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The reaction of a carbonyl compound with ammonia in the presence of a reducing agent is called reductive amination.

In this reaction, the unstable imine formed is reduced and undergoes catalytic hydrogenation to form a primary amine.

If the reaction uses primary amine or secondary amine, secondary or tertiary amines can be prepared by reductive amination. The amine is taken in excess to ensure complete reaction

Reductive amination involves two steps: reaction of the amine with the carbonyl and catalytic hydrogenation of produced imine or enamine.

The reaction between amine and carbonyl occurs between the nucleophilic nitrogen of amine and electrophilic carbon of the carbonyl. A trace amount of acid catalyzes it. In the second step, the imine or enamine formed is reduced sing hydrogen and a metal catalyst. The metal catalyst mainly used is platinum.

This reaction is used because a C=NH bond is more easily reduced than a C=O bond due to less stability of imine or enamine.

In reductive amination, the carbonyl oxygen is replaced by an amino group. Therefore, the starting materials for a given product can be determined by breaking the C-N bond in the product and adding oxygen to the carbon atom.

a. The carbonyl starting material can be obtained by replacing the C-N bond in the bond with the C=O bond.

The structure of the required carbonyl is:

Carbonyl required for amino acid a

b. The carbonyl starting material can be obtained by replacing the C-N bond in the bond with the C=O bond.

The structure of the required carbonyl is:

Carbonyl required for amino acid b