 | |
| Names | |
|---|---|
| Preferred IUPAC name Lithium triethylboranuide | |
| Other names Superhydride LiTEBH | |
| Identifiers | |
3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.040.963 |
| EC Number |
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| UNII | |
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| Properties | |
| 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 |
| reactive | |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | highly flammable corrosive Causes burns Probable Carcinogen |
| GHS labelling:[1] | |
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| Danger | |
| H250,H260,H314,H335 | |
| 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) | |
| Safety data sheet (SDS) | External MSDS |
| Related compounds | |
Relatedhydride | Lithium borohydride sodium borohydride sodium hydride lithium aluminium hydride |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Lithium triethylborohydride is theorganoboron compound with the formulaLiEt3BH. Commonly referred to asLiTEBH orSuperhydride, it is a powerfulreducing agent used inorganometallic andorganic chemistry. It is a colorless or white liquid but is typically marketed and used as a THF solution.[2] The related reducing agentsodium triethylborohydride is commercially available astoluene solutions.
LiBHEt3 is a stronger reducing agent thanlithium borohydride andlithium aluminium hydride.
LiBHEt3 is prepared by the reaction oflithium hydride (LiH) andtriethylborane (Et3B) intetrahydrofuran (THF):
The resulting THF complex is stable indefinitely in the absence of moisture and air.
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 thediol. Similarlylactones reduce to diols. α,β-Enones undergo 1,4-addition to give lithiumenolates.Disulfides reduce tothiols (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 andketals are not reduced by LiBHEt3. It can be used in the reductive cleavage ofmesylates andtosylates.[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 reducespyridine andisoquinolines topiperidines and tetrahydroisoquinolines respectively.[7]
The reduction of β-hydroxysulfinyl imines with catecholborane and LiBHEt3 producesanti-1,3-amino alcohols shown in (8).[8]
LiBHEt3 reacts exothermically, potentially violently, with water, alcohols, and acids, releasing hydrogen and thepyrophorictriethylborane.[2]
