Lecture 33 – Chapter 20 : Ester Hydrolysis Ester hydrolysis – acid catalyzed Ester hydrolysis – base catalyzed (saponification) Lecture 33 – Chapter 21 : Ester Enolates Ester enolate formation – a-deprotonation Ester enolate reacting with ester – Claisen condensation

Carboxylic Acid Esters Tetronolide derivative – beetle sex attractant Fatty acid Ester (triglyceride)

Carboxylic Acid Esters – hydrolysis Acid-catalyzed hydrolysis Basic hydrolysis – saponification

Fatty acid biosynthesis carbon chain extended by 2, can go up to C16, C18, C20 iteratively

Chapter 21: Deprotonation of a-H in Esters Choice of base is important Saponification competes with deprotonation when hydroxide used Last step of saponification is irreversible, leads to carboxylate salt Use the base that corresponds to the OR’ group on the ester

Claisen: Same setup as the simple aldol reaction Both enolate and ester present in mixture: Claisen condensation results: b-keto ester

Examples 2 a-H required to send reaction to the Claisen product Always need acid in second step to quench anion

Intramolecular Claisen Condensation – the Dieckmann Both the nucleophile (enolate) and electrophile are now in same system Intramolecular Claisen condensation results – cycle formed Protonation still required to isolate b-keto ester product