Published TCIMAIL newest issue No.197
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Johnson-Claisen Rearrangement
The Johnson-Claisen rearrangement is one of the varieties of Claisen rearrangements and gives γ,δ-unsaturated esters from allyl alcohols and orthoacetates. In this reaction, an allyl alcohol and an orthoacetate react by treatment with an acid and heat to produce a ketene acetal in situ. The ketene acetal rearranges and affords a γ,δ-unsaturated ester, which results in a two-carbon elongation. The Eschenmoser-Claisen rearrangement and Ireland-Claisen rearrangement are similar to the Johnson-Claisen rearrangement when they are used properly according to the proper choice of substrates and conditions.
- Reagents:
- Methyl orthoacetate, Ethyl orthoacetate, Organic acids
- Reactants:
- Allyl alcohols
- Products:
- γ,δ-Unsaturated esters
- Scheme:
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- Original literature:
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- Simple stereoselective version of the Claisen rearrangement leading to trans-trisubstituted olefinic bonds. Synthesis of squalene
- Review literature:
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- Claisen Rearrangement over the Past Nine Decades
