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Payne rearrangement
The Payne rearrangement is the isomerization, under basic conditions, of 2,3-epoxy alcohols to isomeric 2,3-epoxy alcohols with inversion of configuration. Aza- and thia-Payne rearrangements of aziridines and thiiraniums, respectively, are also known.〔Hanson, R. ''Org. React.'' 2002, ''60'', 1. 〕
==Introduction==
Under basic, protic conditions, 2,3-epoxy alcohols undergo a rearrangement in which the alcohol oxygen opens the epoxide with inversion of configuration, forming an isomeric 1,2-epoxy alcohol. Overall, the Payne rearrangement represents a migration of the epoxide. Although the migration itself is fully reversible, nucleophilic opening under Curtin–Hammett conditions provides good yields of functionalized diols derived from a single epoxy alcohol isomer.〔Seeman, J. I. ''Chem. Rev.'' 1983, ''83'', 83.〕 Intramolecular electrophilic trapping of the new alkoxide generated upon rearrangement may also be used to drive the reaction to completion. In some cases, the thermodynamic difference between epoxide isomers is large enough to obtain a single isomer in synthetically useful yield without relying on kinetic differences associated with trapping.
''(1)''File:PayneGen.png
Strongly basic conditions are required to induce equilibration, which limits the synthetic utility of the transformation to substrates lacking base-labile functionality. Many epoxy alcohol equilibria are very finely balanced;〔Payne, G. B. ''J. Org. Chem.'' 1962, ''27'', 3819.〕 however, taking advantage of the trapping strategies described above may lead to high yields of single isomers.
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