1. WWU -- Chemistry The Claisen Ester Condensation Taken from: http://atom.chem.wwu.edu/kriz/org_2 1c.ppt http://atom.chem.wwu.edu/kriz/org_2 1c.ppt

2. WWU -- Chemistry The Claisen Ester Condensation Esters, like aldehydes and ketones, have acidic  -hydrogens. When an ester bearing an  -hydrogen is treated with a strong base, a condensation reaction takes place to yield a  -ketoester.

3. WWU -- Chemistry The Claisen Ester Condensation NOTE: The alkoxide should match the alkyl group of the ester in order to avoid a competing transesterification.

4. WWU -- Chemistry Claisen Ester Condensation -- Mechanism (Part One)

5. WWU -- Chemistry Claisen Ester Condensation -- Mechanism (Part Two)

6. WWU -- Chemistry The Key to Claisen Ester Condensations The  -carbon of the donor attaches itself to the carbonyl carbon of the acceptor. The alkyl group of the acceptor leaves to form a C=O bond.

7. WWU -- Chemistry Example

8. Another Example

9. WWU -- Chemistry Example of a Ring Formation This reaction is known as the Dieckmann cyclization.

10. WWU -- Chemistry What if we mixed two different esters? As in the case with the aldol condensation, if we mixed two different esters, the result would be a mixture of products. However, we can do this deliberately, in what is known as a crossed Claisen ester condensation.

11. WWU -- Chemistry Crossed Claisen Condensation In the crossed Claisen condensation, we choose one of the esters to be the acceptor. The acceptor does not have  -hydrogens. The other ester, the donor, does have  - hydrogens. It can react with base to form a nucleophilic enolate ion. With such an experimental design, the crossed Claisen condensation can be used successfully.

12. WWU -- Chemistry Crossed Claisen Condensation -- An Example

13. WWU -- Chemistry Synthesize this: