Claisen rearrangement

Organic Chemistry Reaction Mechanism

1. Claisen Rearrangement The aliphatic Claisen Rearrangement is a [3,3]-sigmatropic rearrangement in which an allyl vinyl ether is converted thermally to an unsaturated carbonyl compound.

2. Mechanism:

3. Conditions: All Claisen Rearrangement reactions described to date require temperatures of > 100if uncatalyzed. Generally diphenyl ether is used as the catalyst.

4. diphenyl ether 473 K > This reaction leads to the rearrangement of allyl aryl ethers to allyl phenols. Aromatic Claisen Rearrangement Reaction

5. Mechanism of Aromatic Claisen Rearrangement The aromatic Claisen Rearrangement is followed by a rearomatization by enolisation.

6. Note: When the ortho-position is substituted, rearomatization cannot take place. The allyl group must first undergo a Cope Rearrangement to the para-position before tautomerization is possible.

7. Points To Ponder In this rearrangement reaction , carbon which gets attached to benzene nucleus is vinylic and not allylic. Para-isomer is obtained if ortho-position is blocked by alkyl group.

8. Example: Here the vinylic deuterium gets attached to benzylic carbon in the product.

9. Problem: N Identify N ?