Lithium triethylborohydride

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Lithium triethylborohydride
Skeletal formula of lithium triethylborohydride
IUPAC name
Lithium triethylborohydride
Other names
3D model (JSmol)
ECHA InfoCard 100.040.963
Molar mass 105.95 g/mol
Appearance Colorless to yellow liquid
Density 0.890 g/cm3, liquid
Boiling point 66 °C (151 °F; 339 K) for THF
Main hazards highly flammable
Causes burns
Probable Carcinogen
Safety data sheet External MSDS
R-phrases (outdated) 11-14/15-19-34
S-phrases (outdated) 16-26-33-36/37/39-43-45
NFPA 704
Flammability code 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g. diesel fuelHealth code 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasReactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazard W: Reacts with water in an unusual or dangerous manner. E.g. sodium, sulfuric acidNFPA 704 four-colored diamond
Related compounds
Related hydride
sodium borohydride
sodium hydride
lithium aluminium hydride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Lithium triethylborohydride is the organoboron compound with the formula LiEt3BH. Commonly referred to as LiTEBH or Superhydride, it is a powerful reducing agent used in organometallic and organic chemistry. It is a colorless or white solid but is typically marketed and used as a THF solution.[1] The related reducing agent sodium triethylborohydride is commercially available as toluene solutions.

LiBHEt3 is a stronger reducing agent than lithium borohydride and lithium aluminium hydride.


LiBHEt3 is prepared by the reaction of lithium hydride (LiH) and triethylborane (Et3B) in tetrahydrofuran (THF):

LiH + Et3B → LiEt3BH

Its THF solutions are stable indefinitely in the absence of moisture and air.


Alkyl halides are reduced to the alkanes by LiBHEt3.[2][3][1]

LiBHEt3 reduces a wide range of functional groups, but so do many other hydride reagents. Instead, LiBHEt3 is reserved for difficult substrates, such as sterically hindered carbonyls, as illustrated by reduction of 2,2,4,4-tetramethyl-3-pentanone. Otherwise, it reduces acid anhydrides to alcohols and the carboxylic acid, not to the diol. Similarly lactones reduce to diols. α,β-Enones undergo 1,4-addition to give lithium enolates. Disulfides reduce to thiols (via thiolates). LiBHEt3 deprotonates carboxylic acids, but does not reduce the resulting lithium carboxylates. For similar reasons,

Epoxides undergo ring-opening upon treatment with LiBHEt3 to give the alcohol. With unsymmetrical epoxides, the reaction can proceed with high regio- and stereo- selectivity, favoring attack at the least hindered position:[2]

Reduction of epoxide.png

Acetals and ketals are not reduced by LiBHEt3. It can be used in the reductive cleavage of mesylates and tosylates.[4] LiBHEt3 can selectively deprotect tertiary N-acyl groups without affecting secondary amide functionality.[5] It has also shown to reduce aromatic esters to the corresponding alcohols as shown in eq 6 and 7.

Ester to alcohol.png

LiBHEt3 also reduces pyridine and isoquinolines to piperidines and tetrahydroisoquinolines respectively.[6]
The reduction of β-hydroxysulfinyl imines with catecholborane and LiBHEt3 produces anti-1,3-amino alcohols shown in (8).[7]

Betaimmine reduction.png


LiBHEt3 reacts exothermically, potentially violently, with water, alcohols, and acids, releasing hydrogen and the pyrophoric triethylborane.[1]


  1. ^ a b c Marek Zaidlewicz, Herbert C. Brown "Lithium Triethylborohydride" Encyclopedia of Reagents for Organic Synthesis 2001, John Wiley & Sons. doi:10.1002/047084289X.rl148
  2. ^ Marek Zaidlewicz, Herbert C. Brown (2001). "Lithium Triethylborohydride". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rl148.CS1 maint: uses authors parameter (link)
  3. ^ Brown, H.C.; Kim, S.C.; Krishnamurthy, S. "Selective reductions. 27. Reaction of alkyl halides with representative complex metal hydrides and metal hydrides. Comparison of various hydride reducing agents" J. Org. Chem. 1980, 45, 1-12. doi:10.1021/jo01293a018
  4. ^ Baer, H.H.; Mekarska-Falicki, M. Can. J. Chem. 1985, 63, 3043.
  5. ^ Tanaka, H.; Ogasawara, K. Tetrahedron Lett. 2002, 43, 4417.
  6. ^ Blough, B.E.; Carroll, F. I. "Reduction of isoquinoline and pyridine-containing heterocycles with lithium triethylborohydride (Super-Hydride®)" Tetrahedron Lett. 1993, 34, 7239. doi:10.1016/S0040-4039(00)79297-5
  7. ^ Kochi, T; Tang, T.P.; Ellman, J.A. J. Am. Chem. Soc. 2002, 124, 6518.