Editing Ester (section)

=== Claisen condensation and related reactions ===
Esters can undergo a variety of reactions with carbon nucleophiles. They react with an excess of a Grignard reagent to give tertiary alcohols. Esters also react readily with [[enolate]]s. In the [[Claisen condensation]], an enolate of one ester ('''1''') will attack the carbonyl group of another ester ('''2''') to give tetrahedral intermediate '''3'''. The intermediate collapses, forcing out an alkoxide (R'O<sup>−</sup>) and producing β-keto ester '''4'''.

[[File:Claisen condensation - general mechanism.svg|center|The Claisen condensation involves the reaction of an ester enolate and an ester to form a beta-keto ester.]]

Crossed Claisen condensations, in which the enolate and nucleophile are different esters, are also possible. An [[Intramolecular reaction|intramolecular]] Claisen condensation is called a [[Dieckmann condensation]] or Dieckmann cyclization, since it can be used to form rings. Esters can also undergo condensations with ketone and aldehyde enolates to give β-dicarbonyl compounds.<ref>Carey 2006, pp. 919–924.</ref> A specific example of this is the [[Baker–Venkataraman rearrangement]], in which an aromatic ''ortho''-acyloxy ketone undergoes an intramolecular nucleophilic acyl substitution and subsequent rearrangement to form an aromatic β-diketone.<ref>Kürti and Czakó 2005, p. 30.</ref> The [[Chan rearrangement]] is another example of a rearrangement resulting from an intramolecular nucleophilic acyl substitution reaction.