sec-Butyllithium
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sec-Butyllithium is the chemical compound with the formula CH3CHLiCH2CH3, abbreviated sec-BuLi or s-BuLi This organolithium reagent is used as a source of sec-butyl carbanion in organic synthesis.[1]
Sec-BuLi can be prepared by the reaction of sec-butyl halides with lithium metal:[2]
- CH3CHClCH2CH3 + 2 Li → CH3CHLiCH2CH3 + LiCl
The carbon-lithium bond is highly polar, rendering the carbon very nucleophilic and basic, as in other organolithium reagents. Sec-butyllithium is more basic than primary organolithium reagents such as n-butyl lithium. It is also more sterically hindered, though it is still useful for syntheses.
sec-BuLi is employed for deprotonations of particularly weak carbon acids where the more conventional reagent n-BuLi is unsatisfactory. It is, however, so basic that its use requires greater care than for n-BuLi. For example diethyl ether is attacked by sec-BuLi at room temperature in minutes, whereas its solutions of n-BuLi are stable.[1] Many transformatins involving sec-butyllithium are similar to those involving other organolithium reagents. For example, sec-BuLi react with carbonyl compounds and esters to form alcohols. With copper(I) iodide sec-BuLi forms lithium di-sec-butylcuprates. The first two reactions can also be accomplished by using sec-butylmagnesium bromide, a Grignard reagent; in fact, the latter is the typical reagent for this purpose.
[edit] References
- ^ a b Ovaska, T. V. "s-Butyllithium" in Encyclopedia of Reagents for Organic Synthesis, 2001 John Wiley & Sons: New York. doi:10.1002/047084289X.rb397
- ^ Hay, D. R.; Song, Z.; Smith, S. G.; Beak, P. (1988). "Complex-induced proximity effects and dipole-stabilized carbanions: kinetic evidence for the role of complexes in the α-lithiations of carboxamides". J. Am. Chem. Soc. 110: 8145–8153. doi:.
