Synlett 2008(19): 3073-3074  
DOI: 10.1055/s-2008-1067229
SPOTLIGHT
© Georg Thieme Verlag Stuttgart ˙ New York

Lithium Aluminum Hydride: A Powerful Reducing Agent

Srinivasarao Yaragorla*
Organic Chemistry Division-I, Indian Institute of Chemical ­Technology, Hyderabad 500007, India
Fax: +91(40)27160512; e-Mail: syaragorla@gmail.com;
Further Information

Publication History

Publication Date:
12 November 2008 (online)

Introduction

Lithium aluminum hydride (LiAlH4) is a powerful reducing agent used in organic synthesis [¹] and is commonly abbreviated as LAH. It is more powerful than the related reagent sodium borohydride because of the relatively weaker Al-H bond compared to the B-H bond. It reduces a vast number of functional groups. For example, it converts esters, [²a] [b] carboxylic acids [²c] and carbonyl compounds [²d] into the corresponding alcohols; α,β-unsaturated ketones are reduced to allylic alcohols. [²e] When epoxides are reduced using LAH, the reagent attacks the less hindered end of the epoxide, usually producing a secondary or tertiary alcohol. Epoxycyclohexanes are reduced to give axial alcohols preferentially. [²f] Using LAH, amines can be prepared by the reduction of amides, [²g] [h] oximes, [²i] nitriles, nitro compounds or alkyl azides. LAH does not reduce simple alkenes, arenes, or alkynes; but alkynes can be reduced if an alcohol group is nearby. [²j]

Figure 1

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