Zinc-mediated ring-expansion and chain-extension reactions of beta-keto esters

Due to their highly strained structures, epoxides can readily undergo ring-opening reactions through nucleophilic substitution, either in the presence of an acid or a base. The nucleophilic substitution reactions in the presence of acid are called acid-catalyzed ring-opening reactions, and nucleophilic substitution reactions in the presence of a base are called base-catalyzed ring-opening reactions. Epoxides undergo base-catalyzed ring-opening reactions in the presence of a strong nucleophile...

Dieckmann cyclization is an intramolecular Claisen condensation of diesters. The reaction occurs in the presence of a base and generates a cyclic β-ketoester as the final product. Commonly, 1, 6 and 1, 7-diesters are preferred substrates for the reaction since the generated five, and six-membered cyclic β-keto esters are particularly more stable.

Regular Claisen condensation involves the synthesis of β-ketoesters by combining identical ester molecules bearing two α hydrogens in the presence of an alkoxide base. The reaction commences with the deprotonation of the acidic α hydrogen by the base to form a resonance stabilized ester enolate. This nucleophilic ion then attacks the carbonyl center of another ester molecule to generate a tetrahedral alkoxide intermediate. Next, the expulsion of the alkoxide group from the intermediate restores...

Epoxides that are three-membered ring systems are more reactive than other cyclic and acyclic ethers. The high reactivity of epoxides originates from the strain present in the ring. This ring strain acts as a driving force for epoxides to undergo ring-opening reactions either with halogen acids or weak nucleophiles in the presence of mild acid. The acid catalyst converts the epoxide oxygen, a poor leaving group, into an oxonium ion, a better leaving group, making the reaction feasible. The...

The Knoevenagel condensation is an aldol-type reaction involving the condensation of aldehydes or ketones with active methylene compounds such as β-diesters to produce substituted olefins.

Acetoacetic ester synthesis is a method to obtain ketones from alkyl halides and β-keto esters. The reaction occurs in the presence of an alkoxide base that abstracts the acidic proton of the β-keto esters. The step results in an enolate ion which is doubly stabilized. The enolate then reacts with an alkyl halide via the SN2 process to produce an alkylated ester intermediate with a new C–C bond. The hydrolysis of the intermediate, followed by acidification, results in an alkylated β-keto acid.