Organolithium reagents standardization

Standard organolithium reagents such as butyllithium, ec-butyllithium or tert-butyllithium deprotonate rapidly, if not instantaneously, the relatively acidic hydrocarbons of the 1,4-diene, diaryhnethane, triarylmethane, fluorene, indene and cyclopentadiene families and all terminal acetylenes (1-alkynes) as well. Butyllithium alone is ineffective toward toluene but its coordination complex with A/ ,A/ ,iV, iV-tetramethylethylenediamine does produce benzyllithium in high yield when heated to 80 To introduce metal into less reactive hydrocarbons one has either to rely on neighboring group-assistance or to employ so-called superbases. 

Each of the following molecules can be used to standardize a solution of an organolithium reagent. 

Enantioselective additions of organolithiums to aldehydes are employed to synthesize chiral secondary alcohols, but these reactions are also quite frequently used for testing new chiral ligands and additives. The latter is usually performed with the standard addition of organolithium reagent RLi, in many cases n-butyllithium, -BuLi) to benzaldehyde [Eq. (1)], L denotes a chiral ligand] [9, 15,17-19]. 

Lithium di-isopropylamide (LDA), which is a very popular strong base , can be obtained by the reaction of lithium with di-isopropylamine in the presence of styrene. This is therefore a useful alternative to the usual methods for preparing LDA, i.e. from alkyl- or aryl-lithiums and di-isopropylamine. The benzyl alcohol (1) is a convenient self-indicating standard for the determination of the above mentioned organolithium reagents since a >1.01 molar equivalent of RLi is sufficient to give the dianion of (1) which has an intense red colour. ... 

A self-indicating standard for the detn. of organolithium reagents. Bp 278-279°, Bpi 122-125°. 

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