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Full Paper
A Lewis Acid Promoted Asymmetric Umpolung Reaction with ChiralN-Sulfinyl Imines as the Electrophiles
Article first published online: 25 APR 2005
DOI: 10.1002/ejoc.200400775
Copyright © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Additional Information
How to Cite
Xu, X., Liu, J.-y., Chen, D.-j., Timmons, C. and Li, G. (2005), A Lewis Acid Promoted Asymmetric Umpolung Reaction with ChiralN-Sulfinyl Imines as the Electrophiles. European Journal of Organic Chemistry, 2005: 1805–1809. doi: 10.1002/ejoc.200400775
Publication History
- Issue published online: 25 APR 2005
- Article first published online: 25 APR 2005
- Manuscript Received: 28 OCT 2004
- Abstract
- Article
- References
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Keywords:
- Amino ketones;
- Asymmetric synthesis;
- 1,3-Dithianes;
- N-Sulfinyl imines;
- Umpolung
Graphical Abstract
Abstract
An new asymmetric umpolung reaction has been developed by reacting N-sulfinyl imines with 2-lithio-2-phenyl-1,3-dithiane. The reaction was conducted at between –20 and–25 °C in THF in the presence of Et2AlCl as the Lewis acid promoter. Excellent diastereoselectivities (up to >95 % de) and chemical yields (64–95 %) have been achieved for nine substrates with all individual isomers separated and characterized. The absolute structure of the chiral products has been unambiguously determined by synthetic conversions to a known sample. 2-Lithio-2-phenyl-1,3-dithiane was found to be much less reactive than its 2-methyl counterpart, which was reported very recently. All individual isomers have been readily separated by column chromatography. The absolute structure of the chiral products has been unambiguously determined by conversion into a known compound. This method provides an easy access to enantiomerically pure α-amino ketones. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)