)n] by reductive intercalation method.
Adducts of cinnamic acid (1,3- and 1,4-adducts) by reacting with C-C double of cinnamic acid.

Preparation

tert-Butyllithium is not sold in large quantities. The industrial and laboratory preparations are the same: the reaction of t-butyl chloride with lithium metal in a hydrocarbon solvent. However, tert-Butyllithium is much more difficult to produce than the other isomeric butyllithium compounds and some special precautions must be taken to obtain good yields. Principally, the lithium metal must be finely divided and must contain several percent sodium. It has also been found that t-butyl alcohol in the butyl chloride is beneficial. The solvent of choice is pentane. Vigorous reflux is necessary for good yield since it apparently helps to remove lithium chloride from the surface of the metal, and pentane refluxes at about the optimum temperature. If hexane is used at the same temperature, a significantly lower yield is obtained.