Syntheses and Applications of (Thio)Urea-Containing Chiral Quaternary Ammonium Salt Catalysts.
European J Org Chem
; 2014(4): 802-809, 2014 Feb.
Article
em En
| MEDLINE
| ID: mdl-25339849
ABSTRACT
We herein report our efforts to obtain a new class of systematically modified bifunctional (thio)urea-containing quaternary ammonium salts based on easily obtainable chiral backbones. Among the different classes of catalysts that were successfully synthesized, those based on trans-1,2-cyclohexane diamine were found to be the most powerful for the asymmetric α-fluorination of ß-keto esters. Selectivities up to 937 could be obtained by using only 2 mol-% of the optimized catalyst. The importance of the bifunctional nature of these catalysts was demonstrated by control experiments using simplified monofunctional catalyst analogues, which gave almost racemic product only.
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MEDLINE
Idioma:
En
Revista:
European J Org Chem
Ano de publicação:
2014
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Article
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Áustria