This gentle variant of the Claisen Rearrangement employs the allyl ester of a carboxylic acid instead of an allyl vinyl ether. The ester is converted to its silyl-stabilized enolate (silyl ketene acetal), which rearranges at temperatures below 100 °C.
The immediate product of the rearrangement, a carboxylic acid silyl ester, cannot be isolated and is hydrolyzed during workup. The Ireland-Claisen Rearrangement thus offers ready access to chain-extended carboxylic acids.
Mechanism of the Ireland-Claisen Rearrangement
As with the Claisen Rearrangement, the Ireland modification also proceeds with a high degree of stereoselectivity:
An advantage of the Ireland-Claisen Rearrangement is the option of controlling the enolate geometry through the judicious choice of solvent: