Ireland-Claisen Rearrangement

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.

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Mechanism

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:

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Recent Literature

Catalytic Diastereoselective Reductive Claisen Rearrangement
S. P. Miller, J. P. Morken, Org. Lett., 2004, 60, 2743-2745.