Claisen Condensation-百灵威

The Claisen condensation uses a base to forms a β-keto ester from two identical esters with α-hydrogens The base abstracts an α-hydrogen from one of the esters, producing an enolate, which attacks the carbonyl group of the second ester, releasing an OR group to form a β-keto group.

Lab Tips:

If an alkoxide base is used, it should match the alcohol portion of the ester to prevent a mixture of products.^[1]
Cyclic β-keto esters (five- and six-membered rings and occasionally larger rings) can be synthesized from two esters tethered together in a Dieckmann condensation.^[1]
If two different esters are used, one should not have any α-hydrogens (e.g. esters of aromatic acids, formic acid, oxalic acid) to prevent a mixture of products.^[1]
If more reactive acylating agents (e.g. acid anhydrides and acyl halides) are used, an inert solvent avoids solvolysis of the acylating agent. ^[1]
If more reactive acylating agents (e.g. acid anhydrides and acyl halides) are used, an inert solvent avoids solvolysis of the acylating agent. ^[1,3]

_{1. Kürti, L., Czakó, B. (2005). Strategic Applications of Named Reactions in Organic Synthesis; Background and Detailed Mechanisms. Burlington, MA: Elsevier Academic Press.
2. Carey, F.A., Sundberg, R.J. (2001). Advanced Organic Chemistry Part B: Reactions and Synthesis (4th ed.). New York: Kluwer Academic/Plenum Publishers.
3. McMurry, J. (2000). Organic Chemistry (5th ed.). Pacific Grove, CA: Brooks/Cole.}

Reagents: 1 Equiv of Base (Alkoxide that matches the alcohol portion of the ester, LDA, or NaH), Solvent (Alcohol that matches the alcohol portion of the ester), Acid Work-Up
Reactant: Two Esters (at least one with an α-hydrogen) or One Ester (with an α-Hydrogen) and an Acyl Halide or Anhydride
Product: β-Keto Ester
Type of Reaction: Condensation

Mechanism

Related Compounds

Alkoxide Base

Alcohols

Claisen Condensation

Mechanism

Original Reaction Paper

Top Citations

Related Reactions

Related Compounds