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:
Copper-Catalyzed Reductive Ireland-Claisen Rearrangements of Propargylic Acrylates and Allylic Allenoates
S. Guo, K. C. Wong, S. Scheeff, Z. He, W. T. K. Chan, K.-H. Low, P. Chiu, J. Org. Chem., 2022, 87, 429-452.
Global Diastereoconvergence in the Ireland-Claisen Rearrangement of Isomeric Enolates: Synthesis of Tetrasubstituted α-Amino Acids
T. J. Fulton, A. Q. Cusumano, E. J. Alexy, Y. E. Du, H Zhang, K. N. Houk, B. M. Stoltz, J. Am. Chem. Soc., 2020, 142, 21938-21947.