posted on 2002-11-08, 00:00authored byAlan Armstrong, Ghafoor Ahmed, Belen Dominguez-Fernandez, Barry R. Hayter, J. Steven Wailes
Several α-substituted N-carbethoxytropinones have been evaluated as catalysts for asymmetric
epoxidation of alkenes with Oxone, via a dioxirane intermediate. α-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 α-acetoxy derivative 7 affords the highest enantioselectivities.