A Mannich base is a beta-amino-ketone, which is formed in the reaction of an amine, formaldehyde (or an aldehyde) and a carbon acid.[1] The Mannich base is an endproduct in the Mannich reaction, which is nucleophilic addition reaction of a non-enolizable aldehyde and any primary or secondary amine to produce resonance stabilized imine (iminium ion or imine salt). The addition of a carbanion from a CH acidic compound (any enolizable carbonyl compound, amide, carbamate, hydantoin or urea) to the imine gives the Mannich base.[2]

Base catalysed Mannich reaction forming Mannich base

Reactivity

With primary or secondary amines, Mannich bases react with additional aldehyde and carbon acid to larger adducts HN(CH2CH2COR)2 and N(CH2CH2COR)3. With multiple acidic hydrogen atoms on the carbon acid higher adducts are also possible. Ammonia can be split off in an elimination reaction to form enals and enones.

References

  1. ^ March, Jerry (1985), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 3rd edition, New York: Wiley, ISBN 9780471854722, OCLC 642506595
  2. ^ Mannich base applied in this example: V. J. Belinelo; G. T. Reis; G. M. Stefani; D. L. Ferreira-Alves; 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 (6): 830–837. doi:10.1590/S0103-50532002000600016.
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