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 |
---|---|
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 |
Funding
We thank the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013) ERC Grant Agreement No. 279850 (J.E.T. and A.T.D.) as well as the EPSRC, UK and AstraZeneca plc, UK (Case award to J.J.D.) for financial support. A.D.S. thanks the Royal Society, London, UK, for a Wolfson Merit Award. We also thank the EPSRC UK National Mass Spectrometry Facility at Swansea University.
ASJC Scopus subject areas
- Catalysis
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry