T-Butyllithium

Abstract

[594-19-4] C4H9Li (MW 64.06) InChI = 1S/C4H9.Li/c1-4(2)3;/h1-3H3; InChIKey = BKDLGMUIXWPYGD-UHFFFAOYSA-N (strong base capable of lithiating weak acids;1 useful for heteroatom-faciliated lithiations;2-4 reagent of choice for lithium–halogen exchange;5 can add to π-bonds1, 6) Physical Data: colorless solid; decomposes above 140 °C with loss of LiH; sublimes at 70 °C/0.1 mmHg. X-ray structures of the solvent-free tetramer and the ether-solvated dimer7a and 13C NMR studies in hydrocarbon8a and ethereal solutions7b have been reported. Solubility: sol hydrocarbon solvents, diethyl ether, and THF but should be used at low temperature; half-lives in various solvents have been reported;9 reacts violently with H2O and other protic solvents. Form Supplied in: commercially available as an approximately 1.7 M solution in pentane or heptane. Tetrameric in hydrocarbons,8 dimeric in diethyl ether,7 monomeric in THF10a although earlier reported as dimeric.1, 10b In combination with tertiary polyamines such as N,N,N′,N′‐Tetramethylethylenediamine (TMEDA), 1,4‐Diazabicyclo[2.2.2]octane (DABCO), or N,N,N′,N″,N″‐Pentamethyldiethylenetriamine (PMDTA), reactivity is often increased.1, 11 Analysis of Reagent Purity: since the concentrations of commercial solutions vary appreciably, especially after the original seal is broken, it is necessary to standardize solutions of the reagent prior to use. The classical Gilman double titration method is described in detail by Wakefield.1b A particularly convenient method for routine analyses involves titration of the reagent with s-butyl alcohol using 1,10-phenanthroline or 2,2′-biquinoline as indicator.13 A variety of other methods have been described.14 Preparative Method: the reaction of tert-butyl chloride with 1–2% Na–Li alloy in dry pentane requires particular attention to detail to achieve a reasonable yield of the reagent. Detailed procedures should be consulted.1b,12 Handling, Storage, and Precautions: solutions of the reagent are pyrophoric and the reagent may ignite spontaneously upon exposure to air, producing a purple flame. It is prudent to conduct all operations involving tert-BuLi behind a shield. In case of fire, a dry-powder extinguisher should be used: in no case should an extinguisher containing water or halogenated hydrocarbons be used to fight an alkyllithium fire. Bottles and reaction flasks containing the reagent should be flushed with N2 or preferably Ar and kept tightly sealed to preclude contact with oxygen or moisture. The reagent may be cautiously transferred under an inert gas atmosphere using standard syringe/cannula techniques.1b Most reactions of tert-butyllithium are exothermic and for this reason are usually carried out at temperatures well below ambient. For detailed handling techniques see Wakefield.1b