Lithium triethylborohydride
Names | |
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Preferred IUPAC name Lithium triethylboranuide | |
Other names Superhydride LiTEBH | |
Identifiers | |
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ChemSpider |
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ECHA InfoCard | 100.040.963 |
EC Number |
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InChI
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Properties | |
Chemical formula | Li(C2H5)3BH |
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 |
Solubility in water | reactive |
Hazards | |
Occupational safety and health (OHS/OSH): | |
Main hazards | highly flammable corrosive Causes burns Probable Carcinogen |
GHS labelling:[1] | |
Pictograms | |
Danger | |
Hazard statements | H250, H260, H314, H335 |
Precautionary statements | P210, P222, P223, P231+P232, P260, P261, P264, P271, P280, P301+P330+P331, P302+P334, P303+P361+P353, P304+P340, P305+P351+P338, P310, P312, P321, P335+P334, P363, P370+P378, P402+P404, P403+P233, P405, P422, P501 |
NFPA 704 (fire diamond) | 3 2 2 W |
Safety data sheet (SDS) | External MSDS |
Related compounds | |
Related hydride | Lithium borohydride 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). Y verify (what is YN ?) 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 liquid but is typically marketed and used as a THF solution.[2] 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.
Preparation
LiBHEt3 is prepared by the reaction of lithium hydride (LiH) and triethylborane (Et3B) in tetrahydrofuran (THF):
- LiH + Et3B → LiEt3BH
The resulting THF complex is stable indefinitely in the absence of moisture and air.
Reactions
Alkyl halides are reduced to the alkanes by LiBHEt3.[3][4][2]
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:
Acetals and ketals are not reduced by LiBHEt3. It can be used in the reductive cleavage of mesylates and tosylates.[5] LiBHEt3 can selectively deprotect tertiary N-acyl groups without affecting secondary amide functionality.[6] It has also been shown to reduce aromatic esters to the corresponding alcohols as shown in eq 6 and 7.
LiBHEt3 also reduces pyridine and isoquinolines to piperidines and tetrahydroisoquinolines respectively.[7]
The reduction of β-hydroxysulfinyl imines with catecholborane and LiBHEt3 produces anti-1,3-amino alcohols shown in (8).[8]
Precautions
LiBHEt3 reacts exothermically, potentially violently, with water, alcohols, and acids, releasing hydrogen and the pyrophoric triethylborane.[2]
References
- ^ "Lithium triethylhydroborate". pubchem.ncbi.nlm.nih.gov. Retrieved 19 December 2021.
- ^ a b c Zaidlewicz, M.; Brown, H.C. (2001). "Lithium Triethylborohydride". Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons. doi:10.1002/047084289X.rl148. ISBN 0471936235. Retrieved 2022-02-18.
- ^ Marek Zaidlewicz; Herbert C. Brown (2001). "Lithium Triethylborohydride". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rl148. ISBN 0471936235.
- ^ Brown, H. C.; Kim, S. C.; Krishnamurthy, S. (1980-02-01). "Selective reductions. 27. Reaction of alkyl halides with representative complex metal hydrides and metal hydrides. Comparison of various hydride reducing agents". J. Org. Chem. 45 (5): 849–856. doi:10.1021/jo01293a018. Retrieved 2022-02-18.
- ^ Baer, H.H.; Mekarska-Falicki, M. (November 1985). "Stereochemical dependence of the mechanism of deoxygenation, with lithium triethylborohydride, in 4,6-O-benzylidenehexopyranoside p-toluenesulfonates". Canadian Journal of Chemistry. 63 (11): 3043. doi:10.1139/v85-505. Retrieved 2022-02-18.
- ^ Tanaka, H.; Ogasawara, K. (2002-06-17). "Utilization oh lithium triethylborohydride as a selective N-acyl deprotecting agent". Tetrahedron Lett. 43 (25): 4417. doi:10.1016/S0040-4039(02)00844-4. Retrieved 2022-02-18.
- ^ Blough, B.E.; Carroll, F.I. (1993-11-05). "Reduction of isoquinoline and pyridine-containing heterocycles with lithium triethylborohydride (Super-Hydride®)". Tetrahedron Lett. 34 (45): 7239. doi:10.1016/S0040-4039(00)79297-5. Retrieved 2022-02-18.
- ^ Kochi, T.; Tang, T.P.; Ellman, J.A. (2002-05-14). "Asymmetric Synthesis of syn- and anti-1,3-Amino Alcohols". J. Am. Chem. Soc. 124 (23): 6518–6519. doi:10.1021/ja026292g. PMID 12047156. Retrieved 2022-02-18.
