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Reduction of Amides to Amines

Reduction of Amides to Amines: Mechanism

Presumably, the mechanism of the reduction of tertiary amides with lithium aluminum hydride initially involves hydride addition.

Fig.1

Since the carbonyl oxygen is a better leaving group than the nitrogen group, lithium trialkyl aluminate is released, and the reduction proceeds to yield the amine.

Fig.2

Release of the aluminate generates an iminium ion which reacts further by addition of a hydride ion. Hydrolyses of the intermediate yields the amine.

Fig.3

The reduction of primary and secondary amides is analogous to that of tertiary amides. However, in this case it is not the amide that is the reactant but its conjugated base. This intermediate is formed by deprotonation of the amide with the strong base lithium aluminum hydride.

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