Mannich base

A mannich base is an amine, which is formed in the reaction of electrophilic imine salt and enol of a carbonyl compound (usually ketone or aldehyde). Mannich base is an endproduct in the Mannich reaction, which is is nucleophilic addition reaction of an aldehyde and any primary or secondary amine to produce resonance stabilized Schiff base (iminium ion or imine salt). The addition of a carbanion from a CH acidic compound (in the example below diethyl malonate or other enolizable carbonyl compound, amide, carbamate, hydantoin or urea) to the schiff base gives the Mannich base.

Step 1. A secondary amine reacts with formaldehyde to a mesomeric stabilised carbenium-immonium ion

Scheme 3. nucleophilic addition of carbanion from malonic ester on the iminium salt

References

• Mannich base applied in this example: V. J. Belinelo, G. T. Reis, G. M. Stefani, D. L. Ferreira-Alves and D. Piló-Veloso (2002). "Synthesis of 6a,7b-dihydroxyvouacapan-17b-oic acid derivatives. Part IV: mannich base derivatives and its activities on the electrically stimulated Guinea-pig ileum preparation" (open access). Journal of the Brazilian Chemical Society 13: 830-837.mk:Манихова база