LiOtBu

Lithium tert-butoxide, abbreviated LiOtBu, is an organolithium reagent widely used as a strong, bulky, non-nucleophilic base in organic synthesis. It consists of the tert-butoxide anion coordinated to a lithium cation (formula C4H9OLi). The tert-butyl group provides substantial steric hindrance, giving high basicity while limiting nucleophilicity.

Preparation and forms are typical of organolithiums: LiOtBu is commonly prepared in situ by deprotonation of tert-butanol with n-butyllithium in dry ether or THF, yielding LiOtBu and butane. Commercially, it is available as a solid or as solutions in hydrocarbon solvents or THF. It is highly moisture- and air-sensitive and is normally stored under inert atmosphere.

Properties and handling: LiOtBu appears as a white to off-white solid or pale solution and dissolves in polar aprotic solvents such as THF and diethyl ether. It reacts vigorously with water and oxygen, releasing heat and tert-butanol; therefore, it must be handled under inert gas with appropriate PPE in a fume hood.

Applications: In organic synthesis, LiOtBu is employed to deprotonate weak acids to form metal enolates and related species. Its bulky, non-nucleophilic nature makes it suitable for generating enolates from ketones, esters, malonates, and nitriles, and for promoting E2 eliminations with hindered substrates. Reactions are typically conducted in THF at low temperatures (for example, −78 to 0 °C) to control reactivity.

Safety: LiOtBu is a reactive organizational chemical requiring careful handling, proper storage under inert atmosphere, and avoidance of exposure to moisture. Similar bulky bases include KOtBu and NaOtBu.