- v
- t
- e
- Li2
- LiAlCl4
- Li1+xAlxGe2−x(PO4)3
- LiAlH4
- LiAlO2
- LiAl1+xTi2−x(PO4)3
- LiAs
- LiAsF6
- Li3AsO4
- LiAt
- Li[AuCl4]
- LiB(C2O4)2
- LiB(C6F5)4
- LiWF6
- LiBF4
- LiBH4
- LiBO2
- LiB3O5
- Li2B4O7
- LiAsF6
- Li2SnF6
- Li2TiF6
- Li2ZrF6
- Li2B4O7·5H2O
- LiBSi2
- LiBr
- LiBr·2H2O
- LiBrO
- LiBrO2
- LiBrO3
- LiBrO4
- Li2C2
- LiCF3SO3
- CH3CH(OH)COOLi
- LiC2H2ClO2
- LiC2H3IO2
- Li(CH3)2N
- LiCHO2
- LiCH3O
- LiC2H5O
- LiCN
- Li2CN2
- LiCNO
- Li2CO3
- Li2C2O4
- LiCl
- LiCl·H2O
- LiClO
- LiFO
- LiClO2
- LiClO3
- LiClO4
- LiCoO2
- Li2CrO4
- Li2CrO4·2H2O
- Li2Cr2O7
- CsLiB6O10
- LiD
- LiF
- Li2F
- LiF4Al
- Li3F6Al
- FLiBe
- LiFePO4
- FLiNaK
- LiGaH4
- Li2GeF6
- Li2GeO3
- LiGe2(PO4)3
- LiH
- LiH2AsO4
- Li2HAsO4
- LiHCO3
- Li3H(CO3)2
- LiH2PO3
- LiH2PO4
- LiHSO3
- LiHSO4
- LiHe
- LiI
- LiIO
- LiIO2
- LiIO3
- LiIO4
- Li2IrO3
- Li7La3Zr2O12
- LiMn2O4
- Li2MoO4
- Li0.9Mo6O17
- LiN3
- Li3N
- LiNH2
- Li2NH
- LiNO2
- LiNO3
- LiNO3·H2O
- Li2N2O2
- LiNa
- Li2NaPO3
- LiNaNO2
- LiNbO3
- Li2NbO3
- LiO−
- LiO2
- LiO3
- Li2O
- Li2O2
- LiOH
- Li3P
- LiPF6
- Li3PO4
- Li2HPO3
- Li2HPO4
- Li3PO3
- Li3PO4
- Li2Po
- Li2PtO3
- Li2RuO3
- Li2S
- LiSCN
- LiSH
- LiSO3F
- Li2SO3
- Li2SO4
- Li[SbF6]
- Li2Se
- Li2SeO3
- Li2SeO4
- LiSi
- Li2SiF6
- Li4SiO4
- Li2SiO3
- Li2Si2O5
- LiTaO3
- Li2Te
- LiTe3
- Li2TeO3
- Li2TeO4
- Li2TiO3
- Li4Ti5O12
- LiTi2(PO4)3
- LiVO3·2H2O
- Li3V2(PO4)3
- Li2WO4
- LiYF4
- LiZr2(PO4)3
- Li2ZrO3
- Hemolithin (extraterrestrial protein)
- Organolithium reagents
- CH3COOLi
- C4H6LiNO4
- LiC2F6NO4S2
- LiN(SiMe3)2
- Li3C6H5O7
- C5H5Li
- LiN(C3H7)2
- (C6H5)2PLi
- C18H35LiO3
- C6H13Li
- C4H9Li
- CH3CHLiCH2CH3
- (CH3)3CLi
- C12H28BLi
- CH3Li
- Li+C10H8−
- C5H11Li
- C5H3LiN2O4
- C6H5Li
- LiC2CH3
- LiO2C(CH2)16CH3
- C4H5LiO4
- LiEt3BH
- LiOC(CH3)3
- C9H18LiN
- LiC2H3 Vinyllithium
- LiC
11H
23COO
- Amblygonite
- Berezanskite
- Brannockite
- Cryolithionite
- Darapiosite
- Darrellhenryite
- Elbaite
- Fluorine Elbaite
- Fluor-liddicoatite
- Emeleusite
- Eucryptite LiAlSiO4
- Faizievite
- Hectorite
- Hsianghualite
- Jadarite LiNaSiB3O7OH
- Keatite Li(AlSi2O6)
- Kunzite
- Lavinskyite
- Lepidolite
- Lithiophilite LiMnPO4
- Lithiophosphate Li3PO4
- Manandonite
- Manganoneptunite
- Nambulite
- Neptunite
- Olympite
- Petalite LiAlSi4010
- Pezzottaite Cs(Be2Li)Al2Si6O18
- Rossmanite
- Saliotite
- Sogdianite
- Spodumene LiAl(SiO3)2
- Sugilite
- Tiptopite
- Tourmaline
- Triphylite LiFePO4
- Zabuyelite Li2CO3
- Zektzerite
- Zinnwaldite
- LixBey
- HLiHe+
- LiFHeO
- LiHe2
- (HeO)(LiF)2
- La2/3-xLi3xTiO3He
- Aluminium–lithium alloys
- Heteroatom-promoted lateral lithiation
- LB buffer
- Lithium atom
- Lithium medication
- LiNixCoyAlzO2
- LiNixMnyCozO2
- Lithium soap
- Lithium Triangle
- Lucifer yellow
- Magnesium–lithium alloys
- NASICON
- Environmentally friendly red light flare