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
3D model (JSmol)
3587206
ChemSpider
ECHA InfoCard 100.009.026
EC Number
  • 209-927-7
UNII
  • InChI=1S/C4H9.Li/c1-3-4-2;/h3H,4H2,1-2H3; checkY
    Key: VATDYQWILMGLEW-UHFFFAOYSA-N checkY
  • 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
  • [Li]C(C)CC
  • CC([Li])CC
Properties
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).
checkY verify (what is checkY☒N ?)
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]

References
  1. Ovaska, T. V. (2001). "s-Butyllithium". Encyclopedia of Reagents for Organic Synthesis. New York: John Wiley & Sons. doi:10.1002/047084289X.rb397. ISBN 0471936235..
  2. 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 (24): 8145–8153. doi:10.1021/ja00232a029.
  3. Wietelmann, Ulrich; Bauer, Richard J. (2000-06-15), "Lithium and Lithium Compounds", in Wiley-VCH Verlag GmbH & Co. KGaA (ed.), Ullmann's Encyclopedia of Industrial Chemistry, Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, pp. a15_393, doi:10.1002/14356007.a15_393, ISBN 978-3-527-30673-2, retrieved 2022-05-07
  4. Plavsic, D.; Srzic, D.; Klasinc, Leo (1986). "Mass spectrometric investigations of alkyllithium compounds in the gas phase". The Journal of Physical Chemistry. 90 (10): 2075–2080. doi:10.1021/j100401a020. ISSN 0022-3654.
  5. Fraenkel, Gideon; Henrichs, Mark; Hewitt, Michael; Su, Biing Ming (1984). "Structure and dynamic behavior of a chiral alkyllithium compound: carbon-13 and lithium-6 NMR of sec-butyllithium". Journal of the American Chemical Society. 106 (1): 255–256. doi:10.1021/ja00313a052. ISSN 0002-7863.
  6. Bauer, Walter.; Winchester, William R.; Schleyer, Paul von R. (1987-11-01). "Monomeric organolithium compounds in tetrahydrofuran: tert-butyllithium, sec-butyllithium, supermesityllithium, mesityllithium, and phenyllithium. Carbon-lithium coupling constants and the nature of carbon-lithium bonding". Organometallics. 6 (11): 2371–2379. doi:10.1021/om00154a017. ISSN 0276-7333.
  7. Glaze, William H.; Lin, Jacob; Felton, E. G. (1965). "The Thermal Decomposition of sec-Butyllithium". The Journal of Organic Chemistry. 30 (4): 1258–1259. doi:10.1021/jo01015a514. ISSN 0022-3263.
  8. Glaze, William H.; Lin, Jacob; Felton, E. G. (1966). "The Pyrolysis of Unsolvated Alkyllithium Compounds". The Journal of Organic Chemistry. 31 (8): 2643–2645. doi:10.1021/jo01346a044. ISSN 0022-3263.
  9. Crépy, Karen V. L.; Imamoto, Tsuneo (2005). "Preparation of (S,S)-1,2-bis(tert-Butylmethylphosphino)ethane ((S,S)-t-bu-bisp*) as a Rhodium Complex". Organic Syntheses. 82: 22. doi:10.15227/orgsyn.082.0022.
  10. Wang, X.; de Silva, S. O.; Reed, J. N.; Billadeau, R.; Griffen, E. J.; Chan, A.; Snieckus, V. (1995). "7-Methoxyphthalide". Org. Synth. 72: 163. doi:10.15227/orgsyn.072.0163.
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