Phenyllithium

Phenyllithium, commonly written as PhLi, is an organolithium compound used as a strong base and nucleophile in organic synthesis. Its formula is C6H5Li. It is typically prepared by halogen–lithium exchange from bromobenzene or other aryl halides with lithium metal in dry ether solvents, giving PhLi and LiBr. In solution, PhLi exists as aggregated species (dimers to higher-order oligomers) whose extent depends on solvent and concentration. It is typically sold as solutions in diethyl ether or THF and is highly reactive and pyrophoric.

PhLi reacts rapidly with moisture and air, producing benzene and lithium hydroxide; it must be handled under inert atmosphere and strictly dry conditions.

In chemical reactions, phenyllithium acts as a powerful nucleophile and base. It reacts with carbon dioxide to yield lithium benzoate, which on acidic workup affords benzoic acid. It adds to aldehydes and ketones to form secondary or tertiary alcohols after aqueous workup; for example, reaction with benzaldehyde yields benzhydryl alcohol derivatives. It also reacts with epoxides to give secondary alcohols with expanded carbon skeleton. PhLi is used to prepare other aryl lithium species via transmetalation or to generate reactive intermediates for subsequent carbon–carbon bond formation.

Storage: PhLi solutions are kept under an inert atmosphere at low temperature; solid PhLi is rarely handled outside specialized facilities. Safety: extremely reactive and flammable, reacts violently with water and oxygen; use appropriate protective equipment and fume hood.