Hydrogenation triethyl boron lithium

Hydrogenation triethyl boron lithium
IUPAC name Hydrogenation triethyl boron lithium
Another name Superhydride LiTEBH
Identification information
CAS registration number	22,560-16-3
Characteristic
Chemical formula	Li(C2H5)3BH
Molar mass	105.95 g/mol
The appearance	Colorless liquid tinged with the yellow
Density	0.890 g/cm3, liquid
The boiling point	66 degrees Celsius (in THF solution)
Solubility to water	Water and reaction
The risk
The main risk	Strong flammable (F) Corrosive (C)
NFPA 704	2 3 2 W
R phrase	11-14/15-19-34
S phrase	16-26-33-36/37/39-43-45
Associated material
Associated hydride	Sodium borohydride Hydrogenation sodium Lithium aluminum hydride
I can put a case, the data without the special mention for normal temperature (25 degrees Celsius), the ordinary pressure (100 kPa).

The reagent which is used for hydride reduction with a kind of the organometallic with hydrogenation triethyl boron lithium (すいそか トリエチルホウ そ lithium, lithium triethylborohydride, LiTEBH). The rational formula is LiBH(C₂H₅)₃. Nucleophilicity and the selectivity that THF solution is commercially available under the trademark of Super-Hydride (super hydride) are extremely agents strong hydride.

The reaction form of LiTEBH is similar to boron hydride lithium (LiBH₄) lithium aluminum hydride (LiAl_H4, LAH), but the nucleophilicity exceeds farther than them it.

Table of contents

History

The compounds such as LiTEBH where lithium hydride (LiH) and hydrogenation sodium (NaH) and trialkyl borane (R₃B) were tied to are H. of University of Chicago C. Brown and H. I. I was discovered by シュレジンジャー while a wartime study (War Research) was carried out during the period of 1942-45 years [¹].

Preparation

When LiTEBH reacts lithium hydride and triethyl borane in THF, it is formed approximately quantitatively.

LiH + B(C₂H₅)₃ → LiBH(C₂H₅)₃

When I filter provided solution and remove excessive lithium hydride, clear solution is provided. If there is it under the inert gas, stability can store this THF solution. A marketing product is available.

Reaction

Summary

LiTEBH conducts the following reduction reactions.

1. Aldehyde、Ketone、Ester、Carboxylic acid halide、Carvone acid anhydrideをAlcoholI return まで.
2. I cleave lactone and assume it diol.
3. I add 1,4-to α,β-enone and give enolate.
4. I cut the third grade amide and assume it alcohol.
5. I replace halogen atom of the organic halide with hydrogen.

Generally, the reaction is quantitative fast and does not do it with a problem even if the substrate has steric hindrance.

Each reaction

Aldehyde and ketone are reduced to alcohol by LiTEBH of 1 equivalent. This reduction reaction moves even a bulky substrate such as the-tert-butyl ketone.

R(=O)R' + LiTEBH → RCHR'OH

It becomes first class alcohol and diol each when I add LiTEBH of 2 equivalents to ester and lactone. For example, 1,4-butanediol is provided in 94% of yield from γ-butyrolactone [²].

Of the epoxide a position is a solid-specific, and opening ring takes place. An attack of hydride happens to carbon of the one having a small steric hindrance for S_N2 from the other side of epoxide oxygen. For example, from 1-methyl-1,2-epoxycyclohexane, 1-methyl-1-cyclohexanol is provided [²]. On the other hand, acetal and the ketal do not react with LiTEBH.

The sulfonate such as メシラート or トシラート receives nucleophilic substitution by LiTEBH, and they give the product which they hydrogenated of deoxygenating it [³].

R-OS(_O2)R + LiTEBH → H-R

Of the third grade amide and when react LiTEBH to carbamate and an acyl group on nitrogen is removed secondary amine become lithium amide. ^[4]

RR'N(C=O)R'' + LiTEBH → RR'NLi

I hydrogenate pyridine and isoquinoline and change it to piperidine and the tetrahydroisoquinoline [⁵].

Attention in the use

LiTEBH causes water and alcohol and acid and intense exothermic reaction and produces flammable hydrogen gas. Furthermore, triethyl borane of the pre-stage of LiTEBH shows autoignition characteristics. In addition, LiTEBH and the solution let eyes, skin, the respiratory tract burn themselves.

References

1. ^ Krishnamurthy, S. Aldrichimica Acta. 1974, 7, 55.
2. ^ ^{a b} Brown, H.C.; Kim, S.C.; Krishnamurthy, S. J. Org. Chem. 1980, 45, 1-12. DOI: 10.1021/jo01289a001
3. ^ Baer, H. H.; Mekarska-Falicki, M. Can. J. Chem. 1985, 63, 3043-3052.
4. ^ Tanaka, H.; Ogasawara, K. Tetrahedron Lett. 2002, 43, 4417-4420. DOI: 10.1016/S0040-4039(02) 00844-4
5. ^ Blough, B. E.; Carroll, F. I. Tetrahedron Lett. 1993, 34, 7239-7242. DOI: 10.1016/S0040-4039(00) 79,297-5

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