Abstract
N-Heterocyclic carbene (NHC)-catalysed redox [4+2]-hetero-Diels-Alder reactions of α-aroyloxyaldehydes with either β,γ-unsaturated α-ketoesters or α,β-unsaturated γ-ketoesters generates substituted syn-dihydropyranones in good yield with excellent enantioselectivity (up to >99:1 er). The product diastereoselectivity is markedly dependent upon the nature of the unsaturated enone substituent. The presence of either electron-neutral or electron-rich aryl substituents gives excellent diastereoselectivity (up to >99:5 dr), while electron-deficient aryl substituents give reduced diastereoselectivity. In these cases, the syn-dihydropyranone products are more susceptible to base-promoted epimerisation at the C(4)-position under the reaction conditions, accounting for the lower diastereoselectivity obtained.
Original language | English |
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Pages (from-to) | 355-366 |
Number of pages | 12 |
Journal | Tetrahedron Asymmetry |
Volume | 28 |
Issue number | 2 |
Early online date | 19 Jan 2017 |
DOIs | |
Publication status | Published - 15 Feb 2017 |
ASJC Scopus subject areas
- Catalysis
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry