Asymmetric Aldol Reaction Catalyzed by New Recyclable Polystyrene-supported l-proline in the Presence of Water

Abstract

Two l-proline-based linear polystyrene anchored catalysts (1a–b) have been efficiently synthesized. By using only 5 mol% of catalysts, the corresponding products of the aldol reaction were obtained in good yields (up to 91%) with excellent anti diastereoselectivity (up to 93:7) and enantioselectivity (up to 98% ee) in DMF in the presence of water. The yields of these reactions in the ketone/water mixture were lower than those in wet DMF (up to 84%). However, the stereoselectivity was comparable (up to 92:8 anti/syn ratio and 96% ee, respectively). In addition, catalysts 1a–b could be recovered by a simple precipitation and filtration process. They can also be re-used for at least five times without obvious loss of catalytic efficiency.