Polystyrene supported benzoylthiourea—pyrrolidine organocatalyst for the enantioselective Michael addition

Herein the preparation of a swellable pearl-like copolymer of styrene with anchored (S)-1-benzoyl-3-(pyrrolidine-2-ylmethyl)thiourea (20–600 μm) and its application as a recyclable organocatalyst for the Michael addition of ketones to functionalized β-nitrostyrenes is described. The rate of the reaction taking place in the matrix of the swellable polymeric catalyst was comparable with the reaction rate in homogeneous medium. The corresponding functionalized 4-nitroketones were formed quantitatively with the enantiomeric excesses up to 98% ee. After a fivefold recycling of the catalyst, no decrease in the yield was detected, but the enantioselectivity was slightly lowered (95 → 88% ee).

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