Support by the Fonds der Chemischen Industrie and by BASF SE is gratefully acknowledged. A.B. acknowledges COST membership (CM0905, Organocatalysis).
Characterization of the Key Intermediates of Carbene-Catalyzed Umpolung by NMR Spectroscopy and X-Ray Diffraction: Breslow Intermediates, Homoenolates, and Azolium Enolates†
Article first published online: 28 AUG 2013
Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Angewandte Chemie International Edition
Volume 52, Issue 42, pages 11158–11162, October 11, 2013
How to Cite
Berkessel, A., Yatham, V. R., Elfert, S. and Neudörfl, J.-M. (2013), Characterization of the Key Intermediates of Carbene-Catalyzed Umpolung by NMR Spectroscopy and X-Ray Diffraction: Breslow Intermediates, Homoenolates, and Azolium Enolates. Angew. Chem. Int. Ed., 52: 11158–11162. doi: 10.1002/anie.201303107
- Issue published online: 10 OCT 2013
- Article first published online: 28 AUG 2013
- Manuscript Received: 13 APR 2013
- Fonds der Chemischen Industrie
- NMR spectroscopy;
- reaction mechanisms;
- X-ray diffraction
Caught in the act: Diamino enols, diamino dienols, azolium enolates, and azolium enols are postulated intermediates of the N-heterocyclic carbene catalyzed umpolung of aldehydes and enals. Several of these elusive reaction intermediates were generated with the saturated imidazolidin-2-ylidene SIPr (R=2,6-bis(2-propyl)phenyl) and characterized by NMR spectroscopy and X-ray crystallography.