LAH

(Lithium Aluminum Hydride)

Other Names:

Lithium tetrahydroaluminate

Lithium alanate

General Information:

Structure:

CAS Number: 16853-85-3

Molecular Weight: 37.95 g/mol

Appearance: Grey powder

Lithium Aluminum Hydride (LAH) is a reagent used extensively in organic synthesis for reduction. LAH is very reactive towards H2O in an exothermic process that leads to the potentially dangerous liberation of H2 gas. LAH also reacts readily with protic solvents. Despite low solubility, LAH is typically used in ether and THF. LAH is most commonly sold commercially as a solid or as a 1M solution in THF.

Common Uses:

Reagent for the reduction of esters to alcohols

Procedure excerpt:

The SM (900 mg, 4.1 mmol) in dry THF (6.5 mL) was added dropwise to a suspension of LiAlH4 (188 mg, 4.9 mmol) in dry THF (6.5 mL) at 0 C under N2. The mixture was stirred . . .

[full procedure]

Reagent for the reduction of nitriles to amines

Procedure excerpt:

To a solution of the SM (0.792 g, 2.88 mmol) in dry ether under argon at 0 C was added LiAlD4 (0.225 g, 5.35 mmol). The reaction was stirred for 1 h, after which time . . .

[full procedure]

Reagent for the reduction of carboxylic acids to alcohols

Procedure excerpt:

A solution of the SM (350 g, 2.10 mol) in THF (1.4 L) was added to a slurry of LiAlH4 (95.9 g, 1.40 mol) in THF (2.5 L) at 0 C. The reaction mixture was stirred at RT for 30 min, then . . .

[full procedure]

Reagent for the reduction of nitro groups to amines

Procedure excerpt:

To a mixture of LiAlH4 (78.6 g, 2.00 mol) in dry THF (1 L) at 0 C was added a solution of the SM (78 g, 0.404 mol) in THF (200 mL). The reaction mixture was stirred at 70 C . . .

[full procedure]

Safety:

The reactivity of lithium aluminum hydride (LAH) with H2O is exothermic and forms H2 (gas).

References:

1) Patent Reference: WO2015144799, page 106, (18.8 MB)

2) UK Pat App GB2463151A, page 153

3) Patent Reference: WO2016014463, page 90, (6.7 MB)

4) Patent Reference: WO2016014463, page 94, (6.7 MB)

5) Smith, M. B.; March's Advanced Organic Chemistry, 7th Edition

6) Wikipedia: Lithium aluminium hydride (link)

7) www.sigmaaldrich.com: Lithium aluminum hydride (link)