1 / 14

The Claisen Ester Condensation

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

cassia
Download Presentation

The Claisen Ester Condensation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Claisen Ester Condensation

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

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

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

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

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

  7. Example

  8. Another Example

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

  10. Effect of Chain Length on the Rate of Ring Closure WWU -- Chemistry

  11. 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.

  12. Crossed Claisen Condensation • In the crossed Claisen condensation, we choose one of the esters to be the acceptor. The acceptor does not have a-hydrogens. • The other ester, the donor, does have a-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.

  13. Crossed Claisen Condensation -- An Example

  14. Synthesize this:

More Related