Sigmatropic rearrangement

Ireland-Claisen rearrangement

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Why is the forward reaction favoured in the Claisen rearrangement if sigmatropic reactions are reversible? A carbonyl group results in the product (compare keto-enol stability).The [3,3] sigmatropic rearrangement can be further enhanced by sticking an oxygen outside the ring. This is employed in the Ireland-Claisen rearrangement, where a silyloxy group can be bolted on to the Claisen set up. This has wide applications synthetically, since the silyloxy group can be easily hydrolysed, with the achievement of a new C-C bond in the product.

Richard Windsor - Undergraduate Final Year Project 2008

Y. Chai, S. Hong, H. A. Lindsay, C. McFarland and M. C. McIntosh, Tetrahedron, 2002, 58, 2905–2928.