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3.7.1.8 The Johnson–Claisen Rearrangement

DOI: 10.1055/sos-SD-203-00213

Zeh, J.; Hiersemann, M.Science of Synthesis: Stereoselective Synthesis, (20113366.

In an analogous manner to the EschenmoserClaisen rearrangement, the allyl vinyl ethers required for the JohnsonClaisen rearrangement are prepared by the in situ condensation of an allylic alcohol with an ortho ester.[‌16‌] This condensation proceeds in stepwise manner through an initial transacetalization to give the mixed ortho ester, followed by elimination of an alcohol to generate the 2-alkoxy-substituted allyl vinyl ether. The transacetalization process requires high temperature and the presence of a Brønsted acid catalyst, e.g. propanoic acid. As this process is reversible, the eliminated alcohol, which in most cases is methanol or ethanol, is removed to shift the equilibrium towards the allyl vinyl ether.

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