Lithium diisopropylamide-LDA

Lithium diisopropylamide (LDA) is a strong, non-nucleophilic base that is widely used. Because of its reactivity with many solvents, it has historically been generated in the laboratory by reaction of n-butyllithium and diisopropyl amine. Recently, LDA has become commercially available as a solution in THF/heptane/ethyl benzene. The commercially available material is frequently colored, making titration difficult. 

Freshly prepared LDA has varying stability, being most stable in alkanes and 1:1 alkanes:THF. Homemade LDA should be stored cold to extend its shelf-life. The preparation of LDA is representative of other lithium amide bases, such as lithium tetramethylpiperidide and lithium hexamethyl disilylamide. 

To a solution of diisopropylamine (3.44 g, 4.76 ml, 0.0341 mole) in THF (25 mL) at −78 ºC (methanol–dry ice bath) is added a solution of n-butyllithium (1.61 M in hexane, 21.1 mL, 0.0340 mol) with stirring under argon. The solution is warmed to 0 ºC in 15 min to provide an approximately 0.7 M solution of LDA.

Reference: Enders, D.; Pieter, R.; Renger, B.; Seebach, D. Org. Synth. 1978, 58, 113 or Enders, D.; Pieter, R.; Renger, B.; Seebach, D. Org. Synth. 1988, Coll. Vol. 6, 542.

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