Reactions of enamines and enolates

An enamine is an unsaturated compound derived by the reaction of an aldehyde or ketone with a secondary amine followed by loss of H2O.
The word “enamine” is derived from the affix en-, used as the suffix of alkene, and the root amine. This can be compared with enol, which is a functional group containing both alkene (en-) and alcohol (-ol).

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This article is about a class of chemical compounds. For the chemical company, see Enamine Ltd.
The general structure of an enamine

An enamine is an unsaturated compound derived by the condensation of an aldehyde or ketone with a secondary amine.[1][2] Enamines are versatile intermediates.[3][4]

Condensation to give an enamine.[5]

The word "enamine" is derived from the affix en-, used as the suffix of alkene, and the root amine. This can be compared with enol, which is a functional group containing both alkene (en-) and alcohol (-ol). Enamines are considered to be nitrogen analogs of enols.[6]

If one of the nitrogen substituents is a hydrogen atom, H, it is the tautomeric form of an imine. This usually will rearrange to the imine; however there are several exceptions (such as aniline). The enamine-imine tautomerism may be considered analogous to the keto-enol tautomerism. In both cases, a hydrogen atom switches its location between the heteroatom (oxygen or nitrogen) and the second carbon atom.

Enamines are both good nucleophiles and good bases. Their behavior as carbon-based nucleophiles is explained with reference to the following resonance structures.

EnamineResStructures.png

References

  1. ^ Clayden, Jonathan (2001). Organic chemistry. Oxford, Oxfordshire: Oxford University Press. ISBN 0-19-850346-6. 
  2. ^ Smith, Michael B.; March, Jerry (2007), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (6th ed.), New York: Wiley-Interscience, ISBN 0-471-72091-7 
  3. ^ Enamines: Synthesis: Structure, and Reactions, Second Edition, Gilbert Cook (Editor). 1988, Marcel Dekker, NY. ISBN 0-8247-7764-6
  4. ^ R. B. Woodward, I. J. Pachter, and M. L. Scheinbaum (1974), 2,2- (Trimethylenedithio)cyclohexanone, Org. Synth. 54: 39 ; Coll. Vol. 5: 1014 
  5. ^ R. D. Burpitt and J. G. Thweatt (1968), Cyclodecanone, Org. Synth. 48: 56 ; Coll. Vol. 5: 277 
  6. ^ Imines and Enamines | PharmaXChange.info

See also

  • Thorpe reaction

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