Stereoselective synthesis of (E)-trisubstituted alpha,beta-unsaturated amides and acids

F J P Feuillet, M Cheeseman, M F Mahon, S D Bull

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22 Citations (SciVal)


Potassium alkoxides of N-acyl-oxazolidin-2-one-syn-aldols undergo stereoselective elimination reactions to afford a range of trisubstituted (E)-alpha,beta-unsaturated amides in > 95% de, that may be subsequently converted into their corresponding (E)-alpha,beta-unsaturated acids or (E)-alpha,beta-unsaturated oxazolines in good yield. syn-Aldols derived from alpha,beta-unsaturated aldehydes gave their corresponding trisubstituted (E)-alpha,beta-unsaturated-amides with poorer levels of diastereocontrol, whilst there was a similar loss in (E)- selectivity during elimination of syn-aldols derived from chiral aldehydes. These elimination reactions proceed via rearrangement of the potassium alkoxide of the syn-aldol to a 1,3-oxazinane-2,4-dione enolate intermediate that subsequently eliminates carbon dioxide to afford a trisubstituted (E)- alpha,beta-unsaturated amide. The (E)- selectivity observed during the E1cB-type elimination step has been rationalised using a simple conformational model that employs a chair-like transition state to explain the observed stereocontrol.
Original languageEnglish
Pages (from-to)2976-2989
Number of pages14
JournalOrganic and Biomolecular Chemistry
Issue number16
Publication statusPublished - 2005

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ID number: ISI:000230964400012


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