Chiral and Achiral Lithium Amides Having a Fluorous Ponytail: Preparation and Evaluation as a Recycling Reagent for Lithium Enolate Generation

Abstract

Diisopropylamine derivatives bearing a perfluoroalkyl chain were prepared and converted to the corresponding lithium amides by treatment with n-butyllithium. The fluorous lithium amides reacted with ketones to efficiently produce lithium enolates. Asymmetric deprotonation of prochiral ketones was also studied using lithium amides derived from chiral fluorous amines, which gave optical yields comparable with the parent nonfluorous chiral lithium amides. These reusable fluorous amines can be easily recovered by liquid-liquid extraction or chromatographic separation.

Key words

fluorous - chiral amine - enolate - LDA - asymmetric deprotonation - recycling

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These structures were optimized by MMMF using Spartan 04 with freezing geometries around lithium.