Aluminum Hydride

Introduction

A diethyl ether solution of three equivalents of lithium aluminum hydride with one equivalent of aluminum chloride generates a mild reducing hydride known as ‘Aluminum Hydride’ (AlH₃). [1] This reagent is very useful in synthetic organic chemistry and is easily prepared in situ and used immediately. Lithium aluminum hydride is a powerful reducing agent that can reduce several functional groups. By minimizing its reducing power, selective functional groups can be reduced. In this regard, mixed hydrides have gained a lot of interest in hydride chemistry. Adding a Lewis acid could decrease the reducing power of lithium aluminum ­hydride. AlH₃ reduces a wide variety of functional groups. [1] These include aldehydes, ketones, [2] [3] quinines, carboxylic ­acids, anhydrides, acid chlorides, esters, and lactones from which the corresponding alcohol is isolated as product. Similarly, amides, nitriles, oximes and isocyanates are reduced to amines. However, nitro compounds are inert to AlH₃. Interestingly sulfides and sulfones are unreactive but disulfides and sulfoxides can be reduced. Tosylates are not reduced.

References

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