Its intramolecular form is called the Dieckmann cyclization and produces either five- or six-membered rings.  
Its intramolecular form is called the Dieckmann cyclization and produces either five- or six-membered rings.  Its crossed form, common in the biosynthesis of fatty acids, only takes place if one its reactants has no alpha-hydrogens.  In its intermolecular form, it begins with an acid-base reaction between a formation of an ester enolate by an alkoxide base.  The enolate acts as a nucleophile and attacks the carbonyl carbon of another ester molecule.  The resulting tetrahedral intermediate collapses to give the final product, a beta-keto-ester.  FTP, name this reaction, the ester analogue of the aldol condensation.
Its intramolecular form is called the Dieckmann cyclization and produces either five- or six-membered rings.  
Claisen condensation