Enantioselective Organocatalytic Conjugate Addition of Fluorocarbon Nucleophiles to alpha,beta-Unsaturated Aldehydes
2009 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 15, no 39, 10013-10017 p.Article in journal (Refereed) Published
Highly chemo- and enantioselective organocatalytic conjugate additions of fluorocarbon nucleophiles to alpha,beta-unsaturated aldehydes and the construction of a quaternary carbon stereocenter bearing a fluorine atom with high enantioselectivity was reported. After extensive screening of catalysts and conditions, it was found that chiral amines 5-9 catalyzed the conjugate addition of FBSM 2a to enal 1a to form the corresponding bfluorobis(sulfonyl)methyl aldehyde 3a, which was reduced in situ to the alcohol derivative 4a, with enantiomeric excess (ee) values ranging from nearly racemic to 95%. Chiral protected diarylprolinols catalyzed the transformation with the highest stereoselectivity under reaction conditions and mediated the formation of 3a with high chemoselectivity. The highest enantioselectivity was achieved in toluene. The enantioselectivity was improved, possibly due to stabilization of the iminium intermediate, by the addition of an acid additive and performing the transformation in ethanol.
Place, publisher, year, edition, pages
2009. Vol. 15, no 39, 10013-10017 p.
aldehydes, asymmetric catalysis, chemoselectivity, fluorine, organocatalysts
IdentifiersURN: urn:nbn:se:kth:diva-32790DOI: 10.1002/chem.200901260ISI: 000270854200010ScopusID: 2-s2.0-70349655526OAI: oai:DiVA.org:kth-32790DiVA: diva2:412853
QC 201104262011-04-262011-04-202011-04-26Bibliographically approved