An enamine is a functional group with the formula R₂N−C(R')=CR₂. Enamines are reagents used in organic synthesis and are intermediates in some enzyme-catalyzed reactions.

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 nitrogen analogs of enols.

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

Enamines can be easily produced from commercially available starting reagents. Commonly enamines are produced by condensation of secondary amines with ketones and aldehydes.. The condensing ketone and aldehyde must contain an α-hydrogen. The associated equations for enamine formation follow:

In some cases, acid-catalysts are employed. Acid catalysis is not always required, if the pK_aH of the reacting amine is sufficiently high (for example, pyrrolidine, which has a pK_aH of 11.26). If the pK_aH of the reacting amine is low, however, then acid catalysis is required through both the addition and the dehydration steps. Common dehydrating agents include MgSO₄ and Na₂SO₄.

Methyl ketone self-condensation is a side-reaction which can be avoided through the addition of TiCl₄ into the reaction mixture (to act as a water scavenger).

Primary amines are usually not used for enamine synthesis. Instead, such reactions give imines:

Imines are tautomers of enamines. The enamine-imine tautomerism is analogous to the keto-enol tautomerism.