In this tutorial video, we examine the intramolecular Claisen condensation known as the Dieckmann cyclization. An intramolecular reaction is one in which the nucleophile and the electrophile are within the same molecule. Therefore in this case, both the two required esters are tethered to one another. The enolate of one ester attacks the carbonyl carbon of the other via nucleophilic acyl substitution.