Enantioselective epoxidation of alkenes catalyzed by 2-fluoro-N-carbethoxytropinone and related tropinone derivatives.
Several alpha-substituted N-carbethoxytropinones have been evaluated as catalysts for asymmetric epoxidation of alkenes with Oxone, via a dioxirane intermediate. alpha-Fluoro-N-carbethoxytropinone (2) has been studied in detail and is an efficient catalyst which does not suffer from Baeyer-Villiger decomposition and can be used in relatively low loadings. This ketone was prepared in enantiomerically pure form using chiral base desymmetrization of N-carbethoxytropinone. Asymmetric epoxidation catalyzed by 2 affords epoxides with up to 83% ee. Among other derivatives tested, the alpha-acetoxy derivative 7 affords the highest enantioselectivities.
Armstrong
Alan
A
School of Chemistry, University of Nottingham, Nottingham NG7 2RD, U.K. a.armstrong@ic.ac.uk
Ahmed
Ghafoor
G
Dominguez-Fernandez
Belen
B
Hayter
Barry R
BR
Wailes
J Steven
JS