Formula C4H9Li | ||
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sec-Butyllithium is an organometallic compound with the formula CH3CHLiCH2CH3, abbreviated sec-BuLi or s-BuLi. This chiral organolithium reagent is used as a source of sec-butyl carbanion in organic synthesis.
sec-BuLi can be prepared by the reaction of sec-butyl halides with lithium metal:
The carbon-lithium bond is highly polar, rendering the carbon basic, as in other organolithium reagents. Sec-butyllithium is more basic than the primary organolithium reagent, n-butyllithium. 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 ether solutions of n-BuLi are stable. Many transformations 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.