Klaissen Condensation Cheat Sheet

Key Definitions

• Klaisen Condensation: A reaction between two esters or an ester and a carbonyl compound in the presence of a strong base, forming a β-keto ester or a β-diketone. ✅

• Enolate Ion: A negatively charged ion formed when a carbonyl compound is deprotonated at the alpha position. ✅

Important Concepts

Mechanism Overview

• Base: A strong base (e.g., NaOEt, LDA) deprotonates the alpha hydrogen of an ester.

• Nucleophilic Attack: The enolate ion attacks the carbonyl carbon of another ester or carbonyl compound.

• Formation of β-keto ester: The result is a β-keto ester or β-diketone after hydrolysis.

Conditions

• Requires dry conditions to avoid hydrolysis of reactants. ⚠️

• Common bases used: sodium ethoxide (NaOEt), sodium hydride (NaH). ✅

Key Formulas

• RCOOR': First ester

• R''C(=O)R''': Second carbonyl compound

• Base: Strong base used for deprotonation

Common Mistakes to Avoid

Common Mistake: Forgetting to use a strong base can lead to no reaction or poor yields.

Memory Tricks

Tip: "KLAISEN" — Ketone, Loses an alpha Acidic hydrogen, Involves Strong base, Ester + Nucleophile.

Key Diagrams

           RCOOR' + Base
                |
                v
        Enolate Ion (R'CO−)
                |
                v
         R'CO− + R''C(=O)R'''
                |
                v
          β-keto ester