Synthesis of Cinchona Alkaloid Sulfonamide Polymers as Enantioselective Catalysts for the Michael Addition Reaction of β-Ketoester and Nitrostyrene

Abstract

Mizoroki–Heck (MH) polymerization of cinchonidine‐based sulfonamide dimers produces polymers containing a chiral sulfonamide moiety in each repeat unit. Quinidine sulfonamides are known to have excellent catalytic activity in the asymmetric Michael addition reaction of β‐ketoester and nitrostyrene. We found that cinchonidine sulfonamides used as bifunctional chiral catalysts showed even higher stereoselectivity in the same reaction. The polymers synthesized by MH polymerization also showed high levels of diastereo‐ and enantioselectivity (up to 99% enantiomeric excess) in the reaction. Owing to the insolubility of the polymeric catalysts, they were separated easily from the reaction mixture and reused several times without any loss of catalytic activity.

Bifunctional Sulfonamide as Hydrogen Bonding Catalyst in Catalytic Asymmetric Reactions: Concept and Application in the Past Decade

“…Organocatalytic conjugate additions of trans-β-nitrostyrene with other nucleophiles, such as acetylacetone [49] , indole derivates [10] , β-ketoesters [50] , were also reported by several groups. The reactions using 2-oxindole as Michael donor were always challenging due to the difficulties in the deprotonation ).…”