Industrial Synthesis of Citral

Example of a tandem sigmatropic rearrangement

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Sn2Click the structures and reaction arrows in sequence to view the 3D models and animations respectively

Citral is a compound which can be used in the synthesis of vitamin A. This industrial synthesis is made up of two different [3,3]-sigmatropic rearrangements done in sequence.

The first is a Claisen rearrangement which involves an oxygen in the chair-like transition state. More details of the Claisen rearrangement can be found here. The second part of the single step reaction is a Cope-rearrangement, in which only carbons are involved in the chair-like transition state. These two reactions happen in succession when the two starting materials are heated together, and the reaction is driven by formation of a conjugated carbonyl group in the product.

Final Year Project 2013: Ilona Blee

J. Nowicki, Molecules, 2000, 5, 1033–1050.