An Unexpected Directing Effect in the Asymmetric Transfer Hydrogenation of α,α-Disubstituted Ketones
摘要:
alpha,alpha-Disubstituted ketones containing an aromatic ring or alkene are reduced in high enantiomeric excess using an asymmetric transfer hydrogenation catalyst. The sense of reduction indicates that the unsaturated region of the ketone adopts a position adjacent to the Ru-bound eta(6)-arene ring in the reduction transition state.
as zeolites and clays, catalyse the intramolecular hydroxyalkylation (cyclialkylation) of several arylalkyl epoxides in moderate to excellent conversions and selectivities. The use of solid acids in these cyclialkylations provides a cleaner, better alternative to conventional Lewis and Brønsted acids, enabling a more facile workup of reaction mixtures and, in several cases, better selectivities.
The reductive ring opening of epoxides is a powerful transformation to convert readily accessible epoxides into a diverse array of valuable alcohols, including pharmaceuticals, agrochemicals, and functional polymers. Although significant progress has been made, the established methods were limited to titanocene-catalyzed reactions. Herein, we report an unprecedented zirconocene-catalyzed ring opening