Sec-Butyllithium

sec-BuLi can be prepared by the reaction of sec-butyl halides with lithium metal:{{cite journal |author1=Hay, D. R. |author2=Song, Z. |author3=Smith, S. G. |author4=Beak, P. | title = Complex-induced proximity effects and dipole-stabilized carbanions: kinetic evidence for the role of complexes in the α-lithiations of carboxamides | journal = J. Am. Chem. Soc. | year = 1988 | volume = 110 | pages = 8145–8153 | doi = 10.1021/ja00232a029 | issue = 24}}

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sec-Butyllithium is a colorless viscous liquid.{{Citation |last1=Wietelmann |first1=Ulrich |title=Lithium and Lithium Compounds |date=2000-06-15 |url=https://onlinelibrary.wiley.com/doi/10.1002/14356007.a15_393 |encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry |pages=a15_393 |editor-last=Wiley-VCH Verlag GmbH & Co. KGaA |place=Weinheim, Germany |publisher=Wiley-VCH Verlag GmbH & Co. KGaA |language=en |doi=10.1002/14356007.a15_393 |isbn=978-3-527-30673-2 |access-date=2022-05-07 |last2=Bauer |first2=Richard J.|url-access=subscription }} Using mass spectrometry, it was determined that the pure compound has a tetrameric structure.{{Cite journal |last1=Plavsic |first1=D. |last2=Srzic |first2=D. |last3=Klasinc |first3=Leo |date=1986 |title=Mass spectrometric investigations of alkyllithium compounds in the gas phase |url=https://pubs.acs.org/doi/abs/10.1021/j100401a020 |journal=The Journal of Physical Chemistry |language=en |volume=90 |issue=10 |pages=2075–2080 |doi=10.1021/j100401a020 |issn=0022-3654|url-access=subscription }} It also exists as tetramers when dissolved in organic solvents such as benzene, cyclohexane or cyclopentane. The cyclopentane solution has been detected with ⁶Li-NMR spectroscopy to have a hexameric structure at temperatures below −41 °C.{{Cite journal |last1=Fraenkel |first1=Gideon |last2=Henrichs |first2=Mark |last3=Hewitt |first3=Michael |last4=Su |first4=Biing Ming |date=1984 |title=Structure and dynamic behavior of a chiral alkyllithium compound: carbon-13 and lithium-6 NMR of sec-butyllithium |url=https://pubs.acs.org/doi/abs/10.1021/ja00313a052 |journal=Journal of the American Chemical Society |language=en |volume=106 |issue=1 |pages=255–256 |doi=10.1021/ja00313a052 |issn=0002-7863|url-access=subscription }} In electron-donating solvents such as tetrahydrofuran, there exists an equilibrium between monomeric and dimeric forms.{{Cite journal |last1=Bauer |first1=Walter. |last2=Winchester |first2=William R. |last3=Schleyer |first3=Paul von R. |date=1987-11-01 |title=Monomeric organolithium compounds in tetrahydrofuran: tert-butyllithium, sec-butyllithium, supermesityllithium, mesityllithium, and phenyllithium. Carbon-lithium coupling constants and the nature of carbon-lithium bonding |url=https://pubs.acs.org/doi/abs/10.1021/om00154a017 |journal=Organometallics |language=en |volume=6 |issue=11 |pages=2371–2379 |doi=10.1021/om00154a017 |issn=0276-7333|url-access=subscription }}

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.

The compound decomposes slowly at room temperature and more rapidly at higher temperatures, giving lithium hydride and a mixture of butenes.{{Cite journal |last1=Glaze |first1=William H. |last2=Lin |first2=Jacob |last3=Felton |first3=E. G. |date=1965 |title=The Thermal Decomposition of sec-Butyllithium |url=https://pubs.acs.org/doi/abs/10.1021/jo01015a514 |journal=The Journal of Organic Chemistry |language=en |volume=30 |issue=4 |pages=1258–1259 |doi=10.1021/jo01015a514 |issn=0022-3263|url-access=subscription }}{{Cite journal |last1=Glaze |first1=William H. |last2=Lin |first2=Jacob |last3=Felton |first3=E. G. |date=1966 |title=The Pyrolysis of Unsolvated Alkyllithium Compounds |url=https://pubs.acs.org/doi/abs/10.1021/jo01346a044 |journal=The Journal of Organic Chemistry |language=en |volume=31 |issue=8 |pages=2643–2645 |doi=10.1021/jo01346a044 |issn=0022-3263|url-access=subscription }}

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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.{{cite journal |doi=10.15227/orgsyn.082.0022| title=Preparation of (S,S)-1,2-bis(tert-Butylmethylphosphino)ethane ((S,S)-t-bu-bisp*) as a Rhodium Complex | journal=Organic Syntheses | year=2005 | volume=82 | page=22|first1=Karen V. L.|last1=Crépy|first2= Tsuneo|last2=Imamoto |doi-access=free}} It is also effective for lithiation of arenes.{{cite journal |doi=10.15227/orgsyn.072.0163|first1=X.|last1=Wang|first2=S. O.|last2=de Silva|first3=J. N.|last3=Reed|first4=R.|last4=Billadeau|first5=E. J.|last5=Griffen|first6=A.|last6=Chan|first7=V.|last7=Snieckus|title=7-Methoxyphthalide|journal=Org. Synth.|year=1995|volume=72|page=163}}

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Category:Organolithium compounds

Category:Sec-Butyl compounds