Examples:

5.2.9 Mannich Reaction

This three-component condensation reaction is useful for bonding aliphatic carbon to the reactive positions of phenols, pyrroles and indoles. For example, pyrrole reacts with HCHO and dimethylamine to give 2-dimethylaminomethylpyrrole.

A similar result has been observed with indole. The substitution takes place at 3-position to give gramine.