Enolate

An enolate is the conjugate base formed by removing an alpha proton from a suitable carbonyl compound. Oxygen-centred and carbon-centred resonance contributors help explain its ability to react at either site.

An enolate whose nucleophilic carbon is conjugated to a carbonyl through an additional unsaturated unit.

An enolate derived by deprotonation alpha to an ester carbonyl.

An enolate favoured after equilibration under the stated conditions. It is often more substituted, but aggregation, solvent and counterion can change the preference.

An enolate preferentially formed under conditions where deprotonation site selection is not equilibrated, often at a less hindered alpha carbon with a bulky strong base.

Preference for forming or reacting one enolate of a carbonyl compound with more than one alpha site. A less substituted kinetic enolate and an equilibrated more substituted enolate can give different carbon skeletons.

Reaction of an enolate with an acyl electrophile. carbon acylation of a ketone enolate gives a 1,3-diketone; O-acylation gives a different connectivity.

A carboxylic acid treated with sufficient strong base can lose both its acidic O–H proton and an alpha C–H proton. Carbon alkylation of the resulting dianion followed by protonation yields an alpha-substituted acid.

Enolate alkylation forms a carbon–carbon bond by attack of an enolate carbon on an alkyl electrophile, commonly through an SN2 reaction. Solvent, counterion, aggregation and electrophile identity affect competition with oxygen alkylation.

Conjugate reduction followed by carbon-electrophile trapping of the resulting enolate. The original enone alpha position determines the alkylation site before any later equilibration.

Oxygen-centred attack of an enolate on an acylating reagent forms an enol ester or carbonate. Carbon acylation gives a different connectivity, so the ambident nucleophile's two resonance representations should not be confused with two equivalent products.