Sec-Butyllithium

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.^[1]

sec-Butyllithium

Skeletal formula of sec-butyllithium
Skeletal formula of tetrameric sec-butyllithium
Names
IUPAC name sec-Butyllithium
Systematic IUPAC name Butan-2-yllithium
Identifiers
CAS Number	598-30-1 Y
3D model (JSmol)	Interactive image Interactive image
Beilstein Reference	3587206
ChemSpider	10254345 Y
ECHA InfoCard	100.009.026
EC Number	209-927-7
PubChem CID	102446
UNII	5YV3GII1TB Y
CompTox Dashboard (EPA)	DTXSID80883459
InChI InChI=1S/C4H9.Li/c1-3-4-2;/h3H,4H2,1-2H3; Y Key: VATDYQWILMGLEW-UHFFFAOYSA-N Y InChI=1/C4H9.Li/c1-3-4-2;/h3H,4H2,1-2H3;/rC4H9Li/c1-3-4(2)5/h4H,3H2,1-2H3 Key: VATDYQWILMGLEW-MHILWDCKAX
SMILES [Li]C(C)CC CC([Li])CC
Properties
Chemical formula	C4H9Li
Molar mass	64.06 g·mol−1
Acidity (pKa)	51
Hazards
Safety data sheet (SDS)	Fisher MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Synthesis

sec-BuLi can be prepared by the reaction of sec-butyl halides with lithium metal:^[2]

Properties

Physical properties

sec-Butyllithium is a colorless viscous liquid.^[1][3] Using mass spectrometry, it was determined that the pure compound has a tetrameric structure.^[4] It also exists as tetramers when dissolved in organic solvents such as benzene, cyclohexane or cyclopentane.^[3] The cyclopentane solution has been detected with ⁶Li-NMR spectroscopy to have a hexameric structure at temperatures below −41 °C.^[5] In electron-donating solvents such as tetrahydrofuran, there exists an equilibrium between monomeric and dimeric forms.^[6]

Chemical properties

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. 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.^[1]

The compound decomposes slowly at room temperature and more rapidly at higher temperatures, giving lithium hydride and a mixture of butenes.^[7][8]

Applications

Many transformations involving sec-butyllithium are similar to those involving other organolithium reagents.

In combination with sparteine as a chiral auxiliary, sec-butyllithium is useful in enantioselective deprototonations.^[9] It is also effective for lithiation of arenes.^[10]